Loss of ADAR1 in tumours overcomes resistance to immune checkpoint blockade

Area of Science:

• Immunology
• Oncology
• Molecular Biology

Background:

• Many cancer patients do not respond to immune checkpoint blockade (ICB) or develop resistance.
• Impaired antigen presentation due to acquired mutations is a common cause of ICB resistance.
• RNA editing plays a critical role in regulating cellular responses to immune stimuli.

Purpose of the Study:

• To investigate the role of the RNA-editing enzyme ADAR1 in tumor response to immunotherapy.
• To determine if loss of ADAR1 function can overcome resistance to ICB.
• To elucidate the mechanisms by which ADAR1 influences anti-tumor immunity.

Main Methods:

• Studied the effects of ADAR1 loss-of-function in tumor cells.
• Analyzed A-to-I RNA editing levels of interferon-inducible RNAs.
• Investigated the activation of PKR and MDA5 pathways.
• Assessed tumor sensitization to PD-1 checkpoint blockade.

Main Results:

• Loss of ADAR1 function profoundly sensitizes tumors to immunotherapy.
• Reduced ADAR1 activity leads to decreased A-to-I editing of interferon-inducible RNAs.
• This results in activation of PKR and MDA5, promoting tumor growth inhibition and inflammation.
• Loss of ADAR1 overcomes PD-1 blockade resistance caused by impaired antigen presentation.

Conclusions:

• ADAR1 acts as an inhibitory checkpoint limiting innate ligand sensing in anti-tumor immunity.
• Targeting ADAR1 can sensitize tumors to immunotherapy and overcome resistance.
• Inducing inflammation via ADAR1 inhibition may bypass the need for CD8+ T cell recognition, offering a general strategy against immunotherapy resistance.