Abstract 1698: Novel evidence that blood plasma vitronectin is a major chemoattractant for cancer cells and its pro-migratory activity is suppressed/chaperoned after binding to fibrinogen

Proceedings: AACR 107th Annual Meeting 2016; April 16-20, 2016; New Orleans, LA Background. One of the crucial problems with cancer therapy is migration of cancer cells that leave primary tumor and migrate to vital organs where they form metastases. Throughout the years several factors have been identified that direct metastatic process including growth factors, chemokines, bioactive lipids or extracellular nucleotides. To our surprise however, we noticed that highly diluted plasma (1%) possess remarkable chemokinetic activity against several cancer cell lines that highly exceeds those observed for optimal doses of chemokines (e.g. SDF-1) and growth factors (e.g. HGF/SF), that are considered as a main metastatic factors present in plasma. Aim of the study. Based on this observation our aim was to identify the “factor/s” responsible for this remarkable chemokinetic activity of normal diluted 1% plasma. Experimental strategies. We employed several human cancer cell lines and different dilutions of normal human, murine and bovine plasma and serum in Transwell migration assays, adhesion and cell signaling studies. We tested effect of heat inactivation, protease exposure, dialysis and molecular filtration on chemotactic activity of plasma. We also used gel filtration followed by hydrophobic interaction chromatography (HIC) to identified plasma fractions with the most potent chemotactic activity that were further analyze using MassSpec. Results. We found that remarkable chemokinetic activity of highly diluted 1% plasma against malignant cells, rapidly decreased at higher plasma concentration (>5%). Our initial characterization studies revealed that this “activity” is sensitive to proteolytic treatment, is not removed from plasma by dialysis and is temperature sensitive. The similar effect has been observed for diluted 1% serum however chemotactic responsiveness of serum was maintained with its higher concentrations. Based on this we hypothesized possible involvement of inhibitory effect of fibrinogen, which was subsequently confirmed in experiments where fibrinogen was removed from plasma or it was added to serum. Finally, gel filtration followed by HIC and MasSpec analysis allow us to identify several possible candidates that were further tested in in vitro experiments. These studies revealed that vitronectin (VTN) is a main factor responsible for observed chemotactic response and that its effect can be inhibited by fibrinogen. Conclusions. Our data indicate that VTN present in normal plasma is a main migration inducing factor responsible for metastasis of malignant cells and that VTN is more potent chemoattractant than already known pro-metastatic chemokines or growth factors. Pro-migratory effect of VTN is neutralized/chaperoned by fibrinogen what may explain preference in migration of tumor cells into lymphatic vessels and body cavities, where concentration of fibrinogen is low. Citation Format: Gabriela Schneider, Nichola C. Garbett, Ewa Bryndza, Agata Poniewierska-Baran, Michael L. Merchant, Karol Serwin, Zachariah P. Sellers, Barbara Dolegowska, Mariusz Z. Ratajczak. Novel evidence that blood plasma vitronectin is a major chemoattractant for cancer cells and its pro-migratory activity is suppressed/chaperoned after binding to fibrinogen. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1698.