Expression of prostate cancer-associated transcript 6 in serum of patients with liver cancer and the effect of its interference on biological function of liver cancer cells

Objective To investigate the expression of prostate cancer-associated transcript 6 (PCAT6) in the serum of hepatocarcinoma patients and its effect on the proliferation, migration, invasion and apoptosis of Hep3B cells. Methods The qPCR method was used to detect the level of long non-coding RNA (lncRNA) PCAT6 in serum and THLE-3, Hep3B and HepG2 cells. The Hep3B cells were randomly divided into blank control group (NC group), negative empty vector transfection group (si-con group) and lncRNA PCAT6 silencing group (si-PCAT6 group). Western blotting was used to detect the expression of matrix metalloproteinase (MMP)-2, MMP-9, cleaved cysteinyl aspartate-specific protease (Caspase)-3, cleaved Caspase-9, phosphatidylinositol 3 kinase (PI3K), phosphorylated-PI3K (p-PI3K), protein kinase B (Akt), and phosphorylated Akt (p-Akt) proteins. The cell proliferation was measured by methyl thiazol tetrazolium (MTT) assay. The apoptosis was examined by flow cytometry, and the migration and invasion was tested detected by Transwell chamber method. The SPSS 21.0 software was used for statistical analysis, and the measurement data were expressed as mean±standard deviation (SD). Results The expression level of lncRNA PCAT6 in patients with moderate or high differentiation (60.94%) was significantly higher than that in patients with low differentiation (6.25%) (χ2=22.968, P<0.01). The percentage of patients with high expression of lncRNA PCAT6 in T-stage Ⅱ-Ⅳ (57.81%) was significantly higher than that in stage Ⅰ (9.38%) (χ2=8.529, P<0.01). The expression of lncRNA PCAT6 in Hep3B cells (3.72±0.67) and HepG2 cells (3.38±0.53) was significantly higher than that in THLE-3 cells (1.03±0.14) (t=9.322 and 8.144, P<0.05). The expression of lncRNA PCAT6 (0.21±0.11) in si-PCAT6 group was significantly lower than that in si-CON group (0.96±0.15) (t=9.915, P<0.05), and the cell viability was significantly reduced at 24 h, 48 h and 72 h (t=3.280, 6.144 and 6.373, P<0.05). Western blotting showed that the expression of cleaved Caspase-3, cleaved Caspase-9, p-pi3k and p-Akt increased significantly (t=11.408, 14.628, 8.683 and 9.585, P<0.01), and the expression of MMP-2 and MMP-9 decreased significantly in si-PCAT6 group (t=10.568 and 10.814, P<0.01). The apoptosis rate of Hep3B cells increased significantly (t=21.075, P<0.01), and the migration and invasion of Transwell cells decreased significantly (t=12.816 and 12.707, P<0.01). Conclusion The serum lncRNA PCAT6 is highly expressed in HCC patients, which is related to the degree of HCC differentiation and T stage. Silencing lncRNA PCAT6 can inhibit the biological behaviors of HCC probably by inhibiting the Akt signaling pathway activation. Key words: Long non-coding RNA; Prostate cancer-associated transcript 6; Liver cancer; Biological function