In combination with the use of an antibody against the cytotoxic T lymphocyte antigen-4 (CTLA-4), an inhibitor of T-cell responses, vaccination with Id2kd-Neuro2a cells of mice bearing established neuroblastoma tumors has been shown not only to suppress the tumor growth but also to eradicate the tumor itself [331]. This evidence concerns the gene CTLA4 and neoplasm.