The atypical IκB factor IκBδ enhances CD8 T cell accumulation and effector functions in solid tumors

Area of Science:

• Immunology
• Cancer Biology
• Molecular Biology

Background:

• Tumors evade immune control by limiting T cell survival, expansion, and cytotoxic function.
• CD8+ tumor-infiltrating lymphocytes (TILs) are crucial for anti-tumor immunity but face significant constraints within the tumor microenvironment.
• Understanding molecular mechanisms that overcome these constraints is vital for enhancing cancer immunotherapy.

Purpose of the Study:

• To identify molecular factors that enhance the anti-tumor efficacy of CD8+ TILs.
• To investigate the role of IκBδ, a member of the IκB family, in regulating TIL function and anti-tumor responses.
• To determine how IκBδ influences TIL accumulation, effector function, and exhaustion.

Main Methods:

• Utilized genetic manipulation (depletion and overexpression) of IκBδ (encoded by *Nfkbid*) in CD8+ T cells.
• Assessed TIL accumulation, expansion, and cytotoxic capacity in tumor models.
• Analyzed the expression of exhaustion-associated transcription factors and inhibitory receptors.
• Investigated the functional roles of different IκBδ protein isoforms.

Main Results:

• Depletion of *Nfkbid* impaired TIL accumulation and promoted tumor growth.
• Ectopic IκBδ overexpression enhanced TIL expansion, reduced exhaustion markers, and increased cytotoxic molecule production, leading to improved tumor control.
• Distinct regions of IκBδ differentially regulate T cell accumulation versus effector function and exhaustion.

Conclusions:

• IκBδ is a critical molecular lever that overcomes major limitations in CD8+ TIL anti-tumor efficacy: impaired accumulation and diminished effector function.
• Targeting IκBδ represents a promising strategy for enhancing the effectiveness of cancer immunotherapies.
• The findings highlight separable programs for TIL accumulation and effector differentiation, regulated by IκBδ.