RPS6KB1 and breast cancer: In addition, we observed that MKI-1 inhibited ENSA phosphorylation at 6 h and it did not modulate the phosphorylation levels of other AGC kinases, including AKT, p70S6K, and GSK-3β, in breast cancer cells, whereas AT13148 and GKI-1 modulated these kinases (Supplementary Figure 2), suggesting that MKI-1 had a greater capacity for MASTL inhibition than other inhibitors.