PO-405 Blockade of endothelial cell glycolysis to improve current immunotherapy

Introduction Tumour blood vessels are highly abnormal, they are leaky and poor perfused. This creates a hypoxic microenvironment and limits the delivery of nutrients, chemotherapy and immune cells. Tumour vessel abnormalities are due to pathological angiogenesis by hyperglycolytic tumour endothelial cells (TECs). Cantelmo et al recently showed that blocking the glycolytic activator PFKFB3 in TECs by the small compound 3PO normalised the tumour vasculature, improved oxygenation and the delivery and efficacy of cytoxic agents. Here, we investigate if tumour vessel normalisation (TVN) induced by PFKFB3 blockade enhances intratumoral T cell infiltration and activation, and increases the efficacy of immune-checkpoint inhibition. We also characterised the effect of TVN on cancer cell metabolism, to make them more vulnerable to immune-mediated killing. Material and methods We injected B16 mouse melanoma cells subcutaneously in wild-type mice and treated the tumor-bearing mice with either 3PO or vehicle. We analysed the intratumoral T cell infiltration and activation by immunofluorescence and FACS analysis. We also treated tumor-bearing mice with the immune-checkpoint inhibitor anti-PD1 alone or in combination with 3PO. Cancer cell metabolism upon TVN was assessed by radioactive flux analysis and measurement of oxygen consumption rate in freshly isolated cancer cells exposed to 3PO in vivo. Results and discussions Ongoing work suggests that 3PO treatment significantly increases intratumoral T cell infiltration compared to controls. Tumor-infiltrating T cells appeared to be more activated and proliferative. Furthermore, upon 3PO treatment, cytotoxic short-lived effector (CD44+ KLRG1+ CD127-) and IFNg+ T cells increased compared to controls. The combination of 3PO with anti-PD1 significantly inhibited tumour growth in comparison to 3PO or anti-PD1 monotherapy. Metabolic analysis of isolated cancer cells showed increased oxygen consumption, glucose and fatty acid oxidation in tumours treated with 3PO. Conclusion Our data suggest that TVN induced by PFKFB3 blockade in TECs: (i) increases the immunogenecity of intrinsically resistant tumours, both in terms of T cell infiltration and activation; (ii) reprograms cancer cells towards a more oxidative metabolism. This results in increased cancer cell susceptibility to immune responses and in overall increased efficacy of immune-checkpoint inhibition. Further research will elucidate how TVN regulates T cell activation and reprogramms cancer cell metabolism.