Cisplatin sensitivity of testis tumour cells is due to deficiency in interstrand-crosslink repair and low ERCC1-XPF expression

Abstract

BackgroundCisplatin based chemotherapy cures over 80% of metastatic testicular germ cell tumours (TGCT). In contrast, almost all other solid cancers in adults are incurable once they have spread beyond the primary site. Cell lines derived from TGCTs are hypersensitive to cisplatin reflecting the clinical response. Earlier findings suggested that a reduced repair capacity might contribute to the cisplatin hypersensitivity of testis tumour cells (TTC), but the critical DNA damage has not been defined. This study was aimed at investigating the formation and repair of intrastrand and interstrand crosslinks (ICLs) induced by cisplatin in TTC and their contribution to TTC hypersensitivity.ResultsWe observed that repair of intrastrand crosslinks is similar in cisplatin sensitive TTC and resistant bladder cancer cells, whereas repair of ICLs was significantly reduced in TTC. γH2AX formation, which serves as a marker of DNA breaks formed in response to ICLs, persisted in cisplatin-treated TTC and correlated with sustained phosphorylation of Chk2 and enhanced PARP-1 cleavage. Expression of the nucleotide excision repair factor ERCC1-XPF, which is implicated in the processing of ICLs, is reduced in TTC. To analyse the causal role of ERCC1-XPF for ICL repair and cisplatin sensitivity, we over-expressed ERCC1-XPF in TTC by transient transfection. Over-expression increased ICL repair and rendered TTC more resistant to cisplatin, which suggests that ERCC1-XPF is rate-limiting for repair of ICLs resulting in the observed cisplatin hypersensitivity of TTC.ConclusionOur data indicate for the first time that the exceptional sensitivity of TTC and, therefore, very likely the curability of TGCT rests on their limited ICL repair due to low level of expression of ERCC1-XPF.

Molecular mechanisms of cisplatin resistance

“…Thus, ERCC1 expression (be it measured at the mRNA or protein level) has been negatively correlated with survival and/or responsiveness to cisplatin-based regimens in several human neoplasms including bladder (Bellmunt et al, 2007), colorectal (Shirota et al, 2001), gastric (Metzger et al, 1998), esophageal , head and neck (Handra-Luca et al, 2007;Jun et al, 2008) and ovarian cancers (Dabholkar et al, 1992), as well as non-small cell lung cancer (NSCLC) (Olaussen et al, 2006). ERCC1 also participates in interstand crosslink repair (ICR), and ICR proficiency appears to be reduced and augmented in cisplatinsensitive and cisplatin-resistant tumor cells, respectively (Zhen et al, 1992;Usanova et al, 2010).…”

ERCC1 function in nuclear excision and interstrand crosslink repair pathways is mediated exclusively by the ERCC1-202 isoform

“…A key role of the ERCC1/XPF heterodimer was first demonstrated in the nucleotide excision repair (NER) pathway. The 5′-3′ structure-specific endonuclease activity of the complex was subsequently shown to be also required for the Fanconi anemia (FA) pathway of interstrand crosslink repair (ICL-R), [1][2][3] as well as for homology-directed repair (HDR) of DNA double-strand breaks (DSB). [4][5][6][7] XPF is catalytically active, while ERCC1 tethers the activity of the complex to the site of repair through physical interactions with the core machinery complexes of several repair pathways (see ref.…”

A DFT/ECP-Small Basis Set Modelling of Cisplatin: Molecular Structure and Vibrational Spectrum

“…Among them, only five more Pt(II) complexescarboplatin, oxaliplatin, nedaplatin, lobaplatin and heptaplatin-have gained international or local marketing approval [8,17]. At present, cisplatin remains amongst the most widely used platinum chemotherapeutics, with particular effectiveness in the treatment of testicular, ovarian and bladder cancer [9,18,19].…”