Tissue Plasminogen Activator Induces Pancreatic Cancer Cell Proliferation by a Non-Catalytic Mechanism That Requires Extracellular Signal-Regulated Kinase 1/2 Activation through Epidermal Growth Factor Receptor and Annexin A2

Tissue plasminogen activator (tPA) is overexpressed in pancreatic ductal carcinoma and is involved in tumor progression. This effect is probably mediated through the activation of angiogenesis, cell invasion, and cell proliferation. Previous studies support the notion that the effects of tPA on cell invasion require its proteolytic activity. Here, we report the molecular mechanism responsible for the proliferative effects of tPA on pancreatic tumor cells. tPA activates the extracellular signal-regulated kinase 1/2 signaling pathway in a manner that is independent of its catalytic activity. We also show that at least two membrane receptors, epidermal growth factor receptor and annexin A2, which are overexpressed in pancreatic cancer, are involved in the transduction of tPA signaling in pancreatic tumors. This observation suggests the establishment of an amplification loop in tumor cell proliferation. Double immunofluorescence experiments showed co-localization of tPA/epidermal growth factor receptor and tPA/annexin A2 in pancreas cancer cells. These results add novel insights into the non-catalytic functions of tPA in cancer and the molecular mechanisms behind the effects of this protease on cell proliferation, including a role for epidermal growth factor receptor.