Decreased MACC1 expression in osteosarcoma cells reverses the decline of dendritic cells activation and the cytotoxicity

Objective: Metastasis-associated in colon cancer-1 (MACC1), a novel protein highly expressed in a variety of cancers, is closely related to tumor progression, metastasis and prognosis. Dendritic cells (DCs) can be activated by exogenous tumor antigens to kill tumor cells directly. The purpose of this study was to investigate the effect of MACC1 in osteosarcoma cells on DCs activation and cytotoxicity. Methods: MACC1 gene expression was determined by RT-qPCR in four osteosarcoma cell lines, in which 143B cells expressed the highest level of MACC1, and were selected as the target cell line. By lentivirus infection generating MACC1 shRNA, MACC1 was knocked downed in 143B cells (143B-i cells). Human DCs, isolated from PBMCs, were divided into four groups: i) control group (no stimulation); ii) DCs group (with stimulation); iii) DCs/143B group (DCs and 143B cells were co-cultured); and iv) DCs/143B group (DCs and 143B-i cells were co-cultured). Results: Co-culture of DCs with 143B cells inhibited DCs activation and decreased DCs induced cytotoxity as evidenced by reduced DCs activation markers expression, IL-12 secretion and LDH release. However, MACC1 knockdown reversed the above-mentioned effects. Furthermore, the immunofluorescence indicating the endocytosis of 143B cell fragments into DCs was decreased by MACC1 knockdown. Conclusion: This study suggests the recovered activation and cytotoxicity of DCs by MACC1 knockdown in osteosarcoma cells.