Mesothelial cells promote early ovarian cancer metastasis through fibronectin secretion
Hilary A. Kenny, … , David Bowtell, Ernst Lengyel
Hilary A. Kenny, … , David Bowtell, Ernst Lengyel
Published September 9, 2014
Citation Information: J Clin Invest. 2014;124(10):4614-4628. https://doi.org/10.1172/JCI74778.
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Mesothelial cells promote early ovarian cancer metastasis through fibronectin secretion

Abstract

Ovarian cancer (OvCa) metastasizes to organs in the abdominal cavity, such as the omentum, which are covered by a single layer of mesothelial cells. Mesothelial cells are generally thought to be “bystanders” to the metastatic process and simply displaced by OvCa cells to access the submesothelial extracellular matrix. Here, using organotypic 3D cultures, we found that primary human mesothelial cells secrete fibronectin in the presence of OvCa cells. Moreover, we evaluated the tumor stroma of 108 human omental metastases and determined that fibronectin was consistently overexpressed in these patients. Blocking fibronectin production in primary mesothelial cells in vitro or in murine models, either genetically (fibronectin 1 floxed mouse model) or via siRNA, decreased adhesion, invasion, proliferation, and metastasis of OvCa cells. Using a coculture model, we determined that OvCa cells secrete TGF-β1, which in turn activates a TGF-β receptor/RAC1/SMAD-dependent signaling pathway in the mesothelial cells that promotes a mesenchymal phenotype and transcriptional upregulation of fibronectin. Additionally, blocking α5 or β1 integrin function with antibodies reduced metastasis in an orthotopic preclinical model of OvCa metastasis. These findings indicate that cancer-associated mesothelial cells promote colonization during the initial steps of OvCa metastasis and suggest that mesothelial cells actively contribute to metastasis.

Authors

Hilary A. Kenny, Chun-Yi Chiang, Erin A. White, Elizabeth M. Schryver, Mohammed Habis, Iris L. Romero, Andras Ladanyi, Carla V. Penicka, Joshy George, Karl Matlin, Anthony Montag, Kristen Wroblewski, S. Diane Yamada, Andrew P. Mazar, David Bowtell, Ernst Lengyel

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Figure 4

Inhibition of fibronectin in mesothelial cells or omentum impairs OvCa cell adhesion, invasion, and proliferation.

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Inhibition of fibronectin in mesothelial cells or omentum impairs OvCa c...
(A) Fibronectin knockdown in primary human mesothelial cells. Immunoblot analysis of fibronectin in primary human mesothelial cells transfected with fibronectin-specific (FN), vitronectin-specific (Vn), or control (NC) siRNA. Functional assays investigating the effect of fibronectin knockdown in mesothelial cells on OvCa cell adhesion (30 minutes), invasion (24 hours), and proliferation (96 hours). Primary human mesothelial cells were transfected with fibronectin-targeted or control siRNA, followed by addition of fluorescently labeled SKOV3ip1 and HeyA8 OvCa cells, which were detected using a fluorescence reader (mean ± SEM; n = 5 [adhesion and proliferation], 3 [invasion]; 3 independent experiments). *P < 0.05, Student’s t test. (B) Fibronectin knockdown in pieces of full human omentum. Left: Transfection of fibronectin siRNA (specifically designed for in vivo use) in pieces of full human omentum (72 hours); FN1 mRNA downregulation was confirmed in detached surface cells (after scraping off surface cells of the omentum) using qRT-PCR. Right and bottom: Adhesion, invasion, and proliferation of OvCa cells was inhibited on full human omentum when fibronectin expression in omental surface cells decreased (mean ± SEM; n = 5; 3 independent experiments). *P < 0.05, Student’s t test.