Elafin promotes tumour metastasis and attenuates the anti-metastatic effects of erlotinib via binding to EGFR in hepatocellular carcinoma

Elafin is a serine protease inhibitor critical for host defence. We previously reported that Elafin was associated with the recurrence of early-stage hepatocellular carcinoma (HCC) after surgery. However, the exact role of Elafin in HCC remains obscure. HCC tissue microarrays were used to investigate the correlation between Elafin expression and the prognosis of HCC patients. In vitro migration, invasion and wound healing assays and in vivo lung metastasis models were used to determine the role of Elafin in HCC metastasis. Mass spectrometry, co-immunoprecipitation, western blotting, and immunofluorescence staining assays were performed to uncover the mechanism of Elafin in HCC. Dual-luciferase reporter and chromatin immunoprecipitation assays were employed to observe the transcriptional regulation of Elafin. Elafin expression was frequently increased in HCC tissues compared to normal tissues, and high Elafin expression in HCC tissues was correlated with aggressive tumour phenotypes and a poor prognosis in HCC patients. Elafin dramatically enhanced the metastasis of HCC cells both in vitro and in vivo by interacting with EGFR and activating EGFR/AKT signalling. Moreover, Elafin attenuated the suppressive effects of erlotinib on HCC metastasis. Besides, Elafin was transcriptionally regulated by Sp1 in HCC cells. Clinically, Elafin expression was positively correlated with Sp1, Vimentin, and EGFR signalling in both our HCC tissue microarrays and TCGA database analysis. Upregulation of Elafin by Sp1 enhanced HCC metastasis via EGFR/AKT pathway, and overexpression of Elafin attenuated the anti-metastatic effects of erlotinib, suggesting a valuable prognostic biomarker and therapeutic target for HCC.