Vaccination with mRNA-Electroporated Dendritic Cells Induces Robust Tumor Antigen-Specific CD4+ and CD8+ T Cells Responses in Stage III and IV Melanoma Patients

PURPOSE:

Electroporation of dendritic cells (DC) with mRNA encoding tumor-associated antigens (TAA) has multiple advantages compared to peptide loading. We investigated the immunologic and clinical responses to vaccination with mRNA-electroporated DC in stage III and IV melanoma patients. Experimental design: Twenty-six stage III HLA*02:01 melanoma patients scheduled for radical lymph node dissection (stage III) and 19 melanoma patients with irresectable locoregional or distant metastatic disease (referred to as stage IV) were included. Monocyte-derived DC, electroporated with mRNA encoding gp100 and tyrosinase, were pulsed with keyhole limpet hemocyanin and administered intranodally. TAA-specific T-cell responses were monitored in blood and skin-test infiltrating lymphocyte (SKIL) cultures.
RESULTS:

Comparable numbers of vaccine-induced CD8(+) and/or CD4(+) TAA-specific T-cell responses were detected in SKIL cultures; 17/26 stage III patients and 11/19 stage IV patients. Strikingly, in this population, TAA-specific CD8(+) T cells that recognize multiple epitopes and produce elevated levels of IFNg upon antigenic challenge in vitro, were significantly more often observed in stage III patients; 15/17 versus 3/11 stage IV patients, P = 0.0033. In stage IV patients, one mixed and one partial response were documented. The presence or absence of IFNg-producing TAA-specific CD8(+) T cells in stage IV patients was associated with marked difference in median overall survival of 24.1 months versus 11.0 months, respectively.
CONCLUSION:

Vaccination with mRNA-electroporated DC induces a broad repertoire of IFNg producing TAA-specific CD8(+) and CD4(+) T-cell responses, particularly in stage III melanoma patients. Clin Cancer Res; 18(19); 5460-70. ©2012 AACR.