J8H, a mouse mAb, recognizes an extracellular epitope of α6 integrin and was a generous gift from Dr. Arnoud Sonnenberg (27 (link)). The integrin α6 rat mAb J1B5 was generated by Dr. Caroline Damsky (29 (link)). AA6NT a rabbit pAb, was generated against a recombinant fragment of the N-terminal integrin α6 β-barrel domain and was used for immunohistochemistry (IHC) analysis of archival material. In contrast, AA6A is a rabbit pAb, recognizing the intracellular C-terminal domain of α6 integrin was previously characterized by us and used for western blot analysis (21 (link)). Donkey anti-mouse Alexa conjugated antibodies and anti-Rabbit HRP antibodies were obtained from Invitrogen (Carlsbad, CA). Human, single chain, activated, urokinase was obtained from Millipore (Temecula, CA). Growth Factor Reduced Matrigel was from BD Biosciences (Bedford, MA).