Human breast tumor-infiltrating CD8⁺ T cells retain polyfunctionality despite PD-1 expression

Area of Science:

• Immunology
• Oncology

Background:

• CD8+ T cells are crucial for anti-tumor immunity and immunotherapy response.
• PD-1 expression on T cells often indicates exhaustion, impacting anti-tumor activity.

Purpose of the Study:

• To investigate the functional state of CD8+ tumor-infiltrating lymphocytes (TILs) in human breast and melanoma tumors.
• To compare the functionality of CD8+ TILs from breast tumors versus melanoma.
• To assess the potential of breast tumor CD8+ TILs for immunotherapy.

Main Methods:

• Analysis of CD8+ T cells from human breast and melanoma tumors.
• Assessment of T cell exhaustion markers, including PD-1 expression.
• Evaluation of effector functions such as cytokine production and degranulation capacity.
• Testing the ability of breast tumor CD8+ TILs to kill cancer cells using bi-specific antibodies.

Main Results:

• Human breast tumor CD8+ TILs exhibit PD-1 expression but retain robust effector cytokine production and degranulation capacity.
• Melanoma CD8+ TILs show a significant reduction in cytokine production and degranulation.
• CD8+ TILs from breast tumors demonstrated potent cancer cell killing via bi-specific antibodies.
• Breast tumor CD8+ TILs maintain polyfunctionality despite PD-1 expression.

Conclusions:

• CD8+ TILs in human breast tumors retain significant anti-tumor functionality, including polyfunctionality, even with PD-1 expression.
• These findings suggest that breast tumor CD8+ TILs are viable candidates for developing effective immunotherapies.
• Melanoma CD8+ TILs display a more pronounced exhausted phenotype compared to breast tumor CD8+ TILs.