Assessment of p53 and ATM Functionality in Chronic Lymphocytic Leukemia By Multiplex Ligation-Dependent Probe Amplification

The ATM-p53 DNA damage response pathway plays a crucial role in chemoresistance in CLL, as indicated by the adverse prognostic impact of genetic aberrations of TP53and ATM. Identifying and distinguishing TP53and ATMfunctional defects has become relevant as epigenetic and posttranscriptional dysregulation of the ATM/p53 axis is increasingly being recognized as underlying cause of chemoresistance. Also, specific treatments sensitizing TP53-or ATM-deficient CLL cells are emerging. We therefore developed a new ATM-p53 functional assay with the aim to (i) identify and (ii) distinguish abnormalities of TP53versus ATMand (iii) enable the identification of additional defects in the ATM-p53 pathway. Previously we showed that a reverse transcriptase multiplex ligation-dependent probe amplification (RT-MLPA) procedure which quantifies expression levels of the p53-targets, CDKN1A, BBC3and Bax, in CLL cells following irradiation is able to determine p53 functionality. With the aim of identifying and distinguishing abnormalities of TP53versus ATMand enabling the identification of additional defects in the DDR, we developed a new RT-MLPA based functional assay.