Fig. 2: Sudden impact of WWOXd cells by WWOXf cells from suspension leads to activation of the survival IκBα/ERK/WWOX signaling in WWOXd cells, and WWOXf cells die.

a, b MEF Wwox knockout cells were transiently overexpressed with ECFP-IκBα, EGFP-ERK, and DsRed-WWOX, followed by culturing for 24–48 hr and adding MEF wild type cells from suspension for time-lapse FRET microscopy. Activation of the IκBα/ERK/WWOX survival signaling occurred in knockout cells (shown as FRETc in artificial white color and marked in red stars). Apoptosis occurred in the wild type cells (white stars). Also, see Supplementary Videos 10 and 11. c, d Upon sudden impact with the Wwox knockout cells from suspension, MEF wild type cells did not activate the ectopic IκBα/ERK/WWOX signaling complex (red stars). Knockout cells did not undergo apoptosis (white stars). Also, see Supplementary Videos 12 and 13. e, f By sudden impact with L929S from suspension, activation of the ectopic IκBα/ERK/WWOX signaling complex in breast MDA-MB-231 cells occurred (red). Apoptosis of L929S also occurred (white stars). g Upon sudden confrontation with L929S, MDA-MB-231 cells exhibited a gradual increase in the activation of TCF/LEF promoter, as determined by green fluorescence of time-lapse microscopy. h Under similar conditions, L929S exhibited a rapid increase in the activation of TCF/LEF promoter in response to the sudden impact by MDA-MB-231 cells from suspension.