Selenium and vitamin E may offer protection against prostate cancer by changing the expression of certain genes in prostates linked to tumors, says a new study from Texas. Writing in the Journal of the National Cancer Institute, scientists from the University of Texas MD Anderson Cancer Center in Houston report that exposure of biopsy samples from people with cancer to vitamin E, selenium or both, expressed different genes, with the combined exposure producing results similar to that observed in people with no prostate cancer. “To the best of our knowledge, this study was the first detailed systematic pathological interrogation to be completed in preoperative patients with favorable risk prostate cancer,” wrote lead author Dimitra Tsavachidou.
A number of studies, most notably the Nutritional Prevention of Cancer study and the Alpha-tocopherol, Beta-carotene Cancer Prevention study, have reported that the nutrients, alone or in combination, may reduce the risk of prostate cancer. Despite great promise over vitamin E and selenium, recent results from the Selenium and Vitamin E Cancer Prevention Trial (SELECT) reported no significant differences between any of the groups in relation to prostate cancer risk. The results were greeted with disappointment, while many in both academia and industry indicating that, given positive results from previous clinical trials and epidemiological studies, the design of SELECT, including the supplements used, may have undermined the results.
The new data from Texas adds to the debate and appears to indicate that, at a gene expression level at least, vitamin E and selenium do offer protection against prostate cancer. The door creaks open again Tsavachidou and her co-workers took prostate biopsy samples from surgically removed prostate after pre-operative treatment with vitamin supplements in order to investigate if there are any effects on gene expression. The researchers report that the expression of certain genes did differ between tumor samples from patients who had taken vitamin E (400 IU, all-rac-alpha-tocopherol), selenium (200 micrograms of L-selenomethionine), both supplements, or placebo.
So, where do we stand? In an insightful accompanying editorial in the JNCI, Eric Klein, MD, from the Glickman Urological and Kidney Institute in Ohio, said the new study is “… noteworthy for demonstrating that even short-term exposure (i.e., 3 – 6 weeks) to these agents can affect expression of a majority of the genes interrogated and, in the robust demonstration of the utility of the preprostatectomy model, for deriving information on modulation of biomarkers.” “Certainly, the findings lend credence to the previous evidence that selenium and vitamin E might be active as cancer preventatives,” added Dr Klein. In an attempt to rationalize the differences between epidemiological and in vitro studies and randomized trials like SELECT, Klein said that randomized controlled trials “do not always validate what we believe biology indicates and that our model systems are imperfect measures of clinical outcomes in the real world”.