Objective: Mesenchymal stem cells (MSCs) have prominent immunomodulatory roles in the tumor microenvironment. The current study intended to elucidate Treg subsets and their cytokines after exposing naïve T lymphocytes to adiposederived MSCs (ASCs).

Materials and methods: In this experimental study, to obtain ASCs, breast adipose tissues of a breast cancer patient and a normal individual were used. Magnetic cell sorting (MACS) was employed for purifying naïve CD4⁺ T cells from peripheral blood of five healthy donors. Naïve CD4⁺ T cells were then co-cultured with ASCs for five days. The phenotype of regulatory T cells (Tregs) and production of interleukine-10 (IL-10), transforming growth factor beta (TGF-β) and IL-17 were assessed using flow cytometry and ELISPOT assays, respectively.

Result: CD4⁺CD25^-FOXP3⁺CD45RA⁺ Tregs were expanded in the presence of cancer ASCs but CD4⁺CD25⁺Foxp3⁺CD45RA⁺ regulatory T cells were up-regulated in the presence of both cancer- and normal-ASCs. This up-regulation was statistically significant in breast cancer-ASCs compared to the cells cultured without ASCs (P=0.002). CD4⁺CD25⁺ FOXP3⁺Helios⁺, CD4⁺CD25^- FOXP3⁺Helios⁺ and CD25⁺ FOXP3⁺CD73⁺CD39⁺ Tregs were expanded after co-culturing of T cells with both cancer-ASCs and normal-ASCs, while they were statistically significant only in the presence of cancer-ASCs (P<0.05). Production of IL-10, IL-17 and TGF-β by T cells was increased in the presence of either normal- or cancer-ASCs; however, significant effect was only observed in the IL-10 and TGF-β of cancer-ASCs (P<0.05).

Conclusion: The results further confirm the immunosuppressive impacts of ASCs on T lymphocytes and direct them to specific regulatory phenotypes which may support immune evasion and tumor growth.