Tumor Lymphatic Function Regulates Tumor Inflammatory and Immunosuppressive Microenvironments.

Area of Science:

• Oncology
• Immunology
• Vascular Biology

Background:

• Aberrant lymphatic vessel proliferation is common in solid tumors.
• Lymphatic dysfunction contributes to an immunosuppressive tumor microenvironment.
• Dysfunctional lymphatics promote the accumulation of immunosuppressive cells.

Purpose of the Study:

• To investigate the role of dysfunctional lymphatic vessels in regulating the tumor microenvironment.
• To determine the impact of lymphatic dysfunction on anti-tumor immune responses.
• To explore lymphatic vessels as a potential therapeutic target in cancer.

Main Methods:

• Utilized a transgenic mouse model with lymphatic endothelial cell-specific diphtheria toxin receptor.
• Performed local ablation of lymphatic vessels in mice bearing melanoma and breast cancer tumors.
• Analyzed peritumoral fluid and intratumoral immune cell populations.
• Assessed tumor growth and PD-L1 expression.

Main Results:

• Lymphatic ablation led to increased peritumoral edema and accumulation of immunosuppressive cells (macrophages, myeloid-derived suppressor cells, Tregs).
• Elevated inflammatory cytokine expression (TNFα, IFNγ, IL1β) was observed after lymphatic ablation.
• Tumors in lymphatic-ablated mice showed reduced cytotoxic T cell infiltration and increased PD-L1 expression, resulting in accelerated tumor growth.

Conclusions:

• Dysfunctional tumor lymphatic vessels significantly regulate the tumor microenvironment and immune response.
• Targeting lymphatic dysfunction, potentially in combination with immunotherapy, could be a viable strategy to inhibit tumor progression.