TSPO is a novel biomarker for prognosis that regulates cell proliferation through influencing mitochondrial functions in HCC.

The disorder of mitochondrial functions plays a key role in oncogenesis. It is known that TSPO (18-kDa translocator protein) lies in a peculiar location at the interface between the mitochondria and the cytosol. TSPO is found in many types of tissues and is associated with multiple cellular processes, including apoptosis, cell proliferation and the regulation of mitochondria. However, the involvement of TSPO in hepatocellular carcinoma (HCC) remains unclear. In this study, we found that TSPO is upregulated in HCC tissue and is associated with poor differentiation and poor survival. Multivariate analyses showed that TSPO was an independent predictive factor for poor prognosis in HCC patients. For the first time, we provided evidence that TSPO knockdown suppressed HCC cell proliferation in vitro. Hence, TSPO knockdown-induced apoptosis by disturbing mitochondrial function by enhancing the formation of reactive oxygen species (ROS) and decreasing the mitochondrial membrane potential (ΔΨm). An assay exploring the underlying mechanism revealed that TSPO knockdown modulated apoptotic regulatory proteins by regulating the ERK signaling pathway. Through a functional assay and an in vivo mouse model, the anti-cancer effect of PK11195, a specific ligand of TSPO, on HCC was revealed. In summary, TSPO may potentially serve as a prognostic biomarker, and TSPO might be a potential therapeutic target for HCC.