An mRNA vaccine targeting angiogenesis elicits a robust immune response and inhibits tumor growth and angiogenesis in two mouse melanoma models

Background: Angiogenesis is essential for tumor growth, metastasis, and the establishment of an immunosuppressive microenvironment. By supporting nutrient delivery and modulating immune cell infiltration, tumor-driven angiogenesis promotes both malignant progression and immune evasion. Among its key regulators, adrenomedullin (AM) is a potent pro-angiogenic factor frequently overexpressed in solid tumors. To explore its therapeutic potential, we developed an mRNA vaccine encoding a fusion antigen composed of a small keyhole limpet hemocyanin (KLH) peptide, as a hapten, linked to mouse AM. Methods: The in vitro transcribed mRNA was encapsulated in lipid nanoparticles (LNPs) and administered to C57BL/6 mice, with empty LNPs serving as controls. The vaccine was evaluated in two distinct melanoma models: an experimental lung metastasis model induced by intravenous injection of B16-F10 melanoma cells, and a subcutaneous melanoma model. After four immunizations, melanoma cells were injected, followed by a fifth immunization. Mice were sacrificed once tumors reached humane endpoints and blood and organs were analyzed. Results: Vaccinated mice exhibited significant increases in anti-AM IgG titers (p= 0.040) and CD8+ T cell numbers (p=0.033) compared to controls. In the lung metastasis model, immunization resulted in a significant reduction in both the number (p=0.028) and size of lung metastases (p=0.020) as well as a decrease in the number of tumor-associated blood vessels (p=0.046), without disrupting normal vasculature as assessed in SMAA-GFP transgenic mice. In the subcutaneous model, vaccination delayed tumor initiation (p=0.005) and reduced tumor volume (p=0.004), accompanied by decreased tumor angiogenesis (p=0.045). Importantly, no systemic toxicity or significant changes in weight were observed. Conclusion: By targeting angiogenesis, the KLH-AM mRNA vaccine effectively impaired tumor growth in melanoma models. These results highlight AM as an important pro-angiogenic factor driving tumor vascularization and support further development of AM-directed mRNA therapeutic vaccination as a strategy to disrupt angiogenesis-dependent tumor progression.This study was funded by Agencia Estatal de Investigación (AEI, Spain)'s project PID2022-136735OB-I00.