Abstract
Vascular Endothelial Growth Factor C (VEGF-C) is a key lymphangiogenic growth factor expressed by many types of cancer. Here, we investigated the effects of tumor-derived VEGF-C on the therapeutic efficacy of oncolytic virotherapy with avian paramyxoviruses APMV-1 (NDV) and AMPV-4. Treatment of B16F10 tumors not expressing VEGF-C with either virus led to tumor growth delay, and complete responses were rare. In contrast, when tumors expressed VEGF-C, viral therapy led to complete remission and long-term immunological memory in most mice. Upon re-challenge, most mice remained tumor- and metastasis-free for over 18 months, indicating durable immunity. VEGF-C induced tumor lymphangiogenesis, which correlated with high CD8 (+) and CD4 (+) T-cell densities in proximity of lymphatic vessels. Spectral flow cytometry revealed distinct changes in the composition and activation of CD8 (+) , CD4 (+) T cells and NK cells associated with complete remission. In responders, tumors were highly enriched in CD8 (+) CD25 (+) PD-1 (+) effector T cells. Composition of T cells was altered in sentinel and in contralateral lymph nodes, indicating a systemic immune response. Taken together, these data demonstrate VEGF-C-induced changes in tumor immune landscape which are critical for achieving complete response and support combining VEGF-C with APMV virotherapy as a novel highly effective strategy for cancer treatment.