Abstract:

Objective To investigate the molecular mechanism of SUMO specific protease 1 (SENP1) regulating endoplasmic reticulum stress transcription regulator X-box binding protein 1 (XBP1) in the proliferation of liver cancer cells. Methods The pathological samples of 180 patients with primary liver cancer in the Department of Hepatobiliary Surgery of Inner Mongolia People's Hospital from January 2012 to January 2020 were collected. The expressions of SENP1 and XBP1 in liver cancer, adjacent tissues and different liver cancer cell lines were detected. The correlation between SENP1 positive expression and clinicopathological features of liver cancer patients was analyzed. Immunofluorescence and flow cytometry were used to detect the effect of SENP1 siRNA on XBP1 and apoptosis. SUMO1 expression on XBP1 surface was detected and the effect of SENP1 siRNA on SUMO formation of XBP1 was detected by immunoprecipitation. Results The expression levels of SENP1 in liver cancer and adjacent tissues were 16.332±4.371 and 6.840±2.238, with a statistically significant difference (t=-5.073, P=0.017). The expression levels of XBP1 in liver cancer and adjacent tissues were 6.641±2.482 and 16.051±4.452, with a statistically significant difference (t=3.592, P=0.032). The expression of SENP1 was correlated with stage (χ²=6.724, P=0.010) and metastasis (χ²=6.265, P=0.012). Immunofluorescence staining showed that the expressions of XBP1 in L02 (0.509±0.219), MHCC97-L (0.092±0.022) and HCCLM3 (0.086±0.014) cells were significantly different (F=6.378, P=0.004), while the expression of XBP1 in MHCC97-L and HCCLM3 cells was significantly lower than that in L02 cells (P=0.023; P=0.021). The expression levels of SENP1 in L02, MHCC97-L and HCCLM3 cells were 0.109±0.079, 0.802±0.392 and 0.921±0.352, with a statistically significant difference (F=7.783, P=0.004), while the expression level of SENP1 in MHCC97-L and HCCLM3 cells was significantly higher than that in L02 cells (P=0.039; P=0.016). After transfection of SENP1 siRNA into MHCC97-L and HCCLM3 cells, the expressions of XBP1 increased (0.462±0.192, t=3.664, P=0.022; 0.524±0.203, t=3.383, P=0.028); the expressions of SENP1 decreased (0.153±0.093, t=2.790, P=0.049; 0.165±0.104, t=3.568, P=0.023). The results of flow cytometry showed that the apoptosis rates of L02, MHCC97-L, HCCLM3, MHCC97-L+SENP1 siRNA and HCCLM3+SENP1 siRNA cells were (20.80±3.11)%, (2.02±1.20)%, (0.12±0.01)%, (7.01±1.80)%, (6.20±2.01)%, with a statistically significant difference (F=1.025, P=0.030). The apoptosis rate of MHCC97-L and HCCLM3 cells was significantly lower than that of L02 cells (P=0.040; P=0.010), the apoptosis rate of MHCC97-L+SENP1 siRNA and HCCLM3+SENP1 siRNA cells was significantly higher than that of MHCC97-L and HCCLM3 cells (both P=0.009). Immunoprecipitation results showed that the expression levels of XBP1 in L02, MHCC97-L, HCCLM3, MHCC97-L+SENP1 siRNA, HCCLM3+SENP1 siRNA cells were 11.943±5.043, 7.467±1.903, 2.051±0.913, 9.532±3.012, 8.731±3.102, and SUMO1 expression levels were 10.158±4.005, 5.871±3.075, 1.941± 0.907, 8.658±4.878, 7.169±4.677, and the differences were statistically significant (F=11.730, P=0.010; F=8.548, P=0.001). The expressions of XBP1 and SUMO1 in MHCC97-L (P=0.028; P=0.038) and HCCLM3 (P<0.001; P<0.001) cells were lower than those in L02 cells, XBP1 expression in HCCLM3+SENP1 siRNA cells was higher than that in HCCLM3 cells (P=0.001), and SUMO1 expression in MHCC97-L+SENP1 siRNA cells and HCCLM3+SENP1 siRNA cells respectively was higher than that in MHCC97-L (P=0.045) and HCCLM3 (P=0.039) cells. Conclusion SENP1 siRNA can promote the apoptosis of liver cancer cells by up regulating SUMO modification of XBP1.

Key words: Liver neoplasms, Apoptosis, XBP1, SUMO