Immunological efficacy of herbal medicines in prostate cancer patients treated by personalized peptide vaccine

Summary

This randomized phase II study investigated the immunological efficacy of herbal medicines (HMs) using Hochu-ekki-to and Keishi-bukuryo-gan in combination with personalized peptide vaccination (PPV) for castration-resistant prostate cancer (CRPC). Seventy patients with CRPC were assigned to two arms; PPV plus HMs or PPV alone. Two to four peptides were chosen from 31 peptides derived from cancer antigens for the eight-time subcutaneous injection of PPV according to the patient's human leukocyte antigen type and levels of antigen-specific immunoglobulin G (IgG) titer before PPV treatment. Peptide-specific cytotoxic T lymphocyte (CTL), IgG, regulatory T cells (Treg), monocytic myeloid-derived suppressor cells (Mo-MDSC), and interleukin-6 (IL-6) responses were measured before and at the 8th vaccination. Clinical outcomes were also analyzed. The combination therapy of PPV with HMs was well tolerated without severe adverse events. There was no significant change in antigen-specific IgG, CTL, Treg or clinical outcomes. The combination therapy of PPV with HMs stabilized the frequency of Mo-MDSC (1.91% to 1.92%, p = 0.96) and serum levels of IL-6 (19.2 pg/ml to 16.1 pg/ml, p = 0.63) during the treatment. On the other hand, the frequency of Mo-MDSC and levels of IL-6 in the PPV alone group were significantly increased (0.91% to 1.49% for Mo-MDSC and 9.2 pg/ml to 19.4 pg/ml for IL-6, respectively). These results suggested that the combined usage of HMs has the potential to prevent the immunosuppression induced by Mo-MDSC or IL-6 during the immunotherapy. More research is needed to validate the findings of the present study.

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