SphK1/S1P Axis Regulate PPARγ Levels to Program Metabolically Fit Anti-Tumor T Cells

Abstract

Abstract Metabolic competition with highly glycolytic tumor and overcoming tumor-induced suppression are prerequisites for achieving prolonged tumor control by adoptive T cell therapy (ACT). Given the importance of sphingosine-1-phosphate (S1P) signaling that are independent of immune cell trafficking, we evaluated if altering sphingosine kinase (SphK) mediated S1P level have benefits for anti-tumor T cell response. A comparison of melanoma epitope gp100 reactive T cell receptor transgenic pMel vs. pMel-SphK1−/− mice derived splenic T cells showed better control of subcutaneously established murine B16-F10 melanoma, increased infiltration at the tumor site with activated pMel-SphK1−/− T cells. Additionally, pMel-Sphk1−/−T cells also exhibited enhanced recall response tracked in different organs after secondary antigen exposure. Mechanistically, we found that attenuation of SphK1/S1P signaling results in higher Sirt1 (an NAD+ dependent protein deacetylase) activity, lower PPARγ activity and higher retention of FOXO1 in the nucleus. While higher nuclear localization of FOXO1 regulates higher migration of SphK1−/− CD8+ T cells, lower PPARγ activity endows them with increased ability to use their stored lipid content even in starved condition and decreased iTreg generation. Owing to their efficacious utilization of lipid as fuel, Sphk1−/− T cells persist longer in nutrient deprived tumor microenvironment. In reciprocal studies, endogenous production of S1P in Sphk1−/− T cells (transfected with WT Sphk1 vector) enhanced PPARγ expression and thereby reversed their phenotype in terms of iTreg generation and lipid utilization. Overall, these data highlight that strategies targeting SphK/S1P axis improves efficacy of ACT.