Effect of matrix metalloproteinase-2 on the ability of human dendritic cells to prime inflammatory TH2 cells via an IL-12 and OX40L dependent pathway.

Abstract

10622 Background: Antigens expressed by melanoma cells (MAA) and recognized by T lymphocytes have been used in various immunization strategies to treat cancer patients. However, the therapeutic efficacy of these approaches remains limited. Because MMP-2 (matrix metalloproteinase-2) activity is critical for melanoma progression, this protein represents a unique antigen for vaccine therapy. Methods: CD4+ T cells were stimulated with overlapping MMP-2 peptides. After 12 days, MMP-2-specific responses were determined by intracellular staining of cytokines. Specific T cells from positive samples were enriched and cloned using limiting dilution. Cytokine production was assessed by ELISA, intracellular staining, or cytometric bead array method. Results: We identified 11 novel CD4 MMP-2-derived epitopes, and showed that the corresponding T cells, detected in the CD45RO+/CD62L- memory fraction, displayed an inflammatory TH2 profile, i.e. mainly secreting TNF, IL-4 and IL-13 and expressing the TH2-specific transcription factor GATA-3. In contrast, CD4+ T cells that recognize other associated MAAs were typically TH1. Interestingly, naïve T cells primed with active MMP-2 gave rise to TH2 specific cells, while naïve T cells primed with peptides generated IFNg-secreting specific cells, consistent with a TH1 profile. Accordingly, we showed that the MMP-2 enzyme inhibited IL-12p35 production and induced OX40L expression by DCs. Both events were responsible for the TH2 skewing of MMP-2-specific T cells and other MAA-specific T cells. Furthermore, MMP-2 specific TH2 cells were found in 13 tumor-infiltrating lymphocyte populations out of the 31 melanoma patients tested. Conclusions: The protease activity of MMP-2 influences DC phenotype, more precisely IL-12 production and OX40L expression, which are responsible for the observed TH2 lineage commitment of MMP-2-specific T cells and other MAA-specific T cells. These findings open the way to therapeutic strategies skewing these already frequent and diverse MMP-2-specific responses towards a more efficient anti-tumor TH1 phenotype to treat melanoma patients. No significant financial relationships to disclose.