Hyperthermia‐stimulated tonsil‐mesenchymal stromal cells suppress hematological cancer cells through downregulation of IL‐6

Abstract There are contradictory reports on the use of mesenchymal stromal cells (MSCs) in cancer therapy. Variable outcomes have been associated with several factors including cancer pathology, experimental procedure, MSC source tissue, and individual genetic differences. It is also known that MSCs exert their therapeutic effects with various paracrine factors released from these cells. The profiles of the factors released from MSCs are altered by heat shock, hypoxia, oxidative stress, starvation or various agents such as inflammatory cytokines, and their therapeutic potential is affected. In this study, the antitumor potential of conditioned media (CM), which contains paracrine factors, of mild hyperthermia‐stimulated mesenchymal stromal cells derived from lymphoid organ tonsil tissue (T‐MSC) was investigated in comparison with CM obtained from T‐MSCs grew under normal culture conditions. CM was obtained from T‐MSCs that were successfully isolated from palatine tonsil tissue and characterized. The cytotoxic effect of CM on the growth of hematological cancer cell lines at different concentrations (1:1 and 1:2) was demonstrated by methylthiazoldiphenyl‐tetrazolium bromide analysis. In addition, the apoptotic effect of T‐MSC‐CM treatment was evaluated on the cancer cells using Annexin‐V/PI detection method by flow cytometry. The pro/anti‐apoptotic and cytokine‐related gene expressions were also analyzed by real‐time polymerase chain reaction post T‐MSC‐CM treatment. In conclusion, we demonstrated that the factors released from hyperthermia‐stimulated T‐MSCs induced apoptosis in hematological cancer cell lines in a dose‐dependent manner. Importantly, our results at the transcriptional level support that the factors and cytokines released from hyperthermia‐stimulated T‐MSC may exert antitumoral effects in cancer cells by downregulation of IL‐6 that promotes tumorigenesis. These findings reveal that T‐MSC‐CM can be a powerful cell‐free therapeutical strategy for cancer therapy.