ARID1A mutations protect follicular lymphoma from FAS-dependent immune surveillance by reducing RUNX3/ETS1-driven...

Area of Science:

• Immunology
• Oncology
• Molecular Biology

Background:

• The FAS receptor and FAS ligand (FASLG) are critical for B cell selection in germinal centers (GCs).
• Defects in FAS-mediated apoptosis can drive lymphoproliferation and B cell malignancies like follicular lymphoma (FL).
• ARID1A mutations are clinically relevant in FL, but their pathogenic mechanism is unclear.

Purpose of the Study:

• To investigate the role of ARID1A mutations in the pathogenesis of follicular lymphoma.
• To elucidate the mechanism by which ARID1A alterations affect FAS expression and immune surveillance.
• To assess the impact of these alterations on lymphoma cell sensitivity to apoptosis and CAR T cell therapy.

Main Methods:

• Analysis of 151 FL patient biopsies to determine ARID1A mutation frequency and FAS expression.
• Functional experiments in BCL2-translocated lymphoma cells to study ARID1A's regulation of FAS.
• Investigation of the RUNX3/ETS1 complex in FAS gene regulation and assessment of CAR T cell killing assays.

Main Results:

• ARID1A mutations were recurrent (18%) and disruptive in FL, correlating with significantly lower FAS protein expression.
• ARID1A loss reduced FAS expression independently of promoter accessibility, implicating a RUNX3/ETS1 co-transcriptional complex.
• Reduced FAS levels conferred resistance to FASLG-induced apoptosis and diminished CAR T cell-mediated killing.

Conclusions:

• ARID1A mutations promote FL immune evasion by downregulating FAS expression via impaired RUNX3 regulation.
• This mechanism highlights how FL cells escape FAS-dependent immune surveillance.
• The findings have implications for the efficacy of T cell-based immunotherapies, including CAR T cells, in FL treatment.