First familial prostate cancer gene identified

American geneticists claim to have pinpointed the first prostate cancer gene that runs in families.  It is suggested that mutations in the gene may account for as many as 5 percent of all human prostate cancer cases.

The gene was spotted by analysing the incidence of mutations in the gene in several extended Utah families that had a high frequency of prostate cancer.  Its position (on the long arm of chromosome 17) was indicated by what is called a linkage analysis which measures how often the disease is inherited together with so-called marker genes whose location has already been mapped on the chromosome.  Genes that lie close to each other on the chromosome tend to be inherited together.  Many of the ill-fated members of the Utah families had inherited a particularly lethal variant of the gene, which has been dubbed HPC2, for Human Prostate Cancer gene 2.

Risk increased tenfold

Men who carry that mutant gene, which encodes a protein with a single altered amino acid, appear to have a 60 to 80 percent likelihood of developing prostate cancer over their lifetime - a tenfold higher risk than the average man.  (Researchers are in the midst of a hunt for another prostate cancer gene, HPC1, but they have not found it yet.)

The results were presented in the American Journal of Human Genetics last September by Sean Tavtigian, vice president for cancer research at biotech company, Myriad Genetics, based in Salt Lake City, Utah.

At this point, the researchers are almost positive they've got the right gene but they still do not know what, precisely, HPC2 does.  'We're about 99 percent sure that it's a prostate cancer susceptibility gene,' Tavtigian says.  'Researchers will need to check for HPC2 mutations in more large families with a high incidence of prostate cancer before we can be sure the gene is truly a prostate cancer susceptibility gene'.  He compared his results with the better established work which identified the breast cancer genes BRCA1 and BRCA2.

Myriad Genetics' results open the door for developing a genetic test for prostate cancer susceptibility, similar to the tests for BRCA1 and BRCA2 and breast cancer susceptibility.  Tavtigian predicts, with the natural optimism of US start up companies, that reliable test will be developed within the next two years.