Bhattacharyya Nandan, Chen Huan-Chao, Wang Liming, Banerjee Spira
Department of Cancer Biology, Lerner Research Institute, The Cleveland Clinic Foundation, OH 44195, USA.
Gene Expr. 2002;10(3):115-23.
The 39-kDa DNA polymerase beta (pol beta) is an essential enzyme in short-patch base excision repair pathway. A wild-type and a truncated forms of pol beta proteins are expressed in primary colorectal and breast adenocarcinomas and in a primary culture of renal cell carcinoma. To test whether pol beta has a contributory role in tumorigenicity of human tumor cell lines, we have undertaken a study to determine expression of pol beta in colon, breast, and prostate tumor cell lines. Unlike primary colon tumor cells, three types of pol beta mRNA have been identified in HCT116, LoVo, and DLD1, colon tumor cell lines. A 111-bp-deleted pol beta transcript was expressed in MCF7, a breast tumor cell line, but not in primary breast tumor cells. An expression of a smaller pol beta transcript has been revealed in DU145, a prostate tumor cell line, whereas, a single base (T) deletion in mRNA at codon 191 was found in prostate cancer tissue. Interestingly, a wild-type pol beta transcript was also expressed in all tumor cell lines similar to primary tumor cells. Furthermore, the cell extract of LoVo exhibited highest gap-filling synthesis function of pol beta when the extract of DU145 showed lowest activity. MNNG, a DNA alkylating agent, enhanced the gap-filling synthesis activity in extracts of LoVo cell line. Furthermore, the cellular viability of LoVo and HCT116 cells is sensitive to MNNG when DU145 cells are resistant. These results demonstrate heterogeneity in pol beta mRNA expression, which may be a risk factor related to tumorigenic activities of tumor cell lines.
39 kDa的DNA聚合酶β（polβ）是短片段碱基切除修复途径中的一种关键酶。野生型和截短形式的polβ蛋白在原发性结直肠癌和乳腺癌以及肾细胞癌的原代培养物中均有表达。为了测试polβ在人类肿瘤细胞系致瘤性中是否起作用，我们开展了一项研究来确定polβ在结肠、乳腺和前列腺肿瘤细胞系中的表达情况。与原发性结肠肿瘤细胞不同，在结肠肿瘤细胞系HCT116、LoVo和DLD1中已鉴定出三种类型的polβ mRNA。在乳腺肿瘤细胞系MCF7中表达了一种缺失111 bp的polβ转录本，但在原发性乳腺肿瘤细胞中未表达。在前列腺肿瘤细胞系DU145中发现了较小的polβ转录本的表达，而在前列腺癌组织中发现mRNA第191密码子处有单个碱基（T）缺失。有趣的是，与原发性肿瘤细胞类似，野生型polβ转录本也在所有肿瘤细胞系中表达。此外，当DU145细胞提取物的活性最低时，LoVo细胞提取物显示出最高的polβ缺口填补合成功能。DNA烷化剂MNNG增强了LoVo细胞系提取物中的缺口填补合成活性。此外，当DU145细胞具有抗性时，LoVo和HCT116细胞的细胞活力对MNNG敏感。这些结果表明polβ mRNA表达存在异质性，这可能是与肿瘤细胞系致瘤活性相关的一个风险因素。
