Moreover, we showed that human protein PDIA1, but not PDIA3, increased cancer cell adhesion to the endothelial monolayer and collagen type I. Altogether, our results provide evidence that PDIA1 is important in regulating cancer cell adhesion to ECM proteins and endothelium by disulphide re-arrangement of ecto-sulfhydryls [26,27,28,37], in addition to its anti-cancer effects, attributed to cycle–cycle regulation by intracellular PDI. Here, P4HB is linked to cancer.