OVEREXPRESSION OF PROTEIN-KINASE-C-ALPHA AND PROTEIN-KINASE-C-BETA ISOZYMES BY STROMAL DENDRITIC CELLS IN BASAL AND SQUAMOUS-CELL CARCINOMA

Protein kinase C (PKC) isozymes transduce signals from cell surface re ceptors and thereby regulate important cellular functions in skin incl uding keratinocyte growth and differentiation. Overexpression of indiv idual PKC isozymes results in aberrant cell growth and in certain inst ances tumorigenicity. PKC is implicated in tumour promotion in mouse s kin. Abnormal expression of PKC has been reported in several human can cers. We have, therefore, investigated expression of PKC-alpha and -be ta in basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) by immunohistochemistry. Sections were stained with specific antibodies t o PKC-alpha, PKC-beta, CD1a, T cells, B cells and dermal dendritic cel ls (factor XIIIa), using an immunoperoxidase technique. PKC-alpha and PKC-beta were not detected in tumour cells in BCCs or SCCs. In SCCs, P KC-beta immunostaining revealed positively stained inflammatory and de ndritic cells scattered through the stroma; PKC-alpha immunostaining w as essentially negative. In contrast, in BCCs, PKC-alpha+ and PKC-beta + dendritic and spindle-shaped cells were observed in the stroma, imme diately adjacent to the tumour islands. Double-labelling experiments s howed that: a proportion (approximately 20%) of PKC-beta+ dendritic ce lls also expressed factor XIIIa, BCCs depend on stroma for growth; PKC regulates expression of type IV collagenase and stromelysin III and i nteractions between tumour and stroma may be important in determining tumour invasion and metastasis. Therefore, overexpression of PKC-alpha and -beta by stromal dendritic cells in BCCs suggests that PKC activa tion may be involved in stromal/tumour interactions in these tumours.