βIII-Tubulin is a Brake on Extrinsic Cell-Death in Pancreatic Cancer

Abstract

The microtubule protein, {beta}III-tubulin, has been implicated as a prognostic, pro-survival, and chemoresistance factor in some of the most lethal malignancies including pancreatic ductal adenocarcinoma (PDAC). However, precise survival mechanisms controlled by {beta}III-tubulin in cancer cells are unknown. Here, we report an unexpected role of {beta}III-tubulin as a brake on extrinsic caspase 8-dependent apoptosis in PDAC. We show that {beta}III-tubulin knockdown frees death-receptor DR5 to increase its membrane diffusion, clustering, and activation of cell-death. We demonstrate that {beta}III-ubulin silencing increases sensitivity of PDAC cells to chemotherapeutic and microenvironment-derived extrinsic cell-death signals including TRAIL, TNF, and FasL. Finally, nanoparticle delivery of {beta}III-tubulin siRNA to mouse orthotopic PDAC tumours in vivo and human patient-derived PDAC tumour explants ex vivo increases extrinsic apoptosis and reduces tumour progression. Thus, silencing of {beta}III-tubulin represents an innovative strategy to unleash a suicide signal in PDAC cells and render them sensitive to microenvironment and chemotherapy-derived death signals.