STAT3 and cancer: As members of KLKs have been suggested to modulate cytokine and TGF‐β in some cancer types (Kryza et al., 2016), we also analyzed phosphorylation of Smad 2 (TGF‐β pathway), Stat3 (cytokine and growth factor pathways) in two different in vitro cell models; (a) in KLK7‐overexpressing melanoma M74 cells (upon stable transfection with a KLK7 expression vector, see section below), grown under serum‐free conditions, and (b) in Mewo cells, stimulated with recombinant KLK7 under serum‐free conditions.