Desarrollo de inhibidores del factor de transcripción FOXP3 para su uso en estrategias de inmunoterapia

Abstract

The transcription factor FOXP3 plays a major role in the control of immune homeostasis mediated by T regulatory cells (Treg). Although Treg are essential for the prevention of autoimmune diseases, their immunoregulatory function may hinder the induction of immune responses against cancer and infectious agents. Thus, development of inhibitors of FOXP3 might give new therapeutic opportunities for these diseases. In a previous work we identified a peptide (named P60) able to impair Treg activity in vitro and in vivo. The first aim was characterize the mechanism of the P60 peptide and its optimization, here we show that P60 binds to the intermediate region of FOXP3 and inhibits its homodimerization and interaction with AML1. By using a panel of P60-derived peptides with alanine substitutions at each position we analyzed their relevance on their functions and we can identify peptides P60-D2A, P60-D2A-S5A lineal and cyclic version and P60-D2A-S5A-P11A with higher Foxp3 binding affinity and stronger biological activity than the original P60. This study provides important structure¿function relationships essential for further drug design. The second aim was identification of new peptides derived from Foxp3 with the ability to inhibit protein-protein interactions. We found that a short synthetic peptide able to inhibit FOXP3/NFAT interaction impaired suppressor activity of conventional Treg in vitro. Also, this peptide upregulated CD40L expression on effector T-cells and enhanced T-cell proliferation and IL-2, IFN-γ IL-6 or IL-17 production in response to TCR stimulation. The inhibitory peptide impaired effector T cell conversion into iTreg in the presence of TGF-β. Moreover, in vivo peptide administration showed antitumor efficacy in mice bearing Hepa129 or TC1 tumor cells. Our results suggest that inhibition of NFAT/FOXP3 interaction might improve antitumor immunotherapies.