Human prostate cancer bone metastases have an actionable immunosuppressive microenvironment

Area of Science:

• Oncology
• Immunology
• Cancer Biology

Background:

• Bone metastases are a severe complication of advanced cancers, particularly prostate cancer (PCa).
• Metastatic PCa in bone is currently incurable and resistant to immunotherapy.
• The bone marrow (BM) microenvironment plays a critical role in cancer progression and immune evasion.

Purpose of the Study:

• To characterize the immune landscape of the bone marrow microenvironment in prostate cancer bone metastases.
• To identify key molecular mechanisms driving immunosuppression in this setting.
• To explore therapeutic strategies targeting local immune dysfunction.

Main Methods:

• Single-cell analysis of bone marrow samples from patients with PCa bone metastases, involved and uninvolved BM, and healthy controls.
• Comparative analysis of tumor-infiltrating immune cells and stromal components.
• In vivo studies using mouse models of PCa bone metastases to test therapeutic interventions.

Main Results:

• Metastatic PCa is associated with significant immune distortion, including T cell exhaustion and altered macrophage phenotypes.
• Overexpression of the chemokine CCL20 by myeloid cells and its receptor CCR6 on T cells were identified as key players.
• Disrupting the CCL20-CCR6 axis in a mouse model restored T cell function and prolonged survival.

Conclusions:

• The bone marrow microenvironment in metastatic PCa exhibits profound immunosuppression.
• The CCL20-CCR6 axis is a critical mediator of this local immune evasion.
• Targeting the CCL20-CCR6 pathway represents a promising therapeutic strategy for overcoming resistance to immunotherapy in PCa bone metastases.