Downregulation of MCT1 inhibits tumor growth, metastasis and enhances chemotherapeutic efficacy in osteosarcoma through regulation of the NF-κB pathway.

Monocarboxylate transporter isoform 1 (MCT1) is an important member of the proton-linked MCT family and has been reported in an array of human cancer cell lines and primary human tumors. MCT1 expression is associated with developing a new therapeutic approach for cancer. In this study, we initially showed that MCT1 is expressed in a variety of human osteosarcoma cell lines. Moreover, we evaluated the therapeutic response of targeting MCT1 using shRNA or MCT1 inhibitor. Inhibiting MCT1 delayed tumor growth in vitro and in vivo, including in an orthotopic model of osteosarcoma. Targeting MCT1 greatly enhanced the sensitivity of human osteosarcoma cells to the chemotherapeutic drugs adriamycin (ADM). In addition, we observed that MCT1 knockdown significantly suppressed the metastatic activity of osteosarcoma, including wound healing, invasion and migration. Further mechanistic studies revealed that the antitumor effects of targeting MCT1 might be related to the NF-κB pathway. Immunochemistry assay showed that MCT1 was an independent positive prognostic marker in osteosarcoma patients. In conclusion, our data, for the first time, demonstrate that MCT1 inhibition has antitumor potential which is associated with the NF-κB pathway, and high MCT1 expression predicates poor overall survival in patients with osteosarcoma.