Tumor Microenvironmental Barriers to T Cell Infiltration in Breast Cancer

Area of Science:

• Immunology
• Oncology
• Biomedical Engineering

Background:

• Effective antitumor immunity relies on cytotoxic T cells infiltrating tumors, surviving, and maintaining function.
• Hormone receptor-positive breast cancers often exhibit limited T cell infiltration, hindering immune responses.
• Tumor microenvironment barriers, including vascular, chemokine, and extracellular matrix factors, impede T cell access.

Purpose of the Study:

• To investigate the hierarchical barriers limiting T cell infiltration in breast tumors.
• To explore strategies for enhancing T cell entry and function within the tumor microenvironment.
• To identify approaches for improving the efficacy of cancer immunotherapies like checkpoint blockade.

Main Methods:

• Analysis of T cell trafficking pathways from lymph nodes to tumors.
• Evaluation of endothelial adhesion molecules and blood vessel integrity.
• Assessment of chemokine gradients and extracellular matrix properties (e.g., stiffness, composition).

Main Results:

• Tumor blood vessel integrity, chemokine gradients, and extracellular matrix characteristics critically control T cell infiltration.
• Interactions between these barriers, such as matrix stiffness compressing vessels, exacerbate T cell exclusion.
• Preclinical and early clinical data suggest vascular normalization, chemokine reprogramming, and matrix remodeling can improve T cell access.

Conclusions:

• Overcoming T cell exclusion requires addressing multiple interdependent barriers within the tumor microenvironment.
• Targeting vascular normalization, chemokine signaling, and extracellular matrix remodeling shows promise for enhancing immunotherapy.
• Biomarker-guided combination therapies are likely necessary to enable T cell entry and preserve function for durable clinical benefit.