HCLS1 and B-cell chronic lymphocytic leukemia: HS1 is phosphorylated by SYK and LYN kinases on BCR engagement and its hyperphosphorylation correlates with a worst outcome in CLL patients.77TCL1-tg/Hs1−/− mice show accumulation of leukemic cells in all lymphoid tissues and shorter survival than TCL1-tg mice.78 As the genetic inactivation of Hs1 produces the same effects of hyperphosphorylation, Scielzo et al. conclude that phosphorylation has an inhibitory effect on HS1.