Hill B T, Shellard S A, Hosking L K, Fichtinger-Schepman A M, Bedford P
Laboratory of Cellular Chemotherapy, Imperial Cancer Research Fund, Lincoln's Inn Fields, London, U.K.
Int J Radiat Oncol Biol Phys. 1990 Jul;19(1):75-83. doi: 10.1016/0360-3016(90)90137-9.
In vitro exposure of a human testicular teratoma continuous cell line to fractionated X-irradiation resulted in the expression of resistance to cisplatin. In two independently-derived sublines, designated SUSA-DXR13 and SUSA-DXR10 resulting from treatment with either 13 fractions of 1.5 Gy (dose required to reduce survival by 1 log) or 10 fractions of 3 Gy (dose required to reduce survival by 2 logs) respectively, the IC50 values for cisplatin were 2- and 3.1-fold higher than that of the parental cell line. These sublines were cross-resistant to carboplatin (approximately 2-fold) but not to adriamycin and they showed unaltered radiosensitivities. The SUSA-DXR10 subline expressed some cross-resistance to mitomycin C and melphalan but none to Carmustine (BCNU). Total glutathione content was significantly reduced in both SUSA-DXR10 and SUSA-DXR13 cells, but the activities of associated enzymes, including the glutathione S-transferases, peroxidase and reductase were not modified significantly in the resistant sublines. Resistance in the SUSA-DXR10 subline was associated with significantly decreased 195mcisplatin uptake (p less than 0.01), but this was not reflected in a reduced level of drug bound to the DNA. The formation and removal of four platinum-DNA adducts were immunochemically quantitated. Immediately following drug treatment there was a higher level of total platination of the DNA in the resistant subline indicative of increased tolerance to DNA damage. After an 18 hr post treatment incubation, there was an indication of some repair capacity in this SUSA-DXR10 cell line, which was not apparent in the parental cells. Neither the parental nor the SUSA-DXR10 cell line was proficient in the repair of the major adduct Pt-GG, whereas both lines repaired the monofunctional adduct and the adduct Pt(GMP)2. SUSA-DXR10 cells were also able to repair the intrastrand adduct Pt-AG and interstrand crosslinks, unlike the repair deficient parental cells. Higher levels of interstrand crosslinks were characteristic of the SUSA-DXR10 subline. These observations therefore implicate both enhanced repair and increased tolerance of DNA damage as mechanisms of resistance to cisplatin resulting from in vitro exposure of a human teratoma cell line to fractionated X-irradiation.
将人睾丸畸胎瘤连续细胞系进行体外分次X线照射后，该细胞系对顺铂产生了抗性。在用13次1.5 Gy（使存活率降低1个对数所需剂量）或分别用10次3 Gy（使存活率降低2个对数所需剂量）处理后产生的两个独立亚系，即SUSA - DXR13和SUSA - DXR10中，顺铂的IC50值分别比亲代细胞系高2倍和3.1倍。这些亚系对卡铂有交叉抗性（约2倍），但对阿霉素没有交叉抗性，并且它们的放射敏感性未改变。SUSA - DXR10亚系对丝裂霉素C和美法仑有一定交叉抗性，但对卡莫司汀（BCNU）没有交叉抗性。SUSA - DXR10和SUSA - DXR13细胞中的总谷胱甘肽含量均显著降低，但在抗性亚系中，包括谷胱甘肽S - 转移酶、过氧化物酶和还原酶在内的相关酶活性没有明显改变。SUSA - DXR10亚系中的抗性与195m顺铂摄取显著降低有关（p小于0.01），但这并未反映在与DNA结合的药物水平降低上。对四种铂 - DNA加合物的形成和去除进行了免疫化学定量。药物处理后立即发现，抗性亚系中DNA的总铂化水平较高，表明对DNA损伤的耐受性增加。处理后孵育18小时后，表明SUSA - DXR10细胞系有一定的修复能力，而亲代细胞中不明显。亲代细胞系和SUSA - DXR10细胞系都不能有效修复主要加合物Pt - GG，而两系都能修复单功能加合物和加合物Pt(GMP)2。与缺乏修复能力的亲代细胞不同，SUSA - DXR10细胞也能够修复链内加合物Pt - AG和链间交联。链间交联水平较高是SUSA - DXR10亚系的特征。因此，这些观察结果表明，增强的修复和对DNA损伤增加的耐受性都是人畸胎瘤细胞系体外暴露于分次X线照射后产生对顺铂抗性的机制。
