Abstract A021: Nutrient competition in the tumor microenvironment alters NK cell metabolism in Pancreatic Cancer

Abstract

Abstract Tumor cells present constant nutritional demand of macronutrients and micronutrients for their rapid growth needs. Often this nutrient limitation hampers the function of anti-tumor immune cells, which need basal energy levels to execute cytotoxic effects against malignant cells. Hence, we investigated nutrient limitation-induced metabolic alterations in NK cells that regulate the anti-tumor activity of NK cells. Using 2D cultures and PDAC organoid models, we demonstrate that pancreatic tumor cells exhaust vitamin B6 (VB6) in the co-culture milieu, causing reduced killing activity of NK cells. Additionally, we demonstrate that PDAC patients have significantly reduced plasma VB6 as compared to the healthy counterparts. This data aligns with the epidemiological studies showing that VB6 intake reduces the risk of pancreatic cancer incidence. Moreover, we noted a significant reduction in circulating VB6 in the pancreatic tumor-bearing mice as compared to healthy counterparts. Utilizing mass spectrometry-based metabolomics we noted that limitation of the VB6 prevents glycogen breakdown in NK cells. This was validated by follow up electron microscopy-based studies that demonstrated glycogen depots in NK cells that were very prominent upon inhibiting glycogenolysis. Metabolic tracing studies demonstrated that NK cells require VB6 for intracellular glycogen breakdown. Correspondingly, knocking down glycogen phosphorylase, a key enzyme involved in glycogen breakdown abrogated anti-tumoral NK cell function. Notably, supplementation of co-cultures in 2D and organoid models and in vivo orthotopic mouse models, with VB6 restored NK cell function against pancreatic tumor cells. In parallel, we observed dependence of tumor cell metabolism on VB6 for sustaining growth. Accordingly, we observed that tumor cells actively deplete VB6 in tumor microenvironments, as observed by comparing VB6 levels in circulation and in tumor interstitial fluids. Finally, we observed that VB6 supplementation in combination with inhibitors targeting VB6-driven metabolic pathway dependencies in tumor cells effectively enhances NK cell frequency and diminishes tumor burden in vivo. These studies demonstrate a novel role of glycogen breakdown as a critical energy source for activated NK cells and demonstrate, for the first time a key role of glycogenolysis in NK cell cytotoxic activities. Our results expand the understanding of the critical role of micronutrients (vitamin B6) in regulating cancer progression and anti-tumor immunity and open new avenues for developing NK cell-based immunotherapies for PDAC patients. Citation Format: Kamiya Mehla. Nutrient competition in the tumor microenvironment alters NK cell metabolism in Pancreatic Cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr A021.