fibrin and Carcinoma--Lewis-Lung

The attachment of circulating tumor cells to the blood vessels of distant organs is an important step in metastasis. We show here that experimental lung metastasis by two cell lines, B16F1 melanoma and 3LL lung carcinoma, is greatly reduced in transgenic mice that lack plasma fibronectin. This multifunctional adhesive glycoprotein becomes cross-linked to fibrin during clotting. Here, we report that eliminating plasma fibronectin from the blood circulation reverses the prometastatic effects of blood clotting and tumor cell integrin alphavbeta3. In vitro studies showed that fibrin-fibronectin complexes, but not purified fibrin, supported tumor cell attachment and invasion. These functions correlate with the ability of fibrin-fibronectin complexes to induce the activation of integrin alphavbeta3. Our findings reveal an important contribution of plasma fibronectin in lung metastasis. Furthermore, they suggest that the previously noted effects of blood clotting on lung metastasis might be mediated in part by a fibronectin-alphavbeta3 integrin axis, in which plasma fibronectin has to be incorporated into the blood clot.

Topics: Animals; Blood Coagulation; Carcinoma, Lewis Lung; Cell Adhesion; Fibrin; Fibronectins; Integrin alphaVbeta3; Lung Neoplasms; Melanoma, Experimental; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neoplasm Invasiveness

Antibodies and other macromolecular therapeutics can gain access to tumor cells via leaky tumor vessels. Inhibition of vascular endothelial growth factor (VEGF) signaling can reduce the vascularity of tumors and leakiness of surviving vessels, but little is known about how these changes affect the distribution of antibodies within tumors. We addressed this issue by examining the distribution of extravasated antibodies in islet cell tumors of RIP-Tag2 transgenic mice and implanted Lewis lung carcinomas using fluorescence and confocal microscopic imaging. Extravasated nonspecific immunoglobulin G (IgG) and antibodies to fibrin or E-cadherin accumulated in irregular patchy regions of stroma. Fibrin also accumulated in these regions. Anti-E-cadherin antibody, which targets epitopes on tumor cells of RIP-Tag2 adenomas, was the only antibody to achieve detectable levels within tumor cell clusters at 6 hours after i.v. injection. Treatment for 7 days with AG-013736, a potent inhibitor of VEGF signaling, reduced the tumor vascularity by 86%. The overall area density of extravasated IgG/antibodies decreased after treatment but the change was less than the reduction in vascularity and actually increased when expressed per surviving tumor vessel. Accumulation of anti-E-cadherin antibody in tumor cell clusters was similarly affected. The patchy pattern of antibodies in stroma after treatment qualitatively resembled untreated tumors and surprisingly coincided with sleeves of basement membrane left behind after pruning of tumor vessels. Together, the findings suggest that antibody transport increases from surviving tumor vessels after normalization by inhibition of VEGF signaling. Basement membrane sleeves may facilitate this transport. Antibodies preferentially distribute to tumor stroma but also accumulate on tumor cells if binding sites are accessible.

Topics: Adenoma, Islet Cell; Animals; Antibodies, Neoplasm; Axitinib; Cadherins; Carcinoma, Lewis Lung; Fibrin; Imidazoles; Immunoglobulin G; Indazoles; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microspheres; Neovascularization, Pathologic; Signal Transduction; Vascular Endothelial Growth Factor A

Vascular endothelial growth factor (VEGF)-induced vascular permeability (VP) is a hallmark of tumor growth and metastasis. Previous studies have shown a requirement for Src kinase in VEGF-mediated VP and signaling in blood vessels. In this study, we have examined the effect of Src-mediated reduced VP on tumor growth and metastasis. The growth and spontaneous metastasis of VEGF-expressing tumor cells were determined in Src-knockout (src(-/-)) or control mice (src(+/+) or src(+/-)). In comparison to control mice, src-null mice had a significant reduction in tumor-induced VP as well as a subsequent reduction in spontaneous metastasis. In contrast, primary tumor weight and vascular density were unchanged between src-null and control mice. Consistent with a role for Src in the extravasation of tumor cells from the circulation, direct intravenous injection of lung carcinoma cells resulted in a more than 2-fold reduction in lung tumor burden in src-null mice compared to control mice. The comparison of the results from the experimental metastasis and the spontaneous metastasis models suggests that there are defects in VP in the primary site of Src-deficient mice and that there may be an essential role for Src and Src-mediated VP in tumor metastasis to the lung.

Topics: Animals; Capillary Permeability; Carcinoma, Lewis Lung; Cell Line, Tumor; Cell Proliferation; Fibrin; Fibrin Fibrinogen Degradation Products; Lung Neoplasms; Melanoma, Experimental; Mice; Mice, Inbred C57BL; Mice, Knockout; Neoplasm Metastasis; Neovascularization, Pathologic; src-Family Kinases; Vascular Endothelial Growth Factor A