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 μL, 2.5×10⁷/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 μmol/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.