The advanced hepatocellular carcinoma (HCC), such as the recurrent tumor after liver transplantation (LT), is an obstacle of HCC treatment. The aim of this study was to discover the underlying mechanism of HCC progression caused by non-coding RNAs (ncRNAs).
To this end, we investigated the selected patient cohort of matching primary and recurrent HCC after receiving LT. The recurrent tumors after LT were regarded as clinical models of the advanced HCC. Microarrays were used to profile lncRNA and mRNA expression in HCC recurrent and primary tissue samples. The mRNA profile characteristics were analyzed by bioinformatics. Two cell lines, HepG2 and QGY-7703, were used as HCC cell models. The protein-coding potential, length, and subcellular location of the interested lncRNAs were examined by bioinformatics, Northern blot, fluorescent in situ hybridization (FISH), and quantitative RT-PCR (qRT-PCR) assays. HCC cell proliferation was detected by CCK-8, doubling time and proliferation marker gene quantitation assays. DNA replication during the cell cycle was measured by EdU/PI staining and flow cytometry analyses. Promoter activity was measured using a luciferase reporter assay. Interactions between DNA, RNA, and protein were examined by immunoprecipitation and pull-down assays. The miRNA-target regulation was validated by a fluorescent reporter assay.
Both lncRNA and mRNA profiles exhibited characteristic alterations in the recurrent tumor cells compared with the primary HCC. The mRNA profile in the HCC recurrent tissues, which served as model of advanced HCC, showed an aberrant cell cycle regulation. Two lncRNAs, the highly expressed lncRNA in recurrent HCC (HERH)-1 and HERH-4, were upregulated in the advanced HCC cells. HERH-1/4 enhanced proliferation and promoted DNA replication and G1-S transition during the cell cycle in HCC cells. HERH-1 interacted with the transcription factor CREB1. CREB1 enhanced cyclin A2 (CCNA2) transcription, depending on HERH-1-CREB1 interaction. HERH-4 acted as an miR-29b/c sponge to facilitate CCNA2 protein translation through a competing endogenous RNA (ceRNA) pathway.
The oncogenic lncRNA HERH-1/4 promoted CCNA2 expression at the transcriptional and post-transcriptional levels and accelerated cell cycle progression in HCC cells. The HERH-1-CREB1-CCNA2 and HERH-4-miR-29b/c-CCNA2 axes served as molecular stimuli for HCC advance.