CTLA4 and neoplasm: Conjugating the CD80 protein improves efficacy of the nanoparticles, as interaction of this ligand with the CTLA-4 receptor is shown to induce cell death.18 Conjugating the VEGF antibody results in increased specificity of the delivery system toward VEGF-positive osteoblasts with CTLA-4, resulting in the best approach for preventing tumor growth and stimulating cell death.