SIMULTANEOUS INHIBITION OF MTORC1 AND PPAR GAMMA DRIVES THE DIFFERENTIATION OF HUMAN MONOCYTES INTO IMMUNOGENIC DENDRITIC CELLS

DIAZ, FERNANDO ERRA; BLEICHMAR, LUCÍA; MAZZITELLI, I.; MELUCCI GANZARAIN, CLAUDIA; THIBODEAU, ASA; MARCHES, RADU; DALOTTO MORENO, TOMÁS; RABINOVICH, GABRIEL A.; UCAR, DUYGU; GEFFNER, JORGE

San Luis

Congreso; Reunion Anual Sociedad Argentina Inmunologia 2023; 2023

Monocytes are characterized by remarkable plasticity and can differentiate into macrophages (Mo-Macs) or dendritic cells (Mo-DCs). The mechanisms underlying this cell fate decision are still poorly understood. However, by culturing monocytes in the presence of GM-CSF + IL-4, large numbers of Mo-DCs can be generated in vitro (GMIL4 Mo-DCs) . Despite significant differences between these cells and DCs found in vivo, this remains the most widely used method to study human DC biology and to obtain DCs for use in the context of vaccines. We report that pharmacological inhibition of mTORC1 (Temsirolimus) or PPARγ (GW9662), in the presence of GM-CSF and in the absence of IL-4, induces differentiation of human monocytes into Mo-DCs in vitro. Moreover, compared to GMIL4 Mo-DCs, we observed that concomitant inhibition of mTORC1 and PPARγ pathways induced the differentiation of Mo-DCs with remarkable phenotypic stability, a stronger immunogenic profile and a higher capacity to induce the expansion of antigen-specific CD8 T cells (GMTGW Mo-DCs). Bulk RNAseq of monocytes undergoing differentiation (8h culture) and sorted Mo-DCs, revealed different transcriptional profiles between GMIL4 and GMTGW Mo-DCs, suggesting distinct differentiation pathways and cell identities. In this scenario, PCA analysis of the transcriptional profiles showed that GMTGW Mo-DCs have greater similarity to blood and tumor-associated cDC2 cells than GMIL4-Mo DCs. In addition, GMTGW-Mo DCs exhibit a strong type I interferon signature and lower expression of several inhibitory ligands and receptors, including PD-L1, and significant Langerin (CD207) expression in a subpopulation of cells compared to GMIL4-Mo DCs. In summary, we here describe a previously uncharacterized differentiation pathway that induces the generation of Mo-DCs, with potential implications for DC vaccination and cancer immunotherapy.