Molecular mechanisms of mutation enhancement by serum factors from pancreatic cancer patients and purification of the factors.

调控人类细胞变异的分子机制是一个有趣的生物学问题。本研究发现，胰腺癌患者血清因子和人胰腺癌细胞培养的条件培养基可增强人RS细胞株的变异性。RS细胞是由人类胎儿成纤维细胞建立的，对远紫外光（UV）致突变性高度敏感。与未用血清因子或培养基处理的辐照细胞相比，在紫外线照射前用血清因子或培养基预培养的人RS细胞可导致瓦阿因耐药性（Oua^R）突变的频率增加。在中等处理的RSa细胞中，观察到分子伴侣GRP78/Bip mRNA和蛋白的表达水平下降。利用GRF78/Bip mRNA的反义寡核苷酸进行的研究表明，与模拟处理的细胞相比，反义寡核苷酸处理的RSb细胞更容易受到紫外线诱导的K-ras密码子12碱基替换突变的影响。因此，GRP78/Bip的下调可能参与了人类细胞易变性的增强。

The molecular mechanisms that regulate mutability of human cells are intriguing biological problems. The present study revealed that mutability of human RS cell strain was enhanced by serum factors From pancreatic cancer patients and conditioned medium from cultures of a human pancreatic cancer cell line. RS cells, established from human fetal fibroblasts, are highly sensitive to far-rultraviolet light (UV) mutagenicity. Preculture of human RS cells with the serum factors or the medium prior to irradiation with UV resulted in an increase in the frequency of ouabain resistance (Oua^R) mutations, compared with cells irradiated but not treated with either the serum factors or the medium. Decreases in expression levels of the molecular chaperone GRP78/Bip mRNA and protein were observed in the medium-treated RSa cells. Studies using antisense oligonucleotides for GRF78/Bip mRNA showed that the antisense oligonucieotide-treated RSb cells were more susceptible to UV-induced K-ras codon 12 base substitution mutations than mock-treated cells, as determined by PCR and differential dot-blot hybridization. Thus, down-regulation of GRP78/Bip was suggested to be involved in the enhancement of mutability of human cells.