Age‐Related Changes in Myeloid Cells and Their Impact on Subcutaneous Melanoma Growth in Mice

Our findings highlight a context-dependent immune response to melanoma with aging, indicating that age-related variations in melanoma growth and immunotherapy response are not ubiquitous. Age-accelerated tumor growth is associated with increased immunosuppressive cell populations alongside enhanced Gr-1⁺ myeloid cell-mediated immunosuppression driven in part by myeloperoxidase. Myeloperoxidase deficiency effectively reduced Gr-1⁺ myeloid cell immunosuppression, decreased reactive oxygen species, and diminished extracellular trap formation, thereby eliminating age-dependent differences in tumor growth and immunotherapy response. This work underscores the impact of aging on Gr-1⁺ myeloid cells on cancer progression and immunotherapy efficacy.