Microsatellite instability of dinucleotide tandem repeat sequences is higher than trinucleotide, tetranucleotide and pentanucleotide repeat sequencesin prostate cancer

In order to investigate whether the change in length of simple repetitive g enomic sequences (microsatellite instability) is associated with prostate c ancer, we analyzed 40 prostate cancer samples with 44 microsatellite loci m arkers on chromosomes 1, 3, 5, 6, 8, 9, 11, 13, 16, 17 and X. DNA was extra cted from normal and tumor cells of 40 microdissected cancer samples, ampli fied by PCR and analyzed for microsatellite instability using 44 primers fo r dinucleotide, trinucleotide, tetranucleotide and pentanucleotide repeat s equences. The results of this study demonstrate that 45% of the prostate ca ncer specimens (18 out of 40) showed microsatellite instability (MSI) at a minimum of one locus using dinucleotide repeat sequences. Two out of 40 sam ples (5%) showed MSI at a minimum of one locus using three different trinuc leotide repeat primers (AR, SR and TBP). Ten out of 40 (25%) samples showed MSI at a minimum of one locus using five different tetranucleotide repeat primers (HPRT1, HPRTII, MYCL1, RE, REN). There were no MSI observed in samp les using pentanucleotide repeat sequences. There were no MSI in benign pro static hyperplasia samples (25 samples). These experiments suggest that the microsatellite instability of dinucleotide tandem repeat sequences is much higher than trinucleotide, tetranucleotide and pentanucleotide repeat sequ ences in prostate cancer. The MSI with different lengths of nucleotide repe at sequences did not correlate with the stage and grades of prostate cancer .