Apoptotic modulators enhance oncolytic virus-induced cytokine killing in acute myeloid leukaemia (AML).

Abstract

BACKGROUND: Approximately 3000 adult patients are diagnosed with AML in the UK each year. Current intensive treatments are not well-tolerated by elderly patients, and the 5-year survival rate is only 5-15%, highlighting the need for novel and effective therapies. Oncolytic viruses (OVs) preferentially replicate in cancer cells, resulting in direct oncolysis and induction of innate and adaptive anti-tumour immunity. Unfortunately, the efficacy of OVs remains relatively unexplored in AML. METHODS: Using human AML cell lines, healthy-donor peripheral blood mononuclear cells (PBMC) and AML patient samples, we investigated whether combination with clinically applicable apoptotic modulators (SMAC/BH3 mimetics) can potentiate OV-induced cytokine-mediated killing. RESULTS: We confirmed that OVs stimulate PBMCs to produce inflammatory cytokines, which can induce AML cell death. Bystander cytokine-mediated killing was also significantly enhanced in combination with SMAC/BH3 mimetics, with the optimal combination partner varying with AML subtype. We identified interferon (IFN)-alpha and tumour necrosis factor (TNF)-alpha as potential mediators of AML cytotoxicity, and SMAC/BH3 mimetics enhanced AML cell death following direct OV infection, indicating autocrine-paracrine signalling events. Pivotally, we confirmed that apoptotic modulators were effective in combination with both Live- and UV-inactivated virus. CONCLUSION: This work has identified a novel reovirus-based combination-immunotherapy for the treatment of AML.