CD44 EXPRESSION IN MELANOCYTIC LESIONS - A MARKER OF MALIGNANT PROGRESSION

CD44 is the major human cell surface receptor for hyaluronate and func tions in a diverse range of physiological processes. Alternative splic ing of a single gene generates a family of splice variants (CD44v1-10) in addition to the standard isoform, CD44H. Expression of CD44, parti cularly CD44v6, has been described to correlate with metastasis format ion in various tumours, although evidence in malignant melanoma is inc onclusive. In this study, we explored the immunohistochemical pattern of CD44 expression in a range of melanocytic lesions using a panel of monoclonal antibodies raised to CD44H and the variants v3, v4/5, v6 an d v8/9. Skin biopsies of 106 lesions from 100 patients were assessed a nd included benign and dysplastic naevi, melanoma in situ, malignant m elanomas in horizontal and vertical growth phase, and cutaneous and ly mph node metastases. CD44H was highly expressed in benign and dysplast ic naevi and in melanoma in situ. However, expression within melanomas diminished with increasing invasiveness, and the pattern of expressio n observed correlated significantly with the growth phase of the lesio n rather than its Breslow thickness. CD44 splice variants were not det ected in any lesions. These results suggest a possible role for downre gulation of CD44H in modulating the biological behaviour of malignant melanoma.