MMP9 and melanoma: Although the role of tumor cell–derived FAPα in melanoma is less well-characterized, it is well established that FAP+ stromal fibroblasts contribute to a tumor-promoting microenvironment by secreting pro-inflammatory and pro-invasive factors such as IL-6, IL-8, MMP-2, and MMP-9, which support melanoma progression, invasion, and therapy resistance [90].