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金沢大学先進予防医学研究センター / 金沢大学医薬保健研究域医学系, Multidrug resistance-associated protein 3 (MRP3) is a carrier-type transport protein belonging to the ABC transporters. In this study, we investigated the safety and immunogenicity of a MRP3-derived peptide (MRP3765) as a vaccine and characterized the MRP3-specific T cell responses induced. Twelve hepatocellular carcinoma (HCC) patients treated with hepatic arterial infusion chemotherapy (HAIC) were enrolled. The MRP3-derived peptide was emulsified in incomplete Freund's adjuvant and administered via subcutaneous immunization three times weekly. No serious adverse drug reactions to the peptide vaccine were observed, and the vaccination was well tolerated. The vaccination induced MRP3-specific immunity in 72.7% of the patients. In a phenotypic analysis, the largest post-vaccinated increase in MRP3-specific T cells was due to an increase in cells with the effector memory phenotype. Among the 12 patients, one patient showed a partial response, nine showed a stable disease, and two showed a progressive disease. The median overall survival time was 14.0 months. In conclusion, the safety, effects of immune boosting, and possible prolongation of overall survival by the MRP3-derived peptide demonstrate the potential of the peptide to provide clinical benefit in HCC patients. © 2015.

Human telomerase reverse transcriptase (hTERT) is a catalytic enzyme required for telomere elongation. In this study, we investigated the safety and immunogenicity of an hTERT-derived peptide (hTERT461) as a vaccine and characterized the hTERT-specific T cell responses induced. Fourteen hepatocellular carcinoma (HCC) patients were enrolled in the study. The hTERT-derived peptide was emulsified in incomplete Freund's adjuvant and administered via subcutaneous immunization three times biweekly. The maximum toxicity observed was grade 2 according to the common terminology criteria and mainly consisted of skin reactions at the site of vaccination. The vaccination induced hTERT-specific immunity in 71.4% of patients and 57.1% of patients administered with hTERT461 peptide-specific T cells could prevent HCC recurrence after vaccination. In phenotypic analysis, the post-vaccinated increase in hTERT-specific T cells was due to an increase in cells with the effector memory phenotype, with the potential to produce multiple cytokines. Seven hTERT-specific T cell receptors were obtained from the vaccinated patients, showing their cytotoxic activities to hTERT-derived peptide-bearing cells. In conclusion, the safety and effects of immune boosting by hTERT461 peptide have shown the potential of the peptide to provide clinical benefits in HCC patients.