Evidence that vitronectin is a potent migration-enhancing factor for cancer cells chaperoned by fibrinogen: a novel view of the metastasis of cancer cells to low-fibrinogen lymphatics and body cavities

Abstract

Diluted (1%) plasma induces migration of malignant cell lines much more strongly than potent pro-metastatic factors. To characterize the factor(s) present in diluted plasma responsible for this phenomenon we performed i) heat inactivation, ii) dialysis, iii) proteinase K treatment, and iv) molecular size filtration studies. We found that this remarkable pro-migratory activity of diluted normal plasma is associated with a ~50–100-kD protein that interacts with GαI protein-coupled receptors and activates p42/44 MAPK and AKT signaling in target cells. Since this pro-migratory activity of 1% plasma decreases at higher plasma concentrations (> 20%), but is retained in serum, we hypothesized that fibrinogen may be involved as a chaperone of the protein(s). To identify the pro-migratory protein(s) present in diluted plasma and fibrinogen-depleted serum, we performed gel filtration and hydrophobic interaction chromatography followed by mass spectrometry analysis. We identified several putative protein candidates that were further tested in in vitro experiments. We found that this pro-migratory factor chaperoned by fibrinogen is vitronectin, which activates uPAR, and that this effect can be inhibited by fibrinogen. These results provide a novel mechanism for the metastasis of cancer cells to lymphatics and body cavities, in which the concentration of fibrinogen is low, and thus suggests that free vitronectin stimulates migration of tumor cells.

Vitronectin in the Ascites of Human Ovarian Carcinoma Acts as a Potent Chemoattractant for Ovarian Carcinoma: Implication for Metastasis by Cancer Stem Cells

“…Figure 2B shows that plasma that is enriched in fibrinogen inhibits pro-migratory effect of 10% ascites whereas plasma from which fibrinogen has been chemically extracted does not possess this inhibitory activity. This confirms our previous observation that fibrinogen acts as a natural inhibitor of protein/peptide-based pro-migratory factor that is present in plasma and intestines fluids [11, 12]. …”

“…Our studies with diluted 1% plasma revealed a novel role for fibrinogen that act as chaperone of vitronectin in diluted plasma and serum [11, 12]. Therefore we decided to test whether we will observe similar inhibitory effect of fibrinogen on ascites fluid-induced migration of ovarian cancer cells.…”

“…Based on our previous work with diluted 1% plasma which identified soluble vitronectin as main chemoattractant present in fibrinogen poor fluids [11, 12] and hypothesized that vitronectin may be a main migration-promoting factor in fibrinogen poor or even free ovarian ascites. To support this, we found that similar to diluted plasma/serum, the main chemoattractant present in ascites fluids is heat inactivation and protein K digest sensitive protein within 50–100 kDa range and that the pro-migratory activity of this protein could be inhibited by fibrinogen.…”

“…Recently, we identified soluble vitronectin as a main chemoattractant present in diluted human plasma/serum and intestinal fluid [11, 12]. We also found that this pro-migratory property of vitronectin is inhibited in presence of fibrinogen which could explain the preference of most tumors cells to migrate to lymphatics and body cavities where concentration of fibrinogen is low.…”

“…The targeting base sequence for human uPAR was as described [12]. As a control, shRNA against Renilla was used [17].…”