Interestingly, it has been postulated that α6β4 integrin released from HDs may promote cancer cell growth, invasion and metastasis [54], possibly through epidermal growth factor receptors, which increase signalling of the PI3K-Akt pathway, the Mitogen-Activated Protein Kinase (MAPK) pathway and the Rho small GTPase pathways [55,56,57,58]. Here, EGFR is linked to cancer.