MUC5AC serves as the nexus for β-catenin/c-Myc interplay to promote glutamine dependency during pancreatic cancer chemoresistance.

Abstract BACKGROUND AND AIMS A major clinical challenge for pancreatic cancer (PC) patients is metabolic adaptation. Neoplastic cells harboring molecular perturbations suffice for their increased anabolic demand and nucleotide biosynthesis to acquire chemoresistance. The mucin 5AC expressed de novo in malignant pancreas promotes cancer cell stemness and is significantly associated with poor patient survival. Identification of MUC5AC-associated drivers of chemoresistance through metabolic alterations may facilitate sculpting a new combinatorial regimen. METHODS The contribution of MUC5AC on glutaminolysis and gemcitabine resistance were examined by TCGA data analysis, RNA sequencing, and immunohistochemistry analysis on pancreatic tissues of KrasG12D; Pdx1-Cre (KC) and KrasG12D; Pdx1-Cre; Muc5ac-/- (KCM) mice. These were followed by metabolite flux assays, biochemical and xenograft studies on MUC5AC-depleted human and murine PC cells. Murine and human pancreatic 3D-tumoroids were used to evaluate gemcitabine's efficacy in combination with β-catenin and glutaminolysis inhibitors. RESULTS Transcriptional analysis demonstrated that high MUC5AC-expressing human and autochthonous murine PC tumors exhibit higher resistance to gemcitabine due to enhanced glutamine utilization and nucleotide biosynthesis. Gemcitabine treatment led to MUC5AC overexpression, resulting in disruption of E-Cadherin/β-catenin junctions and the nuclear translocation of β-catenin, which increased c-Myc expression with a concomitant rise in glutamine uptake and glutamate release. MUC5AC-depletion and glutamine deprivation sensitized human PC cells to gemcitabine, which was obviated by glutamine replenishment in MUC5AC-expressing cells. Co-administration of β-catenin and glutaminolysis inhibitors with gemcitabine abrogated the MUC5AC-mediated resistance in murine and human tumoroids. CONCLUSIONS MUC5AC/β-catenin/c-Myc axis increases the uptake and utilization of glutamine in PC cells and co-targeting this axis along with gemcitabine may improve the therapeutic efficacy in PC.