Institute of Toxicology, Medical Center of the University Mainz, Obere Zahlbacher Str. 67, Mainz, Germany.
Oncogene. 2014 Apr 10;33(15):1964-74. doi: 10.1038/onc.2013.141. Epub 2013 Apr 22.
Malignant melanoma is a cancer characterized by high chemoresistance although p53 is rarely mutated. Here, we show that p53 wild-type melanoma cells acquire resistance to cell death induced by fotemustine (FM), which is a representative of alkylating DNA interstrand cross-linking agents used in melanoma therapy. We show that drug-induced resistance is a result of p53-dependent upregulation of the nucleotide excision repair (NER) genes xeroderma pigmentosum complementation group C (XPC) and damaged DNA-binding protein 2 (DDB2), which stimulate the repair of DNA interstrand cross-links (ICLs) arising from O(6)-chloroethylguanine. Consequently, TP53 mutated cells are unable to repair ICLs, leading to prolonged ATM, ATR and checkpoint kinase 1 (CHK1) activation, and finally apoptosis. The roles of p53 and NER in ICL-triggered cell death were confirmed by knockdown of p53 and XPC. Upregulation of XPC and DDB2 in p53wt cells following a single drug treatment is a robust and sustained response that lasts for up to 1 week. Pretreatment with an inducing dose followed by a high and toxic dose of FM provoked an adaptive response as the killing outcome of the challenge dose was reduced. Upregulation of XPC and DDB2 was also observed in a melanoma mouse xenograft model following systemic administration of FM. Additionally, XPC and DDB2 induction occurred upon treatment with other cross-linking anticancer drugs, such as cisplatin and mafosfamide, indicating it is a general response of cancer cells to this group of chemotherapeutics. Collectively, the data indicate that p53-dependent upregulation of XPC and DDB2 is a key mechanism upon genotoxic stress, whereby melanoma cells acquire resistance towards DNA cross-linking agents. To our knowledge, this is the first demonstration of upregulation of NER following a single dose of a DNA interstrand cross-linker, which is a robust and long-lasting effect that impacts the killing response of cancer cells to subsequent treatments.
恶性黑色素瘤是一种癌症，其特点是化疗耐药性高，尽管 p53 很少发生突变。在这里，我们表明 p53 野生型黑色素瘤细胞对 fotemustine（FM）诱导的细胞死亡产生耐药性，FM 是用于黑色素瘤治疗的烷化 DNA 链间交联剂的代表。我们表明，药物诱导的耐药性是 p53 依赖性上调核苷酸切除修复（NER）基因 Xeroderma Pigmentosum Complementation Group C（XPC）和受损的 DNA 结合蛋白 2（DDB2）的结果，这两种基因刺激 O(6)-氯乙基鸟嘌呤引起的 DNA 链间交联（ICLs）的修复。因此，TP53 突变细胞无法修复 ICL，导致 ATM、ATR 和检查点激酶 1（CHK1）的激活延长，并最终导致细胞凋亡。通过敲低 p53 和 XPC 证实了 p53 和 NER 在 ICL 触发的细胞死亡中的作用。单次药物处理后 p53wt 细胞中 XPC 和 DDB2 的上调是一种强大且持续的反应，可持续长达 1 周。用诱导剂量预处理，然后用高毒性剂量的 FM 引发适应性反应，因为挑战剂量的杀伤结果降低。在 FM 全身给药后，在黑色素瘤小鼠异种移植模型中也观察到 XPC 和 DDB2 的上调。此外，在顺铂和 mafosfamide 等其他交联抗癌药物治疗时也观察到 XPC 和 DDB2 的诱导，表明这是癌细胞对这组化疗药物的一般反应。总的来说，这些数据表明，p53 依赖性上调 XPC 和 DDB2 是一种关键机制，通过这种机制，黑色素瘤细胞获得对 DNA 交联剂的耐药性。据我们所知，这是首次证明单次 DNA 链间交联剂剂量后 NER 的上调，这是一种强大且持久的效应，会影响癌细胞对后续治疗的杀伤反应。
