Identification of HLA-A2- or HLA-A24-Restricted CTL Epitopes Possibly Useful for Glypican-3-Specific Immunotherapy of Hepatocellular Carcinoma

Abstract

Purpose and Experimental Design: We previously reported that glypican-3 (GPC3) was overexpressed, specifically in hepatocellular carcinoma (HCC) and melanoma in humans, and it was useful as a novel tumor marker. We also reported that the preimmunization of BALB/c mice with dendritic cells pulsed with the H-2K^d-restricted mouse GPC3_298-306 (EYILSLEEL) peptide prevented the growth of tumor-expressing mouse GPC3. Because of similarities in the peptide binding motifs between H-2K^d and HLA-A24 (A*2402), the GPC3_298-306 peptide therefore seemed to be useful for the immunotherapy of HLA-A24⁺ patients with HCC and melanoma. In this report, we investigated whether the GPC3_298-306 peptide could induce GPC3-reactive CTLs from the peripheral blood mononuclear cells (PBMC) of HLA-A24 (A*2402)⁺ HCC patients. In addition, we used HLA-A2.1 (HHD) transgenic mice to identify the HLA-A2 (A*0201)–restricted GPC3 epitopes to expand the applications of GPC3-based immunotherapy to the HLA-A2⁺ HCC patients.

Results: We found that the GPC3_144-152 (FVGEFFTDV) peptide could induce peptide-reactive CTLs in HLA-A2.1 (HHD) transgenic mice without inducing autoimmunity. In five out of eight HLA-A2⁺ GPC3⁺ HCC patients, the GPC3_144-152 peptide-reactive CTLs were generated from PBMCs by in vitro stimulation with the peptide and the GPC3_298-306 peptide-reactive CTLs were also generated from PBMCs in four of six HLA-A24⁺ GPC3⁺ HCC patients. The inoculation of these CTLs reduced the human HCC tumor mass implanted into nonobese diabetic/severe combined immunodeficiency mice.

Conclusion: Our study raises the possibility that these GPC3 peptides may therefore be applicable to cancer immunotherapy for a large number of HCC patients.