Opioid growth factor receptor overexpression exerts anti-hepatocellular carcinoma effects by activating P16 and P21 to inhibit proliferation and migration of HepG2 cells

Introduction. Hepatocellular carcinoma (HCC) is the sixth most common type of cancer and the second leading cause of cancer death worldwide [19]. Opioid growth factor (OGF) has been shown to exhibit antitumour potential, binding to OGF receptor (OGFr). Naltrexone (NTX), an OGFr antagonist, is considered as a potential anti-cancer agent. However, the specific mechanism of how OGFr acts on HCC cells is yet to be elucidated. Materials and methods. HepG2 cells were inoculated into subcutaneous areas of nude mice's back (200 mu L, 2.5x107/mL) to establish HCC in vivo models. HepG2 cells were transfected with lentiviral plasmids containing short hairpin RNA (shRNA) targeting OGFr (sh-OGFr) or negative control shRNA (sh-NC), and OGFr over-expression (OE-OGFr) or over-expression negative control (OE-NC) plasmids. Subsequently, male BALB/c nude mice were randomized into Control, sh-NC, sh-OGFr, OE-NC, and OE-OGFr groups (n = 6). Tumour size was measured weekly for four weeks, TUNEL staining for apoptosis, and immunohistochemistry were performed. In vitro, HepG2 cells were randomized into OE-NC, OE-OGFr, and OE-OGFr+NTX (100 mu mol/L) groups, and sh-NC, sh-OGFr, sh-OGFr+sh-P21, and sh-OGFr+sh-P16 groups. Cell viability by CCK8 assay, cell proliferation by EDU staining, cell migration by cell scratch, and Western blot were performed. Results. In vivo, sh-OGFr-transfected HepG2 cells increased tumour weight, volume, and Ki67 expression, decreased P21 and P16 expression, and did not affect apoptosis rate. The effect of OE-OGFr in HepG2 cells was completely the opposite. In vitro, OE-OGFr inhibited HepG2 cells' viability, proliferation, and migration, and further NTX intervention reversed its inhibitory effects. The transfection of HepG2 cells with sh-OGFr+sh-P21 and sh-OGFr+sh-P16 further enhanced the cell proliferation and migration abilities compared to the sh-OGFr group. Conclusions. OGFr overexpression may inhibit HCC progression by activating P16 and P21 expression to inhibit cell proliferation and migration, thereby providing new potential targets for HCC treatment.