In order to investigate the genetic events associated with the initiation and progression of prostate cancer, scientists from the Urologic Oncology Branch (UOB) and the Laboratory of Pathology (LOP) at the NCI have made use of a number of innovative methodologies centered around the procurement of highly purified prostatic cancer cells from heterogeneous tissue. Novel microdissection techniques which allow such procurement were developed in the LOP; the most recent such technique involving laser capture of cells greatly increased the speed and purity of dissection. Chromosomal deletions are often found in the vicinity of genes that protect cells from becoming cancerous. Using DNA prepared from 99 microdissected tumors, scientists in the UOB analyzed 45 genetic markers spanning a number of chromosomal regions that had been previously implicated in prostate carcinogenesis. The highest rate of deletion was observed on human chromosome 8, where the overall rate of loss was 86%. Approximately 80% of the cancers shared a common region of deletion within chromosome 8 (8p21). This region also overlaps a region recently identified as a locus for familial breast cancer. Human prostate cancer is thought to progress through a pre-malignant phase called prostatic intraepithelial neoplasia (PIN) prior to evolving into invasive cancer. In the region of chromosome 8 commonly deleted in cancer, deletions were also found in 63% of PIN lesions. This result suggests that abnormalities on 8p21 may be associated with early stages of prostate cancer development. A physical map of the region is currently being constructed in the UOB, and the UOB and LOP teams have begun analyzing candidate genes which reside in this area. Scientists in the LOP found that microdissected prostate samples also yielded good quality RNA, which has allowed them and the UOB team to analyze differences in gene expression in normal vs. tumor tissue. In addition to looking directly for expression of various genes in specific cell populations, libraries containing expressed genetic sequences were constructed as part of the multidisciplinary Cancer Genome Anatomy Project (CGAP). Twenty prostate libraries were constructed covering a spectrum of biology from normal to pre-malignant to localized and metastatic cancer. These libraries were sequenced at the Genome Sequencing Center at Washington University and found to exhibit high quality representation of both known and heretofore undiscovered genes. Data from large scale library sequencing allows for identification and comparison of genes expressed at distinct stages of tumor progression. The information generated is being used to guide the selection of candidate genes which map to 8p21. Finally, in order to expand upon the available resources for examination of prostate cancer in living cells, cell lines were established by scientists from the UOB and the Surgery Branch. The lines were generated from tissue from nine patients who underwent radical prostatectomy and four patients with advanced prostate cancer who underwent biopsy at the NCI. These lines will allow for future in vitro growth studies.
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