Abstract 4367: Protein kinase D1 induces metabolic switch in pancreatic cancer via modulation of mTORC1
Authors: Kumari Sonam , Khan Sheema , Yallapu Murali , Chauhan Subhash , Jaggi Meena 
Published: August 2019

Objective: Pancreatic cancer (PanCa) is the third most common cause of cancer-related deaths in the US. Protein Kinase D1 (PKD1) is a kinase molecule which is involved in various important cellular signaling processes. While PKD1 has been reported to play a role in PanCa progression, the molecular mechanisms involved have not been adequately studied. Herein, we investigate the underlying mechanisms which enable PKD1 in enhancing glucose metabolism and further contribute to PanCa aggressiveness.

Methods: PanCa cells with high PKD1 expressing (Panc-1 and AsPC-1) and low PKD1 (HPAF-II and BXPC-3) were used in the study. Immunohistochemistry and confocal immunofluorescence were performed to analyze the expression of PKD1 in pancreatic cancer/normal tissues and cells, respectively. The effect of PKD1 gain/loss-in function was investigated on glucose uptake and lactate production in PanCa cells using commercially available kits. Western blotting and real-time PCR experiments were performed to analyze the expression of protein and mRNA levels. MTT assay was conducted to access the influence of PKD1 on cell proliferation. Boyden chamber migration assay and Matrigel invasion assays were performed to determine the migratory and invasive abilities of PanCa cells. The gene silencing was performed using specific siRNAs in the study.

Results: Our results demonstrate that PKD1 upregulates glucose metabolism in PanCa cells as indicated by enhanced glucose consumption and lactate production. The invasive characteristics of PKD1 expressing cells are augmented in presence of L-Lactate and reduced in presence of 2DG. PKD1 overexpression demonstrated enhanced phosphorylation of mTOR (ser-2448), 4EBP1, s6kinase and AKT, suggesting the role of PKD1 in the activation of mTOR pathway. We further observed that the phosphorylation of mTOR (ser-2448) and ps6kinase was attenuated on silencing PKD1 or in presence of Rapamycin, suggesting the role of PKD1 in activation of mTORC1 complex, both being the main effectors of mTORC1. Additionally, the inhibition in the phosphorylation of mTOR (ser-2448) in presence of kinase dead PKD1 suggests that PKD1 phosphorylates/activates mTORC1 in PanCa. Decrease in glucose uptake and lactate production in presence of PKD1 overexpression was observed on silencing raptor but not rictor in the cells, further suggesting the involvement of mTORC1 in PKD1 induced metabolic reprogramming in PanCa. PKD1 induced enhanced phosphorylation of mTOR resulted in an activation of HIF-1α and Glut-1 proteins, involved in abberant glucose metabolism. Additionally, our results also demonstrate that altered glucose metabolism leads to chemoresistance and silencing of PKD1 expression sensitizes PanCa cells to gemcitabine.

Conclusion: Our studies indicate that PKD1 acts as a key regulator of the glucose metabolism via mTOR activation and facilitates proliferation and invasion of PanCa cells.

Citation Format: Sonam Kumari, Sheema Khan, Murali Yallapu, Subhash Chauhan, Meena Jaggi. Protein kinase D1 induces metabolic switch in pancreatic cancer via modulation of mTORC1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4367.