Researchers Link Breast, Prostate Cancer
UCLA researchers have discovered that a gene long associated with breast cancer also plays a role in advanced prostate cancer, the second-leading cause of cancer deaths in men.
Although the results, published in this month’s edition of Nature Medicine, are based on animal studies, the findings could be good news for patients with prostate cancer that has recurred and no longer responds to standard drug therapy.
It could also mean good news for Genentech, the South San Francisco biotechnology company that produces Herceptin, a drug that won federal approval last year for use in 25% to 30% of advanced breast cancer patients--those whose tumors over-express a gene called HER2/neu.
The UCLA team, headed by Dr. Charles L. Sawyers, showed that the same gene, present in all normal tissue, is over-expressed in at least some advanced prostate tumors.
Based on that finding, Sawyers hopes that Herceptin may prove helpful for at least some men in the worst stages of the disease. “I think there is enough reason to plan clinical trials of Herceptin” in prostate cancer, Sawyers said in an interview. “I predict it will not work in everyone, only those that over-express the gene.”
Genentech is considering such trials. “We are definitely looking at other indications for Herceptin, including prostate cancer,” said spokesman Neal Cohen.
Last year, an estimated 184,500 men were diagnosed with prostate cancer, according to the American Cancer Society; the disease claimed 39,200 lives, surpassed only by lung cancer.
Treatment typically involves removal of the prostate gland or bombarding it with radiation. Should the cancer return, the patient is given drugs that block the release of the male sex hormone androgen. Early-stage cancer cells require androgen to keep multiplying. Without it, the tumors recede. But in most cases, for reasons that scientists are only beginning to understand, the tumors adapt, and the patients stop responding to the drugs.
The UCLA team helped explain how that happens in some cases. Introducing extra copies of the HER2/neu gene into early-stage tumors converted them to the drug-resistant kind. That suggests that Herceptin--a genetically engineered antibody that blocks HER2/neu--could be helpful in prostate cancer.
Genentech won approval for Herceptin in breast cancer last October and brought it to market almost immediately. The company reported more than $30 million in Herceptin sales in the final months of 1998.
