Sex-dependent effects in the aged melanoma tumor microenvironment influence invasion and resistance to targeted therapy.

There is documented sex disparity in cutaneous melanoma incidence and mortality, increasing disproportionately with age and in the male sex. However, the underlying mechanisms remain unclear. While biological sex differences and inherent immune response variability have been assessed in tumor cells, the role of the tumor-surrounding microenvironment, contextually in aging, has been overlooked. Here, we show that skin fibroblasts undergo age-mediated, sex-dependent changes in their proliferation, senescence, ROS levels, and stress response. We find that aged male fibroblasts selectively drive an invasive, therapy-resistant phenotype in melanoma cells and promote metastasis in aged male mice by increasing AXL expression. Intrinsic aging in male fibroblasts mediated by EZH2 decline increases BMP2 secretion, which in turn drives the slower-cycling, highly invasive, and therapy-resistant melanoma cell phenotype, characteristic of the aged male TME. Inhibition of BMP2 activity blocks the emergence of invasive phenotypes and sensitizes melanoma cells to BRAF/MEK inhibition. [Display omitted] • Skin fibroblasts show age- and sex-specific changes in proliferation and stress response • Male fibroblasts age faster due to elevated ROS levels • BMP2 is secreted in the aged male dermal microenvironment • BMP2 promotes slow-cycling, invasive, targeted therapy-resistant melanoma tumors Aging-driven and sex-dependent molecular changes in skin fibroblasts drive the emergence of invasive and therapy-resistant melanomas in male mice. [ABSTRACT FROM AUTHOR]