CHEK1 and acute lymphoblastic leukemia: Among B/T-ALL, a diffuse positivity for Chk1, Chk2, Cdc25c, and the phosphorylated forms of Chk1 (Ser345) and Cdc25c (Ser216) was observed; these were detected in 51/54 (96 %), 55/57 (94 %), 57/57 (100 %), 45/56 (80 %), and 38/55 (70 %) of the cases, respectively, whereas 15/55 (27 %) of ALLs was stained for phosphorylated form of Chk2 (Thr68) (Fig. 1d).