WFDC2 (HE4): a potential role in the innate immunity of the oral cavity and respiratory tract and the development of adenocarcinomas of the lung.
BACKGROUND
The Whey Acidic Protein domain is an evolutionarily conserved motif found in a number of proteins, the best studied of which are antiproteinases involved in the innate immune defence of multiple epithelia. We recently characterised the WFDC2 gene which encodes a two WAP domain-containing protein, initially suggested as a marker for epididymis, and showed that it is highly expressed in the lung and salivary gland. The precise location of WFDC2 protein in these sites has not been described.


METHODS
We used immunohistochemistry to localise WFDC2 in normal tissues of the respiratory tract, naso- and oropharynx, as well as in chronically inflamed lung from Cystic Fibrosis and a range of pulmonary carcinomas. We have complemented these studies with molecular analysis of WFDC2 gene expression in primary human lung cell cultures.


RESULTS
WFDC2 is expressed in some epithelial cells of the upper airways as well as in mucous cells and ducts of submucosal glands. No staining was seen in peripheral lung. Intense staining is found in major salivary glands and in minor glands of the nose, sinuses, posterior tongue and tonsil. Studies with the related protein Secretory Leukocyte Protease Inhibitor (SLPI) show that although both proteins are expressed in similar tissues, the precise cellular localisation differs. Significant increases in expression and localisation of WFDC2 are seen in patients with Cystic Fibrosis. SLPI expression was greatly reduced in the same samples. In cultures of tracheobronchial epithelial cells, expression of WFDC2 and SLPI are differentially regulated during differentiation yet WFDC2 is not induced by pro-inflammatory mediators. The majority of adenocarcinomas stain with WFDC2 whilst a significant minority of squamous, small cell and large cell carcinomas exhibit focal staining. There is no clear association with tumour grade.


CONCLUSIONS
We believe that these studies support the hypothesis that WFDC2 may be a component of the innate immune defences of the lung, nasal and oral cavities and suggest that WFDC2 functions in concert with related WAP domain containing proteins in epithelial host defence. We also suggest that WFDC2 re-expression in lung carcinomas may prove to be associated with tumour type and should be studied in further detail.
Bingle
Lynne
L
Department of Oral Pathology, School of Clinical Dentistry, University of Sheffield, Sheffield, UK. l.bingle@sheffield.ac.uk
Cross
Simon S
SS
High
Alec S
AS
Wallace
William A
WA
Rassl
Doris
D
Yuan
Guanglu
G
Hellstrom
Ingegerd
I
Campos
Michael A
MA
Bingle
Colin D
CD
D000230:Adenocarcinoma / Q000276:immunology* / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000276:immunology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D030501:Epididymal Secretory Proteins / Q000096:biosynthesis / Q000502:physiology*; D005260:Female; D006801:Humans; D007113:Immunity, Innate; D008175:Lung Neoplasms / Q000276:immunology* / Q000378:metabolism; D008297:Male; D009055:Mouth / Q000276:immunology*; D011506:Proteins / Q000276:immunology / Q000502:physiology*; D012137:Respiratory System / Q000276:immunology* / Q000473:pathology; D000081102:WAP Four-Disulfide Core Domain Protein 2
D014408:Biomarkers, Tumor; D030501:Epididymal Secretory Proteins; D011506:Proteins; D000081102:WAP Four-Disulfide Core Domain Protein 2; C569698:WFDC2 protein, human