The density of epidermal p53 clones is higher adjacent to squamous cell carcinoma in comparison with basal cell carcinoma.
BACKGROUND
It is well accepted that ultraviolet radiation from the sun can induce and promote growth of skin tumours. Skin cancer develops as a consequence of multiple genetic hits, where an initial, important step includes proliferation of cells susceptible to malignant transformation. Foci of morphologically normal epidermal keratinocytes overexpressing p53 protein are common in chronically sun-exposed skin. Such foci have previously been shown to represent expanding clones of p53-mutated keratinocytes. Although several characteristics concerning epidermal p53 clones remain to be resolved, an important role in skin carcinogenesis is anticipated. The density of epidermal p53 clones in human skin is largely unknown.


OBJECTIVE
To compare the occurrence of epidermal p53 clones in skin surrounding cancers with that in skin surrounding benign melanocytic naevi. To assess the influence of age on frequency and size of epidermal p53 clones in human facial skin.


METHODS
We have analysed the number and sizes of epidermal p53 clones in skin specimens from patients with squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and benign melanocytic naevi. Cases included normal facial skin from four different age groups. Tissue sections were immunohistochemically stained and the presence of p53 clones was recorded. Approximately 1.4 m of epidermis from a total of 112 biopsies was analysed.


RESULTS
We found 128 epidermal p53 clones in biopsy specimens from 112 patients. The results showed that the number and size of p53 clones increase with age. In normal skin adjacent to SCC p53 clones were significantly more numerous and greater in size in comparison with those in normal skin both adjacent to benign naevi and adjacent to BCC. Interestingly, normal skin in the close vicinity of BCC and melanocytic naevi showed similar results regarding both number and size of epidermal p53 clones.


CONCLUSIONS
Our findings suggest a connection between development of epidermal p53 clones and SCC.
Bäckvall
H
H
Department of Genetics and Pathology, University Hospital, 751 85 Uppsala, Sweden.
Wolf
O
O
Hermelin
H
H
Weitzberg
E
E
Pontén
F
F
D000328:Adult; D000367:Age Factors; D000368:Aged; D002280:Basal Cell Carcinoma / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism*; D002999:Clone Cells / Q000378:metabolism; D005260:Female; D016158:Genes, p53 / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D009508:Nevus, Pigmented / Q000235:genetics / Q000378:metabolism; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D016159:Tumor Suppressor Protein p53