EXPRESSION OF THE 27-KDA HEAT-SHOCK PROTEIN IN HUMAN EPIDERMIS AND INEPIDERMAL NEOPLASMS - AN IMMUNOHISTOLOGICAL STUDY

The 27-kDa heat shock protein (HSP27) is a member of the small heat sh ock protein (HSP) family. In addition to its putative function in ther motolerance, this protein may play a part in the regulation of cell gr owth and differentiation. This study was conducted to assess the signi ficance of the expression of HSP27 in human epidermis and in cutaneous neoplasms, Sixty-two biopsy samples from normal human skin and from i nflammatory and neoplastic skin diseases were investigated by immunohi stochemistry on formalin-fixed paraffin-embedded tissue sections, usin g a monoclonal antibody specific for HSP27. In normal human epidermis, HSP27 is expressed in the upper epidermal layers with a cytoplasmic s taining pattern. The basal cell layer does not express detectable amou nts of HSP27. In hair follicles, staining is mainly confined to the ou ter root sheath and to the infundibular epithelium. Melanocytes, derma l fibroblasts and endothelial cells do not express detectable amounts of HSP27, HSP27 could not be detected in fetal skin until the 20th wee k of gestation. Tumour cells in basal and squamous cell carcinomas do not express significant amounts of HSP27. In solar keratoses, seborrho eic keratoses, human papillomavirus (HPV)-induced hyperproliferative l esions and inflammatory skin conditions, HSP27 expression largely rese mbles the pattern observed in normal human skin. HSP27 is expressed in a differentiation-related pattern in normal human epidermis and hyper -proliferative disorders of the epidermis. We conclude that HSP27 may be regarded as a marker of differentiation in epidermal keratinocytes. Absence of HSP27 in the upper epidermal layers may be a marker for ep idermal malignancy.