[Rich66]

1: J Immunother. 2009 May 28. [Epub ahead of print]

Honokiol-mediated Inhibition of PI3K/mTOR Pathway: A Potential Strategy to Overcome Immunoresistance in Glioma, Breast, and Prostate Carcinoma Without Impacting T Cell Function.

Crane C, Panner A, Pieper RO, Arbiser J, Parsa AT.
*Department of Neurological Surgery, University of California, San Francisco, CA daggerDepartment of Dermatology, Emory University School of Medicine, Atlanta, GA.
Inhibition of the phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway is an appealing method for decreasing the immunoresistance and augmenting T cell-mediated immunotherapy. A major impediment to this strategy is the impact of conventional PI3K/mTOR pathway inhibitors on T cell function. In particular, rapamycin, is a well-known immunosuppressant that can decrease the activity of the PI3K/mTOR pathway in tumor cells, but also has a profound inhibitory effect on T cells. Here we show that Honokiol, a natural dietary product isolated from an extract of seed cones from Magnolia grandiflora, can decrease PI3K/mTOR pathway-mediated immunoresistance of glioma, breast and prostate cancer cell lines, without affecting critical proinflammatory T cell functions. Specifically, we show that at doses sufficient to down-regulate levels of phospho-S6 and the negative immune regulator B7-H1 in tumor cells, Honokiol does not significantly impair T cell proliferation or proinflammatory cytokine production. In contrast to classic inhibitors, including LY294002, wortmannin, AKT inhibitor III and rapamycin, Honokiol specifically decreases the PI3K/mTOR pathway activity in tumor cells, but not in freshly stimulated T cells. Collectively, our data define a unique application for Honokiol and provide the impetus to more fully elucidate the mechanism by which T cells are resistant to the effects of this particular inhibitor. Honokiol is clinically available for human testing and may serve to augment T cell-mediated cancer immunotherapy.
PMID: 19483651 [PubMed - as supplied by publisher


http://herbalmedicine.suite101.com/article.cfm/honokiol

Honokiol appears to be non toxic, easily absorbed, and systematically available. This is important since many promising materials like Epigallocatechin Gallate (EGCG) are not absorbed well in the digestive tract. Honokiol also avoids immediate clearing by the liver (first pass effect) and crosses blood barriers that often exclude other compounds.
Recent studies have explored honokiol and found validation for it as a treatment option for anxiety, cancer, peridontal disease, stroke, inflammation, and even weight loss.

Cancer Management

Honokiol has been effective in vitro and in vivo against several types of cancers. It appears to turn off the division of some cancer cells while inducing others to kill themselves (apoptosis). It has antiangiogenesis properties (eliminating the blood supply to tumors) and some studies are recommending it as adjunct treatment with other types of chemotherapy.

Clincancerres.aacrjournals.org/cgi/content/abstract/14/4/1248; Apoptosis
www.jbc.org/cgi/content/abstract/278/37/35501;Antiangiogenesis

Distinguishing Friend from Foe in the Battle Against Cancer

http://www.physorg.com/news77201870.html

excerpt:

Rapamycin, an immunosuppressant used to block organ rejection after transplants, also inactivates proteins stimulating cell division and in clinical trials has been combined with other drugs to halt cancer cell growth.
But to cancer cells, rapamycin is both friend and foe. “Rapamycin is not as successful as initially expected in treating cancer,” explains Ghosh. “Instead of killing cells, you end up triggering a survival response in them.” This study, however, suggests that taking NF-kB out of the game would make rapamycin less “friendly.”
“A major problem of chemotherapy is that sooner or later cancer cells develop resistance, which requires higher and higher doses of chemotherapeutics,” observes Verma, who is also an American Cancer Society professor in Salk's Laboratory of Genetics. “Rapamycin-mediated killing of cancer cells could be increased by inhibiting the function of NF-kB proteins. Our studies provide the basis for arriving at this very important conclusion, which has enormous bearing on cancer treatment.”
Tergaonkar concurs. “Our studies suggest the potential use of NF-kB signaling inhibitors as adjuvants to maximize the effect of rapamycin-based therapeutics. These findings will have a significant impact on human health.”