Preclinical studies of the anti-tumor effects of novel Avian paramyxovirus 4 (APMV-4) oncolytic viral therapy combined with vascular endothelial growth factor-C (VEGF-C) in melanoma.

e15050 Background: Avian paramyxoviruses (APMVs) are negative-sense, single-stranded RNA viruses, of which best known is APMV-1, commonly referred to as Newcastle disease virus (NDV). NDV has been extensively studied as an oncolytic virus (OV) and has been shown to be a promising viral agent for human cancer therapy. We identified APMV-4 as a novel OV from the APMV family, with several advantages over NDV and other classes of OVs. APMV-4 is selective for cancer cells, it is not a human pathogen, there is no pre-existing immunity to this virus in humans, and it can be engineered to deliver various therapeutics. Here, we investigated anti-tumor properties of APMV-4 in mouse tumor models, and the role of Vascular Endothelial Growth Factor-C (VEGF-C), a key lymphangiogenesis factor, on therapeutic effects of AMPV-4. Methods: Anti-tumor effects of OVs were assessed using B16F10 melanoma and CT26.WT colon carcinoma in syngeneic mouse models. Tumor cells were injected intradermally into the flank, and treatment commenced when tumors reached ̃50mm3. Viruses were injected intratumorally (107 PFU) every two days, for a total of four treatments. For studies of VEGF-C, B16F10 cells were transfected with VEGF-C or with an empty vector. Tumor regression and long-term survival were assessed. Mice in complete remission were re-challenged with tumor cells on the opposite side. High-dimensional immunophenotyping using Aurora Spectral flow cytometry was performed on tumor samples collected 12 hr after the 2nd treatment with OVs. Results: Intratumoral administration of APMV-4 extended survival, promoted tumor elimination and conferred protection against re-challenge in murine colon carcinoma and melanoma tumor models, and was more effective than NDV strain LaSota. Expression of VEGF-C in B16F10 melanoma enhanced anti-tumor effects of APMV-4 or NDV, resulting in complete remission in 100% and 86% of mice, respectively (n = 7). Mice remained tumor-free during the 90-day observation period, and following re-challenge remained tumor-free for more than a year. Protection from tumor development upon re-challenge was observed in 71% and 83% of mice treated with APMV-4 or NDV, respectively. Results are representative of two experiments. VEGF-C expression in tumors induced lymphangiogenesis, which correlated with high T-cell densities. Analysis of tumor immune cell composition by flow cytometry revealed multiple unique T-cell and NK-cell subsets associated with complete remission. Conclusions: These studies identify APMV-4 as a novel oncolytic agent with great therapeutic potential and VEGF-C as potent enhancer of anti-tumor immunity. High anti-tumor efficacy of APMV-4/VEGF-C monotherapy, that in preclinical models leads to tumor eradication, indicates great therapeutic and vaccine potential of APMV-4 when combined with VEGF-C.