CHEK1 and neoplasm: A similar analysis of tumour cells growing anchorage-dependently revealed a very weak correlation between Chk1 S296 phosphorylation and Cdc6 (R2 = 0.219) but a similar correlation between total Chk1 protein and Cdc6 (R2 = 0.539) as observed in the xenograft samples (Fig. 6a and Supplementary Fig. S5).