Targeting EP300, a selective dependency in neuroblastoma - PROJECT DESCRIPTION/ABSTRACT Despite increases in treatment intensity, children with high-risk neuroblastoma (NB) have poor survival and significant post-therapy toxicities. The candidate is an Instructor in Pediatrics with 80% protected time for research who is committed to developing novel therapeutics that are desperately needed to improve the lives of children with NB. This is a challenge due to the paucity of currently targetable oncogenic mutations in this tumor. A recent survey identified the histone acetyltransferase (HAT) enzyme EP300, but not its paralog, CBP, as a selective dependency in NB. This identifies an opportunity to inhibit EP300 without severe toxicity, as CBP may compensate for EP300 in many normal cells. To this end, the candidate has developed a proteolysis-targeted chimaera (PROTAC) on-target molecule (“JQAD1”) that degrades EP300 with limited effects on CBP in vitro and in vivo. JQAD1 causes tumor growth delay in vivo with limited toxicity, and is therefore an excellent starting point for developing combinatorial strategies for tumor cell killing. Thus, this proposal builds on a strong foundation of preliminary data to address the central hypothesis that optimized EP300-targeting strategies can be developed to maximize NB cell death while limiting off-target toxicity using structurally-guided chemical biology with faithful in vivo NB modeling. This will be pursued in two specific aims: 1) To experimentally determine the most potent combinations of EP300 degraders and chemotherapies in vitro and in vivo; and 2) To develop improved potency second-generation JQAD compounds with enhanced on- and off-target specificity. In the first aim, to appropriately prepare EP300 degraders for clinical use, experiments will identify effective combinations of conventional chemotherapy agents and JQAD1. The mechanisms of combinatorial compound function, and tractability of this approach will be established in vitro and in PDX models reflecting the biological and clinical heterogeneity of NB. In the second aim, second-generation JQAD molecules will be generated using structurally- based compound development,. These will be tested for effects on EP300 using novel fluorescent in-cell assays, and in mechanistic assays of EP300 function. This proposal is innovative because it uses mechanistic approaches involving state-of-the-art gene knockins, compound development and PROTAC technologies to identify methods to maximize tumor cell death and minimize toxicity. It is significant because targeting EP300 alone represents an ideal strategy to kill NB cells and limit toxicity to normal tissues. This proposal is designed to provide intensive training and mentoring in chemical biology, animal modeling and experimental therapeutics, as well as mentoring in grant writing, leadership training and managerial skills, thereby conferring the necessary skills for an optimal transition to independence. The environment for this proposal is ideal, including scientific experts necessary to complete this work, a strong institutional commitment and ideal guidance of his mentors, Drs. Kim Stegmaier and Jun Qi. Thus, this proposal will facilitate his career goals of becoming an independent, laboratory-based clinician-scientist focused on discovery and therapeutic targeting in cancer.
