ATR and B-cell chronic lymphocytic leukemia: The functional assay was set-up on cell lines recapitulating all TP53 genotypes (EHEB, TP53wt/wt; RAJI, TP53mut/wt; MEC-1 and MAVER1, TP53mut/del; HL-60, TP53del/del) and evaluated in two multi-institutional cohorts, purposely enriched in CLL bearing TP53 disruption: a training cohort of 100 cases and a validation cohort of 40 cases, both characterized by FISH and TP53 direct sequencing.