CK5 [XM26] has been shown to have positive reactivity for CK5 protein and lack of reactivity for CK6 protein by ELISA. CK5 is distributed in many non-keratinizing stratified squamous epithelia such as tongue mucosa, basal epithelia, hair follicles, trachea, as well as basal cells in prostate glands and myoepithelial cells in mammary glands. CK5 is also expressed in most epithelial and biphasic mesotheliomas. CK5 has also been noted in large cell carcinomas and pulmonary squamous cell carcinoma. CK5 is expressed in luminal Type B breast cancers (triple negative).
CK14 is a human intermediate filament protein of 50kDa. CK14 can be used to distinguish stratified epithelial cells from simple epithelial cells. It is expressed in basal epithelium in prostate and myoepithelium in normal breast. CK14 is a useful marker in the differential diagnosis of squamous cell carcinoma with poor clinical outcome. CK14 is also expressed in luminal Type B breast cancers, similar to CK5.
The CK5/CK14 monoclonal antibodies have been shown to be superior to CK5/6 and 34betaE12. Cytokeratin 5/14 may be used to identify basal cells in prostate and myoepithelium cells in breast cancer. Loss of epithelium staining along with p63 typically occurs in PIN (prostatic intraepithelial neoplasia) and prostate cancer. Additionally, CK5/ CK14 + AMACR (P504S) may be added to the panel of antibodies used to assess neoplasia in prostate biopsies. Comprised of: CK5 + CK14 + p63 + P504S has become the standard care for PIN and prostate cancer diagnosis in many histopathology laboratories. Studies have shown that CK5/14-positive sporadic breast cancers arise from glandularly committed progenitor cells and represent about 9% of sporadic invasive ductal breast cancers and 78% of BRCA1-associated tumors.