PDAC-derived exosomes enrich the microenvironment in MDSCs in a -dependent manner through a new calcium related axis.

Unlabelled: Tumor genetics and escape from immune surveillance concur in the poor prognosis of PDAC. In this study an experimental model was set up to verify whether , deleted in about 55% PDAC and associated with poor prognosis, is involved in determining immunosuppression through Exosomes (Exo). Potential mechanisms and mediators underlying -dependent immunosuppression were evaluated by studying intracellular calcium (Fluo-4), Exo-miRNAs (microarray) and Exo-proteins (SILAC). Two PDAC cell lines expressing (BxPC3-+) or not-expressing (BxPC3) were used to prepare Exo-enriched conditioned media, employed in experiments with blood donors PBMCs. Exo expanded myeloid derived suppressor cells (gMDSC and mMDSC, flow cytometry) and altered intracellular calcium fluxes in an dependent manner. BxPC3-+, but mainly BxPC3 Exo, increased calcium fluxes of PBMCs ( = 0.007) and this increased intracellular calcium trafficking characterized mMDSCs. The analysis of de-regulated Exo-miRNAs and transfection experiments revealed hsa-miR-494-3p and has-miR-1260a as potential mediators of associated de-regulated calcium fluxes. Eleven main biological processes were identified by the analysis of -associated de-regulated Exo-proteins, including translation, cell adhesion, cell signaling and glycolysis. A reverse Warburg effect was observed by treating PBMCs with PDAC-derived Exo: BxPC3 Exo induced a higher glucose consumption and lactate production than BxPC3-+ Exo.

Conclusion: PDAC-derived Exo from cells with but mainly from those without expression, create an immunosuppressive myeloid cell background by increasing calcium fluxes and glycolysis through the transfer of -related differentially expressed miRNAs and proteins.