SIMULTANEOUS INHIBITION OF MTORC1 AND PPARG REPROGRAMS MYELOID CELL DIFFERENTIATION IN THE TUMOR MICROENVIRONMENT OF MOUSE B16 MELANOMA-BEARING MICE

BOGADO, MELISA; BLEICHMAR, LUCÍA; MAZZITELLI, IGNACIO; RIVELLI, FEDERICO; MAZZITELLI, BIANCA; DALOTTO MORENO, TOMÁS; RABINOVICH, GABRIEL A.; GEFFNER, JORGE; ERRA DIAZ, FERNANDO

Congreso; Reunion Anual Sociedad Argentina Inmunologia 2023; 2023

Monocytes are highly plastic cells that can differentiate into either macrophages (Mo-Macs) or dendritic cells (Mo-DCs). In the tumor microenvironment, monocytes are the major precursor of tumor-associated macrophages (TAMs), which are known for their ability to promote tumor growth, angiogenesis, invasion, and metastasis. Therefore, the proportion of TAMs in solid tumors is generally associated with tumor progression and poor prognosis. We have previously reported that simultaneous pharmacological inhibition of mTORC1 (Temsirolimus) and PPARg (GW9662) in human monocytes exposed to GM-CSF switches their differentiation from Mo-Macs into highly immunogenic Mo-DCs. Considering these observations, we hypothesized that pharmacological inhibition of these metabolic pathways in vivo might reduce TAM infiltration and enhance Mo-DC differentiation in tumor-bearing mice. To test this hypothesis, C57BL/6 mice were subcutaneously injected with 3x105 B16 melanoma cells and, after 6 days, randomized to receive daily intraperitoneal injections of: a) saline (Control), b) GM-CSF 0,5 ug (GM), c) Temsirolimus (1mg/kg) plus GW9662 (1mg/kg) (TGW) or d) GM-CSF plus Temsirolimus plus GW9662 (GMTGW) (n=3-5 per group). On day 12 of the experiment, mice were euthanized to analyze the tumor immune cell infiltrate by FACS. We observed that mice treated with the drug combination, either in the absence or presence of GM-CSF, had smaller tumors compared to control mice, albeit not reaching statistical significance when comparing each group individually to untreated mice (Control = 879 ± 422, GM = 646 ± 218, TGW = 282 ± 84, GMTGW = 263 ± 47 mm3; mean ± SEM). However, statistical significance was achieved when comparing mice that received the drug combination, regardless of GM-CSF treatment, vs. untreated or GM-CSF treated mice (p=0.02). Tumors were then surgically removed and minced according to standard protocols to generate singlecell suspensions for FACS analysis. We found that mice treated with the combination of Temsirolimus and GW9662, whether or not they received GMCSF, had a lower proportion of F480+ TAMs among tumor-infiltrating CD11b+ myeloid mononuclear cells (p