LncRNA CEBPA-DT promotes liver cancer metastasis through DDR2/β-catenin activation via interacting with hnRNPC

Hepatocellular carcinoma (HCC) is the world's third leading cause of cancer-related death; due to the fast growth and high prevalence of tumor recurrence, the prognosis of HCC patients remains dismal. Long non-coding RNA CEBPA-DT, a divergent transcript of the CCAAT Enhancer Binding Protein Alpha (CEBPA) gene, has been shown to participate in multiple tumor progression. However, no research has established its cancer-promoting mechanism in HCC yet.

CEBPA-DT was identified in human HCC tissues through RNA sequencing. The expression level of CEBPA-DT was assessed by quantitative real-time PCR. The biological effects of CEBPA-DT were evaluated in vitro and in vivo through gain or loss of function experiments. RNA fluorescence in situ hybridization (FISH), RNA immunoprecipitation (RIP) and RNA pull-down assays were applied to investigate the downstream target of CEBPA-DT. Immunofluorescence, subcellular protein fractionation, western blot, and co-immunoprecipitation were performed to analyze the subcellular location of β-catenin and its interaction with Discoidin domain-containing receptor 2 (DDR2).

CEBPA-DT was upregulated in human HCC tissues with postoperative distant metastasis and intimately related to the worse prognosis of HCC patients. Silencing of CEBPA-DT inhibited the growth, migration and invasion of hepatoma cells in vitro and in vivo, while enhancement of CEBPA-DT played a contrasting role. Mechanistic investigations demonstrated that CEBPA-DT could bind to heterogeneous nuclear ribonucleoprotein C (hnRNPC), which facilitated cytoplasmic translocation of hnRNPC, enhanced the interaction between hnRNPC and DDR2 mRNA, subsequently promoted the expression of DDR2. Meanwhile, CEBPA-DT induced epithelial-mesenchymal transition (EMT) process through upregulation of Snail1 via facilitating nuclear translocation of β-catenin. Using DDR2 inhibitor, we revealed that the CEBPA-DT induced the interaction between DDR2 and β-catenin, thus promoting the nuclear translocation of β-catenin to activate transcription of Snail1, contributing to EMT and HCC metastasis.

Our results suggested that CEBPA-DT promoted HCC metastasis through DDR2/β-catenin mediated activation of Snail1 via interaction with hnRNPC, indicating that the CEBPA-DT-hnRNPC-DDR2/β-catenin axis may be used as a potential therapeutic target for HCC treatment.