Autocrine regulation of growth stimulation in human epithelial ovarian carcinoma by serine-proteinase-catalysed release of the urinary-type-plasminogen-activator N-terminal fragment

Abstract

Ovarian carcinomas secrete single-chain urinary-type plasminogen activator (scuPA) and expression of uPA is up-regulated relative to normal ovarian epithelium, leading to an enhanced proteolytic capacity which may facilitate invasion. Furthermore, the uPA receptor (uPAR) is present on ovarian carcinoma cells and is occupied in tumour tissues. In the present study, incubation of scuPA with serum-free conditioned medium from ovarian carcinoma cells resulted in release of a 14 kDa polypeptide. N-terminal sequence analysis identified this fragment as the uPA N-terminal fragment (NTF), which contains a growth-factor and a kringle domain. NTF generation was abolished by serine-proteinase inhibitors, but not inhibitors of matrix metalloproteinases, and was not enhanced by the addition of plasminogen or plasmin. To determine whether ovarian carcinoma-cell growth is altered by uPA, the effect of exogenous scuPA or NTF on proliferation was analysed. Both NTF and scuPA induced a dose-dependent increase in proliferation, with maximal stimulation obtained at 10-20 nM. Furthermore, blocking the interaction of endogenous uPA with uPAR using anti-NTF antibodies significantly inhibited proliferation. Together these data indicate that, in addition to enhancing the invasive activity of ovarian carcinoma cells via increased pericellular proteolysis, uPA also acts as a mitogen for ovarian carcinoma cells, suggesting a biochemical mechanism whereby uPA may contribute to ovarian carcinoma progression by modulating both cell invasion and proliferation.

Proteomic Identification of Lynchpin Urokinase Plasminogen Activator Receptor Protein Interactions Associated with Epithelial Cancer Malignancy

“…36 In addition, in vitro and in vivo studies by Agrez et al have demonstrated that the enhanced expression of the Rvβ6 integrin in colon cancer cells promotes tumor cell growth and extracellular matrix degradation via direct interactions with the MAP kinase signalling pathway. 37,38 As exogenous scuPA is known to promote ovarian cancer cell proliferation through uPAR engagement, 39 we sought to determine whether this could co-ordinately be regulated by the interaction between uPAR and the β6 integrin subunit.…”

Lysophosphatidic acid induction of urokinase plasminogen activator secretion requires activation of the p38MAPK pathway

“…Indeed, the presence of high levels of uPA in ovarian tumor samples correlates with poor prognosis (50,51). UPA induces proliferation (52,53) and migration (54) of ovarian cancer cells. Inhibiting uPA function decreases ovarian cancer invasion and metastasis (55)(56)(57).…”

Integrin αvβ6 sets the stage for colorectal cancer metastasis

“…β6 co-immunoprecipitation with uPAR was confirmed by Western blotting and reverse co-immunoprecipitation using the monoclonal anti-β6 antibody, 6.3G9 [86]. As with the β6•P-ERK2 interaction [28], the expression of uPA and uPAR [87] and the secretion of soluble uPA were demonstrated to enhance tumour growth [88]. Saldanha et al explored the effects of antagonising the uPAR•β6 interaction on cell proliferation.…”