Introduction/Rationale: We elucidated the impact of cancer metabolism components to potentiate the anti-tumoral effects of therapeutic mRNA vaccines. MCT4 facilitates the symport of lactate and protons to the extracellular environment contributing in the acidification of extracellular environment and consequently initiation of immune escape mechanisms by cancer cells and it is highly associated with poor cancer patient prognosis
Methods: CRISP knock out of MCT4 in MC38 cells; in vitro and ex vivo metabolic assays; tumor growth and survival in mice; mRNA-therapy; histology; flow cytometry; isotype tracing.
Results: In vivo studies using MC38 Mct-4 ko tumor cells showed reduced tumor growth and increased rejection rates in immunocompetent mice, while minimal differences in immunodeficient mice, suggesting a high immune response within the MC38 Mct4-KO's tumor microenvironment (TME). We showed that MC38 Mct4-KO TME increased CD8 and CD4 T cell infiltration with higher cytotoxic functionality and a pro-inflammatory environment characterized by enriched nutrients availability, lower level of lactate and reduced hypoxic areas. Therapeutic mRNA vaccinations, conducted in mice with well-engrafted MC38 Mct4-KO tumors, generated a longer survival rate and a more potent cytotoxic intratumoral immune response then MC38 tumor bearing animals. Interestingly, Seahorse® analysis of tumor-infiltrating CD8 T cells from neoAg-mRNA vaccinated mice revealed that cytotoxic lymphocytes within the Mct4-KO TME displayed a modest increase in the maximal respiratory capacity and a significantly elevated spare respiratory capacity then lymphocyte isolated from MC38 tumors, indicating an enhancement of oxidative metabolic program and metabolic stress adaptions in Mct4-KO tumors with reduced lactate.
Conclusion: These findings provide valuable insights into optimizing mRNA vaccination by blocking the lactate transporter MCT4 in cancer cells for more efficient therapies for cancer patients.
