Role of serine-threonine kinase receptor-related protein in the biological function of hepatocellular carcinoma cells

Objective To detect the expression of serine-threonine kinase receptor-related protein (STRAP) in hepatocellular carcinoma (HCC) cells and normal liver tissues, and to explore its biological functions. Methods The relative expression levels of STRAP in 10 HCC cell lines and normal liver tissues were detected, and STRAP overexpression and knockdown cell lines were constructed in HepG2 and SNU449, respectively. The real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) and Western blotting were used to determine the expression of STRAP after the construction of cell lines. The migration and invasion ability of HCC cells was detected by Transwell chamber and Transwell chamber containing Matrigel. Cell proliferation was examined by cell counting kit-8 (CCK-8) and cell clone formation assay, and cell apoptosis was verified by flow cytometry. Results The expression level of STRAP in HCC cell lines was significantly higher than that in normal liver tissues. After STRAP knockdown, the relative expression of mRNA in knockdown group and control group was (0.17±0.19) and (2.22±1.02), respectively. The expression level of the knockdown group was significantly lower than that in the control group (P<0.05), while overexpressing STRAP, the relative expression levels of mRNA in overexpression group and control group were (3.25±0.39) and (1.05±0.37) (P<0.01). After the STRAP gene knockdown, the number of cell clones in control group and knockdown group was (221.30±9.60) and (58.30±4.49) respectively. The number of cells passing through the membrane in control group and knockdown group was (0.76±0.04) and (0.44±0.06) in cell migration assay, and (1.11±0.05) and (0.60±0.05) in cell invasion assay, respectively. In the cell proliferation assay, the number of cell proliferation in the knockdown group decreased as compared with that in the control group at 72, 96 and 120 h. The apoptosis rate in the control group and knockdown group was (4.11±0.12) and (11.73±0.40), respectively. The colony forming ability, migration invasive ability and proliferation ability of SNU449 were significantly inhibited (P<0.05), while the apoptosis was significantly increased (P<0.01). After overexpression of SRTAP gene, the proliferation of HepG2 cells increased at 48, 72, 96 and 120 h as compared with the control group (P<0.001). The cell proliferation assay indicated that the apoptosis rate in the control group and overexpression group was (8.87±0.12) and (8.34±0.06) respectively (P<0.05). Conclusion STRAP is highly expressed in HCC cells, and promotes proliferation, enhances migration and invasion, and inhibits apoptosis of HCC cells. Key words: Carcinoma, hepatocellular; Serine-threonine kinase receptor-related protein; Proliferation; Apoptosis; Metastasis