Dabholkar M, Vionnet J, Parker R, Bostickbruton F, Dobbins A, Reed E
NCI,CLIN PHARMACOL BRANCH,MED OVARIAN CANC SECT,9000 ROCKVILLE PIKE,BLDG 10,RM 12N226,BETHESDA,MD 20892.
Oncol Rep. 1995 Mar;2(2):209-14. doi: 10.3892/or.2.2.209.
We have previously shown that in non-drug-selected human T lymphocytes, DNA repair is the primary determinant of cellular resistance to cisplatin (1). In this system, we have assessed mRNA levels of expression of the nucleotide excision repair (NER) genes ERCC1 and XPA, as well as the alternatively spliced species of ERCC1 which lacks exon VIII. The focus of these studies, was to try to identify the possible relative roles of normal XPA, full-length ERCC1, and alternatively spliced ERCC1, in a system where DNA repair is a clear determinant of cisplatin resistance. ERCC1 expression was directly related to cisplatin-DNA adduct repair capability, as well as directly related to cisplatin resistance, suggesting a primary role for ERCC1 in effecting DNA repair. XPA expression was approximately equivalent in each cell line, regardless of the level of DNA repair activity, suggesting a helper role for the product of this gene. The mRNA levels of the alternatively spliced species of ERCC1 were strongly inversely related to DNA repair activity, suggesting a possible inhibitory influence on the DNA repair process. This interpretation is consistent with alternative splicing of several known oncogenes, where the alternatively spliced species has an inhibitory effect on the full-length gene product. The NER pathway appears to be vitally important in effecting cisplatin resistance in non-drug-selected T lymphocytes. Further, it appears that NER may have at least one inhibitory regulatory component.
我们之前已经表明，在未经药物筛选的人T淋巴细胞中，DNA修复是细胞对顺铂耐药性的主要决定因素(1)。在这个系统中，我们评估了核苷酸切除修复(NER)基因ERCC1和XPA的mRNA表达水平，以及缺少外显子VIII的ERCC1可变剪接变体。这些研究的重点是，在一个DNA修复是顺铂耐药性明确决定因素的系统中，试图确定正常XPA、全长ERCC1和可变剪接的ERCC1可能的相对作用。ERCC1的表达与顺铂-DNA加合物修复能力直接相关，也与顺铂耐药性直接相关，这表明ERCC1在DNA修复中起主要作用。无论DNA修复活性水平如何，XPA在每个细胞系中的表达大致相同，这表明该基因产物起辅助作用。ERCC1可变剪接变体的mRNA水平与DNA修复活性呈强烈负相关，这表明其可能对DNA修复过程有抑制作用。这种解释与几种已知癌基因的可变剪接一致，其中可变剪接变体对全长基因产物有抑制作用。NER途径在未经药物筛选的T淋巴细胞产生顺铂耐药性方面似乎至关重要。此外，似乎NER可能至少有一个抑制性调节成分。
