Epidermal fatty-acid-binding protein in psoriasis, basal and squamous cell carcinomas: an immunohistological study

In human keratinocytes, we have recently characterized a low-molecular-weight cytosolic protein of 15 kD that specifically binds fatty acids (FAs) with high affinity, the epidermal FA-binding protein (E-FABP). The distribution of E-FABP in skin diseases is not known.

To localize by immunohistochemistry the expression of E-FABP in psoriasis, basal and squamous cell carcinomas in order to obtain indirect information, at the cellular level, on the transport of the FAs.

E-FABP was localized in the upper stratum spinosum and stratum granulosum in normal and non-lesional psoriatic skin. In contrast, lesional psoriatic epidermis strongly expressed E-FABP in all suprabasal layers, like nonkeratinized oral mucosa. The basal layer did not express E-FABP reactivity in any of these samples. Accordingly, basal cell carcinomas were E-FABP negative whereas only well-differentiated cells of squamous cell carcinomas expressed E-FABP.

It is unlikely that E-FABP plays a significant role in FA uptake by basal cells. Our data rather indicate that E-FABP expression is related to the commitment of keratinocyte differentiation and that the putative role of E-FABP should not be restricted to the formation of the skin lipid barrier. Since the pattern of E-FABP expression mimics cellular FA transport, our results suggest that lesional psoriatic skin and oral mucosa have a higher metabolism/transport for FAs than normal and non-lesional psoriatic epidermis.