PTEN losses exhibit heterogeneity in multifocal prostatic adenocarcinoma and are associated with higher Gleason grade

Abstract

Prostatic adenocarcinoma is an epithelial malignancy characterized by marked histological heterogeneity. It most often has a multifocal distribution within the gland, and different Gleason grades may be present within different foci. Data from our group and others have shown that the genomic deletion of the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) tumor suppressor gene and the disruption of the ETS gene family have a central role in prostate cancer and are likely to be associated with Gleason grade. In this study, prostate cancer samples were systematically analyzed to determine whether there was concordance between PTEN losses and TMPRSS2–ERG fusion rearrangements, within or between foci in multifocal disease, using well-annotated tissue microarrays (TMAs) consisting of 724 cores derived from 142 radical prostatectomy specimens. Three-color fluorescence in situ hybridization analysis of both the PTEN deletion and the TMPRSS2–ERG fusion was used to precisely map genetic heterogeneity, both within and between tumor foci represented on the TMA. PTEN deletion was observed in 56 of 134 (42%) patients (hemizygous=42 and homozygous=14). TMPRSS2–ERG fusion was observed in 63 of 139 (45%) patients. When analyzed by Gleason pattern for a given TMA core, PTEN deletions were significantly associated with Gleason grades 4 or 5 over grade 3 (P<0.001). Although TMPRSS2–ERG fusions showed a strong relationship with PTEN deletions (P=0.007), TMPRSS2–ERG fusions did not show correlation with Gleason grade. The pattern of genetic heterogeneity of PTEN deletion was more diverse than that observed for TMPRSS2–ERG fusions in multifocal disease. However, the marked interfocal discordance for both TMPRSS2–ERG fusions and PTEN deletions was consistent with the concept that multiple foci of prostate cancer arise independently within the same prostate, and that individual tumor foci can have distinct patterns of genetic rearrangements.