Gemcitabine Potentiates Cisplatin Cytotoxicity and Inhibits Repair of Cisplatin-DNA Damage in Ovarian Cancer Cell Lines

Abstract

Synergistic cytotoxicity between cisplatin and the nucleoside analog gemcitabine was observed in a panel of cisplatin-sensitive (2008, A2780) and -resistant (2008/C13*5.25, A2780/ CP70) human ovarian cell lines. Previous studies have suggested a role for DNA repair in the mechanism of synergy between the two drugs. We therefore further investigated the hypothesis that the synergistic cytotoxicity between gemcitabine and cisplatin in these cell lines may be caused by gemcitabine-mediated inhibition of cisplatin intrastrand adduct (IA) and interstand cross-link (ICL) repair. The effect of gemcitabine on the accumulation and repair of cisplatin IA and ICL in each cell line was then measured directly using gene-specific quantitative polymerase chain reaction and denaturation/renaturation techniques, respectively. Pretreatment of 2008 cells with 1 M gemcitabine for 2 h before exposure to cisplatin for 7 h enhanced the accumulation of cisplatin IA and ICL by 50 and 40%, respectively (P Ͻ 0.05), above that induced by cisplatin alone. To investigate the possibility that the increased accumulation of cisplatin lesions was caused by inhibition of removal of cisplatin damage, 2008 cells were incubated with 200 M cisplatin for 5 h in the presence and absence of gemcitabine and then a further 8 h in the absence of cisplatin. Only 57% IA were removed in the combination treated cells compared with 74% in cisplatin control cells. Similarly, repair of cisplatin ICL was inhibited in the gemcitabine-treated cells compared with the cells treated with cisplatin only (60 versus 72%). These findings demonstrate a direct inhibitory effect of gemcitabine on the repair of cisplatin IA and ICL and suggest a mechanistic basis for the cytotoxic synergy between the two drugs.

Fludarabine increases oxaliplatin cytotoxicity in normal and chronic lymphocytic leukemia lymphocytes by suppressing interstrand DNA crosslink removal

“…This gene-specific assay has been previously used to explore the effects of fludarabine on the repair of cisplatin lesions 24 and to investigate the actions of gemcitabine on cisplatin damage accumulation and repair. 21 Although the requirement of quantitating ICLs in single gene DNA requires a relatively high level of ICLs throughout the …”

“…The formation of ICL in the DHFR gene and the mitochondrial genome was similar, consistent with the findings of others with cisplatin. 21,36,37 Crosslinking of the ␦-globin gene was less, possibly because that drug's accessibility to the DNA may have been limited. Fludarabine significantly inhibited the unhooking of interstrand crosslinks to similar extents in both the nuclear DNA and mtDNA.…”

“…The rationale for combining oxaliplatin with fludarabine is based on preclinical data showing synergistic cytotoxicity between cisplatin in combination with the nucleoside analogs ara-C, 20 gemcitabine, 21,22 clofarabine, 23 and fludarabine. [24][25][26] It has been suggested previously that enhanced crosslink repair is a primary mechanism of resistance to nitrogen mustards in B-CLL.…”

Chemotherapy in advanced biliary tract carcinoma: a pooled analysis of clinical trials

“…The increase of the addition of platinum compounds to gemcitabine is greater compared with the addition to fluoropyrimidines. Synergism of cisplatin and gemcitabine has been demonstrated in cell lines and is based on direct inhibitory effect of gemcitabine on the repair of cisplatin interstrand adducts and interstrand crosslinks (van Moorsel et al, 1999;Moufarij et al, 2003).…”

Recurrent Ovarian Cancer

“…Recent data have suggested that gemcitabine may have a possible role in overcoming platinum resistance by its inhibition of excision repair enzymes (84). The results of smaller phase II trials also suggest that either liposomal doxorubicin or topotecan administered in conjunction with gemcitabine improves tumor response rates compared with historical results observed with single agents (85,86).…”