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UBC Theses and Dissertations

Characterization of the biologic and molecular effects of newly developed oncolytic herpes simplex viruses in acute myeloid leukemia Zheng, Yixin


Acute myeloid leukemia (AML) is a rapidly progressing, often fatal hematopoietic malignancy characterized by clonal expansion of leukemic stem cells and differentiation block in the myeloid lineage, with accumulation of blasts. Progress has been made in identifying therapeutic targets and several approved therapies, but resistance to frontline chemotherapy remains a major cause of treatment failure, highlighting the need for new therapies. Oncolytic viruses are a promising class of therapeutics that rely on tumor specific oncolysis and the generation of a potent adaptive anti-tumor immune response for efficacy. To investigate if newly developed oncolytic herpes simplex viruses (oHSVs), designed to potentiate anti-leukemia immunity, effectively target primitive AML cells, I evaluated oHSV-VG161, which is engineered to express IL-12, IL-15 and the IL-15 receptor alpha subunit, along with a peptide fusion protein capable of disrupting PD-1/PD-L1 interaction. After screening several AML cell lines that expressed relatively high levels of a common HSV entry receptor (TNFRSF14), I demonstrated that VG161-infected OCIAML3 and MOLM13 cells had significantly enhanced cell killing, 2-3 fold higher than control VG160-infected cells. VG161- infected AML cells also induced apoptosis in a timely, dose-dependent manner, with increased protein expression of cleaved PARP, Caspase-3 and Caspase-8. Both VG160 and VG161 viruses replicated efficiently in AML cells, but IL-12 protein expression was only detected in VG161- infected cells. ELISA analysis confirmed the production of IL-12 and IL-15/IL-15RA. Interestingly, the secreted IL-12 could be neutralized by a human IL-12 neutralizing antibody, iv suggesting that functional IL-12 is indeed produced from VG161-infected AML cells. Mechanistically, transcript levels of several immune response genes were highly increased in VG161-infected AML cells, including the type I interferon and other interferon regulating genes such as IRF7, IRF9, ISG54. Moreover, increased phosphorylation of STAT1 and its total protein expression were also found in VG161-infected cells as compared to VG160 control cells. In addition, VG160 or VG161-infected OCIAML3 and MOLM13 cells showed enhanced cell killing when co-cultured with healthy peripheral blood mononuclear cells and increased PD-L1 expression in these cells. Thus, I have demonstrated that newly developed oHSVs engineered with immunomodulatory transgenes effectively target AML cells, suggesting a potential treatment strategy for AML.

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