Molecular Genetics of Prostate Cancer

为了研究与前列腺癌发生和发展相关的遗传事件，来自NCI泌尿肿瘤科（UOB）和病理实验室（LOP）的科学家们采用了许多创新的方法，以从异质组织中获取高度纯化的前列腺癌细胞为中心。在LOP中开发了允许这种采购的新型显微解剖技术；最近的这种技术涉及激光捕获细胞，大大提高了解剖的速度和纯度。染色体缺失通常出现在保护细胞免于癌变的基因附近。利用从99个微解剖肿瘤中制备的DNA，大华大学的科学家们分析了45个遗传标记，这些遗传标记跨越了许多染色体区域，这些区域以前与前列腺癌的发生有关。人类8号染色体的缺失率最高，总缺失率为86%。大约80%的癌症在8号染色体（8p21）内有一个共同的缺失区域。这个区域也与最近发现的家族性乳腺癌的一个位点重叠。人类前列腺癌被认为在演变为浸润性癌症之前，会经历一个称为前列腺上皮内瘤变（PIN）的恶性前阶段。在癌症中通常缺失的8号染色体区域，63%的PIN病变中也发现了缺失。这一结果表明，8p21的异常可能与前列腺癌发展的早期阶段有关。该区域的物理地图目前正在UOB中构建，UOB和LOP团队已经开始分析位于该区域的候选基因。LOP的科学家发现，微解剖的前列腺样本也产生了高质量的RNA，这使得他们和大华大学的团队能够分析正常组织和肿瘤组织中基因表达的差异。除了在特定细胞群中直接寻找各种基因的表达外，作为多学科癌症基因组解剖计划（CGAP）的一部分，还构建了包含表达基因序列的文库。建立了20个前列腺文库，涵盖了从正常到癌前到局部和转移癌的生物学谱。华盛顿大学基因组测序中心对这些文库进行了测序，发现它们对已知和迄今未发现的基因都具有高质量的代表性。来自大规模文库测序的数据允许鉴定和比较在肿瘤进展的不同阶段表达的基因。生成的信息被用来指导选择映射到8p21的候选基因。最后，为了扩大在活细胞中检查前列腺癌的可用资源，大华银行和外科分部的科学家建立了细胞系。这些细胞系来自9名接受根治性前列腺切除术的患者和4名在NCI接受活检的晚期前列腺癌患者的组织。这些细胞系将允许未来的体外生长研究。

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.