IMMUNOTHERAPEUTIC ACTION OF T-BET GENE MODIFIED DENDRITIC CELLS

[摘要] T-bet is a Type-1 transcription factor that regulates the development of Type-1 T cell and Type-1 anti-tumor immunity. T-bet expression in Dendritic Cells (DC) is required for the ability of these antigen-presenting cells (APC) to prime Type-1-polarized T cell responses. Since T-bet is typically expressed by very low frequencies of activated DC (< 1%), we hypothesized that ectopic expression of T-bet as a consequence of recombinant adenovirus (rAd).T-bet transfection would yield a robust population of DC that were capable of (re)polarizing Type-1 anti-tumor T cell responses in vitro and in vivo. Indeed, human DC engineered to express high levels of T-bet strongly potentiated the development of Type-1 T cells from naïve T cells and concomitantly suppressed Th2 and Regulatory T cell (Treg) development in vitro. Interestingly, the superior Type-1 functionality of DC.Tbet seems to be largely independent of intrinsic Interleukin-12 (IL-12) production, as IL-12 neutralizing antibody failed to affect the Type-1 T cell development driven by DC.Tbet. Furthermore, murine DC.Tbet displayed strong anti-tumor function when delivered into tumor sites as a cancer therapeutic modality. The therapeutic efficacy of mDC.Tbet requires the participation of host NK cells and CD8+ T cells, whose induction was independent of the ability of injected mDC.Tbet to produce IL-12 family member cytokines or IFN-γ, or to migrate to tumor-draining lymph nodes (TDLN) based on CCR7 ligand chemokine recruitment. However, optimal therapeutic protection afforded by i.t. delivered mDC.Tbet did require that the injected DC express MHC class I molecules. Analysis of effectively treated tumors revealed early recruitment/activation of NK cells and naïve T cells in the tumor microenvironment within 2 days of intratumoral delivery of DC.Tbet. Hence, my data support a model in which the injected mDC.Tbet serve as dominant drivers for the extranodal (cross)priming of therapeutic immunity within the tumor microenvironment (TME).Gene array analyses performed on human DC.Tbet and control DCs (DC.ψ5) derived from 5 healthy donors revealed numerous differentially expressed genes between DC.Tbet and DC.ψ5 that might associate with the Type-1 polarizing function of DC.Tbet.When taken together, my data suggest that DC.Tbet promote Type-1 anti-tumor immunity through multifaceted cellular and molecular mechanisms.

[发布机构] the University of Pittsburgh