Scientists in Switzerland have discovered a way to block the growth of human colon cancer cells, preventing the disease from reaching advanced stages and the development of liver metastases. The research, published today in EMBO Molecular Medicine, shows that blocking the so-called Hedgehog-GLI pathway can prevent the growth of tumours, metastatic lesions and cancer stem cells, the cells thought to lie at the root of cancer growth.
Colon cancer often begins in a treatable form when it is confined to the bowel wall, but in frequent cases it can develop to an incurable metastatic stage. A Geneva-based research team has discovered the essential role played by HH-GLI in the progression of colon cancer to these late and incurable stages. HH-GLI is a signalling pathway used by cells to communicate with each other, often used to determine position, growth and survival.
"Previous works hinted at the possible role of HH-GLI in colon cancer, but this was denied by other studies, so its involvement was never entirely clear," said lead researcher Professor Ariel Ruiz i Altaba of Geneva University. "In this study we have proven that HH-GLI is essential for the development and growth of colon cancers. The research demonstrates the active presence of HH-GLI signalling in epithelial cells of colon cancers. Moreover, we find that metastatic tumours rely on this pathway for sustained growth. This identifies HH-GLI as a target for novel anti-cancer therapies against so far incurable forms of colon cancer in distant organs, such as the liver."
This research opens the possibility of new anti-cancer therapies, specifically the use of RNA interference and of Cyclopamine, a plant product known to block Hedgehog pathway activity. This and other similar molecules can now be considered for future research as a treatment for terminal patients with metastatic disease and to fight resurgent forms of the disease.
"Recurrence is a major problem in treatment. Even after a patient has displayed an apparent complete recovery from a primary tumour, recurrence at nearby or distal locations has a poor prognosis," said Ruiz i Altaba. "While monitoring recovering mice we noted that tumours began to recur in all cases except for those treated with Cyclopamine for a short period of time after tumour disappearance. The treated mice were kept for up to one year after the treatment and remained healthy and tumour free."
Using these genetic or pharmacologic methods to block HH-GLI activity also prevents cancer stem cell self-renewal. Using a new in vivo assay to test the participation of cells in a growing tumour, the research team demonstrated the essential role of this pathway for the maintenance and survival of cancer cells.
"This work firmly establishes the critical action of HH-GLI in human colon cancer cells, providing the platform for preclinical and future clinical work." concluded Ruiz i Altaba. "The finding that a blockade of HH-GLI for a relatively short period was sufficient to eliminate the tumour and prevent recurrence, without negatively affecting the health of the mice, opens the possibility for the use of a therapeutic window to eradicate the tumour without major side effects."
From Wikipedia:
"Studies suggest that cyclopamine acts as a primary inhibitor of the so-called "hedgehog" signal-transduction pathway in cells. This pathway named for the ligand for the signal protein, is used by cells to help them react to external chemical signals. The pathway carries out important functions in embryonic development and when it goes awry, deformities can occur. However, errant activation of the pathway can also trigger cancer in adult humans, leading to basal cell carcinoma, medulloblastoma, rhabdomyosarcoma, and prostate, pancreatic and breast cancers. A way of controlling the pathway using cyclopamine could turn this problem on its head and provide a way to treat cancer. Many anticancer drugs are paradoxically carcinogenic in healthy individuals[3"
Therapy for metastatic basal cell skin cancer investigated http://www.lifesciencelab.com.au/art...ed/497734.aspx
(excerpt, GDC-0449 is a derivate of cyclopamine)
The results demonstrated GDC-0449, a Hedgehog Pathway Inhibitor, appears to shrink tumours in locally advanced and metastatic BCC.
Known as the “Hedgehog” trial, the clinicians observed a durable clinical benefit —defined as tumour shrinkage visible on X-ray or other physical exam or improvement in symptoms without tumour growth— in 18 of 33 patients evaluated.
Others had stable disease for prolonged periods of time. Only 4 patients had progression of disease.
Preferential killing of breast tumor initiating cells by N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine/tesmilifene.
Deng T, Liu JC, Pritchard KI, Eisen A, Zacksenhaus E.
Toronto General Research Institute-University Health Network, Ontario, Canada.
PURPOSE: N,N-Diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine (DPPE; tesmilifene) is thought to potentiate the antineoplastic effect of cytotoxic drugs. In a phase III randomized trial for metastatic breast cancer using doxorubicin with or without DPPE, addition of the latter resulted in a significant improvement in overall survival and a trend toward a difference in progression-free survival but, paradoxically, no difference in objective tumor response. Here we tested the hypothesis that DPPE targets breast tumor-initiating cells (TICs). EXPERIMENTAL DESIGN: Human breast TICs from pleural effusions were identified as CD44(+):CD24(-/low) cells by flow cytometry and functionally by their ability to form nonadherent spheres in culture. Mouse mammary TICs from two different models of breast cancer were identified as cells capable of initiating spheres in culture and secondary tumors following transplantation into the mammary gland of syngeneic mice. RESULTS: We show that at physiologically attainable concentrations, treatment with DPPE alone reduced tumorsphere formation and viability of CD44(+):CD24(-/low) breast cancer cells. The kinetics of killing varied for the different breast tumor cells and required continuous exposure to the drug. Whereas doxorubicin killed CD44(+):CD24(-/low) and CD44(-):CD24(+) cells equally well, DPPE induced apoptosis preferentially in CD44(+):CD24(-/low) cells. Treatment of Her2/Neu(+) mammary tumor cells with DPPE in vitro efficiently killed TICs, as determined by flow cytometry and transplantation assays; DPPE further cooperated with doxorubicin to completely eradicate tumorigenic cells. CONCLUSIONS: Our results show that continuous treatment with DPPE alone directly targets breast TICs, and provide rationale to test for cooperation between DPPE and known drugs with efficacy toward breast cancer subtypes.
PMID: 19118039 [PubMed - indexed for MEDLINE
Tesmilifene is a Tamoxifen derivative. Please note the significant finding that is so different from the early detectable tumor shrinkage=efficacy paradigm:
"resulted in a significant improvement in overall survival and a trend toward a difference in progression-free survival but, paradoxically, no difference in objective tumor response."
1: Cancer Lett. 2009 Feb 18;274(2):279-89. Epub 2008 Nov 4. Links
Enhancement of cytotoxicity of natural product drugs against multidrug resistant variant cell lines of human head and neck squamous cell carcinoma and breast carcinoma by tesmilifene.
Ferguson PJ, Brisson AR, Koropatnick J, Vincent MD.
Lawson Health Research Institute, London Health Sciences Centre, 790 Commissioners Road, London, Ontario, Canada. peter.ferguson@uwo.ca N,N-diethyl-2-[4-(phenylmethyl)phenoxyl]ethanamine (tesmilifene), a tamoxifen derivative with antihistamine activity, greatly enhanced the survival of doxorubicin-treated, advanced stage breast cancer patients in a phase III trial. However, the molecular basis of tesmilifene action is not firmly established. The effects of tesmilifene on activity of several anticancer drugs was investigated using human head and neck squamous cell carcinoma (HNSCC) and breast carcinoma cell lines as a model system. Multidrug resistant (MDR) variants of an HNSCC cell line, HN-5a/V15e, and a breast carcinoma cell line, MCF-7/V25a, both highly overexpressed mdr1 (ABCB1) mRNA and the proteins P-glycoprotein and glutathione transferase-pi. Drug sensitivities were measured by a vital stain after 4 days of continuous exposure to anticancer drug in the absence and presence of tesmilifene at a concentration that alone had no antiproliferative effect. Tesmilifene had minimal effect on drug cytotoxicity against the parental cell lines. However, the same tesmilifene treatment enhanced cytotoxicity of docetaxel, paclitaxel, epirubicin, doxorubicin, and vinorelbine against both MDR cell lines by up to 50%. Flow cytometric measurement of annexin V/propidium iodide staining demonstrated that tesmilifene increased the killing of HN-5a/V15e cells caused by docetaxel after 24 and 48h exposure. Tesmilifene increased accumulation of radiolabelled vincristine in HN-5a/V15e cells, over 4h, by up to 100%. The results suggest that tesmilifene might be effective in the treatment of tumors that are resistant to natural product drugs. The mechanism of enhancement appears to be related to expression of an ABC pump-dependent, MDR phenotype.
N,N-diethyl-2-[4-(phenylmethyl) phenoxy] ethanamine (DPPE; tesmilifene), a chemopotentiating agent with hormetic effects on DNA synthesis in vitro, may improve survival in patients with metastatic breast cancer.
Brandes LJ.
Department of Medicine and Pharmacology/Therapeutics, University of Manitoba and Section of Hematology/Oncology, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg MB R3E0V9, Canada. brandes@cc.umanitoba.ca
N,N-diethyl-2-[4-(phenylmethyl) phenoxy] ethanamine (DPPE; tesmilifene) is a novel anti-histaminic and chemopotentiating agent that has a hormetic effect on DNA synthesis in MCF (Michigan Cancer Foundation)-7 human breast cancer cells in vitro and stimulates the growth of experimental tumors in rodents. In a prospectively randomized phase three trial (NCIC MA.19), 152 patients who were co-administered DPPE and doxorubicin survived 50% longer (P < 0.03) than 153 patients who were administered the same dose and schedule of doxorubicin alone. At clinically relevant in vitro concentrations that do not inhibit the P-glycoprotein (P-gp) pump, DPPE selectively sensitizes the cancer cells that express the multiple drug resistance phenotype, making them more susceptible to the cytotoxic effects of chemotherapeutic agents, including anthracyclines and taxanes. Based on its previously demonstrated interaction with histamine at CYP3A4, a P450 that metabolizes arachidonic acid, and its induction of high levels of prostacyclin in the gut of rodents, modulation by DPPE of the intracellular concentration of arachidonate products, such as hydroxyeicosatetraeinoic acids, implicated in increased cancer cell proliferation and metastasis, is postulated.
PMID: 18480139 [PubMed - indexed for MEDLINE
Tesmilifene has an intriguing mechanism of action and has been shown in Phase II clinical trials and in one Phase III clinical trial to enhance the activity of anthracyclines and taxanes, as well as cisplatin and 5-FU in a variety of pre-clinical models.
In clinical studies there is evidence that tesmilifene increases the cytotoxic effects of mitoxantrone and cyclophosphamide in prostate cancer and doxorubicin and taxol in metastatic breast cancer. In a Phase III study of patients with metastatic breast cancer, the addition of tesmilifene to doxorubicin resulted in a 50% increase in survival compared with doxorubicin alone. A second Phase III study of metastatic breast cancer in 723 patients treated with epirubicin/cyclophosphamide +/- tesmilifene failed to demonstrate efficacy with this chemotherapy regimen.
Re: Novel Cancer Therapies Aim to Destroy the Disease at Its Root: The Cancer Stem Ce
Oct 15 2009 (Vol. 29, No. 18) BioMarket Trends
Firms Seek to Prove Cancer Stem Cell Hypothesis
CSCs Are Believed Responsible for Tumorigenesis, Metastases, and Recurrence of Disease
Keith A. Markey, Ph.D.
The pharmaceutical and biotech industries have begun to develop targeted inhibitors of pathways that contribute to tumorigenesis and metastasis. These new medicines offer the promise of treating many types of cancer with greater efficacy and fewer unwanted side effects than heretofore possible. An important premise guiding this work is the cancer stem cell (CSC) hypothesis.
While normal stem cells are essential for development, play a key role in tissue maintenance, and aid in repair, cancer stem cells are believed responsible for tumorigenesis, metastases, and cancer recurrence. The first report providing evidence of CSCs identified primitive leukemic cells that could give rise to acute myeloid leukemia in immunodeficient mice.
Since that discovery in 1994, these cells have been found in most solid tumors. Skeptics of the CSC hypothesis have argued that cancer cells may be capable of de-differentiating and that isolation methods for CSCs do not select for all cells with the capacity for self-renewal. Regardless, the hypothesis provides an explanation for differences between cells in a tumor and offers a new rationale for drug design.
Moving from concept to clinic in just over a decade, CSC research has uncovered several promising pathways that a growing number of biopharmaceutical companies are exploring in clinical and preclinical studies.
Notch Pathway
The Notch pathway is an evolutionarily conserved system that regulates cell fate during development and in the adult. Its involvement in cancer depends upon its role in normal cells of that same tissue. If Notch acts as a gatekeeper of stem cells or regulator of precursor cell fate under normal conditions, it acts as an oncogene in promoting malignant growth. On the other hand, it is a tumor suppressor in tissues in which it normally initiates terminal differentiation.
Different points in the pathway have been targeted for drug development. OncoMed Pharmaceuticals’ OMP-21M18 is an antibody that blocks signals by binding to Delta-like ligand. The drug, which is in a clinical trial involving patients with advanced solid tumors, is part of a $1.4 billion collaboration with GlaxoSmithKline. Merck and Roche have inhibitors to γ-secretase that cleaves the Notch receptor releasing the Notch intracellular domain, a transcription factor. Both companies’ drugs are in early testing against solid tumors. Finally, Trojantec is targeting the Notch pathway with a truncated version of Mastermind, a coactivator involved in chromatin-specific transcription. The drug may prove useful against tumors that overexpress Notch signaling components.
P13K/Akt Pathway
The PI3K/Akt pathway’s importance in cancer is partly attributable to PI3K’s (phosphatidylinositol 3-kinase’s) association with oncogenic growth factor receptors, notably for epidermal growth factor, platelet-derived growth factor, and mesenchymal transition factor. The pathway is also prone to mutations associated with oncogenesis, including changes in the catalytic subunit of PI3K that occur in prostate, breast, endometrium, urinary tract, and colon cancers.
Similarly, mutations of the lipid phosphatase PTEN that normally serves to deactivate the PI3K/Akt pathway are found in cancers of the endometrium, brain, skin, and prostate, while mutations in the protein kinase Akt, which is downstream of PI3K, are overexpressed in head and neck squamous cell carcinoma, and in pancreatic and ovarian cancers. Eight drugs targeting the PI3K/Akt pathway are in clinical trials.
Immunotherapies
Immunotherapies are under development against molecules on CSC surfaces that differ in quantity and/or quality from those on normal cells. ImmunoCellular Therapeutics’ ICT-121 vaccine elicits an immune response using a nine amino-acid epitope of the cell marker CD133.
The company is also developing mAbs that identify CSCs for destruction by the immune system. ICT-69, which was recently outlicensed to Roche, uses an antigen specific to ovarian cancer and multiple myeloma, while another project focuses on two cell adhesion molecules, CEACAM5 and -6, that are expressed by precancerous colon and breast cells. MabCure has a similar program, but one that targets less-antigenic cell markers, based on an assumption that they have escaped immune detection. The company has prepared antibodies against ovarian, colorectal, and prostate cancers, as well as melanoma, for diagnostic tests, and later for therapeutic agents.
Molecular Chaperones
Molecular chaperones, or heat shock proteins (Hsps), are integral to protein production, protection from environmental stress, and identification of proteins for degradation. One, Hsp90, has been implicated in oncogenesis, as it is overexpressed in many tumors and may protect them from chemotherapy and radiation.
They may have use as monotherapies, though they probably will be used in combination with chemotherapy and radiotherapy, since blocking Hsp90 should render malignant cells more sensitive to these treatments. Trojantec has developed a derivative of the p21 gene to counter the effects of Hsp90.
Hedgehog Pathway
The Hedgehog pathway provides an intercellular regulatory mechanism that serves essential functions in the normal proliferation and differentiation of stem cells. Mutations in this pathway figure in basal cell carcinoma, medulloblastoma, and other malignancies. Three drugs that interfere with hedgehog signaling are in clinical trials—two, Infinity Pharmaceuticals’ IPI-926 and Genentech/Curis’ GDC-0449, are derivatives of cyclopamine, which has been studied extensively.
Re: Novel Cancer Therapies Aim to Destroy the Disease at Its Root: The Cancer Stem Ce
1: Cell Cycle. 2009 Oct 15;8(20):3297-302. Epub 2009 Oct 10.Links
Retinoid signaling regulates breast cancer stem cell differentiation.
Ginestier C, Wicinski J, Cervera N, Monville F, Finetti P, Bertucci F, Wicha MS, Birnbaum D, Charafe-Jauffret E.
Centre de Recherche en Cancérologie de Marseille, UMR891 Inserm/Institut Paoli-Calmettes, Marseilles, France. christophe.ginestier@inserm.fr
The cancer stem cell (CSC) hypothesis implicates the development of new therapeutic approaches to target the CSC population. Characterization of the pathways that regulate CSCs activity will facilitate the development of targeted therapies. We recently reported that the enzymatic activity of ALDH1, as measured by the ALDELFUOR assay, can be utilized to isolate normal and malignant breast stem cells in both primary tumors and cell lines. In this study, utilizing a tumorsphere assay, we have demonstrated the role of retinoid signaling in the regulation of breast CSCs self-renewal and differentiation. Utilizing the gene set enrichment analysis (GSEA) algorithm we identified gene sets and pathways associated with retinoid signaling. These pathways regulate breast CSCs biology and their inhibition may provide novel therapeutic approaches to target breast CSCs.
PMID: 19806016 [PubMed - in process
Anticancer Res. 2009 Dec;29(12):4959-4964. Retinoid-induced Histone Deacetylation Inhibits Telomerase Activity in Estrogen Receptor-negative Breast Cancer Cells.
Phipps SM, Love WK, White T, Andrews LG, Tollefsbol TO.
Department of Biology, 175 Campbell Hall, 1300 University Boulevard, Birmingham, AL 35294-1170, U.S.A. trygve@uab.edu.
BACKGROUND: Multiple mechanisms regulate cancer-associated telomerase activity at the level of human telomerase reverse transcriptase (hTERT) transcription which may serve as novel targets for anticancer approaches. MATERIALS AND METHODS: The effects of prolonged all-trans retinoic acid (ATRA) exposure on hTERT regulation in estrogen receptor-negative SK-BR-3 breast cancer cells were examined. RESULTS: ATRA had a profound effect on the morphology and proliferation rate of the SK-BR-3 cells. ATRA also hindered the ability of these cancer cells to grow independently, rendering them more like normal somatic cells. The effect of ATRA on the decrease of telomerase activity was found to be associated with a rapid decrease in histone H3-lysine 9 acetylation (H3-K9-Ac) of the hTERT promoter. Extended-exposure to ATRA in these cells also caused the initiation of a putative compensatory mechanism, counteracting the induced surge in apoptosis. CONCLUSION: A rapid decrease of H3-K9 acetylation at the hTERT promoter could be an important mechanism by which ATRA shuts down telomerase activity and mediates its antitumor effects in estrogen receptor-negative breast cancer cells.
PMID: 20044602 [PubMed - as supplied by publisher]
Int J Mol Med. 2010 Feb;25(2):271-80. Influence of LOX/COX inhibitors on cell differentiation induced by all-trans retinoic acid in neuroblastoma cell lines.
Redova M, Chlapek P, Loja T, Zitterbart K, Hermanova M, Sterba J, Veselska R.
Laboratory of Tumor Biology and Genetics, Institute of Experimental Biology, School of Science, Masaryk University, 61137 Brno, Czech Republic.
We investigated the possible modulation by LOX/ COX inhibitors of all-trans retinoic acid (ATRA)-induced cell differentiation in two established neuroblastoma cell lines, SH-SY5Y and SK-N-BE(2). Caffeic acid, as an inhibitor of 5-lipoxygenase, and celecoxib, as an inhibitor of cyclooxygenase-2, were chosen for this study. The effects of the combined treatment with ATRA and LOX/COX inhibitors on neuroblastoma cells were studied using cell morphology assessment, detection of differentiation markers by immunoblotting, measurement of proliferation activity, and cell cycle analysis and apoptosis detection by flow cytometry. The results clearly demonstrated the potential of caffeic acid to enhance ATRA-induced cell differentiation, especially in the SK-N-BE(2) cell line, whereas application of celecoxib alone or with ATRA led predominantly to cytotoxic effects in both cell lines. Moreover, the higher sensitivity of the SK-N-BE(2) cell line to combined treatment with ATRA and LOX/COX inhibitors suggests that cancer stem cells are a main target for this therapeutic approach. Nevertheless, further detailed study of the phenomenon of enhanced cell differentiation by expression profiling is needed.
The selective retinoid X receptor agonist bexarotene (LGD1069, Targretin) prevents and overcomes multidrug resistance in advanced breast carcinoma.
Yen WC, Lamph WW.
Department of Molecular Oncology, Ligand Pharmaceuticals, Inc., 10275 Science Center Drive, San Diego, CA 92121, USA.
Acquired drug resistance represents a major challenge in the therapeutic management of breast cancer patients. We reported previously that the retinoid X receptor-selective agonist bexarotene (LGD1069, Targretin) was efficacious in treating animal models of tamoxifen-resistant breast cancer. The goal of this study was to evaluate the effect of bexarotene on development of acquired drug resistance and its role in overcoming acquired drug resistance in advanced breast cancer. Paclitaxel, doxorubicin, and cisplatin were chosen as model compounds to determine the effect of bexarotene on the development of acquired drug resistance. Human breast cancer cells MDA-MB-231 were repeatedly treated in culture with a given therapeutic agent with or without bexarotene for 3 months. Thereafter, cells were isolated and characterized for their drug sensitivity. Compared with parental cells, cells treated with a single therapeutic agent became resistant to the therapeutic agent, whereas cells treated with the bexarotene combination remained chemosensitive. Cells with acquired drug resistance, when treated with the combination, showed increased sensitivity to the cytotoxic agent. Furthermore, cells treated with the combination regimen had reduced invasiveness and angiogenic potential than their resistant counterparts. These in vitro findings were further confirmed in an in vivo MDA-MB-231 xenograft model. Our results suggest a role for bexarotene in combination with chemotherapeutic agents in prevention and overcoming acquired drug resistance in advanced breast carcinoma.
PMID: 15897247 [PubMed - indexed for MEDLINE
In the past two decades, more than 30 new anticancer drugs have been introduced, but survival rates have improved only marginally for many forms of cancer [65]. In contrast to most cancer cells, cancer stem cells are slow-dividing and have a lowered ability to undergo apoptosis and a higher ability of DNA repair, making them more resistant to traditional methods of cancer treatment such as radiation and chemotherapy. In vitro experiments comparing differentiated breast cancer cells grown under monolayer conditions with CD24-/low CD44+ cancer stem cells grown under mammosphere conditions showed that the stem cell-like population was more resistant to radiation [66]. In addition, stem cells express ABC drug transporters, which protect the cell from cytotoxic agents and may lead to MDR [67]. Current anti-cancer therapy is effective at debulking the tumour mass but treatment effects are transient, with tumour relapse and metastatic disease often occurring as a result of the failure of targeting cancer stem cells. For therapy to be more effective, debulking of differentiated tumours must occur followed by targeting of the remaining surviving, often quiescent, tumour stem cells. This could be accomplished by differentiating BCSCs through differentiating therapy or eliminating them via immunotherapy. Differentiation therapy targeting cancer stem cells
One way to target cancer stem cells is to induce the cancer stem cells to differentiate. Targeting the cancer stem cell pool to differentiate results in the loss of the ability for self-renewal, a hallmark of the cancer stem cell phenotype and the reason behind maintenance of the cancer stem cells. One differentiation agent used in the clinic is retinoic acid (RA) (vitamin A) [68]. RA and vitamin A analogues can promote differentiation of epithelial cells and reverse tumour progression through modulation of signal transduction. RA-based therapy followed by chemotherapy has found use in acute promyeloctyic leukaemia and could also find use in solid tumour therapy [69]. Recently, the use of bone morpho-genetic protein (BMP)-4 has been described as a non-cytotoxic effector capable of blocking the tumourigenic potential of human glioblastoma cells [70]. This therapeutic agent is able to work by reducing proliferation and inducing expression of neural differentiation markers in stem-like tumour-initiating precursors. These findings are intriguing in light of the role that BMP-4 may play in some breast tumours [71]. Finding ways to specifically target BCSCs via differentiation therapy is an application that needs to be further defined. Targeting stem cells for elimination
Much of cancer therapy research is focused on targeting specific markers on tumour cells that are overexpressed or mutated and that often represent essential genes/proteins or pathways thought to be important for the development of the tumour. For instance, traztuzamab (Herceptin®) targets the HER-2/neu (ErbB2) oncogene, a member of the epidermal growth factor receptor (EGFR) kinase family, a protein overexpressed on roughly 30% of breast tumours [72]. While these approaches have seen some clinical successes, the cancer stem cell model predicts that only by targeting the remaining cells left over after treatment, the putative cancer stem cells, will significant clinical remissions of the disease occur. It is important to note not only that tumours may be driven by mutated proteins and inappropriate signalling, but also that epigenetic mechanisms of gene expression of genes involved in 'stem-ness' such as Oct4, Nanog, and Sox2 could be behind tumour formation [73]. Reversal of these epigenetic switches of cancer stem cells could be one novel way to target cancer stem cells. New therapeutics aimed at eliminating cancer stem cells could also be achieved through a variety of methods: targeting the self-renewal signalling pathways critical for cancer stem cells, targeting the ABC drug transporters that cancer stem cells use to evade chemotherapy, or inducing the immune system to eliminate the cancer stem cells through various immunotherapeutic interventions. Targeting of molecular signalling pathways and drug transporters
The use of the steroid-like molecule cyclopamine to inhibit the Hh signalling pathway has shown some promise in inhibiting the growth of medulloblastoma and could be used in treatments of other tumours [68]. The Wnt pathway can also be inhibited through a variety of mechanisms. Targeting of β-catenin has received a lot of attention as RA has been shown to inhibit β-catenin activity [74] and tyrosine kinase inhibitors such as imatinib (Gleevac®) have been shown to down-regulate β-catenin signalling [75]. Finally, the Notch pathway has also been investigated as a target. An antibody capable of blocking Notch-4 has been used ex vivo to block the formation of mammospheres from primary human specimens [76]. This indicates the potential to block the self-renewal capacity of BCSCs in the patient with this antibody and opens up the use of other antibody therapies in the elimination of BCSCs. In vitro experiments have shown the resistance of BCSCs to chemotherapy and radiation. Recent clinical evidence has established that tumourigenic breast cancer cells with high expression of CD44 and low expression of CD24 are resistant to chemotherapy [77]. Breast cancer patients receiving neoadjuvant chemotherapy had an increase in the CD44+/CD24low population of cells following treatment. These cells retained the capacity to form mammospheres (demonstrating self-renewal) and had an enhanced propensity for forming tumours in SCID/Beige mice compared with pretreatment samples, increasing from 4 of 14 (29%) to 7 of 14 (50%) patient samples transferred. Treatment of patients with HER-2-positive tumours with lapatinib, an EGFR and HER-2/neu (ErbB-2) dual-tyrosine kinase inhibitor, resulted in nonstatistically significant decreases in the percentage of CD44+/CD24low population and in the ability for self-renewal as assessed by mammosphere formation. Thus, inhibition of regulatory pathways involved in self-renewal may confer improved clinical outcomes by targeting BCSCs.
Transl Oncol. 2010 Jun 1;3(3):149-52. Loss of tumor-initiating cell activity in cyclophosphamide-treated breast xenografts.
Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA
Address all correspondence to: Steven P. Zielske, PhD, 4310 Med Sci I, Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109. E-mail: szielske@med.umich.edu
Cancer stem cells (CSCs) are a subpopulation of tumor cells with preferential tumor-initiating capacity and have been purported to be resistant to chemotherapy. It has been shown that breast CSC are, on average, enriched in patient tumors after combination neoadjuvant chemotherapy including docetaxel, doxorubicin, and cyclophosphamide (CPA). Here, we investigate the resistance of breast CSC to CPA alone in a xenograft model. CPA treatment led to a 48% reduction in tumor volume during a 2-week period. Cells bearing the CD44(+) CD24(-) phenotype were reduced by 90% (2.5% to 0.24%) in CPA-treated tumors, whereas cells with aldehyde dehydrogenase activity were reduced by 64% (4.7% to 1.7%). A subsequent functional analysis showed that CPA-treated tumors were impaired in their ability to form tumors, indicating loss of functional tumor-initiating activity. These results are consistent with a CSC phenotype that is sensitive to CPA and indicate that some patient CSC may not display the expected resistance to therapy. Deciphering the mechanism for this difference may lead to therapies to counteract resistance.
PMID: 20563255 [PubMed - in process]PMCID: PMC2887643Free PMC Article
SAN ANTONIO - (Business Wire) GenSpera, Inc.
announced today that the Food and Drug Administration (FDA) has approved its Investigational New Drug (IND) application to begin a Phase I study with its target activated pro-drug, G-202, for the
treatment of cancer. GenSpera’s Phase I clinical study is anticipated to begin in the fourth quarter of 2009 at two major cancer centers: the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, in Baltimore, MD, and the University of Wisconsin Carbone Cancer Center, in Madison, WI. The study is designed to enroll patients with cancers that have progressed after treatment with other anti-cancer agents. The primary endpoints of the open-label, dose-escalation study will be to determine the safety, tolerability and pharmacokinetics of the drug, although the design allows the collection of efficacy data as well. “The acceptance of our IND by the FDA constitutes a defining milestone in the development of an entirely new class of anti-cancer agent that is expected to have broad utility across many tumor types,” commented Dr. Craig Dionne, GenSpera CEO. “We are also pleased that this event underscores the company’s drug development capabilities and commitment to timely achievement of important corporate milestones.” G-202 is a pro-drug that is selectively activated within tumors by an enzyme present on the tumor blood vessels. In preclinical testing, G-202 was shown to ablate tumors in animal models of breast cancer, prostate cancer and kidney cancer. GenSpera, Inc. owns and controls all rights to G-202 and anticipates a strategic partnership to maximize the value of the drug as it progresses through future clinical trials. About GenSpera
GenSpera, Inc. is a development stage oncology company focused on therapeutics which deliver a potent, unique and patented drug directly to tumors. GenSpera’s technology platform combines a potent cytotoxin (12ADT) with a pro-drug delivery system that activates the drug only within the tumor. Unlike standard cancer drugs, plant-derived 12ADT kills cells independent of their division rate, thus making it effective at killing all fast- and slow- growing cancers and cancer stem cells. GenSpera’s pro-drug platform is the subject of six issued patents with six additional patents pending.
GenSpera plans to initiate a Phase I cancer trial with its lead drug, G-202, in the fourth quarter of 2009. G-202 targets the established blood vessels that nourish solid tumors, thus destroying the tumor’s blood supply. This is a dramatic improvement upon anti-angiogenic drugs that primarily only stop the growth of new blood vessels. Upon completion of its Phase I trial, GenSpera expects to initiate multiple Phase II trials for G-202 in several different cancer types. The company’s second drug, G-115, will directly target prostate cancer.
For more information, please visit the Company’s website: www.genspera.com.
Explained in prostate cancer context:
Anticancer Agents Med Chem. 2009 Mar;9(3):276-94. A Trojan horse in drug development: targeting of thapsigargins towards prostate cancer cells.
Christensen SB, Skytte DM, Denmeade SR, Dionne C, Møller JV, Nissen P, Isaacs JT.
Department of Medicinal Chemistry, University of Copenhagen, Denmark. sbc@farma.ku.dk
Available chemotherapeutics take advantage of the fast proliferation of cancer cells. Consequently slow growth makes androgen refractory prostate cancer resistant towards available drugs. No treatment is available at the present, when the cancer has developed metastases outside the prostate (T4 stage). Cytotoxins killing cells irrespective of the phase of the cell cycle will be able to kill slowly proliferating prostate cancer cells. Lack of selectivity, however, prevents their use as systemic drugs. Prostate cancer cells secrete characteristic proteolytic enzymes, e.g. PSA and hK2, with unusual substrate specificity. Conjugation of cytotoxins with peptides, which are selective substrates for PSA or hK2, will afford prodrugs, from which the active drug only will be released in close vicinity of the cancer cells. Based on this strategy prodrugs targeted at prostate cancer cells have been constructed and evaluated as potential drugs for prostate cancer. The potency of the thapsigargins as apoptotic agents make these naturally occurring sesquiterpene lactones attractive lead compounds. Intensive studies on structure-activity relationships and chemistry of the thapsigargins have enabled construction of potent derivatives enabling conjugation with peptides. Studies on the mechanism of action of the thapsigargins have revealed that the cytoxicity is based on their ability to inhibit the intracellular sarco-/endoplasmtic calcium pump.
Re: Novel Cancer Therapies Aim to Destroy the Disease at Its Root: The Cancer Stem Ce
Cancer Immunol Immunother. 2009 Aug;58(8):1185-94. Epub 2008 Dec 2. Breast cancer cells expressing stem cell markers CD44+ CD24 lo are eliminated by Numb-1 peptide-activated T cells.
Mine T, Matsueda S, Li Y, Tokumitsu H, Gao H, Danes C, Wong KK, Wang X, Ferrone S, Ioannides CG.
Department of Gynecologic Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA. mine@med.kurume-u.ac.jp Cancer stem cells (CSC) are resistant to chemo- and radiotherapy. To eliminate cells with phenotypic markers of CSC-like we characterized: (1) expression of CD44, CD24, CD133 and MIC-A/B (NKG2 receptors) in breast (MCF7) and ovarian (SK-OV-3) cells resistant to gemcitabine (GEM), paclitaxel (PTX) and 5-fluorouracil (5-FU) and (2) their elimination by Numb- and Notch-peptide activated CTL. The number of cells in all populations with the luminal CSC phenotype [epithelial specific antigen(+) (ESA) CD44(hi) CD24(lo), CD44(hi) CD133(+), and CD133(+) CD24(lo)] increased in drug-resistant MCF7 and SK-OV-3 cells. Similarly, the number of cells with expressed MIC-A/B increased 4 times in drug-resistant tumor cells compared with drug-sensitive cells. GEM(Res) MCF7 cells had lower levels of the Notch-1-extracellular domain (NECD) and Notch trans-membrane intracellular domain (TMIC) than GEM(Sens) MCF7. The levels of Numb, and Numb-L-[P]-Ser(265) were similar in GEM(Res) and GEM(Sens) MCF7 cells. Only the levels of Numb-L (long)-Ser(295) decreased slightly. This finding suggests that Notch-1 cleavage to TMIC is inhibited in GEM(Res) MCF7 cells. PBMC activated by natural immunogenic peptides Notch-1 (2112-2120) and Numb-1 (87-95) eliminated NICD(positive), CD24(hi) CD24(lo) MCF7 cells. It is likely that the immunogenic Numb-1 peptide in MCF7 cells originated from Numb, [P]-lated by an unknown kinase, because staurosporine but not wortmannin and MAPK-inhibitors decreased peptide presentation. Numb and Notch are antagonistic proteins which degrade each other to stop and activate cell proliferation, respectively. Their peptides are presented alternatively. Targeting both antagonistic proteins should be useful to prevent metastases in patients whose tumors are resistant to conventional treatments.
Researchers have created a new type of cancer drug that blocks a “master” protein considered to be untouchable by conventional agents. A team from Harvard University used the drug to suppress signals from a growth-promoting pathway, the Notch signaling pathway, that switches on inappropriately in some cancers. Cancer cells that depend on Notch signaling die when the pathway is blocked, Drs. Gregory L. Verdine, James Bradner, and their colleagues reported in the November 12 Nature. The drug’s primary target is Notch1, a transcription factor that regulates genes involved in the growth and survival of cells. Transcription factors are mutated in various cancers, but these proteins have proved difficult to target directly because of their structures.
To solve this problem, the Harvard team, led in the lab by graduate student Raymond Moellering, designed a drug molecule (called SAHM1) that enters cells and interferes with a protein-protein interaction that is essential for the transmission of cell growth signals via the Notch pathway.
The researchers tested the drug using cells from patients with T-cell acute lymphoblastic leukemia (T-ALL) and a mouse model of the disease. The Notch1 gene is mutated in half of patients with T-ALL and produces an inappropriately active Notch1 protein. Activated Notch signaling has been seen in several other cancers, including lung, ovarian, and pancreatic cancer, and melanoma. “We’ve drugged a so-called undruggable target,” said Dr. Verdine. “This study validates the notion that you can target a transcription factor by choosing a new class of molecules, namely stapled peptides.” The strategy may work for other transcription factors because the molecular logic of these proteins is similar to that of Notch1, he added.
In an accompanying editorial, Drs. Paramjit Arora and Aseem Ansari said that the group’s “remarkable results highlight the potential of molecules that mimic the secondary structures of proteins to target normally intractable protein-protein interactions.”
By Crystal Phend, Senior Staff Writer, MedPage Today
Published: December 12, 2009
Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston.
SAN ANTONIO -- Targeting breast cancer stem cells with experimental "Notch" inhibitors appears promising in the fight against recurrence, researchers said here.
The novel agents, also known as gamma secretase inhibitors, reduced the number of cancer tumor cells, although with little immediate impact on tumor volume, Jenny Chang, MD, of Baylor College of Medicine in Houston, and colleagues found.
Their early phase experiments in mice and a small group of patients suggested a "paradigm shift" in looking at breast cancer treatment, Chang reported at the San Antonio Breast Cancer Symposium.
Conventional therapy largely aims at volume -- shrink and remove the tumor and keep the mass from regrowing, noted William Gradishar, MD, of the Lurie Cancer Center at Northwestern University in Chicago, who moderated a press conference at which the study was discussed.
But the roughly 1% of tumor cells dubbed "mother cells" that produce new stem cells and regular tumor "daughter" cells, typically survive chemotherapy, endocrine therapy, and radiation.Action Points
Caution interested patients that the drugs used in the trial are still investigational and are not FDA approved for any use.
Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered preliminary until published in a peer-reviewed journal.
"The current available therapies really aren't affecting that population of cells," Gradishar added. In fact, one prior study from Chang's group showed that the cancer stem cells actually more than tripled during neoadjuvant chemotherapy. "The cancer stem cell hypothesis is that you need to kill both populations -- the bulk of the tumor as well as the cancer stem cells -- and they're regulated by different mechanisms," Chang said.
To find out what was driving these hardy cells, the researchers did a gene expression analysis, which revealed Notch signaling as the top candidate.
The Notch pathway is involved in normal mammary development, in communication between cells, and in determining what happens to a cell when it divides, thus "regulating the self-renewal of cancer stem cells," Chang said in an interview with MedPage Today.
She and her team implanted mice with human breast cancer biopsy material that included breast cancer stem cells, then gave them a Notch inhibitor (MRK-003) or a placebo.
MRK-003 significantly reduced formation of clusters of tumor cells called mammospheres compared with placebo.
Tumor volume dropped about fourfold over 21 days with the agent compared with about a threefold decrease with placebo or docetaxel alone or in combination with the Notch inhibitor, but the difference between groups was not significant, likely due to the short duration, Chang said.
With this evidence in hand, Chang's group started a Phase Ib/II clinical trial with another Notch inhibitor (MK-0752) -- 35 women were given the Notch inhibitor before each docetaxel administration for six cycles. Compared with baseline biopsies, those taken at the end of treatment had significantly fewer cancer stem cells measured by CD44/CD24 expression. The formation of mammosphere cell clusters fell significantly as well. Again, though, tumor regression wasn't seen immediately with Notch inhibition. It occurred only after several rounds of therapy. This likely reflects daughter cells dying off from chemotherapy with progressively fewer stem cells to repopulate them, Chang said. Given the proposed mechanism, Notch inhibitors are likely to be developed for upfront use in combination with agents to "debulk" the daughter cells or for chronic administration in the adjuvant setting to prevent recurrence, she speculated.
Her group plans a larger Phase II trial, while others are developing agents targeting other cancer stem cell pathways, such as Hedgehog.
"Trying to identify what really makes them grow, to interfere with those pathways may ultimately lead to better outcomes for patients with both early and advanced stage disease," Gradishar said.
The study was funded by Merck, which is developing the gama secretase inhibitor used.
Chang made no disclosures other than the funding for the study.
Gradishar reported being a consultant for Bayer and Nexavar.
Primary source: San Antonio Breast Cancer Symposium
Source reference:
Chang J, et al "Targeting intrinsically-resistant breast cancer stem cells with gamma-secretase inhibitors " SABCS 2009; Abstract 48.
For the First Time, a Glioma - Brain Cancer - may be Eliminated by a Chinese Research/Medical Team, Using a Novel Stem Cell Based Therapy of Cellonis Biotech, Beijing
BEIJING, Dec. 17 2009/PRNewswire-Asia/ -- Using a novel stem cell based technology of Cellonis Biotechnologies, Beijing, a Chinese research/medical team may eliminate a glioma -- brain cancer -- of a 36 year old Norwegian patient in a hospital in Beijing. The treatment shows that the activated immune system can directly kill tumor stem cells as well as cancer daughter cells. The amazing outcome of this novel treatment within a Comprehensive Cancer Therapy tells Cellonis that the future vaccination therapies may be targeted towards cancer stem cell lysates to improve the antigen-presenting Dendritic Cell response.
(Photo: http://www.newscom.com/cgi-bin/prnh/20091217/CNTH007)
Arve Johnsen , 36, from Norway, a patient diagnosed with glioma in 2006 and relapsed in 2009 after surgical resection. He arrived in Beijing in August 2009 with his wife Vanja and a one-year-old daughter, with the hope that the doctors in Norway were wrong. They told the family there is no other option anymore in the Scandinavian countries or in Europe for Arve to control the progress of disease and prolong his life. Driven by the hope that their daughter could grow up with a father, the Johnsen family started a research campaign to find other treatments worldwide, to give Arve a new hope. Comprehensive Cancer Therapy in China
The Johnsen's, having heard about the sustainable success of a Comprehensive Cancer Therapy (CCT) in China, decided to try for this last chance in a country 10,000 km away from Norway. This kind of CCT had been developed in the past few years by a Chinese team of scientific researchers and clinical doctors in Beijing, combining conventional cancer treatments with Traditional Chinese Medicine (TCM) and cell therapies.
The role of cancer stem cells in the tumors cientists previously believed that tumors are lumps of cancer tissue that must be completely removed or destroyed to cure a patient. But over the past few years, researchers have learned that cancer stem cells (CSCs), comprising a small population of cells, appear to be responsible for the initiation, upkeep and relapse of malignant tumors. Even if a tumor is almost completely obliterated, it will regenerate from the surviving CSCs and become even more resistant to treatment than before.
Current therapies, including cell therapy, generally do not target CSCs. This allows CSCs to survive until after chemotherapy or radiation treatments. Killing those cells is a promising strategy to eliminate tumors and prevent them from re-growing.
Prof.
Lily Shum : Perfect integration of stem cells and immunotherapies
"The CSCs may explain why common treatments, particularly chemotherapy, are not sufficient to kill tumors. In fact, despite the continuous development of new chemotherapeutic agents, brain tumors can develop and remain resistant to those therapies. The integration of stem cells and immune technologies seems to give us a chance to find out a new way to target at CSCs," says Prof. Lily Shum , PhD, the chief scientist of Cellonis. "The difficult issue in our project is how to capture and classify CSCs. With our patented technologies, we are able to isolate the CSCs from patient's brain tumor tissues, culture them and induce the multi-drug and radiation resistance. These cells possess very strong carcinogenicity, self-renewal, and also a very strong drug and radiation resistance."
Lily Shum adds, "The Dendritic Cell (DC) is a very useful tool to conduct a specific immune response against brain CSCs." As we know, DC is an antigen-presenting cell that stimulates the innate immune system, as a messenger, it transfers "the information of cancer cell - antigen" to "the killers of the immune system - the T cells," and then T cells can recognize and lyse cells bearing those antigens. "We educate the DC with the brain CSCs, and then conduct the specific immune response which targets the CSCs."
Dr.
Dinggang Li : Comprehensive Cancer Therapies
"The outcome of the first pilot study with Johnsen is amazing. The PET-CT scan for Johnsen shows that all the tumor disappeared after the treatment," says Dr.
Dinggang Li, M.D. PhD. He has developed and conducted CCT for more than 100 international cancer patients in the past few years. DCs loaded with different kinds of brain cancer related antigens that target cancer cells and the CIK cell treatment are the main elements of his comprehensive treatment for cancer. "In the first cycle of treatment, we treated him with comprehensive approaches including SHG-44 loading DC, CIK cell therapy and TCM, but we had not been able to control the progression of the disease, the tumors continued to grow. We gave him the DC therapy which targets brain CSCs in the 2nd cycle of treatment, and it showed a very promising response." Dr. Cindy HAO: More clinical trials to confirm the outcome
Cindy HAO, M.D., CEO of Cellonis Biotechnologies is optimistic for the future of this new brain cancer approach. "It gives us a strong confidence to make more efforts toward this direction. This pilot treatment study shows us that the activated immune system can directly kill tumor stem cells as well as tumor daughter cells. But first of all we need to extend our further clinical trials to confirm the outcome. And it also tells us that the future vaccination therapies may be targeted toward Cancer Stem Cell Lysates to improve the antigen-presenting DC response."
For more information, please contact:
Urs. J. Lienert, M.B.A.
Director International
Cellonis Biotechnologies Co., Ltd.
Floor 7, Huizhong Science & Technology Center
No 1, Shangdi Seventh Road
Haidian District Beijing, 100085
P.R. China
Email: urs.lienert@cellonis.com; Lienert.Cellonis@yahoo.com
Phone: +86-10-6296-2795; Cell: +86-150-1054-7487
Cell: +41-76-584-87-60 (Switzerland)
(from 20 December 2009 to 15 January 2010)
SOURCE Cellonis Biotechnologies
Multi-drug chemoresistance remains one of the most common reasons for chemotherapy failure. The membrane transporter protein ABCG2/BCRP1 has been shown in vitro to effectively reduce the intracellular concentrations of several prominent anticancer chemotherapeutic agents such as mitoxantrone and doxorubicin. Intriguingly, cancer stem cells are known to be characterized by multi-drug chemoresistance. Taking into account that the ABCG2(+) subset of tumor cells are often enriched with cells with cancer stem-like phenotypes, it has been proposed that ABCG2 activity underlies the ability of cancer cells to regenerate post-chemotherapy. Furthermore, we also review evidence suggesting that tyrosine kinase inhibitors, including imatinib and gefitinib, are both direct and downstream inactivators of ABCG2 and, therefore, serve as candidates to reverse cancer stem cell chemoresistance and potentially target cancer stem cells.
PMID: 19708828 [PubMed - indexed for MEDLINE]
Int J Cancer. 2010 Jul 8. [Epub ahead of print] Gamma-tocotrienol as an effective agent in targeting prostate cancer stem cell-like population.
Emerging evidence supports that prostate cancer originates from a rare sub-population of cells, namely prostate cancer stem cells (CSCs). Conventional therapies for prostate cancer are believed to mainly target the majority of differentiated tumor cells but spare CSCs, which may account for the subsequent disease relapse after treatment. Therefore, successful elimination of CSCs may be an effective strategy to achieve complete remission from this disease. Gamma-tocotrienols (gamma-T3) is one of the vitamin-E constituents which have been shown to have anticancer effects against a wide-range of human cancers. Recently, we have reported that gamma-T3 treatment not only inhibits prostate cancer cell invasion but also sensitizes the cells to docetaxel-induced apoptosis, suggesting that gamma-T3 may be an effective therapeutic agent against advanced stage prostate cancer. Here, we demonstrate for the first time that gamma-T3 can down-regulate the expression of prostate CSC markers (CD133/CD44) in androgen independent (AI) prostate cancer cell lines (PC-3 & DU145), as evident from western blotting analysis. Meanwhile, the spheroid formation ability of the prostate cancer cells was significantly hampered by gamma-T3 treatment. In addition, pre-treatment of PC-3 cells with gamma-T3 was found to suppress tumor initiation ability of the cells. More importantly, while CD133-enriched PC-3 cells were highly resistant to docetaxel treatment, these cells were as sensitive to gamma-T3 treatment as the CD133-depleted population. Our data suggest that gamma-T3 may be an effective agent in targeting prostate CSCs, which may account for its anticancer and chemosensitizing effects reported in previous studies.
PMID: 20617516 [PubMed - as supplied by publisher]
Cancer Lett. 2006 Jun 18;237(2):180-7. Epub 2005 Jul 12. Fluoxetine and reversal of multidrug resistance.
Peer D, Margalit R.
Department of Biochemistry, George S. Wise Life Science Faculty, Tel Aviv University, Tel Aviv 69978, Israel
This review centers on recent findings with respect to modulating cancer multidrug resistance (MDR) with the well-known antidepressant fluoxetine (prozac). The MDR phenomena and mechanisms are discussed, including the roles of ABC transporters as MDR-pumps and the potential involvement of cancer stem cells. The three generations of MDR reversal agents (chemosensitizers) are reviewed, introducing the concept of single-pump and multi-pump agents. The current status of chemosensitization is summarized, pointing-out the need for additional agents and outlining experimental criteria for testing novel candidates. Major in vitro and in vivo findings are summarized showing that fluoxetine is a chemosensitizer of the multi-pump type, and proposing it be considered a fourth-generation chemosensitizer. In concluding, we contemplate future prospects of modulating MDR in the clinic.
PMID: 16014320 [PubMed - indexed for MEDLINE]
Cancer Res. 2004 Oct 15;64(20):7562-9. Fluoxetine inhibits multidrug resistance extrusion pumps and enhances responses to chemotherapy in syngeneic and in human xenograft mouse tumor models.
Peer D, Dekel Y, Melikhov D, Margalit R.
Department of Biochemistry, the George S. Wise Life Science Faculty, Tel Aviv University, Tel Aviv, Israel. Multidrug resistance (MDR) operated by extrusion pumps such as P-glycoprotein and multidrug-resistance-associated-proteins, is a major reason for poor responses and failures in cancer chemotherapy. MDR modulators (chemosensitizers) were found among drugs approved for noncancer indications and their derivatives. Yet toxicity, adverse effects, and poor solubility at doses required for MDR reversal prevent their clinical application. Among newly designed chemosensitizers, some still suffer from toxicity and adverse effects, whereas others progressed to clinical trials. Diversities among tumors and among MDR pumps indicate a need for several clinically approved MDR modulators. Here we report for the first time that fluoxetine (Prozac), the well-known antidepressant, is a highly effective chemosensitizer. In vitro, fluoxetine enhanced (10- to 100-fold) cytotoxicity of anticancer drugs (doxorubicin, mitomycin C, vinblastine, and paclitaxel) in drug-resistant but not in drug-sensitive cells (5 and 3 lines, respectively). Fluoxetine increased drug accumulation within MDR-cells and inhibited drug efflux from those cells. In vivo, fluoxetine enhanced doxorubicin accumulation within tumors (12-fold) with unaltered pharmacokinetics. In four resistant mouse tumor models of both syngeneic and human xenograft, combination treatment of fluoxetine and doxorubicin generated substantial (P < 0.001) improvements in tumor responses and in survivals (2- to 3-fold). Moreover, fluoxetine reversed MDR at doses that are well below its human safety limits, free of the severe dose-related toxicity, adverse effects, and poor solubility that are obstacles to other chemosensitizers. This low-dose range, together with the findings reported here, indicate that fluoxetine has a high potential to join the arsenal of MDR reversal agents that may reach the clinic.
Growing evidence has suggested that lack of eradication of the malignant stem cell forms the basis for cancer relapse and progression. In this regard, the clinical experiences of treating chronic myelogenous leukemia (CML), a prototypical stem cell disease, have been instructive, and are illustrative of the challenges facing the treatment of cancer when using potent cytoreductive agents that incompletely eradicate minimal residual disease. On the other hand, several decades of clinical and laboratory experience have demonstrated the curative potential of allogeneic stem cell transplantation for CML and other hematologic malignancies. As reviewed in this chapter, these studies have clearly demonstrated the curative potential of immune-based recognition of tumor cells, including the malignant progenitor cell population. These data set the stage for newer approaches that focus on immune targeting of antigens that are present on the cancer stem cell. Rational immune targeting of the tumor-initiating population critically depends on (1) identifying the unique surface markers of these cells so that they may be isolated, and on (2) defining antigens that are uniquely or preferentially expressed within the malignant cells with stem-cell like functions compared to normal cells. While debate continues as to the exact nature and defining characteristics of the cell population that is capable of propagating tumor, and hence the critical tumor cell sub-population that is required for immune targeting, several promising approaches for cancer immunotherapy are under investigation. Ultimately, combination therapy that includes both pharmacologic cytoreductive agents together with immunologic targeting of malignant stem cell populations may provide an effective curative approach with acceptable toxicity for the treatment of malignant diseases.
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