Understanding viral mechanisms to inform oncolytic therapies for EBV-associated lymphomas in PLWH

Non-Hodgkin lymphomas are a common cause of cancer-related death in people living with HIV (PLWH). Remarkably, despite advances in chemotherapy and antiretroviral therapy, HIV-infected individuals with Epstein- Barr virus (EBV)+ diffuse large B cell lymphoma (DLBCL) suffer from worse overall survival compared to those with EBV- DLBCL. Thus, new therapies need to focus on exploiting EBV, an untapped vulnerability. EBV is acquired orally and can cause infectious mononucleosis. While EBV infects epithelial cells and B cells, it remains latent in B cells. The presence of latent EBV in each cancer cell can be exploited for oncolytic therapies wherein EBV is forced into the lytic/replicative phase followed by genomic incorporation of a nucleoside analog to block DNA replication, resulting in death of the cancer cell. However, the success of oncolytic approaches depends on the fraction of cells in a tumor that is responsive (typically 20-50%) to lytic triggers of EBV. Therefore, understanding the mechanisms underlying lytic trigger susceptibility versus refractoriness and using such knowledge to increase the responsive fraction is key to the success of oncolytic therapies. We seek to identify core upstream mechanisms that disrupt silencing of the EBV gene BZLF1 to initiate expression of the latent-to-lytic switch protein ZEBRA regardless of the specific lytic trigger or cell background. Our studies show that KAP1, a prominent cellular corepressor, is recruited by the DNA-binding protein SZF1 (also a host protein) to epigenetically silence multiple EBV lytic genes (including BZLF1), thereby promoting the refractory state. We have also learned that several lytic triggers in a variety of latent cell backgrounds transcriptionally activate cellular TXNIP, a key trigger of the diabetes-related NLRP3 inflammasome, to activate caspase-1, resulting in KAP1 depletion (but not total loss), and thereby, derepressing BZLF1. This discovery, in cultured B cells and EBV+ lymphoma cells from transplant recipients, allows us to predict and isolate single ‘pro- lytic’ cells in which EBV is poised to enter the lytic phase. Using this novel tool to study events that are upstream of the EBV lytic switch, we will test the hypothesis that core factors drive TXNIP which decreases the stability of the epigenetic repressor KAP1 thereby increasing EBV’s susceptibility to lytic activation, regardless of the trigger. In AIM 1, we will build a unified model of the core factors p300 and MondoA that transcriptionally activate TXNIP to turn the EBV lytic cycle on in pro-lytic cells. In AIM 2, we will elucidate the mechanism and consequences of destabilizing viral genome-bound KAP1 on the lytic phase and consequently, influencing B cell transformation. Many African children with endemic Burkitt lymphoma (eBL) that commonly affects the jaw and other facial bones die each year due to limited access to the highly specialized chemotherapy needed to treat such cancers. Beyond PLWH who have EBV+DLBCL, children with eBL could also benefit from oncolytic therapies as these therapies may be more readily accessible. Project Number: 1R01DE034654-01A1 | Fiscal Year: 2025 | NIH Institute/Center: National Institute of Dental and Craniofacial Research (NIDCR) | Principal Investigator: SUMITA BHADURI-MCINTOSH | Institution: UNIVERSITY OF FLORIDA, GAINESVILLE, FL | Award Amount: $601,309 | Activity Code: R01 | Study Section: HIV Coinfections and HIV Associated Cancers Study Section[HCAC] View on NIH RePORTER: https://reporter.nih.gov/project-details/11186093