The expression of SnoN in normal human skin and cutaneous keratinous neoplasms

SnoN is a member of the ski family of proto-oncogenes. It has been revealed that SnoN plays a role in the regulation of cell growth, vertebrate development, and tumorigenesis. This study investigated the expression and significance of SnoN protein in normal human skin and in the development of seborrheic keratosis (SK), basal cell carcinoma (BCC), and squamous cell carcinoma (SCC) of the skin.

Six frozen sections of normal human skin, three of SK (acanthotic type), six of BCC, six of intraepidermal SCC (actinic keratosis, AK), and six each of poorly and well-differentiated SCC were immunohistochemically stained with a polyclonal antibody against SnoN.

In normal epidermis, strong positive staining was observed in the suprabasal layers, whereas the basal cell layer was entirely unstained. Expression was observed in tumor cells with a squamoid phenotype in SK, but not in BCC. In intraepidermal SCC, although a strong signal was seen in the well-differentiated keratinocytes of the superficial epidermal cell layers, no signal was seen in the poorly differentiated atypical cells situated in the lower epidermis. In invasive SCC, a few scattered cells were positive for SnoN in the well-differentiated sample, but much larger numbers of positive cells were observed in the poorly differentiated sample.

On the basis of our results, it is suggested that SnoN is involved in differentiation in normal skin and benign and nonmetastatic skin tumors, but plays a proto-oncogenic role in undifferentiated SCC.