Colocalization of the tetraspanins, CO-029 and CD151, with integrins in human pancreatic adenocarcinoma:: Impact on cell motility

Purpose: Patients with pancreatic adenocarcinoma have a poor prognosis due to the extraordinary high invasive capacity of this tumor. Altered integrin and tetraspanin expression is suggested to be an important factor. We recently reported that after protein kinase C activation, colocalization of alpha 6 beta 4 with the tetraspanin CO-029 strongly supports migration of a rat pancreatic adenocarcinoma. The finding led us to explore whether and which integrin-tetraspanin complexes influence the motility of human pancreatic tumors. Experimental Design: Integrin and tetraspanin expression of pancreatic and colorectal adenocarcinoma was evaluated with emphasis on colocalization and the impact of integrin-tetraspanin associations on tumor cell motility. Results: The majority of pancreatic and colorectal tumors expressed the alpha 2, alpha 3, alpha 6, beta 1, and beta 4 integrins and the tetraspanins CD9, CD63, CD81, CD151, and CO-029. Expression of alpha 6 beta 4 and CO-029 was restricted to tumor cells, whereas alpha 1, alpha 2, a3, a6, 1, and CD9, CD81, CD151 were also expressed by the surrounding stroma. CD63, CD81, and beta 1 expression was observed at comparably high levels in healthy pancreatic tissue. alpha 3 beta 1 frequently colocalized and coimmunoprecipitated with CD9, CD81, and CD151, whereas alpha 6 beta 4 colocalized and coimmunoprecipitated mostly with CD151 and CO-029. Notably, protein kinase C activation strengthened only the colocalization of CD151 and CO-029 with beta 4 and was accompanied by internalization of the integrin-tetraspanin complex, decreased laminin 5 adhesion, and increased cell migration. Conclusion: alpha 6 beta 4 is selectively up-regulated in pancreatic and colorectal cancer. The association of alpha 6 beta 4 with CD151 and CO-029 correlates with increased tumor cell motility.