HSP4 triggers epithelial-mesenchymal transition and promotes motility capacities of hepatocellular carcinoma cells via activating AKT

Background and aims: Heat shock factor (HSF4) plays a vital role in carcinogenesis and tumour progression. However, its clinical significance implications in hepatocellular carcinoma (HCC) remained elusive.

Methods: RT-PCR and western blot were used to detect the HSF4 expression levels in HCC cells and tissues. Immunohistochemistry staining was performed on a tissue microarray containing 104 HCC patients received radical resection. In vitro effects of HSF4 on proliferation, migration and invasion were determined by colony formation and transwell assays in HCCLM3, Huh7, MHCC97L and SMMC7721 cells. Epithelial-mesenchymal transition (EMT) was identified by RT-PCR, WB and immunofluorescence in HCCLM3 and MHCC97L cells. AKT pathway activation was detected by WB and dual luciferase report system in HCCLM3 and MHCC97L cells.

Results: HSF4 expression was higher in primary HCC tissues derived from recurrent patients, and positively correlated with invasiveness potentials of cell lines. Clinically, patients with high HSF4 expression had significant poorer prognosis. In vitro experiments showed HSF4 silencing inhibited HCC cell proliferation, migration and invasion, whereas HSF4 overexpression had inverse effects. Moreover, silence of HSF4 induced an epithelial-like phenotype, whereas the overexpression of HSF4 resulted in a mesenchymal-like phenotype in HCC by activating AKT pathway. Further experiments showed that HSF4 could activate AKT pathway in a hypoxia-inducible factor-1α (HIF-1α) dependent, but transforming growth factor-β (TGF-β) independent manner.

Conclusions: HSF4 is upregulated in HCC, resulting in greater proliferation, migration and invasion capacities. Moreover, high HSF4 expression is a promising predictive indicator of poor outcome after radical resection. HSF4 may promote aggressive tumour behaviour by enhancing EMT through activating AKT pathway in a HIF1α-dependent manner.