IL6 and neoplasm: Various CAF-secreted solute factors, such as IL-6, IL-33, TGF-β, stromal cell derived factor-1 (SDF-1), and CAF-derived cardiotrophin-like cytokine factor 1 (CLCF1) produce tumor-promoting signals that mediate the signal transduction of tumor cells or other cells in the TME (Song et al. 2021; Landskron et al. 2019; Qin et al. 2018; Tan et al. 2020; Wei et al. 2018).