The homeostatic malfunction of a novel feedback pathway formed by IncRNA021545, miR-330-3p and epiregulin contributes in hepatocarcinoma progression via mediating epithelial-mesenchymal transition

A better understanding of tumor metastasis is urgently required for the treatment and prognosis of hepatocarcinoma patients. Current work contributes a novel ceRNA feedback regulation pathway composed of epiregulin (EREG), microRNA-330-3p (miR-330-3p) and long non-coding RNA 021545 (IncRNA021545) in regulating hepatocarcinoma malignancy via epithelial-mesenchymal transition (EMT) process. Closely correlated, the deficiencies of EREG and IncRNA021545 and the overexpression of miR-330-3p were involved in the clinical progression of hepatocarcinoma. In vitro results showed that 1) IncRNA021545 downregulation promoted, 2) miR-330-3p dysexpression positively correlated, and 3) EREG dysexpression reversely correlated with the migratory and invasive properties of hepatocarcinoma HCCLM3 and Huh7 cell lines. By directly binding to EREG and IncRNA021545, miR-330-3p expression change reversely correlated with their expressions in HCCLM3 and Huh7 cells, which was also confirmed in primary tumors from HCCLM3-xenograft mice in responding to miR-330-3p change. LncRNA021545 and EREG positively regulated each other, and IncRNA021545 negatively regulated miR-330-3p, while, EREG dysregulation unchanged miR-330-3p expression in hepatocarcinoma cells. Furthermore, systemic in vitro cellular characterizations showed that the malfunctions of the three molecules mediated the invasiveness of hepatocarcinoma cells via EMT process through affecting the expressions of E-cadherin, N-cadherin, vimentin, snail and slug, which was further confirmed by in vivo miR-330-3p promotion on the tumorigenicity and metastasis of HCCLM3 bearing nude mice and by in vitro miR-330-3p promotion on the migration and invasion of hepatocarcinoma cells to be antagonized by EREG overexpression through acting on EMT process. Our work indicates, that by forming a circuit signaling feedback pathway, the homeostatic expressions of IncRNA021545, miR-330-3p and EREG are important in liver health. Its collapse resulted from the downregulations of IncRNA021545 and EREG together with miR-330-3p over-expression promote hepatocarcinoma progression by enhancing the invasiveness of tumor cells through EMT activation. These discoveries suggest that miR-330-3p/IncRNA021545/EREG axis plays a critical role in hepatocarcinoma progression and as a candidate for its treatment.