Protein kinase D1 regulates metabolic switch in pancreatic cancer via modulation of mTORC1

Background: Protein kinase D1 (PKD1) is a serine–threonine kinase that regulates various functions within the cell. Herein, we report the significance of PKD1 expression in glucose metabolism resulting in pancreatic cancer (PanCa) progression and chemo-resistance. Methods: PKD1 expression in PanCa was investigated by using immunohistochemistry. Functional and metabolic assays were utilised to analyse the effect of PKD1 expression/knockdown on associated cellular/molecular changes. Results: PKD1 expression was detected in human pancreatic intraepithelial neoplasia lesions (MCS = 12.9; P < 0.0001) and pancreatic ductal adenocarcinoma samples (MCS = 15, P < 0.0001) as compared with faint or no expression in normal pancreatic tissues (MCS = 1.54; P < 0.0001). Our results determine that PKD1 enhances glucose metabolism in PanCa cells, by triggering enhanced tumorigenesis and chemo-resistance. We demonstrate that mTORC1 activation by PKD1 regulates metabolic alterations in PanCa cells. siRNA knockdown of Raptor or treatment with rapamycin inhibited PKD1-accelerated lactate production as well as glucose consumption in cells, which confirms the association of mTORC1 with PKD1-induced metabolic alterations. Conclusion: This study suggests a novel role of PKD1 as a key modulator of the glucose metabolism in PanCa cells accelerating tumorigenesis and chemo-resistance. The remodelling of PKD1-dysregulated glucose metabolism can be achieved by regulation of mTORC1 for development of novel therapeutic strategies.