Solid Tumor Microenvironment Can Harbor and Support Functional Properties of Memory T Cells.

Area of Science:

• Immunology
• Cancer Biology
• T cell biology

Background:

• Robust T cell responses are vital for anti-tumor immunity and patient survival.
• The immunosuppressive tumor microenvironment (TME) hinders both endogenous and adoptive T cell therapies.
• Factors within the TME, including inhibitory signals and suppressive cells, impair T cell function.

Purpose of the Study:

• To compare the phenotype and function of tumor-specific T cells versus tumor-nonspecific bystander memory T cells within the same TME.
• To investigate the impact of the TME on T cell persistence and functionality.
• To identify key factors driving T cell exhaustion in solid tumors.

Main Methods:

• Utilized two distinct TCR transgenic and solid-tumor models.
• Conducted phenotypic and functional comparisons of tumor-specific and bystander CD8 T cells.
• Employed CRISPR-Cas9 gene deletion to assess the role of CXCR3 in T cell trafficking.

Main Results:

• Bystander CD8 T cells maintained memory markers and effector functions, unlike tumor-specific T cells, despite shared TME exposure.
• Bystander T cells exhibited enhanced recall responses to secondary challenges and in situ effector functions.
• CXCR3 was identified as critical for the trafficking of both tumor-specific and bystander T cells to solid tumors.

Conclusions:

• Persistent antigen signaling, not just TME factors, is the primary driver of T cell exhaustion.
• T cells can persist and retain functionality in tumors without cognate antigen stimulation.
• Findings inform strategies for engineering more effective T cell therapies (TCR-T and CAR-T) by modulating antigen and chemokine receptors.