The first paper describes a tumour transplantation approach to examine the effect of impaired translesion DNA synthesis on cisplatin response in aggressive late-stage lung cancers. The researchers used RNA interference to reduce levels of Rev3, an essential component of Polζ, and showed that a 60-70% reduction doubled survival time in cisplatin-treated animals. The team also showed that Rev3-deficient cells showed reduced cisplatin-induced mutations which have been suggested to contribute to secondary malignancies following chemotherapy.
In the second study, the researchers used a mouse model of B-cell lymphoma to show that suppressing Rev1, an essential TSL scaffold protein and dCMP transferase, inhibits both cisplatin- and cyclophosphamide-induced mutagenesis. By performing repeated cycles of tumor engraftment and treatment, the team were also able to show that Rev1 plays a critical role in the development of acquired cyclophosphamide resistance.
The studies show that chemotherapy can not only select for drug-resistant populations of tumour cells but can also directly promote the acquisition of resistance-causing mutations, suggesting that blocking translesion DNA polymerases may have dual anticancer effects by both increasing the sensitivity of tumours to chemotherapy as well as reducing the potential for emergence of drug resistance during treatment. The next challenge will be to identify inhibitors of the translesion DNA polymerases.