Abstract 4852: Carbonic anhydrase IX and hypoxia-induced metabolic adaptations in tumor immune microenvironment: Insights into enhancing anti-PD1 efficacy in lung cancer

Abstract In solid tumors, cancer cell survival is largely driven by hypoxia-induced metabolic changes, including the enhancement of glycolysis and extracellular acidification. This process is facilitated by enzymes such as carbonic anhydrase IX (CAIX), which is upregulated under low oxygen tension to regulate pH by exchanging H+ ions and releasing lactate. These changes contribute to an acidic tumor microenvironment (TME) that alters immune cell functionality, particularly by recruiting tumor-associated macrophages (TAMs) and stimulating immune checkpoints like PD-L1. Our analysis of The Cancer Genome Atlas (TCGA) lung cancer data reveals that CAIX and hypoxia-inducible factor 1a (HIF1a) expression levels are significantly elevated in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) subtypes of non-small cell lung cancer (NSCLC) (p<0.001), with higher CAIX expression correlating with reduced overall survival. Strong correlations between HIF1a and CAIX, HIF1a and PD-L1, and PD-L1 and TAM markers (CD68, CD163) underscore a complex hypoxia-driven immunosuppressive mechanism. As we have reported that coumarin 4-methylumbelliferone (4Mu) modifies HIF1a tumor levels, we aim to test the effect of 4Mu in vitro under hypoxia/normoxia and in vivo combined with antiPD-1 therapy, using Lewis Lung Carcinoma cells (LLC). Hypoxia induces an increase in CAIX levels compared to normoxia (p<0.05), reduces extracellular pH (p<0.05), and increases levels of lactate. However, under hypoxic conditions, 4Mu restored CAIX, pH, and lactate levels to near-baseline levels. Moreover, LLC cells conditioned under hypoxia + 4Mu induced an M1 cytokine profile in macrophages, contrasting with the M2 polarization observed with hypoxia alone. In vivo, 4Mu reduced CAIX expression, and combination of 4Mu with anti-PD1 therapy increased the infiltration of CD8+ and CD4+ T cells and significantly improved anti-tumor efficacy (p<0.01). These findings suggest that targeting CAIX can modulate the TME, enhancing immune responses and potentially improving clinical outcomes for NSCLC patients receiving immunotherapy. Citation Format: Mariel Alejandra Fusco, María Florencia Mercogliano, Marco Aurelio Díaz Gutierrez, Carlos Rafael Picón, Paula Roselló, Mara Stinco, Flavia Piccioni, Constanza Paula Arriola Benitez, Mauricio César De Marzi, Manglio Miguel Rizzo, Mariana Malvicini. Carbonic anhydrase IX and hypoxia-induced metabolic adaptations in tumor immune microenvironment: Insights into enhancing anti-PD1 efficacy in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4852.