http://genesdev.cshlp.org/content/23/5/537.full#sec-1
http://genesdev.cshlp.org/content/23....full.pdf+html
Tumor suppressors and cell metabolism: a recipe for cancer growth.
Abstract
Growing tumors face two major metabolic challenges—how to meet the bioenergetic and biosynthetic demands of increased cell proliferation, and how to survive environmental fluctuations in external nutrient and oxygen availability when tumor growth outpaces the delivery capabilities of the existing vasculature. Cancer cells display dramatically altered metabolic circuitry that appears to directly result from the oncogenic mutations selected during the tumorigenic process. An emerging theme in cancer biology is that many of the genes that can initiate tumorigenesis are intricately linked to metabolic regulation. In turn, it appears that a number of well-established tumor suppressors play critical roles in suppressing growth and/or proliferation when intracellular supplies of essential metabolites become reduced. In this review, we consider the potential role of tumor suppressors as metabolic regulators.
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Cancer therapy is increasingly shifting toward individualized therapeutic approaches based on the genetic abnormalities exhibited by transformed cells. In cancer cells, a given transformation event (i.e., oncogene activation) may play a qualitatively different or essential role in a given pathway compared with its role in normal cells, such that cancer cells become dependent on the activity of a specific oncogene for function and survival, a concept known as oncogene addiction. From this logic, oncogene-driven signal transduction may promote greater dependence on specific metabolic pathways such as glycolysis to maintain tumor growth. When combined with the loss of tumor suppressors that promote metabolic adaptation, cancer cells risk developing greater sensitivity to bioenergetic stress. The LKB1-AMPK-p53 pathway best illustrates exposure of such a metabolic “Achilles' heel” and its impact on tumor survival.
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LKB or p53 deficiency, while permissive for unchecked cell growth, renders cells more susceptible to death by metabolic stress. Moreover, the ability of tumor cells to survive metabolic stress in vivo requires AMPK-dependent activation of p53 (Buzzai et al. 2007), which may explain why metformin, an anti-diabetic therapy, can be anti-tumorigenic (Evans et al. 2005; Huang et al. 2008).
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Understanding the pathways that regulate cancer cell metabolism may lead to greater understanding of cancer development and progression, and has the potential to open a new vista of metabolic therapy for cancer treatment.
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Metformin for Cancer
October 26, 2008
http://cancerx.wordpress.com/2008/10...in-for-cancer/
Metformin’s many physiologic actions include suppressing liver’s own sugar production (”hepatic gluconeogenesis”), increasing insulin sensitivity, enhancing body sugar utilization and decreasing absorption of sugar from the intestines. Overall, we can summarily say that Metformin improves overall sugar metabolism (I have long supported reducing carbohydrate consumption as an adjunct in controlling cancer, perhaps to my colleagues’ consternation if not ridicule. Sugar and cancer is a very important theme, though usually under appreciated by conventional oncologists despite the strength of corollary data. But alas, the topic would be a whole separate blog)
Given so many modern illnesses (eg hyperlipidemia, obesity, diabetes etc) resulting from deranged carbohydrate metabolism, it is not hard to imagine that Metformin may have a role to play in the treatment of conditions resulting from defective insulin signalling (incl. polycystic ovary syndrome [PCOS], infertility, non-alcoholic fatty liver disease (NAFLD) or steato hepatitis, metabolic syndrome X, etc), and these could all be considered “off-label” uses for Metformin as a drug .
A higher incidence of cancer in patients with diabetes has been observed for a century, so much so that Dr Anna Barker, deputy director at the National Cancer Institute estimated that the obesity and diabetes pandemic will cause an additional 30-40% increase in incidence of total solid tumour cancers over the next 10 years – notably in breast, prostate, and colorectal cancer (
Financial Times, Oct 1st, 2008). So it makes common sense that an anti-diabetic medicine may somehow inhibit cancer. More recently, despite many mainstream oncologists curiously still denying a role of sugar and diet for cancer control, science has reviewed an emerging key role for insulin and sugar metabolism or insulin signalling in determining cancer risk, tumor growth or cancer progression (
See recent review “Insulin, Insulin-like growth factors, Insulin resistance and neoplasia” by Pollack MN of McGill University in Am J Clin Nutri 2007 Sep;86(3):s820-2 for an overview), then it is no surprise that Metformin has off-label application potential in cancer treatment, as do drugs from another class of anti-diabetic agents, the PPAR agonists [discussion to be posted in this blog soon].
And there is a bit of evidence for this:-
a) In Vitro (cellular evidence):
Active against breast cancer (Zakikhani M,
Cancer Res. 2006 Nov 1;66(21):10269-73), ovarian cancer (Gotlieb WH et al.
Gynecol Oncol. 2008 Aug;110(2):246-50), prostate cancer (Ben Sahra I, et al.
Oncogene. 2008 Jun 5;27(25):3576-86), glioma brain cancer (Isakovic A,
Cell Mol Life Sci. 2007 May;64(10):1290-302).
Observed mechanisms of action of Metformin against various cancers seems mainly to be related to apoptosis and includes decrease in cyclin D1, AMPK activation leading to inhibition of mTOR and a reduction in translation initiation, selective toxicity to p53-deficient cells, and induction of caspase-dependent apoptosis associated with c-Jun N-terminal kinase (JNK) activation.
b) In Vivo (animal evidence):
Prevention of pancreas cancer in hamsters (Schneider MB,
Gastroenterology. 2001 Apr;120(5):1263-70)
Metformin inhibits development of breast cancer in mice (Anisimov VN,
: Bull Exp Biol Med. 2005 Jun;139(6):721-3)
Metformin suppresses intestinal polyp growth in mice (Tomimoto et al. 2008)
Metformin attenuates growth of lung cancer in mice (Algire C. et al,
Endocr Relat Cancer. 2008 Sep;15(3):833-9)
Metformin inhibits prostate cancer (Ben Sahra I, et al.
Oncogene. 2008 Jun 5;27(25):3576-86)
c) Clinical (human evidence):
Dr. Dario Alessi’s research (U. of Dundee) involving data from patient records over ten years, have shown that patients on metformin showed anywhere between a 30-40% protection against all forms of cancer. While this and lowered instance of breast cancer in women with diabetes treated with Metformin has been known for a while, but recent work presented this year demonstrating Metformin’s role in increasing the response rates of breast cancer patients with diabetes is very exciting:
“Using the M. D. Anderson Breast Medical Oncology database, Drs. Gonzalez-Angulo, Jiralerspong and their team at MD Anderson identified 2,529 women with early-stage breast cancer who received chemotherapy. Of the patients, 68 were diabetic but not taking metaformin and 87 were diabetic and taking the drug. The researchers found that the pathologic complete response rates in the breast cancer patients taking Metformin was 24 percent, three times higher than the rates in patients not taking the drug”
When interviewed, Dr. Gonzalez-Angulo thinks that the result maybe from decreased insulin levels as insulin is a known potent growth factor for cancer. The MD Anderson doctors are planning a trial of Metformin in metastatic breast cancer patients who are obese (and who may thus have insulin resistance and high circulating insulin levels).
My take
Such a benign drug as Metformin can be safely given as an off-label adjunctive treatment in cancer patients, especially breast, ovarian, colorectal, prostate, pancreas and perhaps in glioma patients who have Type 2 diabetes, exhibit metabolic syndrome X, who have elevated circulating insulin levels, or are obese, or even simply those who cannot or do not adhere to a low carb low fat diet.
Future Oncol. 2010 Aug;6(8):1313-23.
Modern approach to metabolic rehabilitation of cancer patients: biguanides (phenformin and metformin) and beyond.
Berstein LM.
N.N.Petrov Research Institute of Oncology, Pesochny-2, Leningradskaja 68, St Petersburg 197758, Russia.
levmb@endocrin.spb.ru.
TEXT
Abstract
Comparing the experience accumulated for more than 40 years in the Laboratory of Endocrinology of Petrov Institute of Oncology (St Petersburg, Russia) with similar approaches practiced elsewhere, evidence supports the reasonability of metabolic rehabilitation of patients suffering from breast cancer or other hormone-dependent malignancies. The primary objective of such approaches is to improve treatment results by ameliorating hormonal-metabolic disturbances, including excess body fat, glucose intolerance, insulin resistance and manifestations of endocrine-genotoxic switchings, and modify tissue and cellular targets or mechanisms related or nondirectly related to the aforementioned disturbances. The relevant measures may be categorized as pharmacological (antidiabetic biguanides exemplified with metformin being most popular but not exclusive) and nonpharmacological (rational nutrition, moderate physical activity and so forth) and used separately or in different combinations.
PMID: 20799876 [PubMed - in process]