Unlocking antitumor immunity with adenosine receptor blockers

Area of Science:

• Immunology
• Oncology
• Pharmacology

Background:

• Tumors create a suppressive tumor microenvironment (TME) to evade immune detection and destruction.
• This immunosuppression is mediated by mechanisms including limited antigen presentation, impaired lymphocyte and natural killer (NK) cell function, and T cell exhaustion.
• While checkpoint inhibitors (e.g., anti-PD-1, anti-CTLA4) improve outcomes for some patients, not all respond, necessitating novel therapeutic strategies.

Purpose of the Study:

• To review the role of adenosine as a critical immunosuppressive factor within the TME.
• To explore adenosine's mechanism of action, particularly its mediation through adenosine A2A receptors (A2AR) and adenosine A2B receptors (A2BR).
• To discuss the potential of targeting adenosine pathways to enhance antitumor immunity and improve cancer patient survival.

Main Methods:

• Literature review focusing on the immunosuppressive functions of adenosine in the tumor microenvironment.
• Analysis of the role of extracellular adenosine triphosphate (ATP) and its metabolite adenosine (ADO).
• Examination of adenosine receptor signaling (A2AR and A2BR) on tumor-associated immune cells.

Main Results:

• Extracellular adenosine, derived from ATP, is abundant in inflamed tumors and promotes immunosuppression.
• Adenosine exerts its immunosuppressive effects through A2AR and A2BR expressed on tumor-associated lymphoid and myeloid cells.
• Adenosine acts as a key immunosuppressive mediator, functioning similarly to checkpoint inhibitors in suppressing antitumor responses.

Conclusions:

• Adenosine is a significant immunosuppressive player in the TME, contributing to immune evasion by tumors.
• Blocking adenosine production or inhibiting A2AR and A2BR presents a promising therapeutic strategy.
• Targeting adenosine pathways holds potential for enhancing antitumor immunity and overcoming resistance to current immunotherapies.