Low-Dose Decitabine Augments the Activation and Anti-Tumor Immune Response of IFN-γ + CD4 + T Cells Through Enhancing IκBα Degradation and NF-κB Activation

CD4 T cells play multiple roles in controlling tumor growth and increasing IFN-γ T-helper 1 cell population could promote cell-mediated anti-tumor immune response. We have previously showed that low-dose DNA demethylating agent decitabine therapy promotes CD3 T-cell proliferation and cytotoxicity; however, direct regulation of purified CD4 T cells and the underlying mechanisms remain unclear. The effects of low-dose decitabine on sorted CD4 T cells were detected both and . The activation, proliferation, intracellular cytokine production and cytolysis activity of CD4 T cells were analyzed by FACS and DELFIA time-resolved fluorescence assays. ubiquitination assay was performed to assess protein degradation. Moreover, phosphor-p65 and IκBα levels were detected in sorted CD4 T cells from solid tumor patients with decitabine-based therapy. Low-dose decitabine treatment promoted the proliferation and activation of sorted CD4 T cells, with increased frequency of IFN-γ Th1 subset and enhanced cytolytic activity and . NF-κB inhibitor, BAY 11-7082, suppressed decitabine-induced CD4 T cell proliferation and IFN-γ production. In terms of mechanism, low-dose decitabine augmented the expression of E3 ligase β-TrCP, promoted the ubiquitination and degradation of IκBα and resulted in NF-κB activation. Notably, we observed that low-dose decitabine treatment induced NF-κB activation in CD4 T cells from patients with a response to decitabine-primed chemotherapy rather than those without a response. These data suggest that low-dose decitabine potentiates CD4 T cell anti-tumor immunity through enhancing IκBα degradation and therefore NF-κB activation and IFN-γ production.