Tumor heterogeneity and alterations in oncogene and tumor suppressor gene in human prostate carcinoma

为了评估ras癌基因激活和p53、p16/CDKN2肿瘤抑制基因突变在人类前列腺癌发展中的潜在作用，我们对9例全前列腺切除术后获得的组织学异质性前列腺肿瘤进行了这些特异性事件的研究。每个肿瘤根据不同的生长或宿主模式划分为5-10个区域。利用聚合酶链反应扩增ras、p53和p16/CDKN2的目标DNA序列，并进行单链构象多态性分析，并通过直接DNA测序进行确认。9例肿瘤中有3例出现ras基因点突变。其中两个包含K-ras密码子13和H-ras密码子61突变，分别在每个病变的一个和三个区域发现。第三个肿瘤在样本的不同部位含有K-ras密码子13和61 2个不同的点突变。限制性片段长度多态性分析显示，4例信息病例中有2例（50%）检测到p53基因多态性密码子72杂合性缺失（LOH），显示片段切割。在三种肿瘤中也检测到p53突变、错义翻转、单碱基插入和两个碱基缺失。在所有肿瘤中均未观察到p16/CDKN2基因纯合缺失，但9例肿瘤中有2例显示p16/CDKN2基因外显子2错义突变。在6个和10个选定的肿瘤区域中，分别仅在一个和两个病灶中检测到突变。目前的研究结果显示，突变的ras、p53和p16/CDKN2偶尔发生在肿瘤的小病灶中，p53的基因突变与ras和p16/CDKN2的基因突变相比，与异质性前列腺癌的侵袭性生长更密切相关。

To assess the potential role of ras oncogene activation and p53, p16/CDKN2 tumor suppressor gene mutations in the development of human prostate carcinoma, nine cases of histologically heterogeneous prostate tumors obtained from total prostatectomies were probed for these specific events. Each tumors was divided into 5-10 areas according to different growth or hostologic patterns. Targeted DNA sequences coding for ras, p53 and p16/CDKN2 were amplified using the polymerase chain reaction and analyzed by single-strand conformational polymorphisms, and confirmed by direct DNA sequencing. Point mutations of the ras gene were found in 3 of the 9 tumors. Two cotained K-ras codon 13 and H-ras codon 61 mutations, found in only one and three areas of each lesion, respectively. The third tumor contained 2 different point mutations in K-ras codons 13 and 61 in different foci of sample. Loss of heterozygosity (LOH) at the polymorphic codon 72 in the p53 gene was detected in 2 of 4 informative cases (50%) showing fragment cleavage by restriction fragment length polymorphism analysis. Mutations in p53, missense transversions, single base insertions and two base deletions, were also detected in three tumors. No homozygous deletions of p16/CDKN2 gene were observed in any of the carcinomas, but two of the nine tumors demonstrated missense mutations in exon 2 of p16/CDKN2 gene. The mutations were detected in only one and two foci, respectively, out of six and ten selected tumor areas. The present results reveal mutated ras, p53 and p16/CDKN2 occasionally occurring in small foci of the tumor, and that genetic mutations in p53, as opposed to those in ras and p16/CDKN2 are more closely associated with invasive growth of heterogeneous prostate carcinoma.