The primary source of CAFs is considered to be resident fibroblasts that undergo transformation [114], which is triggered by growth factors secreted by cancer cells (e.g., TGF-β, Platelet-Derived Growth Factor) [115], inflammatory cytokines such as IL-1β, IL-6, and TNF-α [7,116], hypoxia [117], and direct interaction with cancer cells [118], although the are other sources of CAFs such as the bone marrow [119] and adipose tissue [120]. Here, IL6 is linked to cancer.