Myeloid-derived suppressor cell subtypes differentially influence T-cell function, T-helper subset differentiation,...

Area of Science:

• Immunology
• Oncology
• Cell Biology

Background:

• Cancer progression involves complex interactions between tumor cells and the tumor microenvironment.
• Myeloid-derived suppressor cells (MDSCs) are key immunomodulatory cells influencing cancer pathogenesis.
• MDSCs comprise distinct subtypes, polymorphonuclear (PMN-MDSCs) and monocytic (M-MDSCs), with potentially divergent functions.

Purpose of the Study:

• To investigate the distinct roles of PMN-MDSCs and M-MDSCs in modulating T-cell responses within the tumor microenvironment.
• To determine the impact of MDSC subtypes on clinical outcomes in cancer patients.
• To evaluate the differential effects of ibrutinib therapy on MDSC populations and their function.

Main Methods:

• Analysis of MDSC subtype frequencies and their correlation with T-cell repertoire and clinical data.
• In vivo and in vitro functional assays to assess the immunosuppressive capacity of PMN-MDSCs and M-MDSCs.
• Evaluation of MDSC dynamics and T-cell profiles before and after ibrutinib treatment initiation.

Main Results:

• MDSCs, as a group, correlated with an immunosuppressive T-helper (Th) cell profile and poorer clinical outcomes.
• PMN-MDSCs were more numerous, associated with distinct Th subsets, and more strongly linked to adverse clinical courses than M-MDSCs.
• In vitro, PMN-MDSCs potently inhibited T-cell proliferation and promoted Th17 differentiation, while M-MDSCs exhibited variable suppression influenced by TNFα and promoted a more immunostimulatory T-cell compartment.
• Ibrutinib therapy led to a decrease in PMN-MDSCs but not M-MDSCs, resulting in a less immunosuppressive T-cell environment and correlating with clinical improvement in CLL patients.

Conclusions:

• The balance between PMN-MDSC and M-MDSC populations and their functions significantly influences cancer disease course.
• PMN-MDSCs represent a more potent immunosuppressive subtype compared to M-MDSCs.
• Targeting MDSC subtypes, such as with ibrutinib, may offer a therapeutic strategy to restore anti-tumor immunity and improve clinical outcomes.