DIFFERENTIAL EXPRESSION OF ALPHA-1(IV), ALPHA-2(IV), ALPHA-5(IV) AND ALPHA-6(IV) COLLAGEN CHAINS IN THE BASEMENT-MEMBRANE OF BASAL-CELL CARCINOMA

Type IV collagen, the major component of basement membrane, consists p rimarily of alpha 1(IV) and alpha 2(IV) chains. Recently, other types of collagen IV chains, i.e. alpha 3(IV), alpha 4(IV), alpha 5(IV) and alpha 6(IV) chains, have been identified by protein chemistry and mole cular cloning. We have examined the diversity of the assembly of alpha (IV) chains of the basement membrane surrounding tumour nests of basal cell carcinomas, in tissues from 11 patients, by immunohistochemical analysis using specific monoclonal antibodies to six alpha(IV) chain. The immunostaining profile of each chain differed with respect to the histological subtypes of basal cell carcinoma. In the morphea-like sub type, which was more invasive, alpha 1(IV) and alpha 2(IV) chains were discontinuously stained, and alpha 5(IV) and alpha 6(IV) chains were entirely absent. However, in the superficial subtype, which was non-ag gressive, alpha 1(IV), alpha 2(IV), alpha 5(IV) and alpha 6(IV) chains were well stained compared with the other subtypes of basal cell carc inoma. In addition, in the solid subtype, which showed slow growth and ulceration, alpha 1(IV) and d alpha 2(IV) chains were continuously st ained, and alpha 5(IV) and alpha 6(IV) chains were discontinuous or ab sent. The assembly of alpha 5(IV) and alpha 6(IV) chains into the base ment membrane was inhibited in the solid and morphea subtypes of BCC. This differential expression of type IV collagen chains seems to be as sociated with the invasive potential of basal cell carcinoma.