CABYR, a calcium-binding tyrosine phosphorylation regulated fibrous sheath protein, was initially reported to be testis-specific and subsequently shown to be present in brain tumors, pancreas cancer and lung cancer. This study aimed to investigate the expression and effects of the CABYR-c transcript of CABYR gene in hepatocellular carcinoma.

mRNA and protein expression of CABYR-c was examined in 20 paired hepatocellular carcinoma tissues and adjacent non-cancerous tissues by real-time quantitative RT-polymerase chain reaction (PCR) and western blot analysis respectively. HepG2 cells were treated with the antisense oligodeoxynucleotides targeting CABYR-c mRNA (CABYR-c antisense oligonucleotides [AS ODNs]) for indicated times, the AS ODNs inhibition effect was evaluated by measuring the CABYR-c mRNA expression level of HepG2 cells after treatment using real-time quantitative RT-PCR, then cell proliferation was studied using MTT assay, and cell cycle distribution and apoptosis were detected by flow cytometry as well.

CABYR-c mRNA levels in hepatocellular carcinoma tissues were significantly higher than that in the paired adjacent non-cancerous tissues (27.5 ± 1.2 versus 2.5 ± 0. 9, P<0.01). CABYR-c protein expression level in hepatocellular carcinoma tissues was also significantly higher than that in adjacent non-cancerous tissues. CABYR-c mRNA expression in HepG2 cells was most effective down-regulated after treatment of 600nM CABYR-c AS ODNs for 48h, which was selected for subsequent experiments. Incubation with 600nM CABYR-c AS ODNs inhibited the cell growth of HepG2 cells in a dose- and time-dependent manner. The maximum inhibitory effect achieved at 600nM after 72h treatment (30.92 ± 3.25%, P<0.01). HepG2 cells treated 600nM CABYR-c AS ODNs for 48h exhibited an increasing proportion of cells in G0/G1 phase (P<0.05) and a decreasing proportion of cells in S phase (P<0.05), compared with untreated controls. No obvious differences were observed in G2/M phase. The fraction of apoptotic HepG2 cells in CABYR-c AS ODNs treated group was less than that of untreated control group (P<0.05).

CABYR-c is highly expressed in hepatocellular carcinoma tissues and may play an oncogenic role in heptocarcinogenesis as well as its progression.