A NEW FORM OF TUMOR AND FETAL COLLAGEN THAT BINDS LAMININ

Human breast and colon carcinoma tissues contain a form of collagen, n ot described before, composed of alpha1 chains of similar size (approx imately 100 kDa) but different charge. The three constitutive chains, separated by two-dimensional electrophoresis, are a unique acidic comp onent, undetectable in other collagen types, with an apparent isoelect ric point of 4-5, and two more basic components displaying the same el ectrophoretic behavior as alpha1(III) and alpha1(I), respectively. The acidic chain is structurally distinct from alpha1(I) and displays a c yanogen bromide-derived fragment of similar size to CB5(III). This col lagen in its native state is resistant to trypsin and metalloproteinas e 3, while it is fully degraded by metalloproteinases 1 and 9. Moreove r, this collagen appears able to bind to laminin, as tested by affinit y chromatography. The biological significance of our data is related t o the finding of this collagen form not only in the tumor tissue teste d but also in embryonic-fetal tissues (bovine skin and intestine and h uman umbilical cord). For its peculiar laminin-binding ability and occ urrence in tumoral and embryonic-fetal tissues, we propose to temporar ily term this new collagen form OF/LB collagen (onco-fetal, laminin-bi nding collagen). The presence of OF/LB collagen during development and cancer, and its absence in normal adult tissues, make this protein a potential stromal marker of malignancy.