Decoding the Role of MDSCs in Bone Metastasis: Multicellular Interactions and Clinical Implications

Area of Science:

• Oncology
• Immunology
• Skeletal Biology

Background:

• Bone metastasis is a significant cause of cancer morbidity, involving complex tumor-bone and immune interactions.
• Myeloid-derived suppressor cells (MDSCs) are key players in immune suppression within the bone marrow during metastasis.

Purpose of the Study:

• To review how bone metastases transform the bone marrow into an environment that promotes MDSC expansion and function.
• To discuss the suppressive mechanisms of MDSCs in bone and their impact on anti-tumor immunity.
• To evaluate therapeutic strategies targeting MDSCs in bone metastasis.

Main Methods:

• Synthesis of current evidence on MDSC biology in the bone marrow microenvironment.
• Analysis of MDSC suppressive programs and their effects on immune cells.
• Evaluation of pharmacologic strategies and emerging profiling tools for targeting MDSCs.

Main Results:

• Bone metastases create niches that recruit, sustain, and mature MDSCs, amplifying their suppressive functions.
• MDSCs impair cytotoxic T-cell and NK-cell responses, promoting regulatory T-cell dominance.
• Bone lesions can lead to systemic myeloid spillover, contributing to poor response to immune checkpoint blockade.

Conclusions:

• The bone marrow acts as an 'MDSC amplifier' in bone metastasis, driving immune suppression and treatment resistance.
• Targeting MDSC trafficking, reprogramming, or bone-resorptive feedback loops are potential therapeutic avenues.
• Advanced profiling tools are crucial for understanding bone-specific MDSC heterogeneity and guiding therapy.