Prostate cancer is now the most commonly diagnosed cancer in males, with mortality approaching 25%. Allelic loss of sequences on 8p are relatively frequent events in prostate tumors, suggesting that this chromosomal region may harbor tumor suppressor genes, and that loss of heterozygosity (LOH) for those genes are critical events in prostate tumorigenesis. Past studies designed to examine LOH in prostate cancer have been hampered by the heterogeneous nature of prostate tissue, which makes it difficult to obtain """"""""pure"""""""" tumor samples for study. We have addressed this problem through the combined the use of tissue microdissection and polymerase chain reaction (PCR) techniques. Using these methods, we have observed independent deletion of sequences at 8p22 in 33% and at 8p12 in 55% of Stage C moderately-and poorly-differentiated prostate tumors examined. We have also observed deletion at 8p22 in 25% of prostatic intraepithelial neoplasias (PINs) examined. These observations suggest that LOH on 8p 1) involves one or more specific, critical sequences on 8p that may harbor tumor suppressor genes, and 2) occur frequently in neoplastic and potentially preneoplastic lesions of the prostate. If so, 1) the smallest regions of overlap (SROs) of deletion should be """"""""definable"""""""" on 8p in prostate tumors, and 2) LOH on 8p should be frequently observed in less advanced-Stage B and A- tumors and even in premalignant lesions of the prostate. To test these assumptions, the proposed research in organized into two specific aims:
SPECIFIC AIM 1 : Identify the smallest region(s) of overlap (SROs) of deleted sequences on chromosome 8p in human prostate cancer (CaP), hence, define the region(s) on 8p potentially harboring tumor suppressor genes. To accomplish this aim, we will: a) microdissect tumor areas from paraffin sections from pathologic stage C and D1 lesions; b) purify DNA from these tissues; c) analyze DNA for LOH along the entire length of 8p using microsatellite (MS) and restriction fragment length polymorphism (RFLP) PCR to identify a subset of tumors that demonstrate interstitial deletions on 8p; d) describe the SRO(s) as loci within the 8p interstitial deletions with the highest frequencies of LOH.
SPECIFIC AIM 2 : Determine the frequency of 8p SRO deletion in CaP and other histologic lesions of the prostate. To accomplish this aim, we will use the techniques described above to analyze DNA purified from microdissected: a) metastatic (Stage D1) and localized nonmetastatic (Stage C, B and A) malignant lesions, and b) other histologic lesions in the prostate, including benign prostatic hyperplasia (BPH) and PIN lesions, for frequency of 8p SRO deletion. These studies should provide a first step towards a genetic definition of premalignant lesions in the prostate and the construction of a genetic model for prostate tumorigenesis.
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