Impact of Taurine on the proliferation and apoptosis of human cervical carcinoma cells and its mechanism

Abstract

Background: Cervical cancer has the fourth highest incidence and mortality rate of all cancers in women worldwide; it seriously harms their physical and mental health. The aim of this study was to observe the roles and preliminary mechanism of Taurine (Tau)-induced apoptosis in cervical cancer cells.

Methods: Cells from the human cervical cancer cell line SiHa were transfected with the recombinant plasmid pEGFP-N1-MST1 (mammalian sterile 20-like kinase 1); then, the cell proliferation activity was analyzed by the MTT assay, cell apoptosis by flow cytometry, and the related protein levels by Western blotting.

Results: Tau inhibited the proliferation of SiHa cells and induced apoptosis in these cells (the apoptotic rate was 21.95% in the Tau 160 mmol/L group and 30% in the Tau 320 mmol/L group), upregulated the expression of the MST1 (control, 0.53; Tau 40-320 mmol/L groups, 0.84-1.45) and Bax (control, 0.45; Tau 40-320 mmol/L groups, 0.64-1.51) proteins (P < 0.01), and downregulated the expression of Bcl-2 (control, 1.28, Tau 40-320 mmol/L groups, 0.93-0.47) (P < 0.01). The overexpression of MST1 promoted the apoptosis of SiHa cells, enhanced the apoptosis-inductive effects of Tau (P < 0.01), upregulated the expression of the proapoptotic proteins p73, p53, PUMA (p53 upregulated modulator of apoptosis), and caspase-3, and promoted the phosphorylation of YAP (Yes-associated protein).

Conclusions: Tau inhibited the proliferation and induced the apoptosis of cervical cancer SiHa cells. The MST1 protein plays an important role in the Tau-induced apoptosis of cervical cancer cells.

Figure 1

Inhibition of Tau on the proliferation of cervical cancer cells. ^∗P < 0.05 vs. Control group, ^†P < 0.01 vs. Control group.

Figure 2

Effects of Tau on the apoptosis of cervical cancer cells. The SiHa cells were treated by Tau with different concentrations 0 (control), 20, 40, 80, 160, 320 mmol/L Tau, and 20 μmmol/L DDP for 48 h, and the apoptosis of SiHa cells was detected by the Annexin-V-FITC/PI double staining method. DDP is the positive control. ^∗P < 0.01 vs. the Control group.

Figure 3

Effects of taurine on the expressions of MST1, Bax, and Bcl-2 protein in cervical cancer cells. (A) A representative western blotting is shown. (B-D) Relative protein expression levels of Mst1, Bax, and Bcl-2 were assessed calculating the integral optical density (IOD)-values. IOD values were normalized to those of beta-actin protein. ^∗P < 0.05 vs. Control, ^†P < 0.01 vs. Control.

Figure 4

Effects of MST1 overexpression on Tau-induced apoptosis in SiHa cells. The apoptosis of SiHa cells was detected by Annexin-V-FITC/PI double staining; compared with the Control group or the p-EGFP-NC group, the apoptotic rates in group Tau 160 mmol/L, group p-EGFP-MST1, and group p-EGFP-MST1+ Tau 160 mmol/L were significantly increased (20.52%, 33.19%, and 64.1%, respectively, P < 0.01). Compared with the p-EGFP-MST1 group, the apoptotic rate in group p-EGFP-MST1+ Tau 160 mmol/L still exhibited significant increase (P < 0.01), suggesting that MST1 and Tau may have synergistic effects. ^∗P < 0.01 vs. Control or p-EGFP-NC; ^†P < 0.01 vs. p-EGFP-MST1.

Figure 5

Effects of MST1 overexpression on the mRNA expressions of p73, p53, and PUMA in SiHa cells of different groups. The RT-qPCR results showed that compared with the Control group and the p-EGFP-N1 group, the expression of MST1 mRNA in the p-EGFP-MST1 group and the p-EGFP-MST1+DDP group were significantly increased by 40 times and 70 times, respectively, than the control group (A); the expressions of mRNA of p73 (P < 0.01), p53 (P < 0.05), puma (P < 0.01), and caspase3 (P < 0.01) also increased to varying degrees (B,C); the expressions of CTGF, AREG, and yap in the p-EGFP-MST1 group decreased to varying degrees; compared with the p-EGFP-MST1 group, the expressions of CTGF, AREG, and yap mRNA in the p-EGFP- MST1 + DDP group were significantly decreased (D). ^∗P < 0.05, ^†P < 0.01 vs. Control or p-EGFP-N1; ^‡P < 0.05, ^§P < 0.01 vs. p-EGFP-MST1; ^||P < 0.05, ^¶P < 0.01 vs. DDP.

Figure 6

Effects of Mst1 overexpression on the expressions of YAP, p73, p53, PUMA, and caspase-3 protein. The results of Western blot show that compared with the Control group or the p-EGFP-N1 group, the total MST1 protein expression in the cells was increased by 2.2 times after transfection of p-EGFP-MST1 plasmid (A and B); The YAP protein was significantly decreased (P < 0.01); the Phospho-YAP protein was significantly increased, and the ratio of Phospho-YAP1(Ser127) to YAP was increased by about 4.5 times (A and C); the expressions of p73, p53, PUMA and caspase -3 protein were significantly increased (P < 0.05 or P < 0.01) (A, D and E). Compared with the p-EGFP-MST1 group, the expressions of proapoptotic protein p73, p53, PUMA, and caspase-3 in the p-EGFP-MST1+DDP group were significantly increased (P < 0.01) (A, D and E). ^∗P < 0.05, ^†P < 0.01 vs. Control or p-EGFP-N1; ^‡P < 0.01 vs. p-EGFP-MST1; ^§P < 0.01 vs. 5-DDP.