Expression of keratin mRNAS and proteins in normal salivary epithelia and pleomorphic adenomas

Abstract

Control of keratin (K) gene expression may be important for cell differentiation in complex epithelia such as salivary gland. To investigate differences in distribution between keratin mRNAs and their respective proteins, a combined in situ hybridization (ISH) and immunohistochemical study was undertaken on nine normal salivary glands and seven pleomorphic adenomas. ISH employed riboprobes to K7, K8, K14, K18, and K19. Immunohistochemistry was performed on adjacent sections using monoclonal antibodies (MAbs) to the same keratins. Normal luminal cells showed abundant hybridization with probes for K7, K8, K18, and K19. Keratin 14 mRNA was present in basal and myoepithelial cells at a low level of expression. Proteins of their keratins were strongly stained. Neoplastic cells showed variable expression of mRNA and protein for K7, K8, K18, and K19. There was a high level of K14 mRNA but variable protein. The findings provide evidence that expression of these keratins in normal salivary epithelia is regulated transcriptionally and that in neoplasia this system is in considerable disarray.

Loss of keratin 13 in oral carcinoma in situ: a comparative study of protein and gene expression levels using paraffin sections

“…Although the enhanced immunolocalizations for CK16 in CIS cases corresponded to their definite mRNA levels, the loss of K13 immunopositivities seemed to be partly due to lowered K13 gene expression levels and partly due to unknown posttranslational events. Areas with gene expressions for such keratin subtypes as K1, K6, K7, K8, and K10 have been reported to be wider than their protein ones in normal oral mucosa and salivary glands, 25,26 salivary pleomorphic adenoma, 25 oral epithelial, 26 or epidermal 27 lesions. The tendencies were considered to be possible because the transcript forms might not always be translated to proteins due to some posttranscriptional regulations.…”

“…The tendencies were considered to be possible because the transcript forms might not always be translated to proteins due to some posttranscriptional regulations. 21,[25][26][27] In human skin epidermis, multiple microRNAs are thought to regulate gene expression of keratins during keratinocyte differentiation in vitro and in vivo. 28 Therefore, it is speculated that microRNA-induced repression of the K13 gene translation might occur as posttranscriptional regulation in the oral keratinocytes.…”

Immunohistochemical expression of cytokeratins 7 and 20 in malignant salivary gland tumors

“…Although several investigators have examined the expression of CKs in neoplastic lesions of salivary glands, 19,[21][22][23][24][25][26][27][28][29][30][31] to the best of our knowledge this is the first time that the combined CK7 and CK20 profile of malignant salivary gland tumors is analyzed in a sizeable group of these tumors.…”

“…Such studies have shown that different CKs are localized in the various compartments of normal salivary glands, for example, CK8 and CK18 are expressed in the luminal duct and acinar cells, while CK5 and CK14 are primarily seen in basal duct cells and myoepithelial cells. [21][22][23][24] Interestingly, CK7 has been shown to be expressed to a different degree in the various epithelial salivary gland elements; more specifically, the luminal cells of the salivary ducts are strongly positive for CK7, while the acinar, basal, and myoepithelial cells stain with less intensity or, according to some investigators, not at all. [21][22][23][24] On the other hand, CK20 has been reported to be consistently absent from all salivary gland epithelial elements.…”

“…[21][22][23][24] Interestingly, CK7 has been shown to be expressed to a different degree in the various epithelial salivary gland elements; more specifically, the luminal cells of the salivary ducts are strongly positive for CK7, while the acinar, basal, and myoepithelial cells stain with less intensity or, according to some investigators, not at all. [21][22][23][24] On the other hand, CK20 has been reported to be consistently absent from all salivary gland epithelial elements. 22,24,25 The pattern of CK expression in normal salivary glands has been demonstrated to be recapitulated to some extent in their benign and malignant neoplasms.…”