Extracellular matrix proteins, neural differentiation and melanoma progression

Abstract

Background: Highly invasive melanoma cells traverse the extracellular matrix (ECM) by cell adhesion, ECM proteolysis, and cell migration. Ln5 and Integrin α5β1 play a key role in regulating melanoma growth, invasion, migration, angiogenesis and tissue remodeling. The present work utilizes the in situ 3D tumor matrix of melanomas to study their role in the formation of tumor-vascular-complexes (TVCs), vasculogenesis and tumor invasion.

Material and Methods: Serial frozen and paraffin sections of nodular melanomas were subjected to histochemistry, enzyme histochemistry: dopa oxidase and immunohistochemistry using the monoclonal antibodies HMB45, GFAP, NFP, Syn, Ln5 (laminin 5) & integrin (α5β1) by the avidin/biotin system and assessed in general tumor areas, infiltrating margins, TVCs, vasculogenesis.

Results: General areas: Ln5 shows a range of 75%-100% positivity in pigmented and 5.9%-29.8% cells in amelanotic areas. Integrin α5β1: shows a range of 69.4%-94.8% positivity in pigmented and 4%-55.2% in amelanotic areas. Infiltrating margins: Ln5/Integrin α5β1, are both required for preparing the ECM for spread of the tumor cells and angiogenesis. The cells at the infiltrating margins are positive for both. TVCs: Ln5/Integrin α5β1 expression is highest in the outer layers. Vasculogenesis (VM): Irregular spaces lined by Syn, Ln5/Integrin α5β1 positive tumor cells expand into islands of hemopoeisis, associated with the lining tumor cells. Combined TVCs and VM: In the mixed tumors a combination of TVCs and VM are seen. Irregular crevices appear lined by Ln5/Integrin α5β1 positive cells which flatten to form endothelial tubes which connect with the vascular network. Ln5/Integrin α5β1 positive cells co-express neural markers, NFP and Syn in all areas.

Discussion: In conclusion, Ln5/Integrin α5β1 form the substrate for the advancing cell mass in the outer layers of the TVCs, infiltrating tumor margins and vasculogenic spaces. The architecture and remodeling of the TVCs is maintained with integrin α5β1 providing attachment and dynamic force for tissue compaction, cohesion and migration aided by Ln5. Neural differentiation is associated with migratory ability as indicated by NFP and Syn coexpression with Ln5/Integrin α5β1.