Complex cisplatin-double strand break (DSB) lesions directly impair cellular non-homologous end-joining (NHEJ) independent of downstream damage response (DDR) pathways.

Abstract

The treatment for advanced stage non-small cell lung cancer (NSCLC) often includes platinum-based chemotherapy and IR. Cisplatin and IR combination therapy display schedule and dose-dependent synergy, the mechanism of which is not completely understood. In a series of in vitro and cell culture assays in a NSCLC model, we investigated both the downstream and direct treatment and damage effects of cisplatin on NHEJ catalyzed repair of a DNA DSB. The results demonstrate that extracts prepared from cisplatin-treated cells are fully capable of NHEJ catalyzed repair of a DSB using a non-cisplatin-damaged DNA substrate in vitro. Similarly, using two different host cell reactivation assays, treatment of cells prior to transfection of a linear, undamaged reporter plasmid revealed no reduction in NHEJ compared with untreated cells. In contrast, transfection of a linear GFP-reporter plasmid containing site-specific, cisplatin lesions 6-bp from the termini revealed a significant impairment in DSB repair of the cisplatin-damaged DNA substrates in the absence of cellular treatment with cisplatin. Together, these data demonstrate that impaired NHEJ in combined cisplatin-IR treated cells is likely the result of a direct effect of cisplatin-DNA lesions near a DSB and that the indirect cellular effects of cisplatin treatment are not significant contributors to the synergistic cytotoxicity observed with combination cisplatin-IR treatment.

• Authors: Catherine R Sears, John J Turchi
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 287 Issue 29 Pg. 24263-72 (Jul 13 2012) ISSN: 1083-351X [Electronic] United States
• PMID: 22621925 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Cisplatin

Topics

• Cell Line, Tumor
• Cisplatin (pharmacology)
• DNA Breaks, Double-Stranded (drug effects)
• Flow Cytometry
• Humans
• Microscopy, Fluorescence
• Signal Transduction (drug effects, genetics)