Inhibition of mu-opioid receptor suppresses proliferation of hepatocellular carcinoma cells via CD147-p53-MAPK cascade signaling pathway.

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related deaths. Previous studies have suggested that mu-opioid receptor (MOR), a member of the opioid receptor family, is involved in the pathogenesis of HCC. However, the mechanism by which MOR regulates the biological behavior of HCC is still poorly understood. To address this problem, in this study, we investigated the role of MOR in the proliferation of HCC cell lines and the underlying mechanism. First, RT-PCR, western-blot and immunohistochemistry revealed higher expression of MOR in HCC cells and tissue than in non-tumor cells or adjacent tissue, and elevated expression of MOR was associated with jeopardized survival of HCC patients, as demonstrated by bioinformatic databases. Knockdown of MOR by specific siRNA attenuated the proliferation and migration of HCC cells and this effect could be reversed by rescue experiments, confirming the essential role of MOR in the proliferation of HCC. Moreover, results of colony formation assay, CCK8 test, flow cytometry and western blot suggested that a monoclonal antibody (mAb) specifically against MOR could inhibit proliferation of HepG2 and Huh7 cells via the MOR-CD147-p53-MAPK pathway, and the interaction between MOR and CD147 was verified by immunofluorescence colocalization and co-IP analysis. The mAb against MOR also enhanced the cisplatin-induced apoptosis of HCC cells by downregulating p-ERK, Bcl-2 and upregulating Bax. Taken together, these results suggest that MOR could regulate the proliferation of HCC cells in a CD147-p53-MAPK dependent manner. MOR possesses the potential to be a therapeutic target to treat HCC.