We discovered the cancer-specific antigen glypican-3 (GPC3) and identified peptides that can induce cytotoxic T lymphocytes (CTLs) in an HLA-A24- or -A2-restricted manner and conducted clinical trials of peptide vaccines for hepatocellular carcinoma, ovarian clear cell carcinoma, and pediatric cancer [1,2,3,4,5]. This evidence concerns the gene GPC3 and childhood malignant neoplasm.