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

为探讨ras癌基因激活和p53、p16/CDKN2抑癌基因突变在前列腺癌发生发展中的作用，我们对9例前列腺癌全切除术后组织学异质性肿瘤进行了研究。根据不同的生长或宿主类型，将每个肿瘤划分为5-10个区域。用聚合酶链式反应扩增编码ras、p53和p16/CDKN2的靶DNA序列，单链构象多态分析，DNA直接测序证实。在9个肿瘤中有3个发现ras基因点突变。两个K-ras密码子13和H-ras密码子61突变，分别位于每个病变的一个和三个区域。第三种肿瘤在标本的不同部位存在K-ras密码子13和61的两个不同的点突变。限制性片段长度多态分析显示，在4例有片段切割的信息性病例中，2例(50%)检测到p53基因第72位多态密码子的杂合性缺失(LOH)。在三个肿瘤中也检测到了P53突变，错义颠倒，单碱基插入和两个碱基缺失。未发现p16/CDKN2基因纯合性缺失，但9例肿瘤中有2例存在p16/CDKN2基因外显子2的错义突变。在选定的六个和十个肿瘤区域中，分别只有一个和两个病灶检测到了突变。目前的结果显示，ras、p53和p16/CDKN 2突变偶尔出现在肿瘤的小病灶中，并且p53的基因突变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.