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ALT Neuroblastoma Chemoresistance due to ATM Activation by Telomere Dysfunction is Reversible with the ATM Inhibitor AZD0156

By Balakrishna Koneru, Ahsan Farooqi, Thinhh H Nguyen, Wan Hsi Chen, Ashly Hindle, Cody Eslinger, Monish Ram Makena, Trevor A Burrow, Joanne Wilson, Aaron Smith, Venkatesh Pilla Reddy, Elaine Cadogan, Stephen T. Durant, C. Patrick Reynolds

Posted 07 Apr 2021
bioRxiv DOI: 10.1101/2021.04.06.438692

Cancers overcome replicative immortality by activating either telomerase or an alternative lengthening of telomeres (ALT) mechanism. ALT occurs in ~ 25% of high-risk neuroblastomas and relapse or progression in ALT neuroblastoma patients during or after front-line therapy is frequent and almost uniformly fatal. Temozolomide + irinotecan is commonly used as salvage therapy for neuroblastoma. Patient-derived cell-lines and xenografts established from relapsed ALT neuroblastoma patients demonstrated de novo resistance to temozolomide + irinotecan (as SN-38 in vitro, P<0.05) and in vivo (mouse event-free survival (EFS) P<0.0001) relative to telomerase-positive neuroblastomas. We observed that ALT neuroblastoma cells manifest constitutive ATM kinase activation due to spontaneous telomere dysfunction while telomerase-positive tumors lacked constitutive ATM activation or spontaneous telomere DNA damage. We demonstrated that induction of telomere dysfunction resulted in ATM activation that in turn conferred resistance to temozolomide + SN-38 (4.2 fold-change in IC50, P<0.001). ATM kinase shRNA knock-down or inhibition using a clinical-stage small molecule inhibitor (AZD0156) reversed resistance to temozolomide + irinotecan in ALT neuroblastoma cell-lines in vitro (P<0.001) and in 4 ALT xenografts in vivo (EFS P<0.0001). AZD0156 showed modest to no enhancement of temozolomide + irinotecan activity in telomerase-positive neuroblastoma cell lines and xenografts. ATR inhibition using AZD6738 did not enhance temozolomide + SN-38 activity in ALT neuroblastoma cell lines. Thus, resistance to chemotherapy in ALT neuroblastoma occurs via ATM kinase activation and was reversed with the ATM inhibitor AZD0156. Combining AZD0156 with temozolomide + irinotecan warrants clinical testing in neuroblastoma.

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