TM4SF5 promotes metastatic behavior of cells in 3D extracellular matrix gels by reducing dependency on environmental cues

Abstract

Transmembrane 4 L six family member 5 (TM4SF5) is highly expressed in hepatocellular carcinoma tissues and enhances migration in two-dimensional environments. Here, we investigated how TM4SF5 is involved in diverse pro-metastatic phenotypes in in vivo-like three-dimensional (3D) extracellular matrix gels. TM4SF5-positive cells aggressively formed invasive foci in 3D Matrigel, depending on TM4SF5-mediated signaling activity, cytoskeletal organization, and matrix metallopeptidase (MMP) 2-mediated extracellular remodeling, whereas TM4SF5-null cells did not. The TM4SF5-null cells did, however, form invasive foci in 3D Matrigel following inhibition of Rho-associated protein kinase or addition of collagen I, suggesting that collagen I compensated for TM4SF5 expression. Similarly, TM4SF5-positive cells expressing vascular endothelial-cadherin formed network-like vasculogenic mimicry in 3D Matrigel and collagen I mixture gels, whereas TM4SF5-negative cells in the mixture gels displayed the network structures only upon further treatment with epidermal growth factor. The foci formation also required MMP2-mediated remodeling of the extracellular matrix. Co-cultures exhibited TM4SF5-positive or cancer-associated fibroblasts at the outward edges of TM4SF5-null cell clusters. Compared with TM4SF5-null cells, TM4SF5-positive cells in 3D collagen gels showed a more invasive outgrowth with dramatic invadopodia. These observations suggest that TM4SF5 plays roles in the promotion of diverse metastatic properties with fewer environmental requirements than TM4SF5-negative cells.

Mechanisms of vasculogenic mimicry in hypoxic tumor microenvironments

“…The EMT transcription factor Twist is reported to induce the formation of actin-enriched membrane protrusions called aggressive pseudopods (invasive pseudopods are a special actin-based membrane protrusion found in cancer cells, and degrade ECM by targeting proteases); aggressive pseudopodia can recruit MMP-2, MMP-9, and MMP-14 to the leading edge where they degrade collagen and the basement membrane ECM, thereby promoting tumor invasion and metastasis [199,200]. These types of invasive pseudopodia are more common in cells demonstrating VM, but there are few in-depth studies on their specific regulatory mechanisms [201]. The abundant matrix components involved in VM, including collagen І, IV, and VI, are also involved in VM development.…”