Figure 3.

Caspase-1 activity or IL-1β secretion induced by TNF-α or ATP is significantly suppressed by P2Y₂R knockdown or apyrase (an enzyme that rapidly hydrolyzes extracellular nucleotides) in MDA-MB-231 or RT-R-MDA-MB-231 cells. (A) P2Y₂R mRNA levels were analyzed by RT-PCR to confirm the efficiency of the knockdown in control siRNA (siCTRL)- or P2Y₂R siRNA (siP2Y₂R)-transfected cells. (B and C) siCTRL or siP2Y₂R-transfected cells were stimulated with TNF-α (10 ng/ml) or ATP (10 µM). (B) Caspase-1 activity and (C) IL-1β secretion were measured 3 h and 24 h after treatment, respectively, as described in the Materials and methods. (D and E) The cells were pre-treated with 10 U/ml apyrase for 1 h and stimulated with TNF-α (10 ng/ml). (D) Caspase-1 activity and (E) IL-1β secretion were measured as described in (A). The values represent the means ± SEM of 3 independent experiments. ^**P<0.01, compared to the control (CTRL) of each cells; ^#P<0.05 and ^##P<0.05, compared to the TNF-α treatment of each of the cells; ^†P<0.05 and ^‡P<0.01, compared to the ATP treatment of each of the cells; ^§P<0.05 and ^§§P<0.01, significance between the MDA-MB-231 and RT-R-MDA-MB-231 cells. ATP, adenosine triphosphate; RT-R, radiotherapy-resistant; IL-1β, interleukin-1β; TNF-α, tumor necrosis factor-α.