Fig. 3.

S1PR1-STAT3 formed a positive regulatory loop in GC cells and contributed to drug resistance.

(A) Expression of indicated genes of SGC7901/DDP cells after treated with different concentrations of S1P and DDP for 24 h was detected by Western blot. (B) Expression of indicated genes of SGC7901 cells transfected with S1PR1 over-expression and empty vectors for 48 h was detected by Western blot. (C) SGC7901 cells transfected with S1PR1 overexpression or empty vector cells were treated with fold diluted DDP for 24 h and the cell viability was detected by MTS method. Data were expressed as mean ± SD, n = 4. (D) Expression of indicated genes of SGC7901/DDP cells transfected with S1PR1 siRNA and mock siRNA for 48 h was determined by Western blot. (E) Cell viability of SGC7901/DDP cells, tested by MTS method. Cells were treated with fold diluted DDP for 24 h with or without S1PR1 knocking down. Data were expressed as mean ± SD, n = 4. (F) Cell apoptosis levels of SGC7091/DDP cells were determined by AnnexinV/PI double staining with FACS after indicated treatment for 24 h. The ratio of double negative population of the cells was presented with mean ± SD, n = 5. *P < 0.05 (Student's t-test). (G) Expression of indicated genes of SGC7901/DDP cells transfected with STAT3 siRNA and mock siRNA was detected by Western blot. (H) Cell viability of SGC7901/DDP cells treated with fold diluted DDP for 24 or 48 h after transfection of S1PR1 and mock siRNA was detected by MTS. Data were expressed as mean ± SD, n = 4. *P < 0.05, #P < 0.05 (Student's t-test)