Inhibition of Cytokine Production and Cytotoxic Activity of Human Antimelanoma Specific CD8+ and CD4+ T Lymphocytes by Adenosine-Protein Kinase A Type I Signaling

Abstract

The goal of this study was to investigate the effects of adenosine and its stable analogue 2-chloroadenosine (CADO) on the cytotoxic activity and cytokine production by human antimelanoma specific CD8 + and CD4 + T-helper type 1 (Th1) clones. The cytotoxic activity of CD8 + T cells was inhibited by adenosine and CADO. Using Lab MAP multiplex technology, we found that adenosine inhibits production of various cytokines and chemokines by CD8 + and CD4 + T cells. Studies with CGS21680, a specific agonist of adenosine A 2A receptor (AdoRA 2A ), and ZM241385, an AdoRA 2 -selective antagonist, indicate that the inhibitory effects of adenosine are mediated via cyclic AMP (cAMP)-elevating AdoRA 2A , leading to protein kinase A (PKA) activation. Using cAMP analogues with different affinities for the A and B sites of the regulatory subunits of PKAI and PKAII, we found that activation of PKAI, but not of PKAII, mimicked the inhibitory effects of adenosine on T-cell cytotoxic activity and cytokine production. Inhibitors of the PKA catalytic subunits (H89 and PKA inhibitor peptide 14-22) failed to abrogate the inhibitory effects of CADO. In contrast, Rp-8-Br-cAMPS that antagonizes binding of cAMP to the regulatory I subunit and PKA activation was efficient in blocking the inhibitory effect of adenosine on the functional activity of T cells. Our findings on the ability of adenosine to inhibit the effector function of antimelanoma specific T cells suggest that intratumor-produced adenosine could impair the function of tumor-infiltrating T lymphocytes. Thus, blocking the inhibitory activity of tumor-produced adenosine might represent a new strategy for improvement of cancer immunotherapy. [Cancer Res 2007;67(12):5949-56]

A2A Adenosine Receptor May Allow Expansion of T Cells Lacking Effector Functions in Extracellular Adenosine-Rich Microenvironments

“…The accumulated studies of cAMP-and PKA-mediated inhibition of T cell functions have demonstrated that cAMP-elevating A2AR agonists inhibit cytotoxic activity through down-regulation of Fas ligand and granule exocytosis (27)(28)(29)(30). A2AR-mediated signaling may down-regulate the very early events of TCR signaling because PKA phosphorylates COOH-terminal Src kinase to inhibit T cell activation by interrupting Lck activation (31).…”

Human Tumor Antigen-Specific Helper and Regulatory T Cells Share Common Epitope Specificity but Exhibit Distinct T Cell Repertoire

“…As control, CFSE-labeled clones 11/4 and 4/43 were also incubated with TRAG-3-specific CD4 + Th clone 62/8 or NY-ESO-1-specific CD4 + T cell clone 107/5, respectively. Clones 11/4 and 4/43 were previously described (16,17). Clone 11/4 was tested in cytokine production assays and CFSE proliferation assays to confirm its Th functions.…”

PGE2 inhibits natural killer and γδ T cell cytotoxicity triggered by NKR and TCR through a cAMP-mediated PKA type I-dependent signaling

“…The present study did not investigate the ability of PGE 2 to inhibit NKG2D co-activation of CTL. Nevertheless, the ability of PKA type I to inhibit NKG2D-mediated activation of NK and  T cells, strongly suggests that PGE 2 will inhibit NKG2D signaling in CTL since previous studies demonstrated that the increase of cAMP mediated by PGE 2 leads to PKA type I activation in these cells [29,48].…”