In the ongoing search for cancer-fighting medicines, plant flavonoids are being studied for both prevention and therapy of various types of cancer. One such naturally occurring flavonoid is silibinin, isolated from milk thistle, which studies show may help with bladder and prostate cancer.

Silibinin appears to have a significant impact on bladder cancer cells, say researchers from the University of Colorado Health Sciences Center. They found that treating human cancer cells with silibinin caused a significant slowing of cancer cell growth and in some cases, caused cell death. The researchers recommend future human studies on silibinin.

At the Department of Urology, Georg-August-University, Gottingen in Germany, researchers also demonstrated the cancer preventing potential of silibinin, this time on prostate cancer cells. They say silibin’s positive effect is due to its inhibition of prostate specific antigen, or PSA. Higher PSA levels often signal prostate cancer. In this study, prostate cancer cells were treated with various concentrations of silibinin in the presence or absence of the cancer-promoting male hormone dihydrotestosterone (DHT). PSA secretion from these treated cells was measured and researchers found silibinin down-regulated both PSA expression and PSA secretion. The researchers said it was this down-regulation by silibinin that underscores its possible therapeutic use for prostate cancer.

Sources: Carcinogenesis. 2004 Sep;25(9):1711-20; Planta Med. 2004 May;70(5):397-400