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Keratin intermediate filaments are an essential and major component of the cytoskeleton in epithelial cells. They form a stable yet dynamic filamentous network extending from the nucleus to the cell periphery, which provides resistance to mechanical stresses. Mutations in keratin genes are related to a variety of epithelial tissue diseases. Despite their importance, the molecular structure of keratin filaments remains largely unknown. In this study, we analyzed the structure of keratin 5/keratin 14 filaments within ghost mouse keratinocytes by cryo-electron microscopy and cryo-electron tomography. By averaging a large number of keratin segments, we have gained insights into the helical architecture of the filaments. Two-dimensional classification revealed profound variations in the diameter of keratin filaments and their subunit organization. Computational reconstitution of filaments of substantial length uncovered a high degree of internal heterogeneity along single filaments, which can contain regions of helical symmetry, regions with less symmetry and regions with significant diameter fluctuations. Cross-section views of filaments revealed that keratins form hollow cylinders consisting of multiple protofilaments, with an electron dense core located in the center of the filament. These findings shed light on the complex and remarkable heterogenic architecture of keratin filaments, suggesting that they are highly flexible, dynamic cytoskeletal structures., Competing Interests: MW, ME, SS, TM, RG, OM No competing interests declared, (© 2021, Weber et al.)

Keratins (KRTs), the intermediate filament-forming proteins of epithelial cells, are extensively used as diagnostic biomarkers in cancers and associated with tumorigenesis and metastasis in multiple cancers. However, the diverse expression patterns and prognostic values of KRTs in melanoma have yet to be elucidated. In the current study, we examined the transcriptional and clinical data of KRTs in patients with melanoma from GEO, TCGA, ONCOMINE, GEPIA, cBioPortal, TIMER and TISIDB databases. We found that the mRNA levels of KRT1/2/5/6/8/10/14/15/16/17 were significantly differential expressed between primary melanoma and metastatic melanoma. The expression levels of KRT1/2/5/6/10/14/15/16/17 were correlated with advanced tumor stage. Survival analysis revealed that the high transcription levels of KRT1/5/6/14/15/16/17 were associated with low overall survival in melanoma patients. GSEA analysis indicated that the most involved hallmarks pathways were P53 pathway, KRAS signaling, estrogen response early and estrogen response late. Furthermore, we found some correlations among the expression of KRTs and the infiltration of immune cells. Our study may provide novel insights for the selection of prognostic biomarkers for melanoma.

Keratins are essential elements of the cytoskeleton of normal and malignant epithelial cells. Because carcinomas commonly maintain their specific keratin expression pattern during malignant transformation, keratins are extensively used as tumor markers in cancer diagnosis including the detection of circulating tumor cells in blood of carcinoma patients. Interestingly, recent biological insights demonstrate that epithelial keratins should not only be considered as mere tumor markers. Emerging evidence suggests an active biological role of keratins in tumor cell dissemination and metastasis. In this review, we illustrate the family of keratin proteins, summarize the latest biological insights into keratin function related to cancer metastasis and discuss the current use of keratins for detection of CTCs and other blood biomarkers used in oncology., (Copyright © 2019. Published by Elsevier Ltd.)

Keratins, the epithelial-predominant members of the intermediate filament superfamily, are expressed in a pairwise, tissuespecific and differentiation-dependent manner. There are 28 type I and 26 type II keratins, which share a common structure comprising a central coiled coil α-helical rod domain flanked by two nonhelical head and tail domains. These domains harbor sites for major posttranslational modifications like phosphorylation and glycosylation, which govern keratin function and dynamics. Apart from providing structural support, keratins regulate various signaling machinery involved in cell growth, motility, apoptosis etc. However, tissue-specific functions of keratins in relation to cell proliferation and differentiation are still emerging. Altered keratin expression pattern during and after malignant transformation is reported to modulate different signaling pathways involved in tumor progression in a context-dependent fashion. The current review focuses on the literature related to the role of keratins in the regulation of cell proliferation, differentiation and transformation in different types of epithelia.

Background: Mutations in keratin proteins have been vastly associated with a wide array of genodermatoses; however, mutations of keratins in psoriasis have not been fully investigated. The main aim of the current research was to identify the mutation in K14, K10, K16, and K17 genes in two stages of psoriasis patients., Methods: Ninety-six psoriatic skin biopsies were collected. mRNA transcript of K14, K10, K16, and K17 was prepared, amplified, and sequenced. Sanger sequences of all keratins were further validated for mutational analysis using Mutation Surveyor and Alamut Visual. Then, in silico analysis of protein stability and protein and gene expression of all keratins was performed and validated., Results: Out of 44 mutations, about 75% of keratins are highly pathogenic and deleterious. Remaining 25% mutations are less pathogenic and tolerated in nature. In these 33 deleterious mutations were immensely found to decrease keratin protein stability. We also found a correlation between keratin and Psoriasis Area and Severity Index score which added that alteration in keratin gene in skin causes severity of psoriasis., Conclusions: We strongly concluded that acanthosis and abnormal terminal differentiation was mainly due to the mutation in epidermal keratins. In turn, disease severity and relapsing of psoriasis are mainly due to the mutation of hyperproliferative keratins. These novel keratin mutations in psoriatic epidermis might be one of the causative factors for psoriasis.

Regressive evolution of anatomical traits often corresponds with the regression of genomic loci underlying such characters. As such, studying patterns of gene loss can be instrumental in addressing questions of gene function, resolving conflicting results from anatomical studies, and understanding the evolutionary history of clades. The evolutionary origins of snakes involved the regression of a number of anatomical traits, including limbs, taste buds and the visual system, and by analyzing serpent genomes, I was able to test three hypotheses associated with the regression of these features. The first concerns two keratins that are putatively specific to claws. Both genes that encode these keratins are pseudogenized/deleted in snake genomes, providing additional evidence of claw-specificity. The second hypothesis is that snakes lack taste buds, an issue complicated by conflicting results in the literature. I found evidence that different snakes have lost one or more taste receptors, but all snakes examined retained at least one gustatory channel. The final hypothesis addressed is that the earliest snakes were adapted to a dim light niche. I found evidence of deleted and pseudogenized genes with light-associated functions in snakes, demonstrating a pattern of gene loss similar to other dim light-adapted clades. Molecular dating estimates suggest that dim light adaptation preceded the loss of limbs, providing some bearing on interpretations of the ecological origins of snakes., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Baleen has been harvested by indigenous people for thousands of years, as well as collected by whalers as an additional product of commercial whaling in modern times. Baleen refers to the food-filtering system of Mysticeti whales; a full baleen rack consists of dozens of plates of a tough and flexible keratinous material that terminate in bristles. Due to its properties, baleen was a valuable raw material used in a wide range of artefacts, from implements to clothing. Baleen is not widely used today, however, analyses of this biomolecular tissue have the potential to contribute to conservation efforts, studies of genetic diversity and a better understanding of the exploitation and use of Mysticeti whales in past and recent times. Fortunately, baleen is present in abundance in museum natural history collections. However, it is often difficult or impossible to make a species identification of manufactured or old baleen. Here, we propose a new tool for biomolecular identification of baleen based on its main structural component alpha-keratin (the same protein that makes up hair and fingernails). With the exception of minke whales, alpha-keratin sequences are not yet known for baleen whales. We therefore used peptide mass fingerprinting to determine peptidic profiles in well documented baleen and evaluated the possibility of using this technique to differentiate species in baleen samples that are not adequately identified or are unidentified. We examined baleen from ten different species of whales and determined molecular markers for each species, including species-specific markers. In the case of the Bryde's whales, differences between specimens suggest distinct species or sub-species, consistent with the complex phylogeny of the species. Finally, the methodology was applied to 29 fragments of baleen excavated from archaeological sites in Labrador, Canada (representing 1500 years of whale use by prehistoric people), demonstrating a dominance of bowhead whale (Balaena mysticetus) in the archaeological assemblage and the successful application of the peptide mass fingerprinting technique to identify the species of whale in unidentified and partially degraded samples.

Metaplastic breast carcinoma (MBC) is a heterogenous group of tumors that diverge from conventional glandular differentiation. The metaplastic component can be focal or may be present purely posing diagnostic challenges. Since MBC may show focal immunostaining or may even be negative for some cytokeratins (CK), different CKs are often needed to prove their epithelial origin. OSCAR is a relatively new broad-spectrum anti-CK antibody. Thirty MBC cases diagnosed at our institution were retrieved, including 7 spindle cell carcinomas. Representative slides were immunostained for CK-OSCAR, CK-AE1/AE3, CAM5.2, CK-903, and CK5/6. Nineteen spindle cell lesions were used as controls, including 6 malignant and 10 borderline phyllodes tumor, 1 inflammatory pseudotumor, 1 solitary fibrous tumor, and 1 nodular fasciitis case. All 30 cases (100%) of metaplastic carcinomas were positive for CK-OSCAR, compared with 27/30 (90%, P=0.076) for CK-AE1/AE3, 21/30 (70%, P≤0.01) for CK-903, 19/30 (63.3%, P≤0.01) for CAM5.2, and 15/30 (50%, P≤0.01) for CK5/6. All control cases were negative for CK-OSCAR. All 7 spindle cell carcinomas were also positive for CK-OSCAR (100%) compared with 6/7 (85.7%) for CK-AE1/AE3, 4/7 (57%) for CK-903, 3/7 (42.8%) for CAM5.2, and 2/7 (28.5%) for CK5/6. Our data show that CK-OSCAR is more sensitive than other individual CKs in diagnosing MBC. Coupled with high specificity, CK-OSCAR may potentially be used in lieu of a panel of CKs to identify the epithelial origin of these tumors, especially in spindle cell tumors. This is particularly useful in limited core biopsy specimens, to help guide treatment and simultaneously lower testing costs.

Pleural effusion (PE), excess fluid in the pleural space, is often observed in lung cancer patients and also forms due to many benign ailments. Classifying it quickly is critical, but this remains an analytical challenge often lengthening the diagnosis process or exposing patients to unnecessary risky invasive procedures. We tested the analysis of PE using a multiplexed cytokeratin (CK) panel with targeted mass spectrometry-based quantitation for its rapid classification. CK markers are often assessed in pathological examinations for cancer diagnosis and guiding treatment course. We developed methods to simultaneously quantify 33 CKs in PE using peptide standards for increased analytical specificity and a simple CK enrichment method to detect their low amounts. Analyzing 121 PEs associated with a variety of lung cancers and noncancerous causes, we show that abundance levels of 10 CKs can be related to PE etiology. CK-6, CK-7, CK-8, CK-18, and CK-19 were found at significantly higher levels in cancer-related PEs. Additionally, elevated levels of vimentin and actin differentiated PEs associated with bacterial infections. A classifier algorithm effectively grouped PEs into cancer-related or benign PEs with 81% sensitivity and 79% specificity. A set of undiagnosed PEs showed that our method has potential to shorten PE diagnosis time. For the first time, we show that a cancer-relevant panel of simple-epithelial CK markers currently used in clinical assessment can also be quantitated in PEs. Additionally, while requiring less invasive sampling, our methodology demonstrated a significant ability to identify cancer-related PEs in clinical samples and thus could improve patient care in the future., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

Barrett's esophagus is characterized by a distinct Th2-predominant cytokine profile (IL-4) from in vivo or ex vivo evidence. The detailed role of cytokines in Barrett's esophagus, particularly whether Th2 cytokines are causative factors driving metaplastic processes, remains unknown. In this study, air-liquid interface-cultured human esophageal epithelial cells were stimulated by a Th2 cytokine, IL-4, and Th1 cytokines, TNF-α and IL-1β, continuously for 10 days. Barrier function was determined by transepithelial electrical resistance. Morphological changes were investigated by hematoxylin and eosin staining. Keratin profile (keratin 7, 8, 13, and 14) and squamous differentiation markers (involucrin) were investigated by RT-quantitative PCR, Western blotting, and immunohistochemical staining. Pharmacological inhibitors were used to identify the underlying cellular signaling. We report that IL-4, TNF-α, and IL-1β decrease barrier function, but only IL-4 significantly increases cell layers and changes cell morphology. IL-4 time dependently downregulates the expression levels of the squamous cell markers involucrin and keratin 13 and upregulates the expression levels of the columnar cell markers keratin 7 and 8. Neither TNF-α nor IL-1β shows any effect on these indexes. JAK inhibitor I and PI3K inhibitors significantly block the IL-4-induced changes in the levels of keratin 8 and 13. In conclusion, IL-4 inhibits squamous differentiation program of esophageal epithelial cells and induces differentiation toward columnar cells through the JAK/PI3K pathway. Thus IL-4 may be involved in the early stages of Barrett's esophagus development.

This study aimed to compare epithelial cells derived from human embryonic stem cells (hESCs) to human ameloblast-lineage cells (ALCs), as a way to determine their potential use as a cell source for ameloblast regeneration. Induced by various concentrations of bone morphogenetic protein 4 (BMP4), retinoic acid (RA) and lithium chloride (LiCl) for 7 days, hESCs adopted cobble-stone epithelial phenotype (hESC-derived epithelial cells (ES-ECs)) and expressed cytokeratin 14. Compared with ALCs and oral epithelial cells (OE), ES-ECs expressed amelogenesis-associated genes similar to ALCs. ES-ECs were compared with human fetal skin epithelium, human fetal oral buccal mucosal epithelial cells and human ALCs for their expression pattern of cytokeratins as well. ALCs had relatively high expression levels of cytokeratin 76, which was also found to be upregulated in ES-ECs. Based on the present study, with the similarity of gene expression with ALCs, ES-ECs are a promising potential cell source for regeneration, which are not available in erupted human teeth for regeneration of enamel.

The ability to discriminate between objects manufactured from animal horn and chelonian (turtle, tortoise, or terrapin) shell is important from a cultural and archeological perspective such that it may allow conservators to determine the appropriate treatment and long-term care solution. It would also aid curators in identifying and cataloging items manufactured from these materials. Discrimination and classification is also a valuable tool for those involved in tracking the illegal trade in restricted materials of this nature. Attenuated total reflection infrared (ATR-IR) spectroscopy, using a single reflection diamond internal reflection element (IRE), coupled with discrimination analysis was used to analyze a total of thirty-nine samples (29 calibration samples, 10 validation samples). A discrimination analysis model was constructed using Mahalanobis distances to classify spectra into one of two classes. The model was then subsequently used to successfully classify all validation samples and correctly identify them as animal horn or chelonian shell based on second-derivative spectra of the amide I and II regions. This technique requires minimal to no sample preparation and may be used to nondestructively identify very small samples successfully without performing detailed secondary structural curve-fitting routines. This model should be a valuable resource to museums, conservators, and wildlife management programs for rapidly and reliably discriminating between animal horn and chelonian shell.

Most protein in hair and wool is of two broad types: keratin intermediate filament-forming proteins (commonly known as keratins) and keratin-associated proteins (KAPs). Keratin nomenclature was reviewed in 2006, but the KAP nomenclature has not been revised since 1993. Recently there has been an increase in the number of KAP genes (KRTAPs) identified in humans and other species, and increasingly reports of variation in these genes. We therefore propose that an updated naming system is needed to accommodate the complexity of the KAPs. It is proposed that the system is founded in the previous nomenclature, but with the abbreviation sp-KAPm-nL*x for KAP proteins and sp-KRTAPm-n(p/L)*x for KAP genes. In this system "sp" is a unique letter-based code for different species as described by the protein knowledge-based UniProt. "m" is a number identifying the gene or protein family, "n" is a constituent member of that family, "p" signifies a pseudogene if present, "L" if present signifies "like" and refers to a temporary "place-holder" until the family is confirmed and "x" signifies a genetic variant or allele. We support the use of non-italicised text for the proteins and italicised text for the genes. This nomenclature is not that different to the existing system, but it includes species information and also describes genetic variation if identified, and hence is more informative. For example, GenBank sequence JN091630 would historically have been named KRTAP7-1 for the gene and KAP7-1 for the protein, but with the proposed nomenclature would be SHEEP-KRTAP7-1*A and SHEEP-KAP7-1*A for the gene and protein respectively. This nomenclature will facilitate more efficient storage and retrieval of data and define a common language for the KAP proteins and genes from all mammalian species.

Keratins (Ks) consist of central α-helical rod domains that are flanked by non-α-helical head and tail domains. The cellular abundance of keratins, coupled with their selective cell expression patterns, suggests that they diversified to fulfill tissue-specific functions although the primary structure differences between them have not been comprehensively compared. We analyzed keratin sequences from many species: K1, K2, K5, K9, K10, K14 were studied as representatives of epidermal keratins, and compared with K7, K8, K18, K19, K20 and K31, K35, K81, K85, K86, which represent simple-type (single-layered or glandular) epithelial and hair keratins, respectively. We show that keratin domains have striking differences in their amino acids. There are many cysteines in hair keratins but only a small number in epidermal keratins and rare or none in simple-type keratins. The heads and/or tails of epidermal keratins are glycine and phenylalanine rich but alanine poor, whereas parallel domains of hair keratins are abundant in prolines, and those of simple-type epithelial keratins are enriched in acidic and/or basic residues. The observed differences between simple-type, epidermal and hair keratins are highly conserved throughout evolution. Cysteines and histidines, which are infrequent keratin amino acids, are involved in de novo mutations that are markedly overrepresented in keratins. Hence, keratins have evolutionarily conserved and domain-selectively enriched amino acids including glycine and phenylalanine (epidermal), cysteine and proline (hair), and basic and acidic (simple-type epithelial), which reflect unique functions related to structural flexibility, rigidity and solubility, respectively. Our findings also support the importance of human keratin 'mutation hotspot' residues and their wild-type counterparts.

Objective: The aim of this study was to describe the clinicopathologic and immunohistochemical characteristics of 14 cases of central odontogenic fibroma (COF), and the ultrastructural features of 2 of them., Study Design: Collaborative retrospective study based on the records of 4 oral pathology diagnostic services in Latin America based on the current World Health Organization classification., Results: There were 7 male and 7 female patients (mean age 31.8 years). Eight tumors occurred in the maxilla and 6 in the mandible. Thirteen cases were epithelium-rich and 1 epithelium-poor COF. Three were classified as hybrid COF with giant cell lesion. Mean size of the hybrid lesions were larger than pure COF (3.8 vs. 2.4 cm). Odontogenic epithelial islands were immunoreactive for cytokeratin (CK) AE1/AE3, CK5, CK14, CK19, and 34BE12 and negative for CK1 and CK18. Langerhans cells positive for S-100 and CD1a were found within the epithelial islands in 6/6 tested cases. CD68 was expressed in the giant cells of the hybrid lesions and in a few mononuclear cells of 2 cases of COF. Ki-67 index was <1% in all cases. In 6 tumors (42.8%), there were small globular eosinophilic droplets within the epithelial islands, which were positive for collagen type IV, and 9/13 cases (69.2%) were focally positive for smooth muscle actin. In addition to fibroblasts, myofibroblastic differentiation was found in the 2 cases studied ultrastructurally., Conclusions: Immunohistochemistry was useful to confirm the presence of epithelium and to exclude other central fibrous tumors. COF also contains a variable number of mast cells, Langerhans cells, and myofibroblasts, and further studies are needed to better understand the participation of these cells in COF histogenesis., (Copyright © 2011 Mosby, Inc. All rights reserved.)

Keratin IF (KRT) and keratin-associated protein genes encode the majority of wool and hair proteins. We have identified cDNA sequences representing nine novel sheep KRT genes, increasing the known active genes from eight to 17, a number comparable to that in the human. However, the absence of KRT37 in the type I family and the discovery of type II KRT87 in sheep exemplify species-specific compositional differences in hair KRT genes. Phylogenetic analysis of hair KRT genes within type I and type II families in the sheep, cattle and human genomes revealed a high degree of consistency in their sequence conservation and grouping. However, there were differences in the fibre compartmentalisation and keratinisation zones for the expression of six ovine KRT genes compared with their human orthologs. Transcripts of three genes (KRT40, KRT82 and KRT84) were only present in the fibre cuticle. KRT32, KRT35 and KRT85 were expressed in both the cuticle and the fibre cortex. The remaining 11 genes (KRT31, KRT33A, KRT33B, KRT34, KRT36, KRT38-39, KRT81, KRT83 and KRT86-87) were expressed only in the cortex. Species-specific differences in the expressed keratin gene sets, their relative expression levels and compartmentalisation are discussed in the context of their underlying roles in wool and hair developmental programmes and the distinctive characteristics of the fibres produced., (© 2011 John Wiley & Sons A/S.)

Keratins are a highly diverse family of cytoskeletal proteins and important markers of epithelial cell differentiation. In this review, applying the new keratin nomenclature recently introduced, we summarize and discuss the distribution and significance of keratin patterns in cutaneous epithelial tumors in relation to the epithelial structures of normal human skin. The available literature data show that the analysis of keratin profiles broadens our understanding of the differentiation, nature and histogenetic origin of the various, highly singular epithelial tumors arising in the skin. Moreover, keratins may aid in histological diagnosis and, in certain instances, may be helpful for the recognition of tumor malignancy and aggressiveness. Furthermore, we briefly address the topic of keratin-related skin disorders., (© 2011 John Wiley & Sons A/S.)

Cancer is among the major causes of human death and its mechanism(s) are not fully understood. We applied a novel meta-analysis approach to multiple sets of merged serial analysis of gene expression and microarray cancer data in order to analyze transcriptome alterations in human cancer. Our methodology, which we denote 'COgnate Gene Expression patterNing in tumours' (COGENT), unmasked numerous genes that were differentially expressed in multiple cancers. COGENT detected well-known tumor-associated (TA) genes such as TP53, EGFR and VEGF, as well as many multi-cancer, but not-yet-tumor-associated genes. In addition, we identified 81 co-regulated regions on the human genome (RIDGEs) by using expression data from all cancers. Some RIDGEs (28%) consist of paralog genes while another subset (30%) are specifically dysregulated in tumors but not in normal tissues. Furthermore, a significant number of RIDGEs are associated with GC-rich regions on the genome. All assembled data is freely available online (www.oncoreveal.org) as a tool implementing COGENT analysis of multi-cancer genes and RIDGEs. These findings engender a deeper understanding of cancer biology by demonstrating the existence of a pool of under-studied multi-cancer genes and by highlighting the cancer-specificity of some TA-RIDGEs.

First described in 1969, syringoid eccrine carcinoma (SEC) is a rare cutaneous tumor with some controversy regarding its correct definition. It consists of solid nests and small cords in a dense fibrocollagenous stroma. As it is rare, its clinical appearance is not well characterized and its biological behaviour is not defined. It usually affects skin of the scalp, extremities and more rarely, other sites. It behaves as locally aggressive tumor but metastases are rare. Although there have been some previous reports describing clinical presentation and management of SEC in the skin, there has been no previous reports describing clinical findings and management of this tumor in the external auditory canal. We report a case of a 57-year-old female with small solitary mass in left external auditory canal associated with discharge, severe itching and bleeding on manipulation. Complete local excision is the recommended method for diagnosis and treatment of this tumor in the external auditory canal. This extremely rare case serves as a springboard for the diagnosis as well as the management of SEC in external auditory canal., (Copyright 2010 Elsevier Ireland Ltd. All rights reserved.)

Cysts of the tongue are rare, usually derived from epithelia of the embryonic gastrointestinal and respiratory tracts, and classified according to the predominant epithelium lining. These cysts are usually discovered during infancy, more frequently in males, but they may not appear until well into adulthood. The authors report two lingual cysts lined mainly with respiratory, and focally by squamous, epithelium. Periodic acid-Schiff and mucicarmine staining revealed focal positivity in intracystic mucoid material and goblet cells. Immunohistochemical analysis with vimentin, cytokeratins (AE1/AE3, 34betaE12, CK1, CK5, CK6, CK7, CK8, CK10, CK13, CK14, CK16, CK18, and CK19), E-cadherin, beta-catenin, and epithelial membrane antigen showed a similar profile of normal respiratory epithelium, suggesting well-differentiated states. Owing to their controversial origin, these cysts should be named descriptively, as suggested by Manor et al., as lingual cysts with respiratory epithelium.

Mucoepidermoid carcinoma is the most common malignant salivary gland tumor, composed of several different cell types, with controversial histogenesis. The aim of this study was to assess the expression of cytokeratins in mucoepidermoid carcinoma, comparing to cytokeratin expression in normal salivary glands, in order to establish a possible correlation between tumor cells immunostaining and mucoepidermoid carcinoma histogenesis and differentiation. Eighty cases of salivary gland mucoepidermoid carcinoma were immunohistochemically examined with the use of antibodies against cytokeratins 6, 7, 8, 13, 14, 18, and 19. Cytokeratin expression varied according to the cellular type: squamous cells presented high expression of cytokeratins 6, 7, 8, 14, 18, and 19; intermediate and mucous cells of cytokeratin 7; clear and columnar cells of cytokeratins 6, 7, 8 and the latter also expressed cytokeratin 18. Cytokeratin 13 expression was low in all cell types. Cytokeratin immunoexpression in mucoepidermoid carcinoma was variable according to the cellular type; but regardless of the cellular type studied, cytokeratins 7 and 13 were, respectively, constantly high and low expressed. The immunoprofile of the normal salivary glands was variable according to the component but, in general, cytokeratin profile in mucoepidermoid carcinoma showed similarity to the immunoexpression on the excretory duct unit of normal salivary glands.

When the first nomenclature of the keratin protein family was published over 20 years ago, only 19 keratins were thought to exist. Sequencing of the human genome has now revealed that there are 54 keratin genes. As a consequence, the nomenclature needed revision to apply a logical numbering system that includes the more recently identified keratins of the hair follicle.

Keratins are intermediate filament-forming proteins that provide mechanical support and fulfill a variety of additional functions in epithelial cells. In 1982, a nomenclature was devised to name the keratin proteins that were known at that point. The systematic sequencing of the human genome in recent years uncovered the existence of several novel keratin genes and their encoded proteins. Their naming could not be adequately handled in the context of the original system. We propose a new consensus nomenclature for keratin genes and proteins that relies upon and extends the 1982 system and adheres to the guidelines issued by the Human and Mouse Genome Nomenclature Committees. This revised nomenclature accommodates functional genes and pseudogenes, and although designed specifically for the full complement of human keratins, it offers the flexibility needed to incorporate additional keratins from other mammalian species.

Hepatoblastomas (HBs) recapitulate liver development. It is possible that HBs result from malignant transformation of hepatic precursor cells, and they may reflect a blockage in normal development. Here we study the expression of cytokeratins (CKs) in order to delineate the immunoprofile and relationship with liver development, as well as vimentin and alphafetoprotein (AFP), of HBs. Immunohistochemistry was performed in a tissue microarray (TMA) containing representative areas of 18 HBs (fetal and/or embryonal and/or mesenchymal); we also reviewed 11 cases not included in the TMA. No cases stained for CKs 1, 5/6, 7, 10, 13, 15, 16, 20, and 34betaE12. CK8 stained 73.07% of fetal, 50% of embryonal, and 18% of mesenchymal areas. CK18 stained 100% of epithelial areas. CK19 staining was intense and diffuse in 100% of embryonal samples, but it was weaker in fetal areas (66.66%). AE1 stained epithelial areas in all cases, and it stained 29.41% of mesenchymal areas. AE3 stained 84.61% of embryonal and 60% of fetal components. AE1/AE3 showed stronger staining in embryonal (100%) than in fetal areas (76.92%). Vimentin staining was strong in embryonal (66.66%) and mesenchymal (84.61%) components but weak in fetal areas (8%). Alphafetoprotein was positive in only 20% of fetal and 70% of embryonal areas. Our results support the hypothesis that immunoexpression of HBs follows the stages of normal liver development. Embryonal areas look less differentiated, expressing vimentin and biliary epithelium CKs, whereas fetal areas display a more developed phenotype, similar to that of mature hepatocytes. These data aid in understanding the ontogenesis of HBs and may be used in histopathological diagnosis.

Background: We have previously shown that benign pilomatricomas not only maintain the sequential expression of the hair matrix and precortex keratins hHa5 and hHa1 of normal hair follicles in their transitional cell compartment, but also preserve the association of hHa5 expression with that of its regulatory homeoprotein HOXC13 in the lower transitional cell compartment. In contrast, hHa1 expression in the upper transitional cell compartment is uncoupled from the nuclear co-expression of the LEF1/beta-catenin complex seen in normal hair follicles (Cribier et al., J Invest Dermatol 2004; 122: 1078)., Methods: Formalin-fixed paraffin sections of the tumor were examined using a panel of mono- and polyclonal hair and epithelial keratin antibodies as well as antibodies against HOXC13, LEF1, and beta-catenin., Results: Morphologically, the malignant pilomatricoma investigated here clearly deviated from the described major tumor type by a large number of differently sized parakeratotic squamoid whorls emerging within the mass of basaloid cells and surrounded by cells remembering transitional cells, but only rarely containing shadow cells and signs of calcification. We show that hHa5/HOXC13 co-expression was maintained in transitional cell areas, in which hHa1 expression was much stronger than in benign pilomatricomas, but again uncoupled from concomitant nuclear LEF1/beta-catenin expression. Surprisingly, however, and in clear contrast to benign pilomatricomas, these transitional cells co-expressed the epithelial keratins K5, K14, and K17, with the latter being as strongly expressed as hHa1, both also staining the entire inner mass of the parakeratotic whorls., Conclusions: Although the malignant pilomatricoma investigated here was distinctive in that it contained a multitude of parakeratinizing whorls and no signs of calcification, it shared both hHa5/HOXC13 co-expression and disrupted hHa1/beta-catenin-LEF1 expression in its transitional cell compartment around the whorls with benign pilomatricomas. However, in clear contrast to the latter, transitional cells of the malignant tumor also strongly expressed the epithelial keratins K5, K14, and K17. We speculate that the observed dominance of the epithelial differentiation pathway over the competing conventional shadow cell differentiation pathway may prevent massive calcification of the tumor.

Elucidation of the genes encoding structural proteins of the human hair follicle has advanced rapidly during the last decade, complementing nearly three previous decades of research on this subject in other species. Primary among these advances was both the characterization of human hair keratins, as well as the hair keratin associated proteins (KAPs). This review describes the currently known human KAP families, their genomic organization, and their characteristics of expression. Furthermore, this report delves into further aspects, such as polymorphic variations in human KAP genes, the role that KAP proteins might play in hereditary hair diseases, as well as their modulation in several different transgenic mouse models displaying hair abnormalities.

Cytokeratins are fibrous intermediate-filament protein polymers present in almost all animal cells. Their function is related to epithelium structural maintenance, protection from mechanical trauma, and possibly communication between adjacent cells or cytoplasm components. Today there are 20 known cytokeratins, classified according to their molecular weight and pH as type I or acidic (cytokeratins 9-20) and type II or neutral-basic (cytokeratins 1-8). Cytokeratins are always expressed in specific pairs for each type of tissue, composed of one unit of type I and one unit of type II. Primary structural defects of cytokeratins are associated with various keratinization impairments. Two of the better characterized defects are bullous epidermolysis and epidermolytic hyperkeratosis. Anti-cytokeratin monoclonal antibodies are being used for diagnostic purposes to characterize the origin of poorly differentiated tumors and metastatic solid tumors.

Cytokeratins (CKs) are expressed specifically in the cytoplasm of epithelial cells. We investigated the expression of CKs immunohistochemically in basal cell carcinomas (BCCs), epidermis overlying tumour, and skin tumor-associated amyloidosis (STA). Twenty cases of BCC, 11 of which had STA were included to the study. The primary antibodies of CK1-8 (AE3), CK10 (DEK-10), CK14 (LL002), CK17 (E3), CK18 (DC10), CK19 (KS19.1), CK 5/6/18 (LP34), CK8/18 (5D3) were applied to the section immunohistochemically. In BCCs without STA, CK1-8, CK14 and CK17 antibodies were expressed by tumour tissue in all biopsy specimens. In the BCCs with STA, tumour tissue was immunoreactive always with CK1-8 and CK17 antibodies, and commonly immunoreactive with anti-CK 14 antibody. In the epidermis overlying tumour tissue, there was positive immunoreactivity with anti-CK 1-8, CK 5/6/18, CK 10 and CK 14 antibodies in all biopsy specimens. Anti-CK 17 antibody was also positive in 17 biopsy specimens. STA is immunoreactive with anti-CK1-8 in all specimens. There was mild staining with anti-CK5/6/18 and with anti-CK19 whereas no immunoreactivity with anti-CK10 and CK18 antibodies was found. In conclusion, we could not find a significant CK expression difference between BCCs with and without STA. Weak positivity and a few number of CKs were shown in STA when compared with those of BCC and epidermis overlying tumour tissue expressing the more variable CKs. Interestingly, although CKs coexpressed in pairs consisting of one basic and one acidic CK, we detected predominantly basic CKs in STA.

To examine the properties of shadow and ghost cells, 3 kinds of antibodies were raised against human hair proteins and their immunoreactivity was examined in tumors expressing those cells: pilomatrixoma, 14 cases; craniopharyngioma, 17 cases; and calcifying odontogenic cyst (COC), 14 cases. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analyses demonstrated that 2 polyclonal antibodies, PA-HP1 and PA-HP 2, reacted strongly with type I acidic and type II neutral/basic hard alpha-keratins. The other monoclonal antibody, MA-HP1, reacted with type II neutral/basic hard alpha-keratins. Immunohistochemical examination revealed that all 3 antibodies reacted only with the hair shaft in sections of normal skin and dermoid cyst. In all pilomatrixoma cases, 3 antibodies reacted with the cytoplasm of transitional and shadow cells but not with that of basophilic cells. Positive reactions were found only in shadow cells of all 13 adamantinomatous craniopharyngiomas. In all COCs, the antibodies reacted only with ghost cells, not with other epithelial components. Immunoreactivity for phosphothreonine, detected in hard alpha-keratins, also was found in transitional, shadow, and ghost cells. The appearance of shadow or ghost cells might represent differentiation into hair in these 3 kinds of tumors.

To investigate the prognostic value of keratin subtyping in invasive transitional cell carcinomas (TCCs), we performed a systematic study applying 15 different monoclonal keratin antibodies on 53 upper urinary tract TCCs using a tissue microarray technique. Immunoreactivity was correlated with pT stages and tumour grades using the Fisher's exact test. Impact on disease-free survival was analysed using the Kaplan-Meier method and compared by the log-rank test. Immunoreactivity for keratins 5/6, 6, 7, 8, 13, 14, 17, 18, 19, 20, low molecular weight (LMW) keratins (8, 18) and high molecular weight (HMW) keratins (1, 5, 10, 14) was detected in varying quantities. Regarding semi-quantitative assessment, a prognostic impact was found for keratins 5/6, 7, 8, 13, 17, 20 and HMW keratins, with reduced expression or loss of immunoreactivity being significantly associated with disease progression. With respect to analysis of staining patterns, the retention of a basally accentuated labelling for keratin 5/6 and HMW keratin as well as a superficially accentuated labelling for keratin 20 was significantly associated with a favourable outcome. In conclusion, this investigation is the first to demonstrate a possible prognostic value for keratin subtyping in invasive (upper urinary tract) TCCs with respect to metastasis-free survival. Further studies, however, are needed to substantiate our results.

Histopathologic classification of lung carcinoma is important, as a prognostic factor and in the evaluation of treatment modalities. Although the World Health Organization classification of lung cancer is based on routine microscopy, immunohistochemistry is an important additional aspect in modern pathologic practice. This study examines whether the main histologic types of lung carcinomas are more reliably diagnosed with immunohistochemical technique using antibodies for the lung tissue-specific antigen thyroid transcription factor-1 (TTF-1) and a panel of cytokeratin (CK) antibodies. Forty-five cases of lung cancer (12 squamous cell carcinoma, 13 small cell carcinoma, 11 adenocarcinoma, 9 large cell carcinoma [LCC]/pleomorphic carcinoma) were stained with antibodies to CK CAM5.2, CK5, CK7, CK20, and TTF-1. All 45 cases were positive with CAM5.2, 16 of 45 cases with CK5, 34 of 45 cases with CK7, 4 of 45 cases with CK20, and 29 of 45 with TTF-1. Squamous cell carcinoma (epidermoid carcinoma) had the immunophenotype CK5+/TTF-1-, and at least 20% were also positive with CK7. Most nonepidermoid tumors had the "lung-specific" phenotype CK5-/TTF-1+; all small cell carcinomas had the phenotype CK5-/CK8+/TTF-1+, all adenocarcinomas CK5-/CK7+/TTF-1+ and (more than 50%) of LCC CK5-/CK7+/TTF-1+. Thus, more than 50% of LCCs were of the same phenotype as adenocarcinomas. The immunophenotypes of the main histologic types of lung carcinoma are stable and highly reproducible. However, because of considerable overlapping, immunophenotyping should not be used alone for histopathologic classification of lung cancer, but only as an adjunct to light microscopy. It is also suggested that CK5+ lung carcinomas with basaloid features should be regarded as variants of squamous cell carcinoma and not as LCC.

Most of the chick body is covered with feathers, while the tarsometatarsus and the dorsal face of the digits form oblong overlapping scales (scuta) and the plantar face rounded nonoverlapping scales (reticula). Feathers and scuta are made of beta-keratins, while the epidermis of reticula and inter-appendage or apteria (nude regions) express a-keratins. These regional characteristics are determined in skin precursors and require an epidermal FGF-like signal to be expressed. Both the initiation of appendages, their outline and pattern depend on signals from the dermis, while their asymmetry and outgrowth depend on epidermal competence. For example, the plantar dermis of the central foot pad induces reticula in a plantar or feathers in an apteric epidermis, in a hexagonal pattern starting from the medial point. By manipulating Shh levels in the epidermis, the regional appendage type can be changed from scuta or reticula to feather, whereas the inhibition of Wnt7a, together with a downregulation of Shh gives rise to reticula and in extreme cases, apteria. During morphogenesis of plantar skin, the epidermal expression of En-1, acting as a repressor both of Wnt7a and Shh, is linked to the formation of reticula. Finally, in birds, the complex formation of feathers, which can be easily triggered, even in the extra-embryonic somatopleure, may result from a basic genetic program, whereas the simple formation of scales appears secondarily derived, as requiring a partial (scuta) or total (reticula) inhibition of epidermal outgrowth and beta-keratin gene expression, an inhibition lost for the scuta in the case of feathered feet breeds.

Objective: We sought to investigate a novel mutation in the keratin genes assumed to be responsible for a familial case of oral white sponge nevus., Patients and Methods: The affected family consisted of a 36-year-old woman, her 17-year-old daughter, and her 14-year-old son. Keratin 4 and 13 genes extracted from venous blood lymphocytes were amplified by using the polymerase chain reaction and directly sequenced., Results: Sequencing analysis of the 3 patients revealed the presence of a novel heterozygous T-to-C transition mutation in exon 1 of the keratin 13 gene, with no abnormalities detected in the keratin 4 gene., Conclusion: We identified a novel heterozygous missense mutation at 332T>C in the keratin 13 gene believed to be related to the development of white sponge nevus.

Comparative two-dimensional electrophoretic (2-DE) studies were performed over a time-course to examine the effect of oxidation or alkylation on the separation of wool keratin proteins. The effect of oxidation was followed by treating scoured wool fibres with increasing levels of hydrogen peroxide, ranging from 0-12 g/L, using conditions mimicking the industrial wool bleaching process. Peroxide treatment was found to have only a minor effect on the 2-DE separation of the intermediate filament protein (IFP) class. Conversely, peroxide treatment of the 24-28 kDa high sulphur protein (HSP) class, which contains up to 40 cysteine residues per protein, resulted in the gradual disappearance of the major HSP spots correlated with the appearance of a few discrete spots at lower isoelectric point (pI). This suggested that only a few specific cysteine residues were being oxidized to cysteic acid by treatment with hydrogen peroxide. Peroxide treatment also appeared to have affected a discrete number of cysteine residues among proteins in the high glycine-tyrosine protein (HGTP) class, reducing the intensity of the high pI spots, while correspondingly increasing the intensity of those at lower pI. In a separate study, wool proteins were alkylated with iodoacetamide (1 M, pH 8) for periods ranging from 10 min to 48 h. In contrast to treatment with peroxide, the pI values of the HSP spots were unaffected by alkylation, irrespective of the length of this treatment. Alkylation resulted in a shift to lower pI and a loss of resolution of individual spots in the Type I and II IFP trains, to the extent that after 24 h alkylation individual spots in these trains merged. In addition after 1 h the intensity of the high pI Type II IFPs decreased until they were no longer visible on the 2-DE map after 24 h. Similarly as alkylation time increased, the major, high pI HGTP spots decreased in intensity. In unison with their decrease, some of the lower pI spots increased in intensity, while new spots appeared at more acidic pIs. Mass spectral studies indicated that cysteine alkylation was relatively fast, with 70-95% of the cysteines in the keratin proteins being alkylated within the first 10 min, while in the case of the HGTPs there was evidence for noncysteine alkylation occurring within this period. Alkylation of proteins for periods of up to 6 h prior to electrofocusing is being promoted as a better alternative to the current 2-DE protocol of the inclusion of a reductant in the immobilized pH gradient rehydration solution. This study has clearly demonstrated that long alkylation times do not suit all protein types or classes.

Objective: The purpose of this study was to obtain a primary cell culture of bovine origin similar to the conjunctiva in terms of morphology and cell types, which could be of use for in vitro toxicity studies., Methods: After separation from the stroma by enzymatic treatment, conjunctival epithelial cells were dissociated and plated onto collagen-coated Transwell filters (1.13 cm(2) area). One group of plates was maintained in immersion and another was cultured under air-lifted conditions. Anti-epithelial keratin antibodies (AE1/AE3, K4) and antidesmoplakin 1 and 2 were used to characterize the cells by indirect immunofluorescence. The cell layer was examined after histological processing of the Transwell filter. Ultrastructural analysis was carried out by scanning electron microscopy (SEM). The bioelectric parameters transepithelial electrical resistance (TEER), potential difference (PD), short circuit current and paracellular permeability profile of carboxyfluorescein were monitored as indices of the functional characteristics of these cultures. Cytotoxicity was evaluated on morphological and functional (TEER) grounds after treating the cultures with several test substances., Results: Morphological studies showed pure and homogeneous cell cultures. In the SEM analysis, we observed contiguous polygonal cells with numerous short microvilli, a characteristic proportion of light, medium and dark cells and a sparse population of rounded PAS-positive cells, i.e. resembling goblet cells. Air-lifted cultures also showed a tissue-like cellular organization (8-9 layers). Immersion cultures reached a maximum TEER value of around 2.95 kOmega x cm(2) 7 days after plating while in air-lifted cultures TEER peaked up to 5.59 komega x cm(2) 11 days after plating. With regard to the use of bovine conjunctival epithelial cells (BCECs) for cytotoxicity screening, the system responded finely to the insults and yielded morphological and functional results in accordance with data obtained in vivo., Conclusions: BCECs reproduce cell morphology and differentiation of the original tissue and should prove a useful tool for initial studies of drug toxicity., (Copyright 2003 S. Karger AG, Basel)

Background: Calcifying odontogenic cyst (COC) is an uncommon odontogenic lesion with few studies describing its immunohistochemical profile and proliferative activity reported in the literature., Methods: Clinical and histological features and immunohistochemical expression of cytokeratins, Mel-CAM (CD146), bcl-2, PCNA and ki-67, in 10 cases of COC were studied., Results: All 10 cases affected the maxilla, eight intraosseous and two peripheral. Five central cases were cystic and three were cystic associated with odontoma, and the two extraosseous showed solid histological pattern; immunohistochemistry was positive for cytokeratins 8, 14, 19, AE1/AE3 and 34betaE12 and bcl-2 in all cases, and Mel-CAM in six cases. Proliferative activity was greater in the epithelium of central cystic COC in relation to COC associated with odontoma and peripheral lesions., Conclusion: Calcifying odontogenic cysts showed odontogenic cytokeratin profile and bcl-2 and Mel-CAM expression indicate that these proteins may be involved in the development of COC. There were no recurrences after surgery, irrespective of their proliferative activity.

Syringoid eccrine carcinoma is an extremely rare cutaneous malignant tumor, thought to be derived from eccrine sweat apparatus. We report a case of syringoid eccrine carcinoma occurring on the scalp of a 66-year-old woman and analyzed its cytokeratin expression immunohistochemically to clarify its histogenesis. The tumor consisted mainly of numerous small cords and nests extending from the reticular dermis to the subcutaneous tissue, which formed luminal or tubular structures mimicking the nests of syringoma. Immunohistochemical analysis revealed that most tumor cells expressed simple epithelial cytokeratins (CKs 7, 8, 18, 19) suggesting their sweat secretory differentiation, and that a small number of tumor cells showed an expression of stratified epithelial cytokeratins (CKs 5, 14) suggesting their ductal differentiation. We believe that the syringoid eccrine carcinoma of our case may differentiate mainly toward the sweat secretory cells rather than toward the dermal ductal cells.

Five different type I keratins from a teleost fish, the rainbow trout Oncorhynchus mykiss, have been sequenced by cDNA cloning and identified at the protein level by peptide mass mapping using MALDI-MS. This showed that the entire range of type I keratins detected biochemically in this fish has now been sequenced. Three of the keratins are expressed in the epidermis (subtype Ie), whereas the other two occur in simple epithelia and mesenchymal cells (subtype Is). Among the Is keratins is an ortholog of human K18; the second Is polypeptide is clearly distinct from K18. We raised a new monoclonal antibody (F1F2, subclass IgG1) that specifically recognizes trout Is keratins, with negative reactions on zebrafish. A phylogenetic tree has been constructed from a multiple alignment of the rod domains of the new sequences together with type I sequences from other vertebrates such as shark, zebrafish, and human; a recently sequenced lamprey Is keratin was applied as outgroup. This tree shows one branch defining the K18 orthologs and a second branch containing all other type I keratins (mostly subtype Ie). Within this second branch, the teleost keratins form a separate, highly bootstrap-supported twig. This tree leaves little doubt that the teleost Ie keratins diversified independently from the mammalian Ie keratins.

From a teleost fish, the rainbow trout Oncorhynchus mykiss, we have cloned and sequenced cDNAs encoding five different type II keratins. The corresponding protein spots, as separated by 2D-PAGE of trout cytoskeletal preparations, have been identified by peptide mass mapping using MALDI mass spectrometry. Three of the sequenced keratins are expressed in the epidermis (subtype IIe), and two in simple epithelia and mesenchymal cells (subtype IIs). The IIs keratins are both orthologs of human K8. This leaves unsequenced only the trace component S3 of the biochemically established trout keratin catalog. A phylogenetic tree has been constructed from a multiple alignment of the rod domains of the new keratin sequences together with type II sequences from other vertebrates such as shark, zebrafish, and human; lamprey K8 (recently sequenced in our laboratory) has been used as outgroup. This tree suggests, in a highly bootstrap-supported manner, that the teleost IIe keratins diversified independently from the mammalian IIe keratins. In contrast, all the species investigated express K8-like keratins, suggesting that the different IIe branches evolved from K8-like progenitors. The tree also indicates that the published zebrafish sequences represent IIe keratins and that the biochemically identified K8 ortholog in zebrafish has not yet been sequenced.

The keratin proteins from wool can be divided into two classes: the intermediate filament proteins (IFPs) and the matrix proteins. Using peptide mass spectral fingerprinting it was possible to match spots to the known theoretical sequences of some IFPs in web-based databases, as enzyme digestion generated sufficient numbers of peptides from each spot to achieve this. In contrast, it was more difficult to obtain good matches for some of the lower molecular weight matrix proteins. Relatively few peaks were generated from tryptic digests of high-sulfur proteins because of their lower molecular weight and the absence of basic residues in the first two-thirds of the sequence. Their high sequence homology also means that generally only a few of these peptides could be considered to be unique identifiers for each protein. Nevertheless, it was still possible to uniquely identify some of these proteins, while the presence of two peptides in the matrix-assisted laser desorption/ionization time-of-flight mass spectrum allowed classification of other protein spots as being members of this family. Only one major peptide peak was generated by the high-glycine tyrosine proteins (HGTPs) and there were relatively few sequences available in web-based databases, limiting their identification to one HGTP family., ((c)2001 Elsevier Science.)

Due to more efficient chemotherapy protocols, the number of second and even third primary carcinomas is steadily increasing. To denominate the possible origin of a carcinoma, different markers are available as an aid, e.g. hormones, proteins and lipoproteins, secretion products and cytoskeletal proteins. Cytokeratins (CKs) have gained new popularity; however, they have not been extensively evaluated in lung tumours. In our study we evaluated the staining patterns of CK polypeptides 4-8, 10, 13, 14, and 17-20 and high molecular weight (HMW) CK polypeptides in routinely processed primary lung carcinomas and lung metastases of diverse origin. As expected, immunohistochemical investigation gave no clear-cut results, but, with statistical analysis, lung adenocarcinomas could be separated from metastatic adenocarcinomas using CK 5 and 18 and HMW CK (specificity 92.5%, sensitivity 62.5%). The different origin of the metastases could often be detected using CK 18 and CK 20. Lung clear cell carcinomas and large cell carcinomas with clear cell areas could be distinguished from metastatic renal clear cell carcinomas by the CK 7 staining reaction. Squamous cell carcinomas of the lung and metastatic squamous cell carcinomas of the larynx, pharynx and oesophagus could not reliably be separated in part due to the few number of cases available. CK polypeptide typing is thus an additional aid in the differential diagnosis of lung carcinomas versus carcinomas metastatic to the lung.

Cribriform areas are common features of both adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma. Both are malignant salivary gland tumors that share similar histologic patterns, but with marked distinct clinical behavior. This study was undertaken to improve the accuracy of the histopathology diagnostic process, using an immunohistochemical panel to differentiate adenoid cystic carcinoma from polymorphous low-grade adenocarcinoma, with special concern to the common cribriform areas shared by these tumors. Three-microm serial sections of these tumors were submitted to the streptavidin-biotin peroxidase immunotechnique against the monoclonal antibodies anticytokeratins 7, 8, 14 and 19, and anti-integrins beta1, beta3, and beta4. In the neoplastic lobules of adenoid cystic carcinoma cribriform type, the spaces were mainly surrounded by cells negative for the cytokeratins and integrins studied. In the solid type of adenoid cystic carcinoma, the microcystic areas were caused by spaces lined by neoplastic luminal cells positive for cytokeratins and presenting integrins concentrated in the apical pole of these cells. The cribriform areas of polymorphous low-grade adenocarcinoma were composed of cords of luminal cells, positive for cytokeratins and showing integrins disposed in a bipolar pattern. We concluded that cribriform areas of adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma are histologically similar, although not identical. Indeed, their cellular composition is distinct and can be distinguishable from one another by the proteins of the cytoskeleton, by the integrins, or both., (Copyright 2001 by W.B. Saunders Company)

Aims: The aim of this study was to establish the cytokeratin expression profile of different types of thyroid carcinoma., Materials and Methods: The expression of cytokeratins (CKs) 1, 4, 6, 7, 10/13, 18, 19 and 20 in 153 thyroid carcinomas were examined by immunohistochemistry., Results: All papillary carcinomas (n=86) and follicular carcinomas (n=19) showed expression of CK7 and CK18. The staining was often diffuse. CK19 staining was expressed in all papillary carcinomas and the staining was often diffuse. The staining was noted in 68% of follicular carcinomas and the staining was often focal. No difference in the expression was noted between the minimally invasive and widely invasive follicular carcinomas. Poorly differentiated carcinomas (n=10) showed CK7, CK18, CK19 expression in 60%, 60% and 40%, respectively. Anaplastic carcinomas (n=25) expressed CK7 in 84%, CK18 in 80%, CK19 in 76% and CK10/13 in 16%. Medullary carcinomas (n=13) showed CK7 expression in 100%, CK18 in 85% and CK19 in 77%. None of the medullary carcinomas showed diffuse positivity to CK19. All the thyroid carcinomas were negative for CKs 1, 4, 6 and 20., Conclusions: Cytokeratin expression profile for each type of thyroid carcinoma was established., (Copyright 2001 Harcourt Publishers Limited.)

The etiology of biliary atresia (BA) remains unknown, but ductal-plate malformation and insufficient ductal-plate remodeling have been suggested to play important roles, so it is beneficial to examine the maturation and differentiation of bile ducts in BA. Different epithelial types are characterized by the expression of specific cytokeratin (CK) subtypes. CK can therefore serve as a 'lineage marker' of epithelial cells. CK subtypes have not been previously examined in BA. In this study, we examined the maturation of bile-duct cells in BA (n = 45) using immunohistochemistry of CK subtypes, with mouse monoclonal antibodies to CAM5.2, and CK subtypes 7, 8, 13, 14, 17, 19 and 20. We then compared these findings with pediatric non-BA (n = 11) and fetal (n = 21) liver. We semiquantitatively evaluated the findings using a H score method. In the fetal liver, immunoreactivity for CAM5.2, CK-7, CK-8 and CK-19 was detected in bile-duct cells, and CAM5.2 and CK-8 immunoreactivity was also detected in hepatocytes. The distribution of these CK subtypes was the same in fetal, pediatric non-BA and BA liver. However, CK-7 immunoreactivity was markedly weaker in bile ducts of fetal (H scores: ductal plate 0 +/- 0; remodeling 9.5 +/- 40.3; remodeled 37.3 +/- 60.8) and BA (H score: 200.9 +/- 55.3) liver compared to non-BA liver (H score: 251.1 +/- 33.5). In addition, CK-20 was detected in the bile ducts of the fetal and BA liver, but not in non-BA liver. These findings suggest that the expression patterns of CK subtypes in bile-duct cells in BA are similar to that in developing bile-duct cells, which is indicative of bile-duct cell immaturity.

Objectives: It has been suggested that Barrett's epithelium and intestinal metaplasia in the gastric cardia have different cyotokeratin (CK) staining patterns and that Barrett's epithelium can be distinguished by CK staining pattern. The aim of this study was to test the utility of CK staining for distinguishing Barrett's esophagus from gastric intestinal metaplasia., Methods: Topographically mapped gastric biopsy specimens were obtained from patients without Barrett's esophagus, and esophageal biopsies were obtained from patients with long-segment Barrett's esophagus (>3 cm). Serial sections were stained with Genta or El-Zimaity triple stain, and biopsies with intestinal metaplasia were stained with antibodies against CK 4, 13, 7, and 20., Results: Sections from 33 biopsies with Barrett's esophagus, 23 with intestinal metaplasia of the gastric cardia, 27 with intestinal metaplasia of the gastric body, and 33 with intestinal metaplasia of the antrum were examined. CK 4 and CK 13 stained squamous epithelium only. The proposed "diagnostic" CK Barrett's 7/20 pattern was found in only 39% of long-segment Barrett's compared to 35%, 4%, and 24% in intestinal metaplasia from the gastric cardia, body, and antrum, respectively. The criteria proposed had a sensitivity of 45% and a specificity of 65%., Conclusions: These results do not support keratin phenotyping as a tool for differentiating intestinal metaplasia originating in the cardia from intestinal metaplasia of Barrett's.

Craniopharyngiomas are generally considered to arise from the remnants of Rathke's pouch or a misplaced enamel organ. We tried to refine these hypotheses, comparing the subtypes of craniopharyngioma with Rathke's cleft cyst, a known Rathke's pouch derivative, and with ameloblastoma, an enamel organ derivative. Nineteen craniopharyngiomas (14 adamantinomatous and 5 papillary type tumors) and 17 ameloblastomas were immunostained for cytokeratin (CK) 7, CK 8, CK 14, and human hair keratin (HHK). All cases of adamantinomatous craniopharyngioma were CK 7+/CK 8+/CK 14+. Two cases (40%) of papillary craniopharyngioma were CK 7+/CK 8+/CK 14+, whereas the remaining three cases (60%) were CK 7+/CK 8-/CK 14+. Fifteen cases (88%) of ameloblastoma were CK 7-/CK 8+/CK 14+. Only the shadow cells present in adamantinomatous craniopharyngiomas were positive for HHK, which may indicate their follicular differentiation. In Rathke's cleft cyst, ciliated cuboidal cells were CK 7+/CK 8+/CK 14- and metaplastic squamous cells were CK 7+/CK 8/CK 14+. These findings suggest that both subtypes of craniopharyngioma may differ from ameloblastoma in histogenesis, although cytokeratin expression patterns may change during tumor development. Adamantinomatous craniopharyngioma may be related to a heterotopic ectodermal tissue which can differentiate into hair follicles, while papillary craniopharyngioma may arise from Rathke's cleft cyst.

Intermediate filaments (IF) have been recognized as ubiquitous components of the cytoskeletons of eukaryotic cells for 25 yr. Historically, the first IF proteins to be characterized were those from wool in the 1960s, when they were defined as low sulfur keratins derived from "microfibrils." These proteins are now known as the type Ia/type IIa trichocyte keratins that constitute keratin IF of several hardened epithelial cell types. However, to date, of the entire class of >40 IF proteins, the trichocyte keratins remain the only ones for which efficient in vitro assembly remains unavailable. In this paper, we describe the assembly of expressed mouse type Ia and type IIa trichocyte keratins into IF in high yield. In cross-linking experiments, we document that the alignments of molecules within reduced trichocyte IF are the same as in type Ib/IIb cytokeratins. However, when oxidized in vitro, several intermolecular disulfide bonds form and the molecular alignments rearrange into the pattern shown earlier by x-ray diffraction analyses of intact wool. We suggest the realignments occur because the disulfide bonds confer substantially increased stability to trichocyte keratin IF. Our data suggest a novel role for disulfide bond cross linking in stabilization of these IF and the tissues containing them.

Hemidesmosomal attachment of the junctional epithelial cells to the tooth and the ability of the attached cells to divide are essential features of the healthy dentogingival junction. Short chain fatty acids are bacterial metabolites associated with gingival inflammation and periodontal pockets. In vitro, short chain fatty acids have been shown to inhibit epithelial cell division and increase the density of their keratin filaments. This study examined these keratin changes by making use of human gingival keratinocyte cultures, gel electrophoresis and Western blot. Short chain fatty acids, butyrate and propionate, increased the relative amount of keratin proteins in the cells, most strikingly keratin K17. The distribution of K17 was further studied in a culture model for human junctional epithelium and in gingival biopsies. In butyrate-treated cultures of junctional epithelium, K17 expression was markedly increased and extended to the basal cells and to the cells mediating the attachment of the explant to the substratum. In clinically healthy gingiva, K17 was expressed predominantly in sulcular epithelium. The dividing basal cells and the cells attached to the tooth were negative. In advanced periodontitis, a strong reaction for K17 was localised to the pocket epithelium. The inhibition of epithelial cell division and the simultaneous upregulation of K17 in vitro, and the strong expression of this protein in detached pocket epithelium suggest a role for the short chain fatty acids in the degenerative process that leads to subgingival advancement of pathogens and, eventually, to periodontal pocket formation.

Gene expression for the differentiation-specific keratins (K4, K13, K1 and K10) was analyzed in oral non-dysplastic keratoses, oral lichen planus (OLP) and lichenoid reactions (LR) by comparative in situ hybridization (ISH) and immunohistochemistry (IHC) to investigate molecular changes in the altered differentiation pattern from non- to para- or orthokeratinization. At the protein level, K4 and K13 were detected homogeneously in the suprabasal compartment of parakeratotic epithelium but showed reduced expression in orthokeratoses, particularly in the presence of lymphocytes. Corresponding transcripts were restricted to basal and lower prickle cells. Synthesis of K1 and K10 was upregulated and more pronounced in orthokeratotic epithelia. The study showed an alteration in the pattern of differentiation-specific keratins, although involvement of the lymphocytic infiltrate in OLP and LR resulted in further gene modulation. In both diseases, K1 and K10 showed transcriptional control, proteins having the same distribution as their transcripts. This represented a change from post-transcriptional regulation in normal buccal epithelium, in which mRNAs for K1 and K10 are more widely expressed than their proteins. Thus, the pattern of keratin gene expression may be altered in response to frictional/smoking stimuli or immune-mediated mechanisms.