Control of Tumor Architecture and Viability by the Fibronectin-Rich Extracellular Matrix: The Assembly and Disassembly of the Tumor Biofilm

Abstract

Purpose:: Highly invasive uveal melanoma cells generate a highly patterned extracellular matrix amalgam of laminin, type IV collagen, and fibronectin in which the melanoma cells are embedded - vasculogenic mimicry (VM) patterns. The generation of this matrix dampens gene expression and phenotypic behavior characteristic of the invasive cells that generate them, likening these patterns to a biofilm. In this study, we asked two questions: (1) Is it possible to influence tumor cell behavior within VM patterning - the uveal melanoma biofilm - by targeting ECM proteins such as fibronectin and laminin; and (2) Is it possible to prevent the formation of VM patterns by administering antibodies to fibronectin and laminin in highly invasive melanoma cells in culture conditions permissive of pattern formation?

Methods:: Established melanoma cultures with VM patterns were treated with antibodies against laminin, Type IV collagen, and different fibronectin domains, in addition to pioglitazone, a drug known to decrease fibronectin production. Production of fibronectin by tumor cells was measure by Western blotting.

Results:: Anti-fibronectin decreased fibronectin production by melanoma cells dramatically, the tumor matrix dismantled, and tumor cells died within 10 days. These effects were not seen with anti-laminin or anti-collagen IV. Targeting the gelatin/collagen-binding domain of fibronectin was critical for matrix dismantling and tumor cell death, whereas targeting the RGD containing cell binding domain and the extracellular domain B (EDB) had no detectable effects. Anti-fibronectin or pioglitazone (a drug that is known to interfere with fibronectin biosynthesis) blocked the formation of the patterned melanoma biofilm matrix and induced cell death, but had no observable effects on normal fibroblasts, endothelial cells, or poorly invasive melanoma cells.

Conclusions:: Instructions directing tumor architecture and uveal melanoma cell viability reside in the fibronectin-rich extracellular matrix biofilm.

Keywords: melanoma • pathology: experimental • pathobiology