Papel de los macrófagos en la funcionalidad de las terapias celulares adoptivas basadas en CAR T (linfocitos T con receptor de antígeno quimérico) en osteosarcoma

Osteosarcoma is a rare disease that mainly affects children, adolescents, and young people. It can develop in any bone, but the most common ones affected are the proximal humerus and the knees. Nowadays, treatment consists of chemotherapy and surgery. Despite the improvement in the patient’s survival, the 5-year event-free survival remains less than 20% in those with aggressive osteosarcoma. The lack of response in metastatic tumours is the reason why new strategies are needed. In this context, the use of T cells expressing chimeric antigen receptors (CAR T) has shown positive results in the treatment of haematological cancers, such as leukaemia or lymphomas. Nonetheless, the application of this therapy in the treatment of solid tumours, like osteosarcoma, must face some challenges due to the nature of this tumours: the homing of CAR T cells to the tumour, the antigen heterogeneity of solid tumours and the tumour microenvironment. In order to improve the outcome of patients, we need to solve the problems that these obstacles pose to us. The tumour microenvironment is mainly composed of tumour associated macrophages (TAMs), which are involved in numerous immunosuppressive pathways. This tumoral microenvironment (TME) decreases the efficacy of CAR T cell therapy. It was, therefore, the main aim of this work to study the role that macrophages have in the functionality of the CAR T cell therapy by developing an in vitro model. To achieve this goal, peripheral blood-derived human monocytes were isolated and differentiated to M1 and M2 macrophages. They were then cocultured with osteosarcoma cells and CAR T to study their interactions. A successful polarization of the macrophages was achieved. It has been found that M2 macrophages inhibit CAR T’s cytotoxic activity in the short term and M1 macrophages improve their functionality. However, as coculture time progresses, the expression of M1 markers increases in M2 macrophages losing their immunosuppressive potential. This indicates a possible change in phenotype from M2 macrophages to M1 macrophages, improving the activity of CAR T. In conclusion, this study suggests that the phenotype reversal from M2 macrophages to a M1 type macrophage would improve the results of this therapy in the treatment of osteosarcoma. However, further studies are needed to confirm these effects.