Abstract A028: Defining immune pathways involved in the depletion of B-cell precursor acute lymphoblastic leukemia-initiating cells following early-life cytomegalovirus (CMV) infection in mice

Abstract

Abstract Background: B-cell acute lymphoblastic leukemia (B-ALL) is one of the most common forms of childhood cancers. Epidemiological studies have shown contrasting results regarding the role of infections in the risk of leukemia, and there is still no clear explanation for the pro- or anti-leukemia effects. Aim: This study aimed to investigate the influence of cytomegalovirus (CMV) infection on the development of B-ALL and identify the underlying immune mechanisms involved. Materials and Methods: In this study, Eμ-Ret transgenic mice were used as a model for hyperdiploid B-ALL, and luciferase-tagged CMV was used as a common early-life infection. The impact of infection on different subsets of B cells and leukemic initiating cells (LICs) in the bone marrow and spleen of neonatal and adult mice was assessed using multicolor flow cytometry. To gain insights into the mechanisms that impact LICs after infection, we sorted LICs from the splenocytes of infected and non-infected RFP mice seven days after infection, and total RNA sequencing (RNA-seq) was performed for gene expression analysis. We used neutralizing antibodies to evaluate the role of different cytokines/chemokines in mediating LIC depletion in vivo. Results: Significant infection-induced depletion of preleukemic cells occurred in infected neonate Eμ-ret mice on BALBc, BALBc/FVB (F1) and BALBc/C57 (F1) backgrounds. This depletion showed an age-dependent pattern, with only infection in the first week after birth reducing the LICs numbers. Depletion of preleukemia was dependent on Stat4 and p40 homodimer/monomers, but not p40 heterodimers (IL-12 and IL-23). Several chemokines/cytokines, including IFNg and TNFa, showed high levels of expression in the serum of CMV-infected pups but not in adult mice. RNA sequencing indicated that IFNg and TNFa exerted a direct effect on preleukemic cells. In vivo neutralization of IFNg completely blocked the depletion effect of CMV infection. Further experiments confirmed that this cytokine works downstream of the Stat4 signaling pathway. Conclusion: This is the first model to study the impact of CMV infection and the time of its exposure on B-ALL initiating cells. The identified Stat4-, IL12p40 homodimer/monomer-, and IFNg- driven activities could inform future treatment and prevention approaches for B-ALL. Citation Format: Ali Farrokhi, Tanmaya Atre, Citlali Marquez1, Soren Gantt, Gregor Reid. Defining immune pathways involved in the depletion of B-cell precursor acute lymphoblastic leukemia-initiating cells following early-life cytomegalovirus (CMV) infection in mice [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr A028.