Prostate Cancer Gene Identification within Candidate Region in African Americans



 DESCRIPTION (provided by applicant): There are well documented racial disparities in prostate cancer (PCa) incidence and mortality in the United States between African American (AA) and European American (EA) men. These disparities cannot be fully explained by differences in screening or treatment differences by race, and other environmental and biological risk factors have not been well characterized. We hypothesize that racial differences in the distribution of genetic risk factors may contribute to the observed disparities. We recently identified a region on chromosome 7q31-32 that is statistically significantly associated with prostate cancer in AA men, and there is suggestive evidence for association with PCa aggressiveness as well. The identified region is gene-rich, and thus far we have identified two candidate genes (CPED1 and FLNC) in this region. These are genes that have not been well characterized in the literature, however hints of their role in prostate cancer can be found within previous expression studies. Here, we propose to examine the region on chromosome 7q31-32 in greater depth, using existing samples and data from multiple databases. In Aim 1, we first will examine SNP associations in this region in a much larger independent sample set to confirm our original findings (Aim 1.A). We will then examine available online databases, including dbGAP, GEO, and Oncomine for further evidence of association of genes in this region with PCa risk and aggressiveness (Aim 1.B). Based on the findings of Aims 1.A and B, we will select genes and regions to target with a dense tagSNP panel to better refine our genes of interest in 230 AA PCa cases and 230 AA controls. Aim 2 will explore the functional significance of the top five candidate genes identified in our prior work and in Aim 1, including CPED1 and FLNC, using banked tissue samples (Aim 2.A) and cell lines (Aim 2.B). For Aim 2.A, Expression of mRNA will be assessed in 112 fresh frozen PCa samples selected to represent EA men, AA men, high Gleason grade (GG, >4+3) and low GG (<3+4) equally. Protein expression will be assessed using IHC in paraffin embedded PCa samples, using the same race/grade sampling method. For Aim 2.B, multiple cell lines representing a range of PCa aggressiveness and both EA and AA origin will be used to evaluate protein expression and biological function of these proteins. Protein expression will be determined using immunoblot analysis. If clinical data suggest the candidate gene is overexpressed in PCa, we will knock it down, and if expression is lost in PCa we will overexpress it. We will perform cell growth, transformation, migration and invasion assays to determine if altering gene expression will regulate cellular function. We will also perform cell counting assays to measure cell growth over an eight day period. Soft agar and clonogenic assays will be used to assay transformation. Boyden chamber assays will be used to assess changes in migration and invasion. Study results will provide insight into genetic risk factors for PCa that might help explain racial disparities in incidence and mortality and thereby provide biological targets for reducing these disparities.