Pharmacological inhibition of hypoxia induced acidosis employing a CAIX inhibitor sensitizes gemcitabine resistant PDAC cells

The poor prognosis of pancreatic ductal adenocarcinoma (PDAC) is attributed to tumor microenvironment driven by hypoxia regulated carbonic anhydrase IX. Our study elucidates the ability of Methazolamide, a CAIX inhibitor to sensitize resistant PDAC cells. The effect of Methazolamide alone and in combination with gemcitabine on proliferation, migration, tumor inhibition along with its impact on metastasis by influencing HIF-1α/PTEN/Glut1/Glut3 signalling through the expression of CAIX was assessed. Methazolamide induced cytotoxicity in several PDAC cells including patient derived with IC₅₀ 0.7-4.09 mM and 0.29-2.56 mM in monolayer and clonogenic assays respectively. Methazolamide alone and in combination significantly downregulated hypoxia induced expression of HIF-1α and CAIX together with proliferation (Ki-67, Cyclin D1), invasion (Rac-1, Snail), stem cell (Oct-4, Sox-2), angiogenesis (VEGF), glycolysis (Glut1, Glut3) and apoptosis (Bax, Bc1-2 and PTEN) markers in MIA PaCa-2 and PANC-1 cells. In vivo study in PAXF 546L PDX model exhibited profound tumor growth inhibition with downregulation of CD34, Oct-4, Sox-2, C-myc, Nanog, Ki-67, and Rac-1 signalling. Considering inadequate availability of effective therapeutics and importance of CAIX in processes leading to aggressive behavior of PDAC, targeting it by using Methazolamide, a pre-approved drug in combination with gemcitabine represents promising therapeutic approach specifically in metastatic settings.