The role of Nrf2 and ATF2 in resistance to platinum-based chemotherapy.

Abstract

Nrf2 and its role in controlling levels of the AKR family of aldo-keto reductases which have been implicated in resistance to platinum-based chemotherapy was studied in ovarian, cervical and lung cell lines. Nrf2 shRNA knockdowns of cells from different tumor origins were prepared to determine the role of this factor in producing resistance to platinum chemotherapy. Nrf2 knockdowns resulted in marked decreases in AKR1C1, AKR1C2 and to a lesser extent AKR1C3. Additionally, all other candidate enzymes GSTπ and TRX1 were decreased, but their role was difficult to correlate to cytotoxicity. Nrf2 knockdowns exhibited marked increases in mitochondrial membrane depolarization and ROS production following cisplatin treatment, with the cervical ME180R knockdowns exhibiting the greatest effect (AKR1C1 and AKR1C2 levels were decreased in the ME180R and SKOV3 cells to near zero). Oxaliplatin tended to parallel cisplatin, except it markedly stimulated O2- production not [Formula: see text] by oxaliplatin treatment of the ME180R cells. The pJNK/p38 pathway has been implicated in cisplatin cytotoxicity, and significant phosphorylation of pJNK was observed in the SKOV3 and ME180R and p38 in the SKOV3 knockdowns. Phosphorylation of ATF2 was decreased in the Nrf2 knockdowns (Crf38, Srf6, Arf5) which could affect its interaction with JNK and p38. Oxaliplatin treatment showed minimal effects on the JNK/p38 pathway, showing that its mode of action is different although ROS generation appeared an initial step with both drugs. Nrf2 controls a multitude of different candidate genes; however, it did markedly modulate cisplatin resistance through the AKR family. This involved ROS production and activation of the pJNK/p38 pathway with involvement of ATF2.