Purpose: Heat shock protein 105 (HSP105) is overexpressed in a variety of human cancers, including colorectal cancer (CRC) and esophageal cancer (EC). We identified HLA-A24 or A2-restricted HSP105 peptides that can induce HSP105 peptide-specific cytotoxic T lymphocytes (CTLs) (EP1536006, JP5112615, JP5291641, US9,404,925) and curried out a phase I clinical trial of HLA-A24 or A2-restricted HSP105 peptide vaccine in patients with CRC or EC (UMIN ID000017809). In this study, we aimed to demonstrate the immunological efficacy of the novel vaccine. Experimental design: 30 patients (HLA-A24 group; 15 patients, HLA-A2 group; 15 patients) with advanced CRC or EC were enrolled. Two types of vaccine (A24-1 and A24-7 or A2-7 and A2-12) were administered into the patients, matching HLA-types. Immunological responses were analyzed by ex vivo and in vitro IFN-γ ELISPOT assay using peripheral blood mononuclear cells before and after vaccination, and cytokines produced by HSP105-specific CTLs were measured by Cytometric Bead Array assay. We also analyzed the correlation between immunological responses and prognosis. Result: HSP105 peptide vaccines induced HSP105 peptide-specific CTLs in 15 of 30 patients. In HLA-A24 group, there were 7 patients with the induction only in ex vivo and almost all patients (n=13) showed skin reactions of vaccine sites. By contrast, in HLA-A2 group, there were 4 patients with the induction in ex vivo and 6 patients in in vitro, respectively, and only 6 patients with skin reactions of vaccine sites. In all patients, the existence of skin reaction correlated with the induction in ex vivo (p<0.01). The progression-free survival (PFS) and overall survival (OS) were significantly longer in patients with the induction (n=15) than in those without (n=15) (P<0.01, respectively). The peptide-specific CTL frequency correlated with OS and could be a predictive marker of PFS and OS. Furthermore, HSP105 peptide-specific cytokine production was observed in various tissues of 8 patients, such as vaccine injected sites skins, metastatic and primary tumors. It suggested that HSP105-specific CTLs not only accumulated at injected sites but also infiltrated into tumor tissues. Additionally, we succeeded in establishing two types of highly functional HSP105 peptide-specific CTL clones and sequenced the T-cell receptors (TCRs) of these clones. Conclusion: Our results suggested that HSP105 peptide vaccine could improve the prognosis of patients with advanced CRC and EC by inducing the antitumor immune responses. To further extend the efficacy, we are developing TCR-engineered T-cell therapy using TCR sequences obtained from HSP105 peptide-specific CTL clones and intratumoral injection method of this vaccine.

Citation Format: Yasuhiro Shimizu, Toshiaki Yoshikawa, Kojima Takashi, Kayoko Shoda, Kazuto Nosaka, Shoichi Mizuno, Satoshi Wada, Yuki Fujimoto, Tetsuro Sasada, Kenichi Kohashi, Hideaki Bando, Itaru Endo, Tetsuya Nakatsura. Immunologic efficacy of heat shock protein 105 peptide vaccine in patients with advanced colorectal and esophageal cancer [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A017.