Caspase 14 is one of the latter discovered members of the
caspase enzyme family and, although sharing sequence homologies with the other
caspases, it is not involved in apoptosis. Together with its co-factor
filaggrin, it plays an important role in skin barrier formation. It is already known that
caspase 14 proteins are reduced during neoplastic dedifferentiation in
cervical intraepithelial neoplasms and in invasive cervical
carcinomas. Oral
squamous carcinoma tissues have not been systematically evaluated for
caspase 14 expression yet.
Formalin-fixed and
paraffin-embedded samples from oral
squamous carcinomas (n = 36 tumours from 34 patients),
metastases (n = 15) and controls (
leukoplakia, n = 10) were analysed by immunohistochemistry. In
carcinomas, human papilloma virus (
HPV) infection was tested by PCR. Here we demonstrate that, in oral epithelia,
caspase 14 is expressed mainly by cells of the intermediate and superficial cell layers while
filaggrin is expressed only in keratinising foci in
leukoplakia.
Caspase 14 and
filaggrin are co-localised. In invasive oral
carcinomas, reduced expression of
caspase 14 was detectable in 47 % of tumours but was not associated with keratinisation, tumour differentiation or
HPV infection.
Filaggrin was detectable in a subfraction of tumours (56 %) and was restricted to keratinising areas of the
carcinomas. In summary, in contrast to cervical
carcinomas, partial loss of
caspase 14 is not associated with dedifferentiation in neoplastic lesions of the oral mucosa or
HPV infection.