STK26 and cancer: Moreover, the activation of AKT and its downstream GSK3β and BAD was inhibited in MST4 knockdown BT474 cells (Figure 5b), suggesting MST4 is required for AKT and its downstream signaling pathway activation in breast cancer cells and is crucial for cancer cell survival and EMT via the MST4-AKT-BAD or MST-AKT- GSK3β signaling cascade.