Investigation of a possible immunosuppressive bias in dendritic cells derived from cancer patients.

Author(s)

Rodrigo Nalio Ramos

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2011-04-29

Examining board members

Jose Alexandre Marzagao Barbuto; Niels Olsen Saraiva Câmara; Roger Chammas

• Advisor: Jose Alexandre Marzagao Barbuto

Abstract

Dendritic cells (DCs) are the most effective professional antigen-presenting cells. Even considering the possibility of generating DCs in vitro, which allowed the design of antitumor vaccination protocols, mechanisms of peripheral tolerance mediated by regulatory T cells prevent an effective antitumor immune response. The aim of our study was evaluate, in vitro, the induction of regulatory T cells by dendritic cells derived from breast cancer patients.DCs were differentiated from breast cancer patients blood monocytes, for seven days, in the presence of GM-CSF and IL-4 (immature DCs- iDCs) and activated by TNF-<font face=\"Symbol\">a on day five of culture (mature DCs- mDCs). DCs were characterized by flow cytometry to CD1a, CD11c, CD14, CD80, CD86, CD83, CD123, PD-L1, HLA-ABC and HLA-DR expression; the cytokine secretion to IL-10 and bioactive TGF-beta1, by ELISA; and in functional assay by co-culturing DCs with T lymphocytes (CD3+, CD3+CD25neg or CD4+CD25neg) isolated by microbeads. Cell activation (CD25 expression), proliferation (CFSE dilution), cytokine production (IFN-gamma, IL-10 and TGF-beta1) and de novo regulatory T cells (Tregs) generation, were analyzed in these co-cultures after 5 or 6 days. Tregs were characterized by their phenotype (CD4+CD25+CD127LowCTLA-4+Foxp3+) and suppressive capability on allogeneic T cell proliferation. Patients iDCs showed a higher expression of CD86 (two subpopulation: CD86High and CD86Low) and CD123 beyond the elevated production of IL-10 and bioactive TGF-beta1. Co-cultures using patients DCs presented high levels of bioactive TGF-beta1 (298.08 pg/ml x ctrl: 57.63 pg/ml) and induced elevated frequency of Tregs (iDCs: 57% ± 4.1; mDCs: 48% ± 5.0 x ctrl: 2.5% ± 0.7) from CD25neg Foxp3neg precursors, which were able to suppress the allogeneic lymphocyte proliferation. The TGF-beta blocking partially reduced the frequency of induced Tregs by patients DCs. These findings are consistent with the higher frequency of Tregs on peripheral blood of those patients (19.5% ± 2.3 x ctrl 8% ± 2.3) and the presence of DCs also on the blood, showing similar markings with iDCs generated in vitro. Contrastingly, iDCs from healthy donors were better stimulator cells, leading to a higher CD25+ cell frequency (ctrl 35.7% ± 7.9 x 11.8 ± 5.9% CD25+), more intense proliferation of CD4+ (82.7% x 29.4%) and CD8+ (73.8% x 21%) cells and higher production of IFN-gamma (109.85 pg/ml x 7.86 pg/ml) on co-cultures. These data indicate that DCs derived from breast cancer patients show an immunosuppressive bias that is not strictly dependent on DCs maturation status or TGF-beta. Finally, these observations call to caution in the use of patients monocytes for the generation of DC-based vaccines and also contribute to the comprehension of the interactions between the immune system and cancer. (AU)

• FAPESP's process: 09/02074-6 - Investigation of a possible immunossuppressive bias in monocyte-derived dendritic cells from cancer patients
• Grantee: Rodrigo Nalio Ramos
• Support Opportunities: Scholarships in Brazil - Master