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/CDKN 2抑癌基因突变在人前列腺癌发展中的潜在作用，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定事件的探测。每个肿瘤根据不同的生长或宿主类型分为5-10个区域。PCR扩增ras、p53和p16/CDKN 2基因的靶序列，进行单链构象多态性分析，并进行DNA测序。ras基因点突变在9例肿瘤中有3例。K-ras基因第13位密码子和H-ras基因第61位密码子的突变分别出现在每个病变的1个和3个区域。第三个肿瘤在不同的样本病灶中含有K-ras密码子13和61的2个不同的点突变。限制性片段长度多态性分析显示，4例有信息的病例中有2例（50%）在p53基因多态性密码子72处检测到杂合性丢失（洛）。在三个肿瘤中也检测到p53突变，错义颠换，单碱基插入和两个碱基缺失。所有肿瘤均未发现p16/CDKN 2基因纯合性缺失，但有2例p16/CDKN 2基因外显子2发生错义突变。在6个和10个选定的肿瘤区域中，分别仅在1个和2个病灶中检测到突变。目前的结果显示突变ras，p53和p16/CDKN 2偶尔发生在小病灶的肿瘤，和基因突变的p53，而不是那些在ras和p16/CDKN 2更密切相关的异质性前列腺癌的浸润性生长。

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.