Supplemental Figure 3.2. Splenocytes ( CFSE labelled) from naïve WT mice were activated with soluble anti-CD3 and anti-CD28 antibodies in the presence of RFP+Treg cells sorted (as mentioned above) from control, LNIL and TGF-β groups. After 72 hours, cells were havested and surface stained for CD8 T cells and CFSE dilution profile was measured by flow cytometry.
ARTICLE ABSTRACT
Purpose: Expression of inducible nitric oxide synthase (iNOS) in different cellular compartments may have divergent effects on immune function. We used a syngeneic tumor model to functionally characterize the role of iNOS in regulation of CD4+FOXP3+ regulatory T cells (Treg), and optimize the beneficial effects of iNOS inhibition on antitumor immunity.Experimental Design: Wild-type (WT) or iNOS knockout mice bearing established MT-RET-1 melanoma were treated with the small-molecule iNOS inhibitor L-NIL and/or cyclophosphamide alone or in combination. The effect of iNOS inhibition or knockout on induction of Treg from mouse and human CD4+ T cells in ex vivo culture was determined in parallel in the presence or absence of TGFβ1-depleting antibodies, and TGFβ1 levels were assessed by ELISA.Results: Whereas intratumoral myeloid-derived suppressor cells (MDSC) were suppressed by iNOS inhibition or knockout, systemic and intratumoral FOXP3+ Treg levels increased in tumor-bearing mice. iNOS inhibition or knockout similarly enhanced induction of Treg from activated cultured mouse splenocytes or purified human or mouse CD4+ T cells in a TGFβ1-dependent manner. Although either iNOS inhibition or Treg depletion with low-dose cyclophosphamide alone had little effect on growth of established MT-RET1 melanoma, combination treatment potently inhibited MDSC and Treg, boosted tumor-infiltrating CD8+ T-cell levels, and arrested tumor growth in an immune-dependent fashion.Conclusions: iNOS expression in CD4+ T cells suppresses Treg induction by inhibiting TGFβ1 production. Our data suggest that iNOS expression has divergent effects on induction of myeloid and lymphoid-derived regulatory populations, and strongly support development of combinatorial treatment approaches that target these populations simultaneously. Clin Cancer Res; 20(24); 6439–51. ©2014 AACR.
