Low frequency of microsatellite instability in hereditary prostate cancer

Objective To investigate whether there is widespread microsatellite instabi lity (MSI) in families with hereditary prostate cancer (HPC). Patients and methods Eighty-four prostate tumours from 80 Swedish men in 35 families with HPC were screened for genetic instability at microsatellite marker loci BAT-25, BAT-26, BAT-34C4, D2S123 and D17S250. Results MSI was detected in only five individuals from different families. Three tumours (4%) were unstable at more than two MSI loci and hence classi fied high-frequency MSI (MSI-H) according to a previous definition, Interes tingly, two of the MSI-H tumours were from patients in families with both H PC and familial colon cancer. Conclusions Widespread MSI is a rare event in hereditary prostate cancer, i ndicating that defective DNA mismatch repair is not an important element in the genesis of HPC.