EXPRESSION OF PLASMINOGEN ACTIVATORS IN BASAL CELL CARCINOMA

The plasminogen activators, tissue type and urokinase type (tPA and uP A, respectively), have been identified in various malignancies and hav e been implicated in both local growth and metastatic spread. To chara cterize plasminogen activator expression more fully in human basal cel l carcinoma, the localization of uPA and tPA mRNAs was evaluated by li t situ hybridization. Nodular basal cell carcinomas demonstrated uPA e xpression in most cases, whereas the non-nodular subtypes mere negativ e. Message for uPA vas identified within tumour islands (11/12 cases), scattered fibroblast-like stromal cells (6/12 cases), and the basal l ayer of the overlying epidermis (10/12 cases). In addition, signal for uPA was elevated and pronounced in areas where the epidermis merged i nto invasive basal cell carcinoma in the superficial papillary dermis in some cases. Message for uPA was often associated with ulceration or erosion of the overlying epithelium. Expression of tPA was noted in t he epidermis (3/12 cases) and in tumour cells (4/12 cases), but tended to be focal and sparse. These results suggest that complex interactio ns involving uPA expression occur between the tumour, the stroma, and the overlying epidermis. Both the stroma and the epidermis may contrib ute to local spread of the tumour through production of uPA and conseq uent plasmin-mediated activation of collagenases and metalloproteinase s.