Figure 5.

MMP-9 activity is modulated by caspase-1 in a P2Y₂R-dependent manner, in MDA-MB-231 or RT-R-MDA-MB-231 cells. (A) Cells were pre-treated with Ac-YVAD-CMK and then stimulated with TNF-α or ATP for 6 h. MMP-9 gelatinase activity was determined as described in the Materials and methods and quantified. The values represent the means ± SEM of 3 independent experiments. ^*P<0.05 and ^**P<0.01, compared to the control (CTRL) of each of the cells; ^##P<0.05, compared to the TNF-α treatment of each of the cells; ^‡P<0.05, compared to the ATP treatment of each of the cells; ^§P<0.05, comparison between the MDA-MB-231 and RT-R-MDA-MB-231 cells. (B) siCTRL- or siP2Y₂R-transfected RT-R-MDA-MB-231 cells were pre-treated with AR-C 118925XX (AR), a specific P2Y₂R antagonist or not. The cells were then stimulated with ATP, and MMP-9 gelatinase activity was determined as described in the Materials and methods. The values represent the means ± SEM of 3 independent experiments. ^**P<0.05, compared to the CTRL; ^##P<0.01, compared to ATP treatment. ATP, adenosine triphosphate; RT-R, radiotherapy-resistant; IL-1β, interleukin-1β; TNF-α, tumor necrosis factor-α; MMP-9, matrix metalloproteinase-9.