Marker Found for Prostate and Colon Cancer

Researchers have found large amounts of a protein in prostate, colon, and other tumor cells but not in normal cells, making the protein a cancer marker and a potential new diagnostic tool for doctors. The findings were reported in the August 1, 2002, issue of the Journal of Clinical Investigation.

The protein interacts with the gene for Huntington's disease and is called huntingtin interacting protein, or HIP1.It has never before been associated with any type of cancer. The protein appears to be involved in the clathrin-mediated trafficking pathway, along with another protein called htt, which is expressed by the mutated gene responsible for Huntington's disease. The connection to the Huntingon's gene could be important, say the researchers, because people with Huntington's disease rarely get cancer.

"Originally, I thought HIP1 was a tumor-suppressor gene, but it could be a survival factor that prevents cancerous cells from dying or an oncogene causing normal cells to become cancerous,” notes Theodora S. Ross, M.D., Ph.D., an oncologist in the Comprehensive Cancer Center at the University of Michigan (Ann Arbor, USA) who has focused on HIP1 over the past three years. When the researchers made a mutant version of HIP1 by knocking off one segment, the result was massive cell death, suggesting that HIP1 is necessary for cell survival.

No significant HIP1 expression was found in normal prostate epithelial cells. However, as prostate cancer develops and progresses, there is a steady increase in HIP1 expression. "HIP1 was expressed in 50% of tumors from patients in the earliest stages of cancer, 88% of tumors from patients with localized breast cancer, and 100% of patients with metastatic prostate cancer,” says Dr. Ross. The expression pattern varied in melanoma, breast, and ovarian cancers but was consistently overexpressed.




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