Rana P. Singh and team at U Colorado (Denver) have found that silibinin, the major active constituent of silymarin (Milk Thistle) , in mice inhibits lung tumor angiogenesis. They conclude that silibinin “merits investigation as a chemopreventive agent for suppressing lung cancer progression.”

Earlier work has shown that silibinin is helpful for liver toxicity, protects against kidney damage from chemotherapy, and inhibits prostate cancer growth in mice.

The effect of silibinin on prostate cancer cells is one of those stories where most of the research has been done over a number of years by one team, in this case led by Rana Singh at U Colorado. Would be nice to see confirmation from other labs. But silibinin is not going to be a money-tree. Milk Thistle is readily available in normal strengths.

Human trials of silibinin for the treatment of prostate cancer are underway at U. Colorado.

Singh wrote earlier : “silibinin has been entered into phase I/II clinical trials in human PCA patients where preliminary observations were suggestive of its further study in a larger base of the patient population.”

Effect of Silibinin on the Growth and Progression of Primary Lung Tumors in Mice
Rana P. Singh, et al. Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Cancer Center (AMM, RA), University of Colorado Health Sciences Center, Denver, CO

“Silibinin, a flavanone from milk thistle, inhibits the growth of tumors in several rodent models. We examined the effects of dietary silibinin on the growth, progression, and angiogenesis of urethane-induced lung tumors in mice.”

Silibinin, a drug derived from milk thistle, destroys lung cancer in mice, investigators at the University of Colorado, Denver report in the Journal of the National Cancer Institute.

“Urethane-injected mice exposed to silibinin had statistically significantly lower lung tumor multiplicities than urethane-injected mice fed the control diet lacking silibinin (i.e., control mice). Mice that received urethane and 1% (wt/wt) dietary silibinin for 18 weeks had 93% fewer large (i.e., 1.5–2.5-mm-diameter) lung tumors than control mice (mean number of tumors/mouse: 27 in the urethane group versus 2 in the urethane + 1% silibinin group, difference = 25 tumors/mouse, 95% confidence interval [CI] = 13 to 37 tumors/mouse, P = .005). Lung tumors of silibinin-fed mice had 41%–74% fewer cells positive for the cell proliferation markers proliferating cell nuclear antigen and cyclin D1 than lung tumors of control mice. Tumor microvessel density was reduced by up to 89% with silibinin treatment (e.g., 56 microvessels/400x field in tumors from control mice versus 6 microvessels/400x field in tumors from urethane + 1% silibinin-treated mice [difference = 50 microvessels/400x field, 95% CI = 46 to 54 microvessels/400x field; P

Conclusions: Silibinin inhibits lung tumor angiogenesis in an animal model and merits investigation as a chemopreventive agent for suppressing lung cancer progression.”

Other links and sources: Zeenet.com (India)

Milk Thistle, PDQ, National Cancer Institute.

ASCO 2006 Prostate Cancer Symposium
Silibinin synergizes with mitoxantrone to decrease cell viability in prostate cancer cells.

“Silybin-Phytosome, a commercially available formulation containing silibinin, is in phase I testing in prostate cancer patients at the University of Colorado Health Sciences Center.”

Dietary Feeding of Silibinin Inhibits Advance Human Prostate Carcinoma Growth in Athymic Nude Mice and Increases Plasma Insulin-like Growth Factor-binding Protein-3 Levels Rana P. Singh et al. [Cancer Research 62, 3063-3069, June 1, 2002]

Prostate cancer prevention by silibinin.
Rana P. Singh, University of Colorado Cancer Center. Curr Cancer Drug Targets. 2004 Feb

“… silibinin inhibits the growth of in vivo advanced human prostate tumor xenograft in nude mice. Recently, due to its non-toxic and mechanism-based strong preventive/therapeutic efficacy, silibinin has entered in phase I clinical trial in prostate cancer patients.”

Silibinin, Wikipedia entry