WFDC2 / WAP5 antibody

Background of WFDC2 / WAP5 antibody

The whey acidic protein (WAP) domain is a conserved motif, containing eight cysteines found in a characteristic 4-disulphide core arrangement, that is present in a number of otherwise unrelated proteins. One of these proteins, which contains two WAP domains, is HE4 (also known as WFDC2), originally described as an epididymis specific protein but more recently suggested to be a putative serum tumour marker for ovarian cancer and a presumptive role in natural immunity. The HE4 protein expression is not only confined to epidydimis but is expressed in a number of normal human tissues out side the reproductive system, including regions of the respiratory tract and nasopharynx and in a subset of lung tumor cell lines. HE4 gene expression was highest in normal human trachea and salivary gland, and to a lesser extent, lung, prostate, pituitary gland, thyroid, and kidney. Highest level of expression of ESPE4 was observed in adenocarcinomas of the lung, and occasional breast, transitional cell and pancreatic carcinomas (1). The WFDC2 gene under goes extensive splicing in malignant tissues that give rise to five WAP domain containing iso forms (2).
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 localization differs. Significant increases in expression and localization of WFDC2 are seen in patients with Cystic Fibrosis (3). ESPE2 protien is a 124 amino acids (15 kDa) protein. ESPE4 protein has sequence homology to extracellular proteinase inhibitor and is localized on human chromosome 20. The ESPE4 protein is a secreted glycoprotein (Asn-44) that is over expressed in serous and endometrioid ovarian carcinomas (4). There are at least 5 named variants (HE4-V1 to HE4-V5) expressed as a result of alternate splicing and they serve as endopeptidase inhibitors.