During our pharmacodynamic studies of mTOR kinase specific inhibitor AZD8055 in rhabdomyosarcomas, we find that treatment of rhabdomyosarcoma Rh30 cells with AZD8055 leads to downregulation of CHK1 protein, which is accompanied by DNA damage as demonstrated by increased phosphorylation of H2AX (γH2AX) and apoptosis as shown by cleavage of PARP1 (Fig. 1A). Here, CHEK1 is linked to rhabdomyosarcoma.