SYK and acute myeloid leukemia: To more definitively validate that detection of the phosphorylated Y323 site provides the same read-out for SYK activation as the Y525/526 site, we treated AML cell lines exhibiting the highest levels of phosphorylation at Y323 and Y525/526 with increasing concentrations of the SYK inhibitor BAY61-3606 (Figure 2B).