Dendritic cell-based vaccination in metastatic melanoma patients: phase II clinical trial

Abstract

Metastatic and chemoresistant melanoma can be a good target of immunotherapy because it is an intractable cancer with a very poor prognosis. Previously, we tested a dendritic cell (DC)-based phase I vaccine, and confirmed that it was safe. In the present study, we performed a phase II trial of a DC vaccine for metastatic melanoma patients with mainly the HLA-A24 genotype, and investigated the efficacy of the vaccine. Twenty-four patients with metastatic melanoma were enrolled into a phase II study of DC-based immunotherapy. The group included 19 HLA-A24-positive (A*2402) patients and 3 HLA-A2-positive (A*0201) patients. The protocol for DC production was similar to that in the phase I trial. Briefly, a cocktail of 5 melanoma-associated synthetic peptides (gp100, tyrosinase, MAGE-A2, MAGE-A3 and MART-1 or MAGE‑A1) restricted to HLA-A2 or A24 and KLH were used for DC pulsing. Finally, DCs were injected subcutaneously (s.c.) into the inguinal region in the dose range of 1-5x107 per shot. The DC ratio (lin-HLA-DR+) of the vaccine was 38.1±13.3% and the frequency of CD83+ DCs was 25.7±20.8%. Other parameters regarding DC processing were not different from phase I. Immune response-related parameters including the ELISPOT assay, DTH reaction to peptide or KLH, DC injection numbers were shown to be related to a good prognosis. The ELISPOT reaction was positive in 75% of the patients vaccinated. The increase of anti-melanoma antigen antibody titer before vaccination was also shown to be a prognosis factor, but that post-vaccination was not. Based on immunohistochemical analysis, CD8 and IL-17 were not involved in the prognosis. Adverse effects of more than grade III were not seen. Overall survival analysis revealed a significant survival prolongation effect in DC-given melanoma patients. These results suggest that peptide cocktail-treated DC vaccines may be a safe and effective therapy against metastatic melanoma in terms of prolongation of overall survival time.

Figure 1

Serum autoantibody against MAGE antigens in melanoma patients before the vaccination. Sera derived from 31 evaluable cases in the phase I and II trials were analyzed. The ELISA for human antibody detection and the control reaction system were described previously. Recombinant GST-tagged MAGE proteins were used as antigens. Open column, GST alone; closed column, GST-tagged MAGE proteins for antigen.

Figure 2

Immunohistochemical analysis of CD8 and IL-17 expression in melanoma tumors. (A) and (B) tumor tissue from MEL-2; (C) and (D) tumor tissue from MEL-11. (A) CD8 staining, (C) IL-17 staining, (B) and (D) isotype control antibody staining. The counter-staining was performed with the Giemsa stain. Magnification, ×100.

Figure 3

Survival time in melanoma patients given the DC vaccine Thirty-three metastatic melanoma patients enrolled in phase I–II trials were analyzed. Survival data derived from 37 cases of melanoma given best supportive care without DC vaccine were utilized as a control. (A) Survival analysis of melanoma patients with and without the DC vaccine. ○, without DC (n=37); ●, with DC (n=33). (B) Survival analysis for high (≥2) and low (<2) ELISPOT scores. ○, score <2 (n=15); ●, score ≥2 (n=18). The difference was analyzed using the log-rank test. Values of P<0.05 were considered statistically significant.