In vitro induction of T cells that are resistant to A₂ adenosine receptor‐mediated immunosuppression

Abstract

Background and purpose:The increased levels of extracellular adenosine in inflamed tissues down-regulate activated immune cells via the A2A adenosine receptor. This A2A adenosine receptor-mediated immunosuppression is a disqualifying obstacle in cancer immunotherapy as it protects cancerous tissues from adoptively transferred anti-tumour T cells. The aim of this study was to test whether the negative selection of T cells will produce T cells that are resistant to inhibition by extracellular adenosine. Experimental approach: Cytotoxic T lymphocytes (CTL) were developed by mixed lymphocyte culture in the presence or absence of the adenosine receptor agonist 5′-N-ethylcarboxamidoadenosine (NECA). The sensitivity of CTL to adenosine analogues was characterized by cAMP induction, interferon-g production and cytotoxicity. Key results: CTL that could proliferate even in the presence of NECA were less susceptible to inhibition by A2A adenosine receptor agonists, as shown by a much smaller accumulation of cAMP and less inhibition of interferon-g production compared with control CTL. The successful protocol to produce CTL that are both resistant to adenosine-mediated immunosuppression and maintain strong cytotoxicity and interferon-g secretion required NECA to be added only during the expansion stage after the establishment of CTL. In contrast, the priming of resting T cells in the presence of NECA resulted in T cells with impaired effector functions. Conclusions and implications: Adenosine-resistant effector T cells were successfully obtained by exposure of activated T cells to NECA. These in vitro studies form the basis for future attempts to produce anti-tumour T cells that are more effective in adoptive immunotherapy.

Hostile, Hypoxia–A2-Adenosinergic Tumor Biology as the Next Barrier to Overcome for Tumor Immunologists

“…Similar effects were observed with effects of the negatively selected A2AR low anti-tumor T cells –that were resistant to inhibition by adenosine (51). …”

Antiproliferative effects of selective adenosine receptor agonists and antagonists on human lymphocytes: evidence for receptor-independent mechanisms

“…Human lymphocytes are responsible for the adaptive cellmediated immune response and are therefore of particular interest as immunomodulatory targets [4,6,9]. Inhibition of T lymphocyte proliferation and induction of apoptosis leads to immunosuppressive and anti-inflammatory effects.…”

“…Adenosine receptors (ARs) are also found on cells of the immune system and have been recognized to play an important role in inflammatory conditions [4][5][6][7], in which adenosine can act as an antiinflammatory and immunosuppressive mediator mainly via the activation of A 2A receptors. It inhibits TNF-α production and has been implicated as a physiological signal in the apoptotic deletion of T cells during intrathymic cell selection, a process which functions to prevent autoimmunity [8][9][10][11].…”

Modulation of G protein-coupled adenosine receptors by strategically functionalized agonists and antagonists immobilized on gold nanoparticles

“…Many studies have shown that attaching a targeted ligand to NPs enhances their biodistribution within solid tumors [30,31]. Thus, tethering an AR ligand that may have its own anticancer activity, such as an A 3 AR agonist or A 2A AR antagonist [32], could serve both targeting and therapeutic purposes. The methodology introduced in this study for AR agonists and antagonists could potentially be applied to other GPCR ligands.…”