Abstract 6230: Loss of ALK4 function promotes cancer progression by regulating cell surface TGF-β receptor stability

Abstract

Abstract Pancreatic cancer is a lethal disease. More than 50% of pancreatic cancer patients are diagnosed with metastatic disease with a dismal 3% five-year survival rate. There is clearly an urgent need to identify novel targets to treat pancreatic cancer patients. Transforming growth factor-β (TGF-β) signaling is dysregulated during cancer progression, inhibiting tumorigenesis while promoting metastasis. Approximately half of pancreatic cancer patients have mutations of genes in the TGF-β signaling pathway, including SMAD4, SMAD3, TGFBR1, TFGBR2, ACVR1B, and ACVR2A. ALK4 (Activin receptor-like kinase 4), which is encoded by ACVR1B, is a type I receptor in the TGF-β superfamily. Mutation or copy number loss of ALK4 occurs in 34% of pancreatic cancer patients, while ALK4 expression is significantly down-regulated in many cancers, including pancreatic cancer, with low ALK4 expression associated with poor clinical outcomes. Here we demonstrate that loss of ALK4 increases cell migration and invasion, induces epithelial to mesenchymal transition (EMT), and promotes local and distal metastasis in pancreatic cancer models. Loss of ALK4 unexpectedly increases activation of the canonical TGF-β signaling pathway and significantly induces TGF-β-mediated expression of EMT mediators and effectors. Moreover, ALK4 loss increases the cell surface expression of TβRs (TGFβ receptor type I and II), without changing the receptor gene expression, by increasing N-linked glycosylation of TβRs, potentially by altering Golgi morphology and function. Proteomic analysis of newly synthesized proteins induced by ALK4 loss identified galectin-3 (Gal-3) as upregulated. Gal-3 is known to be upregulated by MGAT5 (Alpha-1,6-Mannosylglycoprotein 6-Beta-N-Acetylglucosaminyltransferase) and cross-links MGAT5-modified N-glycans on TβRs at the cell surface, suppressing TβRs endocytosis. Consistent with this observation, loss of ALK4 increased MGAT5 mRNA expression and induced Gal-3 protein expression, suggesting that ALK4 might regulate TβRs stability by promoting lattice formation with Gal-3 and preventing internalization. Taken together, our results suggest that the loss of ALK4 increases TβR receptor stability through regulating receptor glycosylation, activating TGF-β signaling, promoting the EMT transition and cancer progression. Citation Format: Manqi Zhang, Jian Chen, Gerard Conrad Blobe. Loss of ALK4 function promotes cancer progression by regulating cell surface TGF-β receptor stability [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6230.