Immunological efficacy of glypican-3 peptide vaccine in patients with advanced hepatocellular carcinoma

ABSTRACTWe have previously conducted a phase I trial to test the efficacy of a glypican-3 (GPC3) peptide vaccine in patients with advanced hepatocellular carcinoma (HCC); however, its immunological mechanism of action remains unclear. Here, we report a pilot study conducted to evaluate the immunological mechanisms of action of this GPC3 peptide vaccine (UMIN-CTR number 000005093). Eleven patients with advanced HCC were vaccinated with the GPC3 peptide in this trial. The primary end point was GPC3 peptide-specific immune response induced by the GPC3 peptide vaccination. The secondary endpoints were clinical and biologic outcomes. We demonstrated that the present vaccine induced GPC3 peptide-specific cytotoxic T lymphocytes (CTLs), which were found to infiltrate into the tumor. Moreover, we established GPC3 peptide-specific CTL clones from a biopsy specimen: these cells exhibited GPC3 peptide-specific cytokine secretion and cell cytotoxicity. The plasma GPC3 level tended to decrease temporarily at least onc...