Targeted therapy against TERT oncogene-rearranged neuroblastoma

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PROJECT SUMMARY/ABSTRACT Background. TERT oncogene rearrangement with transcriptional super-enhancers leads to substantial TERT over-expression and neuroblastoma in high-risk neuroblastoma patients. Telomerase inhibitors show little anticancer effects and cause life-threatening side effects in childhood brain cancer patients in clinical trials. The transcriptional kinases CDK7 and CDK9 play critical roles in super-enhancer-associated oncogene transcriptional initiation, pause release and elongation respectively, and CKIα induce p53 protein degradation. The CDK7/CDK9/CKIα co-inhibitor A51 suppresses super-enhancer-associated oncogene expression and activates p53 protein expression, resulting in leukemia regression in mice with no toxicity to normal tissues. Preliminary Data. We have found that CDK7/CDK9/CKIα co-knockdown with shRNAs or treatment with the CDK7/CDK9/CKIα co-inhibitor A51 considerably reduced TERT gene expression and MDM2 protein expression, activated p53 protein expression, and induced substantial apoptosis in TERT oncogene- rearranged neuroblastoma, but not normal cells. Analysis of a RNA sequencing gene expression-patient prognosis dataset from 493 neuroblastoma patients, showed that high levels of CDK7 gene expression in human tumor tissues positively correlated with high levels of TERT gene expression, and that high levels of CDK7 and CKIα expression in human neuroblastoma tissues correlated with poor patient prognosis. Specific Aims. (1) To identify the critical roles of CDK7 and CDK9 in inducing TERT gene transcriptional initiation, elongation and over-expression and CKIα in inducing p53 protein degradation in TERT-rearranged neuroblastoma cells; (2) To identify the critical roles of CDK7, CDK9 and CKIα in TERT-rearranged neuroblastoma cell proliferation and survival in vitro and tumor progression in vivo; (3) To define the anticancer efficacy of the CDK7/CDK9/CKIα co-inhibitor A51 against TERT-rearranged neuroblastoma in vitro and in vivo. Outcomes and Significance. We hope to demonstrate that CDK7 and CDK9 co-operatively induce TERT gene transcriptional initiation, pause release, elongation and over-expression, and CKIα induces p53 protein degradation; that CDK7, CDK9 and CKIα co-operatively induce TERT-rearranged neuroblastoma cell proliferation and survival in vitro and tumor progression in vivo; and that the CDK7/CDK9/CKIα co-inhibitor A51 efficiently blocks TERT gene transcriptional initiation, pause release, elongation and expression, activates p53 protein expression, induces neuroblastoma cell apoptosis in vitro, and blocks tumor progression and causes tumor regression in mice xenografted with TERT-rearranged neuroblastoma cell lines or patient-derived neuroblastoma tissues. As A51 is currently in clinical trials in leukemia patients, completion of this project will provide the vital evidence for clinical trials of A51 therapy in patients with TERT gene-rearranged neuroblastoma, against which no targeted therapy is now available for, or has ever be tested in, clinical trials.