Plattner R, Anderson M J, Sato K Y, Fasching C L, Der C J, Stanbridge E J
Department of Microbiology and Molecular Genetics, University of California, Irvine 92717, USA.
Proc Natl Acad Sci U S A. 1996 Jun 25;93(13):6665-70. doi: 10.1073/pnas.93.13.6665.
ras oncogenes are mutated in at variety of human tumors, which suggests that they play an important role in human carcinogenesis. To determine whether continued oncogenic ras expression is necessary to maintain the malignant phenotype, we studied the human fibrosarcoma cell line, HT1080, which contains one mutated and one wild-type N-ras allele. We isolated a variant of this cell line that no longer contained the mutated copy of the N-ras gene. Loss of mutant N-ras resulted in cells that displayed a less transformed phenotype characterized by a flat morphology, decreased growth rate, organized actin stress fibers, and loss of anchorage-independent growth. The transformed phenotype was restored following reintroduction of mutant N-ras. Although loss of the oncogenic N-ras drastically affected in vitro growth parameters, the variant remained tumorigenic in nude mice indicating that mutated N-ras expression is not necessary for maintenance of the tumorigenic phenotype. We confirmed this latter observation in colon carcinoma cell lines that have lost activated K-ras expression via targeted knockout of the mutant K-ras gene.
Ras癌基因在多种人类肿瘤中发生突变，这表明它们在人类致癌过程中发挥重要作用。为了确定持续的致癌性Ras表达对于维持恶性表型是否必要，我们研究了人纤维肉瘤细胞系HT1080，该细胞系含有一个突变的和一个野生型的N-Ras等位基因。我们分离出了该细胞系的一个变体，其不再含有N-Ras基因的突变拷贝。突变型N-Ras的缺失导致细胞呈现出较少转化的表型，其特征为扁平形态、生长速率降低、肌动蛋白应力纤维有序排列以及失去不依赖贴壁生长的能力。重新导入突变型N-Ras后，转化表型得以恢复。尽管致癌性N-Ras的缺失极大地影响了体外生长参数，但该变体在裸鼠中仍具有致瘤性，这表明突变型N-Ras的表达对于维持致瘤表型并非必要。我们通过对突变型K-Ras基因进行靶向敲除从而使激活的K-Ras表达缺失的结肠癌细胞系中证实了后一项观察结果。
