Robo4 vaccines induce antibodies that retard tumor growth

Area of Science:

• Immunology
• Oncology
• Vascular Biology

Background:

• Robo4 is a plasma membrane protein specifically expressed on tumor endothelial cells in adults.
• This specific expression makes Robo4 a potential target for cancer immunotherapy, particularly vaccination.
• Breaking immune tolerance to self-antigens like Robo4 is crucial for effective auto-antigen vaccination.

Purpose of the Study:

• To investigate the efficacy of vaccination against Robo4 as an anti-cancer immunotherapeutic strategy.
• To determine the mechanism of anti-tumor and anti-angiogenic effects induced by Robo4 vaccination.
• To explore the potential of Robo4 conjugates as anti-angiogenic vaccines.

Main Methods:

• Mice were immunized with the extracellular domain of mouse Robo4 fused to human immunoglobulin Fc domain with an adjuvant.
• Assessed antibody response to Robo4 and evaluated health effects.
• Utilized a rodent sponge implantation assay to measure fibrovascular invasion and angiogenesis.
• Tested tumor growth inhibition using syngeneic Lewis lung carcinoma in vaccinated mice, including CD8-deficient, B cell knockout, and IgG1 knockout models.
• Investigated adjuvant-free soluble Robo4-carrier conjugates in carrier-primed mice.

Main Results:

• Robo4 vaccination induced a strong antibody response with no observable adverse health effects.
• Vaccinated mice exhibited impaired fibrovascular invasion and angiogenesis in the sponge assay.
• A significant reduction in Lewis lung carcinoma tumor growth was observed in Robo4-vaccinated mice.
• The anti-tumor effect was maintained in CD8-deficient mice but lost in B cell or IgG1 knockout mice, indicating antibody-dependent cell-mediated cytotoxicity (ADCC).
• Adjuvant-free soluble Robo4-carrier conjugates retarded tumor growth in primed mice.

Conclusions:

• Vaccination against tumor endothelial specific Robo4 effectively inhibits angiogenesis and tumor growth.
• The anti-tumor mechanism appears to involve antibody-dependent cell-mediated cytotoxicity.
• Robo4 conjugates represent a promising strategy for developing novel anti-angiogenic vaccines for cancer therapy.