Transformed human cells produce a new fibronectin isoform by preferential alternative splicing of a previously unobserved exon.

Abstract

Purification and amino acid sequence analysis of a proteolytic fragment of fibronectin (FN) from transformed human cells demonstrated that a high percentage of these FN molecules contains an extra amino acid sequence which is present only in a very low percentage of FN molecules from normal fibroblasts and is undetectable in plasma FN. This new amino acid sequence introduces into the FN molecule a site very sensitive to a number of proteolytic enzymes. By analyzing the cellular mRNA and genomic clones, we have demonstrated that this sequence derives from a differential splicing pattern of the FN mRNA precursors, which leads in transformed cells to a high‐level expression of an extra type III homology repeat (ED‐B) coded for by a previously unobserved exon. Here we also report the complete sequence of this new exon. These results demonstrate that in malignant cells the mechanisms regulating the splicing of FN mRNA precursors are altered.

Characterisation and radioimmunotherapy of L19-SIP, an anti-angiogenic antibody against the extra domain B of fibronectin, in colorectal tumour models

“…This is supported by other studies in different tumour types (Zardi et al, 1987;Carnemolla et al, 1989;Castellani et al, 1994;Kaczmarek et al, 1994;Neri et al, 1997;D'Ovidio et al, 1998;Kosmehl et al, 1999;Tarli et al, 1999;Viti et al, 1999;Ebbinghaus et al, 2004).…”

“…Extra domain-B domain is a complete type III repeat composed of a sequence of 91 amino acids, coded by a single exon and is the most conserved region of FN. It displays 100% homology in all mammalian species (Zardi et al, 1987). It is usually absent in both plasma and tissue FN of adults, except in regenerating tissues, such as some vessels in the endometrium.…”

Novel antibodies as anticancer agents

“…One of the most promising markers previously identified is the extra domain-B (ED-B) of fibronectin, a 91 aa region generated by alternative splicing (Zardi et al, 1987). Its expression is highly associated with the remodeling of the extracellular matrix and angiogenesis.…”

An engineered antibody–interleukin‐12 fusion protein with enhanced tumor vascular targeting properties

“…9 In the past, we have generated in collaboration with the group of Luciano Zardi a high-affinity human monoclonal antibody 10 specific to the EDB domain of fibronectin, a marker of angiogenesis. [11][12][13][14] The L19 antibody was shown to selectively localize to tumor blood vessels in animal models of cancer [15][16][17][18] and in patients with aggressive solid tumors. 19 The L19 antibody in single-chain Fv recombinant antibody format (''scFv(L19)'') was successfully fused to several cytokines 20 and pro-coagulant factors, 21 or chemically conjugated to radionuclides, 17,18 drugs [D.N., unpublished], photosensitizers 22,23 and enzymes.…”