Mitochondria are highly dynamic and undergo constant fusion and fission that are essential for maintaining physiological functions of cells. Recently, we have reported that increased mitochondrial fission promotes autophagy and apoptosis resistance in hepatocellular carcinoma (HCC) cell through ROS-mediated coordinated regulation of NF-κB and p53 pathways. However, little is known about the roles of mitochondrial dynamics in HCC cell proliferation, another key feature of cancer cells. In this study, we systematically investigated the functional role of mitochondrial fission in the regulation of HCC cell proliferation. Furthermore, the underlying molecular mechanisms were deeply explored. We found that, increased mitochondrial fission by forced expression of Drp1 promoted the proliferation of HCC cells both in vitro and in vivo mainly by facilitating G1/S phase transition of cell cycle. Whereas, Drp1 knockdown or treatment with mitochondrial division inhibitor-1 induced significant G1 phase arrest in HCC cells and reduced tumor growth in the xenotransplantation model. We further demonstrated that the proliferation-promoting role of Drp1-mediated mitochondrial fission was mediated via p53/p21 and NF-κB/cyclins pathways. Moreover, the crosstalk between p53 and NF-κB pathways was proved to be involved in the regulation of mitochondrial fission-mediated cell proliferation. In conclusion, our findings demonstrate that Drp1-mediated mitochondrial fission plays a critical role in the regulation of cell cycle progression and HCC cell proliferation. Thus, targeting Drp1-dependent mitochondrial fission may provide a novel strategy for suppressing tumor growth of HCC.
Keywords: NF-κB; cell proliferation; liver cancer; mitochondrial dynamics; p53.