Low frequency of microsatellite instability in hereditary prostate cancer

Objective To investigate whether there is widespread microsatellite instability (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 classified as high-frequency MSI (MSI-H) according to a previous definition. Interestingly, two of the MSI-H tumours were from patients in families with both HPC and familial colon cancer. Conclusions Widespread MSI is a rare event in hereditary prostate cancer, indicating that defective DNA mismatch repair is not an important element in the genesis of HPC.