Fig. 4.

Knockdown of Stim1 increases chemo-sensitivity of cisplatin-resistant osteosarcoma cells to cisplatin treatment. a Cisplatin-resistant MG63/CDDP cells were transfected with negative siRNA (Neg), or different concentrations of Stim1-targeting siRNA (25, 50 and 100 nM) using Hiperfect reagent (Hiper) for 24 h. Stim1 expression was determined by western blotting. **P < 0.01 versus control, n = 4. b Quantification of the thapsigargin (Tg)-induced SOCE amplitude in MG63/CDDP cells transfected with negative or Stim1 siRNA. **P < 0.01 versus control, n = 6. c MG63/CDDP cells were transfected with negative or Stim1 siRNA (50 nM) for 24 h, followed by incubation of cisplatin (10 μM) for another 24 h. Cell viability was examined by CCK-8 assay. *P < 0.05 versus negative; ^## P < 0.01 versus negative + cisplatin, n = 6. d Cell apoptosis was determined by Annexin V-FITC/PI staining followed by flow cytometry. e After treatments mentioned above, the protein expressions of GRP78, CHOP, ATF4 and Stim1 were examined by western blotting. f Densitometric analysis of the above protein expressions. *P < 0.05, **P < 0.01 versus negative; ^## P < 0.01 versus negative + cisplatin; ^&& P < 0.01 versus Stim1 siRNA, n = 6