Abstract 294: Override the doxorubicin-induced G2/M checkpoint using cell-cycle checkpoint inhibitors on acute lymphoblastic leukemia

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Abstract The topoisomerase 2 inhibitor, doxorubicin, has been showed by different groups to induce cell cycle arrest in various kind of tumor cells. Specifically doxorubicin-treated cells activate the G2/M cell cycle checkpoint as a consequence of the induction of DNA damages. During the last years many studies have been showed the efficacy of different cell cycle checkpoint inhibitors in single agent or in combination with various DNA damaging agents. These studies showed that the inhibition of key proteins of the cell cycle, like Chk1 and Wee1, deeply sensitize tumor cells to the treatment with genotoxic agent. On these bases, the aim of the study was to evaluate the efficacy of a selective Chk1/Chk2 inhibitor and a Wee1 inhibitor in combination with doxorubicin for the treatment of acute lymphoblastic leukemia. Firstly we evaluate the effect of doxorubicin treatment on a panel of human B and T ALL cell lines in term of reduction of the cell viability, modification of cell cycle profile and activation of the DNA damage response. For this reason the cells were treated with doxorubicin (0.25, 0.5 and 1uM) for 24 and 48 hours and the reduction of the cell viability was quantified using WST-1 reagents. In all the cell lines treated the cytotoxic effect of doxorubicin was time and dose dependent. Then the induction of the apoptosis (Pi/Annexin V) and the effect on cell cycle profile (Pi staining) was evaluated in all the cell lines. In line with the literature the treatment with doxorubicin arrested the cells in G2/M phase. Then the effect of the combinations between doxorubicin and the two checkpoint kinase inhibitor was assessed in all the cell lines. Different cell lines were treated with doxorubicin (5, 10, 25 and 50 nM for the more sensitive cell lines; 50, 100, 250 and 500 nM for the less sensitive cell lines) in combination with the Chk1/Chk2 inhibitor (2, 5 and 10 nM) for 24 and 48 hours. The combination showed a additively effect in term of reduction of the cell viability and induction of apoptosis. Different cell lines were pre-treated for 18 hours with doxorubicin and then with Chk1/Chk2 inhibitor for different time points. Interestingly the inhibition of both Chk1/Chk2 proteins removed the G2/M arrest induced by the pre-treatment with doxorubicin, progressively reducing the number of cells in G2/M phase, increasing the percentage of cells in sub-G1 phase. Similar results were seen combining a Wee1 inhibitor with doxorubicin on several ALL cell lines. In our opinion the combination between the cell cycle checkpoint inhibitors and doxorubicin could be a promising strategy for the treatment of B/T-ALL. Supported by ELN, AIL, AIRC, progetto Regione-Università 2010-12 (L. Bolondi), FP7 NGS-PTL project. Citation Format: Andrea Ghelli Luserna di Rorà, Ilaria Iacobucci, Enrica Imbrogno, Anna Ferrari, Valentina Robustelli, Cristina Papayannidis, Maria Chiara Abbenante, Antonella Padella, Giovanni Marconi, Sandro Grilli, Giovanni Martinelli. Override the doxorubicin-induced G2/M checkpoint using cell-cycle checkpoint inhibitors on acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 294. doi:10.1158/1538-7445.AM2017-294