Ward R L, Todd A V, Santiago F, O'Connor T, Hawkins N J
Department of Medical Oncology, St. Vincent's Hospital, Darlinghurst, Australia.
Cancer. 1997 Mar 15;79(6):1106-13.
Recent in vitro data indicate that the oncogenic effects of activated ras genes may be mediated, at least in part, through inhibition of apoptotic cell death. To examine this proposition in vivo, the relationship between mutations of the K-ras gene and the frequency of apoptosis was studied in a series of 69 sporadic colorectal neoplasms (11 adenomas and 58 carcinomas).
Mutations in codon 12 of K-ras were determined by a single tube, enriched polymerase chain reaction. Apoptotic cells in tumor sections were identified by in situ end-labeling of fragmented DNA, whereas levels of bcl-2 and p53 proteins were determined by immunohistochemistry.
Tumors with mutant K-ras had a significantly lower apoptotic index than those with the wild-type allele (P < 0.05). They were also more likely to exhibit positive bcl-2 staining (P < 0.05). Adenomas showed significantly greater bcl-2 positivity than carcinomas (89% and 51%, respectively; P < 0.05). The frequency of apoptosis in these tumors was not related to either bcl-2 positivity or p53 status.
These findings suggest that activation of K-ras in colorectal carcinoma may inhibit apoptosis and thus favor tumor progression. Alternatively, this association may reflect an accumulation of K-ras mutations in cells in which normal apoptotic pathways have been impaired.
最近的体外实验数据表明，激活的ras基因的致癌作用可能至少部分是通过抑制凋亡性细胞死亡来介导的。为了在体内检验这一观点，我们在一系列69例散发性结直肠肿瘤（11例腺瘤和58例癌）中研究了K-ras基因的突变与凋亡频率之间的关系。
通过单管富集聚合酶链反应来检测K-ras第12密码子的突变。肿瘤切片中的凋亡细胞通过对断裂DNA进行原位末端标记来识别，而bcl-2和p53蛋白的水平则通过免疫组织化学来测定。
具有突变型K-ras的肿瘤的凋亡指数显著低于具有野生型等位基因的肿瘤（P < 0.05）。它们也更有可能呈现bcl-2染色阳性（P < 0.05）。腺瘤的bcl-2阳性率显著高于癌（分别为89%和51%；P < 0.05）。这些肿瘤中的凋亡频率与bcl-2阳性或p53状态均无关。
这些发现表明，结直肠癌中K-ras的激活可能抑制凋亡，从而促进肿瘤进展。或者，这种关联可能反映了正常凋亡途径受损的细胞中K-ras突变的积累。
