RPL6 Interacts with HMGCS1 to Stabilize HIF-1α by Promoting Cholesterol Production in Hepatocellular Carcinoma

The identification of predictive markers to determine the premetastatic phase before metastasis is critical for developing effective strategies for early detection and prevention. By applying the dynamic network biomarker (DNB) approach to analyze time-series transcriptomic data from a pulmonary metastasis HCC mouse model, it is revealed that the premetastatic phase occurred during the fourth week after implantation. A total of 142 DNB genes are identified as functionally important biomarkers for HCC metastasis, among which 60S ribosomal protein L6 (RPL6) is a core DNB member. RPL6 is significantly upregulated in HCC tissues with extrahepatic metastasis and is strongly correlated with poor prognosis in HCC patients. RPL6 promotes the invasion and metastasis of HCC cells, both in vitro and in vivo. Mechanistically, RPL6 directly binds to the HMGCS1 mRNA 3'UTR, a rate-limiting enzyme in cholesterol biosynthesis, thus increasing HMGCS1 mRNA stability and protein expression and subsequently elevating intracellular cholesterol level. Elevated cholesterol inhibits the ubiquitin-dependent degradation of HIF-1α, which further results in activation of HIF-1α signaling pathway. Together, this study provides new insights into the dynamic transcriptome profiles of HCC pulmonary metastasis and establishes an important role for the RPL6-HMGCS1-HIF-1α axis in HCC metastasis, suggesting potential prognostic biomarkers and therapeutic targets in HCC.