PROJECT SUMMARY/ABSTRACTThere is a fundamental gap in our knowledge to explain the origin of prostate cancer (PCa). Unlike manycancers PCa lacks signature mutations in key oncogenes and tumor-suppressor genes and insteaddisplays large-scale genomic instability. We propose to study subcellular organelle instability as amechanism that results in genomic instability in epithelial cells of the prostate gland. Specifically we focuson centrosomes tiny cytoplasmic organelles that dramatically influence genome integrity. Centrosomes canbecome subcellular pathognomonic structures when they are amplified as is the case in many differentcancers causing mitotic errors genomic instability and inducing tumorigenesis in mouse models.Likewise centrosome loss causes mitotic errors and genomic instability identical to centrosomeamplification but has not been reported in cancer. We discovered recently that human prostateadenocarcinoma lack centrosomes providing a novel mechanistic explanation for genomic instability inPCa. Our long-term goal is to discover the abnormal changes that underlie prostate tumorigenesismalignancy and recurrence and to improve PCa diagnosis and treatment strategies. The objective of thisapplication is to determine the contribution of centrosome loss in driving genomic instability resulting inPCa and to determine the molecular mechanistic basis for centrosome disappearance. Drawn from ourpreliminary data our central hypothesis is that hypoxia is a key physiologically-relevant determinant ofcentrosome loss in the prostate which in turn stimulates genomic instability and tumorigenesis. Therationale for the proposed research is to address the provocative question of how cancer-specific changes insubcellular pathognomonic structures (specifically centrosome loss) transpire and contribute tocarcinogenesis. This hypothesis will be tested in three specific aims: 1) Determine whether centrosome lossis triggered by hypoxia in prostate cells and tumors; 2) Determine whether centrosome loss drivesgenomic instability in normal prostate epithelial cells and promotes tumorigenesis; and 3) Determine ifcentrosome loss is characteristic of high-grade prostatic intraepithelial neoplasia (PIN carcinoma in situ).The approach is innovative because it investigates a novel mechanism of subcellular organelle instabilityduring prostate tumorigenesis: specifically that hypoxia and centrosome biogenesis are mechanisticallycoupled as drivers of genomic instability in prostate tumor formation. The proposed research is significantbecause it tests a new concept that the loss of a critical subcellular organelle is responsible for PCagenomic instability which is both a hallmark and agent of prostate tumor evolution. If we are correctcentrosome loss will be a tangible event early in the genesis of human prostate cancer providing newearly detection and treatment strategies.