Differential expression of α1(IV), α2(IV), α5(IV) and α6(IV) collagen chains in the basement membrane of basal cell carcinoma

Type IV collagen, the major component of basement membrane, consists primarily of α1(IV) and α2(IV) chains. Recently, other types of collagen IV chains, i.e. α3(IV), α4(IV), α5(IV) and α6(IV) chains, have been identified by protein chemistry and molecular cloning. We have examined the diversity of the assembly of α(IV) chains of the basement membrane surrounding turnout nests of basal cell carcinomas, in tissues from 11 patients, by immunohistochemical analysis using specific monoclonal antibodies to six α(IV) chain. The immunostaining profile of each chain differed with respect to the histological subtypes of basal cell carcinoma. In the morphea-like subtype, which was more invasive, α1(IV) and α2(IV) chains were discontinuously stained, and α5(IV) and α6(IV) chains were entirely absent. However, in the superficial subtype, which was non- aggressive, α1(IV), α2(IV), α5(IV) and α6(IV) chains were well stained compared with the other subtypes of basal cell carcinoma. In addition, in the solid subtype, which showed slow growth and ulceration, α1(IV) and α2(IV) chains were continuously stained, and α5(IV) and α6(IV) chains were discontinuous or absent. The assembly of α5(IV) and α6(IV) chains into the basement membrane was inhibited in the solid and morphea subtypes of BCC. This differential expression of type IV collagen chains seems to be associated with the invasive potential of basal cell carcinoma.