STAT3 mediates multidrug resistance of Burkitt lymphoma cells by promoting antioxidant feedback.

Burkitt lymphoma (BL) is a highly aggressive B-cell neoplasm. Although BL is relatively sensitive to chemotherapy, some patients do not respond to initial therapy or relapse after standard therapy, which leads to poor prognosis. The mechanisms underlying BL chemoresistance remain poorly defined. Here, we report a mechanism for the relationship between the phosphorylation of STAT3 on Tyr705 and BL chemoresistance. In chemoresistant BL cells, STAT3 was activated and phosphorylated on Tyr705 in response to the generation of the reactive oxygen species (ROS), which induced Src Tyr416 phosphorylation after multi-chemotherapeutics treatment. As a transcription factor, the elevated phosphorylation level of STAT3Y705 increased the expression of GPx1 and SOD2, both of which protected cells against oxidative damage. Our findings revealed that the ROS-Src-STAT3-antioxidation pathway mediated negative feedback inhibition of apoptosis induced by chemotherapy. Thus, the phosphorylation of STAT3 on Tyr705 might be a target for the chemo-sensitization of BL.