Amplification of Type II Cadherins in Prostate Cancer PRINCIPAL INVESTIGATOR:

Genomic alterations of the 18q chromosomal region have been observed in prostate cancer.We performed array comparative genomic hybridization experiments using prostate cancerspecimens and identified the gain of copy number of a small region at 18q22.1. This relativelygene-poor region includes two cellular adhesion genes, the type II cadherins cadherin 7 andcadherin 19. Alteration of expression of another type II cadherin, cadherin 11, is implicated intumor invasiveness and metastasis in both breast and prostate cancer. Therefore, we sought tostudy if the increased copy number of the 18q22.1 region in prostate cancer results inupregulation of expression of the type II cadherins, cadherin 7 and/or cadherin 19, which mayplay a role in prostate cancer development and/or progression. We verified the gain of copynumber of this region using fluorescence in situ hybridization (FISH) and determined the copynumber to range from 3-7 copies. The smallest region of copy number alteration was identifiedby performing FISH on paraffin-embedded prostate tumors using probes derived from bacterialartificial chromosomes containing 18q22.1 genomic sequences. This narrowed region was 680kilobases and included the cadherin 7 gene and no other known genes. Additionally, FISHanalyses of 12 other tumor types showed that the gain of copy number at 18q22.1 was specificto prostate tumor samples. A survey of 40 prostate tumors with various Gleason scores andstages showed that the gain of copy number of this region was not associated with a particularstage or grade. Polyclonal rabbit antibodies generated against small peptides from cadherins 7and 19 were created for use in immunohistochemistry experiments to analyze the level ofprotein associated with extra copies of the gene. Extensive testing of these antibodies revealedthey were inadequate for immunohistochemistry. Therefore, new antibodies are beinggenerated against bacterially expressed cadherin 7 and cadherin 19 fusion proteins. We haveknocked down RNA expression of cadherin 7 using RNA interference in the 22Rv1 prostatecancer cell line. Following the generation of antibodies to detect protein expression in theknocked-down 22Rv1 cells, in vitro assays for cellular invasiveness and in vivo assays fortumorigenicity will be performed. IMPACT: The discovery of increased copy number of a cellularadhesion gene in prostate cancer could lead to a better understanding of how normal cellularadhesion is altered during acquisition of the metastatic phenotype. Understanding these eventscould potentially lead to the development of new therapeutics designed to interfere with themetastatic process.