Distribution of β₁, α₁, α₂ and α₃ integrin chains in basal cell carcinomas

The integrins are αβ heterodimeric transmembrane proteins mediating cell–substratum as well as cell‐cell interactions. Changes in their expression and/or function seem to occur in a number of malignant epithelial neoplasms and may in part explain their abnormal patterns of growth and differentiation. Using monoclonal antibodies to the β₁ (DH12), α₁ (TS2/7), α₂ (B1.515), and α₃ (E1.56) integrin chains, the α₁β₁ (VLA‐1), α₂β₁ (VLA‐2), and α₃β₁ (VLA‐3) integrin receptors were studied on cryostat sections of 22 basal cell carcinomas (BCCs) and adjacent normal tissues by a standard peroxidase‐antiperoxidase technique. In non‐neoplastic skin, VLA‐2 and VLA‐3 were found in the basal layer, eccrine glands, and cells of the outer root sheath in which VLA‐1 was detected. In BCCs, there was a considerably higher expression of VLA‐2 and VLA‐3 compared with epidermal basal cells but similar to that seen in hair bulb and outer root sheath. In two cases of nodular BCC showing evidence of regression, both VLA‐2 and VLA‐3 were completely negative, in contrast to non‐regressing foci which were strongly positive. The high level of expression of two adhesion molecules (VLA‐2 and VLA‐3) involved in cell‐substratum as well as cell‐cell interactions may account for the more indolent pattern of growth characteristic of BCC and perhaps reflect its high degree of differentiation towards the hair follicle.