KSR1 and leukemia: Given that TPL2 can antagonize KSR1 activity on MEK1 in leukemia cells (Wang and Studzinski, 2011[57]) and KSR2, a KSR1 related protein, can negatively regulate TPL2 activity in HeLa cells (Channavajhala et al., 2003[4]), there may be a competition or antagonism between both proteins for MEK1 occupancy or activation.