STIM1 and leukemia: Because CAMK1 activity is tightly regulated by the calcium signaling, we sought to understand how calcium signaling was affected by Asic3 deletion and found that the STIM1 level, a key mediator of calcium influx, was notably increased in LICs, as well as in YFP+ BM leukemia cells (Figure 5A and Supplemental Figure 7A).