Dempke W C, Shellard S A, Hosking L K, Fichtinger-Schepman A M, Hill B T
Laboratory of Cellular Chemotherapy, Imperial Cancer Research Fund Laboratories, Lincoln's Inn Fields, London, UK.
Carcinogenesis. 1992 Jul;13(7):1209-15. doi: 10.1093/carcin/13.7.1209.
Interactions between cisplatin (CDDP) and irradiation are of potential significance for the combined modality treatment of cancer. Previous data have indicated that following in vitro exposure to X-irradiation certain tumour cells expressed resistance to CDDP. To identify parameters associated with this CDDP resistance, the human ovarian carcinoma cell line SK-OV-3/P was pre-exposed to fractionated X-irradiation (total dose: 50 Gy) in vitro. The resultant subline (SK-OV-3/DKR-10) proved 2-fold resistant to CDDP, but not to acute X-irradiation. Consistent with unaltered dihydrofolate reductase and thymidylate synthase activities, SK-OV-3/DXR-10 cells were neither cross-resistant to methotrexate nor to 5-fluorouracil. Verapamil (6.6 microM) significantly (P less than 0.05) enhanced CDDP-induced cytotoxicity in the resistant DXR-10 subline, but not in the parental cells. Total glutathione levels were significantly (P less than 0.01) lower in the resistant subline and BSO pretreatment failed to influence cytotoxicity, whilst related enzyme activities were not consistently modified in the SK-OV-3/DXR-10 cells. Resistance in these cells was associated with significantly decreased cisplatin uptake (P less than 0.002). Immediately following drug exposure the total platination level of the DNA, quantitated immunochemically, was higher (P less than 0.05) in the resistant subline indicative of increased tolerance to DNA damage. After an 18 h post-treatment incubation the parental cell line appeared proficient in the removal of the intrastrand adduct Pt-AG, but deficient in removing the major adduct Pt-GG and the difunctional Pt-(GMP)2 lesion, whilst the DXR-10 resistant subline appeared proficient in removal of all four Pt-DNA adducts. DNA polymerases alpha and beta activities, however, were comparable in both cell lines. These data implicate both enhanced repair and increased tolerance of DNA damage as mechanisms of resistance to CDDP resulting from in vitro exposure of a human ovarian carcinoma cell line to fractionated X-irradiation.
顺铂（CDDP）与辐射之间的相互作用对于癌症的联合治疗具有潜在意义。先前的数据表明，在体外暴露于X射线后，某些肿瘤细胞对CDDP产生了抗性。为了确定与这种CDDP抗性相关的参数，人卵巢癌细胞系SK-OV-3/P在体外预先接受了分次X射线照射（总剂量：50 Gy）。所得亚系（SK-OV-3/DKR-10）对CDDP具有2倍抗性，但对急性X射线照射无抗性。与二氢叶酸还原酶和胸苷酸合成酶活性未改变一致，SK-OV-3/DXR-10细胞对甲氨蝶呤和5-氟尿嘧啶均无交叉抗性。维拉帕米（6.6 microM）显著（P小于0.05）增强了抗性DXR-10亚系中CDDP诱导的细胞毒性，但对亲本细胞无此作用。抗性亚系中的总谷胱甘肽水平显著（P小于0.01）较低，丁硫氨酸亚砜胺预处理未能影响细胞毒性，而SK-OV-3/DXR-10细胞中的相关酶活性并未持续改变。这些细胞中的抗性与顺铂摄取显著降低（P小于0.002）有关。药物暴露后立即进行免疫化学定量，抗性亚系中DNA的总铂化水平较高（P小于0.05），表明对DNA损伤的耐受性增加。处理后孵育18小时后，亲本细胞系似乎能够有效去除链内加合物Pt-AG，但在去除主要加合物Pt-GG和双功能Pt-(GMP)2损伤方面存在缺陷，而DXR-10抗性亚系似乎能够有效去除所有四种Pt-DNA加合物。然而，两种细胞系中的DNA聚合酶α和β活性相当。这些数据表明，增强的修复和对DNA损伤的耐受性增加均是人类卵巢癌细胞系体外暴露于分次X射线照射后产生CDDP抗性的机制。
