HIF-1α and RACGAP1 promote the progression of hepatocellular carcinoma in a mutually regulatory way

Hypoxia, a condition characterized by low oxygen levels, serves an important role in the progression of hepatocellular carcinoma (HCC). However, the precise molecular mechanisms underlying hypoxia-induced HCC progression are yet to be fully elucidated. The present study assessed the involvement of two key factors, hypoxia-inducible factor-1 alpha (HIF-1 alpha) and Rac GTPase activating protein 1 (RACGAP1), in HCC development under hypoxic conditions. HIF-1 alpha and RACGAP1 genes were overexpressed and knocked down in Hep3B and Huh7 cells using lentiviral transduction and the levels of HIF-1 alpha and RACGAP1 in the cells were assessed using quantitative PCR, western blotting and immunofluorescence. Co-immunoprecipitation experiments were performed to evaluate the interaction between HIF-1 alpha and RACGAP1. Subsequently, the proliferation, apoptosis, migration and invasion of Hep3B and Huh7 cells were assessed using the Cell Counting Kit-8 assay, flow cytometry, Transwell assay and migration experiments. The expression levels of HIF-1 alpha and RACGAP1 in normal and HCC tumor samples were analyzed utilizing the Gene Expression Profiling Interactive Analysis database. Furthermore, correlations between HIF-1 alpha/RACGAP1 gene expression levels and patient survival outcomes were evaluated using the Kaplan-Meier plotter. Knockdown of HIF-1 alpha resulted in a significant decrease in RACGAP1 expression, whilst overexpression of HIF-1 alpha resulted in a significant increase in RACGAP1 expression. Moreover, overexpression and knockdown of RACGAP1 had the same effect on HIF-1 alpha expression. Additionally, it was demonstrated that HIF-1 alpha and RACGAP1 interacted directly within a complex. Overexpression of HIF-1 alpha or RACGAP1 significantly increased proliferation, invasion and migration, and significantly decreased the proportion of apoptotic Hep3B and Huh7 cells. Conversely, knockdown of HIF-1 alpha or RACGAP1 significantly decreased proliferation, invasion and migration, and significantly increased the proportion of apoptotic Hep3B and Huh7 cells. In addition, the combined knockdown or overexpression of HIF-1 alpha and RACGAP1 had a more pronounced effect on HCC cell migration compared with knockdown of HIF-1 alpha alone. Furthermore, there was a significant positive correlation between the expression levels of HIF-1 alpha and RACGAP1 in HCC tissues and patients with HCC and upregulation of both HIF-1 alpha and RACGAP1 demonstrated a lower overall survival probability. In conclusion, HIF-1 alpha and RACGAP1 may synergistically contribute to the development of HCC, highlighting their potential as valuable targets for HCC therapy.