Targeting KAT6A/B activity to induce responsiveness to anti-GD2 immunotherapy in neuroblastoma - Neuroblastoma (NBL) is the most common extracranial solid tumor of childhood, and nearly 50% of affected children will die of their disease despite intensive multimodal therapy, including retinoic acid (RA) and GD2- targeted immunotherapy. Relapse is commonly fatal, underscoring the urgent need for novel therapeutic strategies with potent and durable anti-tumor activity. NBL exists in two interconvertible cell states, adrenergic and mesenchymal, each driven by distinct transcriptional and epigenetic programs. Under therapeutic pressure, cells can transition to the mesenchymal state, promoting treatment resistance and relapse. RA induces growth arrest in adrenergic NBL by suppressing key transcription factors and rewiring the enhancer landscape. However, its effects are transient, and RA resistance, especially in mesenchymal and c-MYC-driven subtypes, is common. Through a drug screen, I identified that PF-9363, a first-in-class tool inhibitor of the histone acetyltransferases KAT6A/B, synergizes with RA to enforce durable growth arrest in NBL both in vitro and in vivo, overcomes RA resistance across multiple NBL subtypes and induces high GD2 expression on GD2low NBL cells, when combined with RA. While KAT6 inhibitors are currently under investigation in early-phase clinical trials in adult cancers, their therapeutic potential in pediatric solid tumors remains unexplored. The goal of this proposal is to define the role of KAT6A and KAT6B as epigenetic modifiers regulating NBL cell state and plasticity and to identify the NBL subtypes most likely to benefit from KAT6 inhibitors. I hypothesize that KAT6A/B control specific transcriptional and chromatin states that limit therapeutic responsiveness to RA and GD2-directed immunotherapies. To test this hypothesis, I will pursue two specific aims: In Aim 1, I will dissect the role of KAT6A/B as epigenetic modifiers limiting the antiproliferative and generegulatory effects of RA in NBL. I will define how KAT6A/B regulate chromatin accessibility, transcriptional programs, and NBL cell state plasticity underlying RA resistance across resistant subtypes. In Aim 2, I will determine how epigenetic reprogramming through KAT6A/B inhibition plus RA upregulates GD2 expression in vivo and evaluate the therapeutic efficacy of this combination with GD2-targeted immunotherapies. This proposal will uncover novel, mechanistically grounded strategies to sensitize NBL to differentiation and GD2-targeting immunotherapy using a new class of epigenetic inhibitors targeting KAT6A/B. For this proposal, I will apply my expertise in NBL biology and transcriptional regulation of cell state. To address key gaps in my training and knowledge, I’ve assembled a career development plan to gain expertise in epigenetic modifiers as regulators of cell state and therapeutic targets in NBL under the mentorship of Dr. Armstrong. This proposal lays a strong foundation for my long-term goal of leading an independent laboratory that focuses on epigenetic dysregulation in pediatric cancer. Justification for the Use of Vertebrate Animals Mouse studies are required to accomplish this project because only in vivo NBL xenograft models permit evaluation of whether KAT6A/B inhibition combined with RA selectively induces GD2 expression in tumor cells, enhances the efficacy of both antibody-based and cellular GD2-targeted immunotherapies, and permits evaluation of treatment-related toxicity. These studies will provide the critical preclinical evidence needed to support future clinical translation.
