Methylation of HSP70 Orchestrates Its Binding to and Stabilization of BCL2 mRNA and Renders Pancreatic Cancer Cells Resistant to Therapeutics

Abstract

Pancreatic cancer is a lethal disease owing to its intrinsic and acquired resistance to therapeutic modalities. The altered balance between pro- and anti-apoptosis signals within cancer cells is critical to therapeutic resistance. However, the molecular mechanisms underlying increased anti-apoptosis signals remain poorly understood. In this study, we report that PRMT1 expression is increased in pancreatic cancer tissues and associated with higher tumor grade, increased aggressiveness and worse prognosis. PRMT1 overexpression increased arginine methylation of HSP70; this methylation enhanced HSP70 binding and stabilization of BCL-2 mRNA through AU-rich elements in 3'-UTR and consequentially increased BCL-2 protein expression and protected cancer cells from apoptosis induced by cellular stresses and therapeutics. RNA binding and regulation function of HSP70 was involved in pancreatic cancer drug resistance and was dependent on protein arginine methylation. These findings not only reveal a novel PRMT1-HSP70-BCL-2 signaling axis that is crucial to pancreatic cancer cell survival and therapeutic resistance, but they also provide a proof of concept that targeted inhibition of this axis may represent a new therapeutic strategy.