Today, Science Translational Medicine published the results of a recent University of Michigan - Ann Arbor study that may signal hope for hundreds of thousands of men with prostate cancer in the same way that the discovery of HER2/neu has brought optimism to scores of women with breast cancer.
Researchers at the University of Michigan Comprehensive Cancer Center (UMCCC) have identified a gene called SPINK1 (serine peptidase inhibitor, Kazal type 1) that is overexpressed in about 10 percent of prostate cancers. Targeting this SPINK1 gene, according to the study, may effectively treat this 10 percent of prostate cancers.
Genetics & Cancer
To understand the potential impact of SPINK1, we can look to the recent discovery of the link between genetics and breast cancer. In the early 2000s, researchers discovered that the overexpression of one particular gene, known as human epidermal growth factor receptor 2 (HER2/neu) was present in about 30 percent of breast cancer cases. Now when breast tumor is discovered, patients are routinely checked for overexpression of HER2/neu gene and the protein that the gene produces. If that overexpression does exist, the medication trastuzumab (marketed as Herceptin) may be prescribed. Trastuzumab interferes with the actions of (and reverses the effects of) overactive HER2/neu and has been shown to effectively improve survival in late-stage breast cancers. Second, the discovery of the action of HER2/neu and the efficacy of trastuzumab has led to increasing investigation of genetic causes for cancer, breast and otherwise.
Gene Therapy & Prostate Cancer
The UMCCC scientists attempted two types of targeted therapies on SPINK1-positive tumors: First, they used a medication called cetuximab (marketed as Erbitrux), a Federal Drug Administation (FDA)-approved drug for colon, head, and neck cancers. Second, the UMCCC scientists also developed a SPINK1 antibody, which acts on prostate cancer much like trastuzumab acts on breast cancer.
In a test performed on lab mice, tumors treated with cetuxmab shrank 40 percent, while those treated with the SPINK1 antibody were reduced by 60 percent. Combined, the new targeted therapy shrunk prostate cancer in 74 percent of cancer-stricken cells.
While one in 10 appears to be a small percentage, that equates to an estimated 21,000 new prostate cancer patients in 2011, but the impact of this discovery is potentially greater. The UMCCC study confirmed that SPINK1 directly correlates to the most aggressive types of prostate cancer. And because traditional prostate cancer treatments are generally not effective for the aggressive and fast-growing incidences of the disease, this new SPINK1-targeted treatment raises hope for men worldwide that there are more useful ways of fighting the worst cases of this disease.
Of course, it may be a while before this treatment gains FDA approval and regular use. While cetuximab is FDA-approved for other cancers, prostate cancer may behave differently in mice than in humans. Clinical trials must be performed on men whose tumors overexpress SRPINK1 in order to discover if they will help these men to survive longer. But the results of this study do auger hope.
One in six American men will develop prostate cancer during the course of his lifetime. While the majority of these men will undergo effective treatment for a slow-growing cancer and will go on to live long and healthy lives, thousands do suffer life-threatening forms of this illness. And this study may be a true leap forward for helping these men.