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

Abstract

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. (Am J Pathol 2007, 170

Tissue Plasminogen Activator Activates NF-κB through a Pathway Involving Annexin A2/CD11b and Integrin-Linked Kinase

“…We surprisingly found that small interfering RNA (siRNA) knockdown of LRP-1, the major cell membrane receptor of tPA mediating multiple cytokine actions of tPA in fibroblasts, 8,[12][13][14][15] had little effect on p65 phosphorylation in macrophages ( Figure 2B), suggesting that LRP-1 does not mediate the tPA-activated NF-kB pathway in macrophages. Instead, knockdown of the expression of annexin A2, another cell-surface receptor for tPA 21,22 that has the signaling potential, 22,24,25 abolished tPA-induced NF-kB activation in macrophages (Figure 2, C and D). Thus, it is clear that annexin A2 but not LRP-1 mediates tPA-activated NF-kB signaling cascade in macrophages.…”

“…20 Annexin A2 has been identified as a major membrane receptor of tPA on endothelial, 21 microglia cells, 22 and other cancer cells, 23 and it is implicated in mediating certain signal transductions. 22,24,25 However, unlike the other well-known tPA receptor, LDL receptor-related protein 1 (LRP-1), annexin A2 is a membrane-associated protein, lacking transmembrane domain to which tPA can only dock. 20,23 It remains unknown how annexin A2 transactivates the intracellular signaling cascade initiated by the binding of extracellular tPA.…”

S100A6 binds to annexin 2 in pancreatic cancer cells and promotes pancreatic cancer cell motility

“…However, we cannot rule out the possibility that the relationship between membranous expression of annexin 2 and S100A6 level is a consequence, rather than a cause, of the effect of S100A6 on motility. In addition, the interaction between annexin 2 and S100A6 may contribute to increased tPA activity, which could lead to a variety of effects, potentially including increased cell motility (Ortiz-Zapater et al, 2007;Sharma and Sharma, 2007).…”

“…The identified proteins included the known binding partners annexin 11 (Mizutani et al, 1992), annexin 2 (Zeng et al, 1993), and tropomyosin (Golitsina et al, 1996) as well as a candidate novel interactor lamin B1. As both S100A6 and annexin 2 are overexpressed in pancreatic cancer, with expression occurring early in the development of the cancer in both cases (Sitek et al, 2005;Vimalachandran et al, 2005;Esposito et al, 2006;Ortiz-Zapater et al, 2007), we focused our attention particularly on annexin 2.…”

“…By contrast, annexin 2 and tropomyosin have been much studied and have roles in cytoskeletal organisation and regulation of actin dynamics (Gerke et al, 2005;Gunning et al, 2008). We chose to focus further studies on annexin 2 as, like S100A6 (Vimalachandran et al, 2005) it is also overexpressed in preneoplastic pancreatic lesions (Sitek et al, 2005;Esposito et al, 2006) and is expressed in a similarly high proportion (480%) of invasive cancers (Paciucci et al, 1998;Chen et al, 2005;Ortiz-Zapater et al, 2007). We report here colocalisation of annexin 2 and S100A6 in the plasma membrane of cultured pancreatic cancer cells and pancreatic tumours.…”