Presence of MUC1 in the epidermal thickening of psoriatic plaques.

Mucin 1 (MUC1) is a transmembrane glycoprotein that protects epithelial cells from injury caused by external stimuli. In addition to this role, MUC1 is involved in cell-cell adhesion, proliferation, motility, invasion and survival. In epithelial cells, MUC1 expression is regulated by binding of TNFα to TNFR1 and activation of the NFκB pathway. In human skin, MUC1 is not expressed in normal epidermis but rather in pre-malignant and malignant conditions. Nevertheless, the expression of MUC1 and its implication in psoriasis vulgaris has not been considered. Here, we show that MUC1 was present in the epidermis of psoriatic plaques observed in 11 biopsies from patients diagnosed with psoriasis vulgaris which were compared with 5 normal human skin. Interestingly, MUC1 in addition to being localized at the apical surface of some suprabasal keratinocytes, was also localized over the entire cell surface of some of these cells and some basal keratinocytes. Conversely, no MUC1 immunoreactivity was detected in the epidermis of normal skin. Additionally, we demonstrated that activated TNFR1, c-Src, IKKα/β and p50/p65 were present in the epidermal thickening. This study demonstrates the presence of MUC1 in psoriatic plaque and suggests a possible role for MUC1 during the motility, migration and survival of human keratinocytes, where activated TNFR1, c-Src and NFκB seem to be required.