Keratin 19: Predicted amino acid sequence and broad tissue distribution suggest it evolved from keratinocyte keratins

Metabolic dysfunction associated steatotic liver disease in patients with plaque psoriasis: a case-control study and serological comparison

Background

The relationship between plaque psoriasis and both MASLD and lean MASLD has not been sufficiently explored in the current literature.

Method

This retrospective and observational study was carried out from January 2021 to January 2023 at The First Affiliated Hospital of Zhejiang Chinese Medical University. Patients diagnosed with plaque psoriasis and a control group consisting of individuals undergoing routine physical examinations were enrolled. The incidence of MASLD and lean MASLD among these groups was compared. Additionally, patients with plaque psoriasis were divided into those with MASLD, those with lean MASLD, and a control group with only psoriasis for a serological comparative analysis.

Results

The incidence of MASLD in the observation group and the control group was 43.67% (69/158) and 22.15% (35/158), respectively (p < 0.01). Furthermore, the incidence of lean MASLD within the observation group and the control group was 10.76% (17/158) and 4.43% (7/158), respectively (p < 0.01). After controlling for potential confounding variables, plaque psoriasis was identified as an independent risk factor for MASLD with an odds ratio of 1.88 (95% cl: 1.10-3.21). In terms of serological comparison, compared to the simple psoriasis group, we observed a significant elevation in the tumor marker CYFRA21-1 levels in both groups compared to the control group with simple psoriasis (p < 0.01). Moreover, the MASLD group exhibited elevated levels of inflammatory markers and psoriasis score, whereas these effects were mitigated in the lean MASLD group.

Conclusion

The prevalence of MASLD and lean MASLD is higher among patients with psoriasis. Those suffering from psoriasis along with MASLD show increased psoriasis scores and inflammatory markers compared to those without metabolic disorders. MASLD likely worsens psoriasis conditions, indicating the necessity of targeted health education for affected individuals to reduce the risk of MASLD, this education should include guidelines on exercise and diet. In serological assessments, elevated levels of cytokeratin 19 fragment (CYFRA21-1) were noted in both MASLD and lean MASLD groups, implying a potential synergistic role between psoriasis and MASLD.

Fusion expression, purification, and characterization of cytokeratin 19 fragments in E. coli for enhanced stability in diagnostic applications

Cytokeratin 19 fragment (CYFRA21-1) serves as a crucial tumor marker in the context of lung cancer patients, playing a pivotal role as a calibrator in the realm of in vitro diagnostics. Nevertheless, during practical application, it has come to light that the recombinantly synthesized full-length CYFRA21-1 antigen exhibits suboptimal stability at the requisite concentration, while the utilization of natural antigens incurs a substantial cost. To address this issue, our investigation harnessed a strategic approach whereby the soluble fragment of cytokeratin 19 (Aa244-400) was integrated into the pET32a vector, subsequently being expressed within E. coli through a fusion with the TrxA protein. This process involved induction of protein expression through 0.2 mM IPTG at 16 °C for a duration of 16 h. After induction, the target protein was purified through Ni affinity and ion exchange chromatography. Subsequent characterization of the targeted protein was executed through the SEC-HPLC technique. The attained CYFRA21-1 antigen, as generated within this study, was effectively incorporated into a chemiluminescence-based in vitro diagnostic detection kit. The results indicate that the fusion protein exhibited commendable reactivity and stability, manifesting a deviation of less than 10 % following incubation at 37 °C for 7 days. Importantly, the production yield achieved a notable magnitude of 300 mg/L, thus rendering it a cost-effective and scalable alternative to natural antigens for clinical diagnostic applications.

Activated breast stromal fibroblasts exhibit myoepithelial and mammary stem cells features

BACKGROUND

Active breast cancer-associated fibroblasts (CAFs) promote tumor growth and spread, and like tumor cells they are also heterogeneous with various molecular sub-types and different pro-tumorigenic capacities.

METHODS

We have used immunoblotting as well as quantitative RT-PCR to assess the expression of various epithelial/mesenchymal as well as stemness markers in breast stromal fibroblasts. Immunofluorescence was utilized to assess the level of different myoepithelial and luminal markers at the cellular level. Flow cytometry allowed to determine the proportion of CD44- and ALDH1-positive breast fibroblasts, while sphere formation assay was used to test the ability of these cells to form mammospheres.

RESULTS

We have shown here that IL-6-dependent activation of breast and skin fibroblasts promotes mesenchymal-to-epithelial transition and stemness in a STAT3- and p16-dependent manner. Interestingly, most primary CAFs isolated from breast cancer patients exhibited such transition and expressed lower levels of the mesenchymal markers N-cadherin and vimentin as compared to their adjacent normal fibroblasts (TCFs) isolated from the same patients. We have also shown that some CAFs and IL-6-activated fibroblasts express high levels of the myoepithelial markers cytokeratin 14 and CD10. Interestingly, 12 CAFs isolated from breast tumors showed higher proportions of CD24^low/CD44^high and ALDH^high cells, compared to their corresponding TCF cells. These CD44^high cells have higher abilities to form mammospheres and to enhance cell proliferation of breast cancer cells in a paracrine manner relative to their corresponding CD44^low cells.

CONCLUSION

Together, the present findings show novel characteristics of active breast stromal fibroblasts, which exhibit additional myoepithelial/progenitor features.

Dynamic changes in protein concentrations of keratins in crop milk and related gene expression in pigeon crops during different incubation and chick rearing stages

1. The objective of this study was to examine the keratin composition of crop milk, the variation of epithelial thickness and keratin (K) gene expression in samples from young pigeon during incubation and chick rearing.2. Crop milk was collected from 1-, 3- and 5-day-old squab crops for keratin content analysis. Results showed that K4 accounted for the highest proportion of all detected keratins.3. In total, 42 pairs of adult pigeons were allocated to seven groups according to different stages to collect crop samples. Gene expression studies showed that the K3 gene expression was maximised at rearing Day 15 (15) and R1 in males and females, respectively. K6a gene level was the greatest at R15 in females, whereas it peaked at incubation Day 4 (I4) in males. The K12, K13, K23 and K80 gene levels were inhibited at the peak period of crop milk formation in comparison with I4. In females, K cochleal expression peaked at I10, whereas it was the greatest at R25 in males. K4 and K14 gene expression was the highest at I10 in females, while K4 and K14 were minimised at I17 and R7 in males, respectively. Gene expressions of K5, K8, K19 and K20 in males and K19 in females were maximised at R1. The K5, K20 and K75 gene levels in females peaked at R7. K75 and K8 expressions in males and females reached a maximum value at R25 and I17, respectively.4. The epithelial thickness of male and female crops reached their greatest levels at R1 and had the highest correlation with K19.5. These results emphasised the importance of keratinisation in crop milk formation, and different keratins probably play various roles during this period. The K19 was probably a marker for pigeon crop epithelium development. The sex of the parent pigeon affected keratin gene expression profiles.

Feline pyloric and duodenal adenoma: A histological and immunohistochemical study

Although pyloric and duodenal adenomas occasionally occur in cats, limited information is currently available on their phenotypes and molecular features. The present study investigated the pathological features of these tumors and the mechanisms underlying their tumorigenesis. Biopsy samples from 8 cats diagnosed with pyloric or duodenal adenomas were examined by histopathology and immunohistochemistry. Normal pyloric and duodenal tissues of cats were assessed for comparison. All cases showed a papillary growth of cuboidal to columnar cells with eosinophilic, ground-glass cytoplasm. Mucin in tumor cells was positive for periodic acid-Schiff and paradoxical concanavalin-A staining, but was negative for Alcian blue. Immunohistochemically, tumor cells were positive for cytokeratin (CK) 19 in 8/8 cases and for CK20 in 5/8 cases, and weakly positive for CD10 in 4/8 cases, CK7 in 3/8 cases, and β-catenin in 2/8 cases. Nuclear accumulation of p53 was not detected in any case. DNA sequencing analysis identified no KRAS or GNAS mutations in the 4/8 cases and 5/8 cases for which the KRAS and GNAS genes could be amplified. The histological and immunohistochemical features of tumor cells were similar to those of mucous neck cells and the pyloric gland of normal feline tissue. The morphology of feline pyloric and duodenal adenomas was consistent with that of pyloric gland adenoma in humans; however, its molecular pathogenesis may differ given the lack of KRAS and GNAS mutations in the feline tumors.

Integrating single-cell RNA-sequencing and functional assays to decipher mammary cell states and lineage hierarchies

The identification and molecular characterization of cellular hierarchies in complex tissues is key to understanding both normal cellular homeostasis and tumorigenesis. The mammary epithelium is a heterogeneous tissue consisting of two main cellular compartments, an outer basal layer containing myoepithelial cells and an inner luminal layer consisting of estrogen receptor-negative (ER⁻) ductal cells and secretory alveolar cells (in the fully functional differentiated tissue) and hormone-responsive estrogen receptor-positive (ER⁺) cells. Recent publications have used single-cell RNA-sequencing (scRNA-seq) analysis to decipher epithelial cell differentiation hierarchies in human and murine mammary glands, and reported the identification of new cell types and states based on the expression of the luminal progenitor cell marker KIT (c-Kit). These studies allow for comprehensive and unbiased analysis of the different cell types that constitute a heterogeneous tissue. Here we discuss scRNA-seq studies in the context of previous research in which mammary epithelial cell populations were molecularly and functionally characterized, and identified c-Kit⁺ progenitors and cell states analogous to those reported in the recent scRNA-seq studies.

Serum thrombospondin-2 is a candidate diagnosis biomarker for early non-small-cell lung cancer

Thrombospondin-2 (THBS2) is a secreted protein overexpressed in numerous cancers and may function as a diagnostic tumor marker. The objective of the present study was to investigate the diagnostic performance of serum THBS2 in early stage non-small-cell lung cancer (NSCLC). Serum THBS2 and Cyfra21-1 level were evaluated in blood samples of 112 patients from NSCLC groups and 51 healthy control (HC) groups. Receiver operator characteristic (ROC) curves were used to evaluate the diagnostic significance. Serum THBS2 level was significantly up-regulated in NSCLC patients compared with healthy control subjects (P<0.0001), and the postoperative THBS2 level decreased significantly (P<0.0001). ROC curves analysis demonstrated that THBS2 was a comparable biomarker as Cyfra21-1 to distinguish early stage NSCLC or lung squamous cell carcinoma (SC) from healthy control subjects. And Cyfra21-1 was observed with significantly improved performances by the combination of THBS2 to distinguish early stage NSCLC (P<0.05) as well as SC (P<0.05) from the control subjects. In addition, THBS2 was estimated to perform well in the diagnosis of patients with Cyfra21-1-negative NSCLC (area under the curve [AUC] = 0.73). In summary, the present study suggested that serum THBS2 might be an early diagnostic biomarker for NSCLC.

Molecular markers for corneal epithelial cells in larval vs. adult Xenopus frogs

Corneal Epithelial Stem Cells (CESCs) and their proliferative progeny, the Transit Amplifying Cells (TACs), are responsible for maintaining the integrity and transparency of the cornea. These stem cells (SCs) are widely used in corneal transplants and ocular surface reconstruction. Molecular markers are essential to identify, isolate and enrich for these cells, yet no definitive CESC marker has been established. An extensive literature survey shows variability in the expression of putative CESC markers among vertebrates; being attributed to species-specific variations, or other differences in developmental stages of these animals, approaches used in these studies and marker specificity. Here, we expanded the search for CESC markers using the amphibian model Xenopus laevis. In previous studies we found that long-term label retaining cells (suggestive of CESCs and TACs) are present throughout the larval basal corneal epithelium. In adult frogs, these cells become concentrated in the peripheral cornea (limbal region). Here, we used immunofluorescence to characterize the expression of nine proteins in the corneas of both Xenopus larvae and adults (post-metamorphic). We found that localization of some markers change between larval and adult stages. Markers such as p63, Keratin 19, and β1-integrin are restricted to basal corneal epithelial cells of the larvae. After metamorphosis their expression is found in basal and intermediate layer cells of the adult frog corneal epithelium. Another protein, Pax6 was expressed in the larval corneas, but surprisingly it was not detected in the adult corneal epithelium. For the first time we report that Tcf7l2 can be used as a marker to differentiate cornea vs. skin in frogs. Tcf7l2 is present only in the frog skin, which differs from reports indicating that the protein is expressed in the human cornea. Furthermore, we identified the transition between the inner, and the outer surface of the adult frog eyelid as a key boundary in terms of marker expression. Although these markers are useful to identify different regions and cellular layers of the frog corneal epithelium, none is unique to CESCs or TACs. Our results confirm that there is no single conserved CESC marker in vertebrates. This molecular characterization of the Xenopus cornea facilitates its use as a vertebrate model to understand the functions of key proteins in corneal homeostasis and wound repair.

Opposing Regulation of Cancer Properties via KRT19-Mediated Differential Modulation of Wnt/β-Catenin/Notch Signaling in Breast and Colon Cancers

Although Keratin 19 (KRT19) has been reported as a tumor cell marker and found to interact with other proteins that modulate cancer properties, its role in cancer prognosis remains to be fully elucidated. We found that KRT19 expression was increased in both colon and breast cancer, but that knockdown of KRT19 showed opposing effects on cancer properties. In colon cancer, KRT19 knockdown resulted in suppression of cancer via downregulation of Wnt/Notch signaling without altering NUMB transcription. In breast cancer, KRT19 knockdown led to an increase in cancer properties because of attenuated Wnt and enhanced Notch signaling. In colon cancer, KRT19 interacted with β-catenin but not with RAC1, allowing the LEF/TCF transcription factor to bind primarily to the LEF1 and TCF7 promoter regions, whereas in breast cancer, KRT19 interacted with the β-catenin/RAC1 complex and led to apparent upregulation of NUMB expression and NUMB-mediated suppression of Notch signaling. These results reveal a novel differential role of KRT19 in carcinogenesis, due to differential modulation of Wnt/β-catenin/Notch signaling crosstalk through various interactions of KRT19 with only β-catenin or with the β-catenin/RAC1 complex, which might have implications for clinical cancer research.

Cytokeratins in the Histological Diagnosis of Malignant Tumors

Cytokeratins, which comprise a multigene family of 20 related polypeptides (CKs 1–20), are constituents of the intermediate filaments of epithelial cells, in which they are expressed in various combinations depending on the epithelial type and the degree of differentiation. Of these, CK 19 (400 amino acids; 44.1 kilodaltons) is an example of a widely distributed CK, being expressed in various epithelia, including many simple epithelia. In contrast, the recently identified CK 20 (424 amino acids; 48.6 kilodaltons) is essentially confined to gastrointestinal epithelia, the urothelium and Merkel cells. The differential expression of individual CKs in various types of carcinomas makes them useful markers for histopathological carcinoma subtyping, providing relevant information concerning the differentiation and origin of carcinomas, especially when tumors first present as metastases. The CKs that are of particular value for differential diagnosis include CK 20, as it is mainly expressed in carcinomas derived from CK 20-positive epithelia; it is also found in bile-tract, pancreatic and mucinous ovarian adenocarcinomas, being absent in most other carcinomas. In certain carcinoma types, the changes in the expression of individual CKs that may occur during tumor progression could be of prognostic relevance. It remains to be established whether the serological detection of fragments of not only widely distributed but also more restrictedly expressed CKs may provide useful serological tumor markers in the future.

A New Nested Primer Pair Improves the Specificity of Ck-19 Mrna Detection by Rt-Pcr in Occult Breast Cancer Cells

Reverse transcription polymerase chain reaction (RT-PCR) of cytokeratin-19 (CK-19) has been widely used to detect small numbers of circulating malignant epithelial cells in the bone marrow or the peripheral blood of patients with breast cancer. However, a high percentage of false positive results has been recorded and conflicting reports question the clinical relevance of this technical approach. We demonstrate that the use of a new nested primer pair for CK-19 RT-PCR avoids false positive results without affecting the sensitivity of the assay. Our experiments were carried out using MCF-7 cells alone or mixed with peripheral blood mononuclear cells (PBMNC) of healthy donors. The results were also validated in a large series of healthy donors and in a preliminary study on a limited number of patients with breast cancer, thus suggesting that our assay is feasible for application in the clinical evaluation of occult malignant epithelial cells.

Potential mechanisms underlying ectodermal differentiation of Wharton's jelly mesenchymal stem cells

Wharton's jelly mesenchymal stem cells (WJMSCs) are being increasingly recognized for their ectodermal differentiation potential. Previously, we demonstrated that when WJMSC were seeded onto an acellular matrix material derived from Wharton's jelly and cultured in osteogenic induction media, generated CK19 positive cells and hair-like structures indicative of ectodermal differentiation of WJMSCs. In this manuscript, we examine the underlying mechanism behind this observation using a variety of microscopy and molecular biology techniques such as western blotting and qPCR. We demonstrate that these hair-like structures are associated with live cells that are positive for epithelial and mesenchymal markers such as cytokeratin-19 and α-smooth muscle actin, respectively. We also show that up-regulation of β-catenin and noggin, along with the expression of TGF-β and SMAD and inhibition of BMP4 could be the mechanism behind this ectodermal differentiation and hair-like structure formation.

CK19 mRNA in blood can predict non-sentinel lymph node metastasis in breast cancer

Reverse-transcription polymerase chain reaction (RT-PCR) is used to detect CK19 mRNA in sentinel lymph node biopsy (SLNB) tissues from breast cancer patients. We examined whether CK19 mRNA in peripheral blood is predictive of non-sentinel lymph node (nSLN) metastasis. Breast cancer cases diagnosed with clinical stage cT1-3cN0 and registered in our medical biobank were identified retrospectively. This study then included 120 breast cancer cases treated at Zhejiang Cancer Hospital from Aug 2014 to Aug 2015, including 60 SLN-positive and 60 SLN-negative cases. CK19 mRNA levels in peripheral blood samples were assessed using RT-PCR prior to tumor removal. During surgery, if SLNB tissue showed evidence of metastasis, axillary lymph node dissection (ALND) was performed. No ALND was performed if SLNB and nSLN tissues were both negative for metastasis. CK19 expression was higher in nSLN-positive patients than in nSLN-negative patients (p < 0.05). Logistic regression indicated that lymphatic vessel invasion and CK19 levels were predictive of nSLN status (p < 0.05). The area under the ROC curve for CK19 was 0.878 (p < 0.05). We conclude that high CK19 levels in peripheral blood may independently predict nSLN metastasis in breast cancer patients.

Cytokeratin expression in mouse lacrimal gland germ epithelium

PURPOSE

The lacrimal gland secretes tear fluids that protect the ocular surface epithelium, and its dysfunction leads to dry eye disease (DED). The functional restoration of the lacrimal gland by engraftment of a bioengineered lacrimal gland using lacrimal gland germ epithelial cells has been proposed to cure DED in mice. Here, we investigate the expression profile of cytokeratins in the lacrimal gland germ epithelium to clarify their unique characteristics.

METHODS

We performed quantitative polymerase chain reaction (Q-PCR) and immunohistochemistry (IHC) analysis to clarify the expression profile of cytokeratin in the lacrimal gland germ epithelium.

RESULTS

The mRNA expression of keratin (KRT) 5, KRT8, KRT14, KRT15, and KRT18 in the lacrimal gland germ epithelium was increased compared with that in mouse embryonic stem cells and the lacrimal gland germ mesenchyme, as analyzed by Q-PCR. The expression level of KRT15 increased in the transition from stem cells to lacrimal gland germ epithelium, then decreased as the lacrimal gland matured. IHC revealed that the expression set of these cytokeratins in the lacrimal gland germ epithelium was different from that in the adult lacrimal gland. The expression of KRT15 was observed in the lacrimal gland germ epithelium, and it segmentalized into some of the basal cells in the intercanulated duct in mature gland.

CONCLUSION

We determined the expression profile of cytokeratins in the lacrimal gland epithelium, and identified KRT15 as a candidate unique cellular marker for the lacrimal gland germ epithelium.

Order and disorder in intermediate filament proteins

Intermediate filaments (IFs), important components of the cytoskeleton, provide a versatile, tunable network of self-assembled proteins. IF proteins contain three distinct domains: an α-helical structured rod domain, flanked by intrinsically disordered head and tail domains. Recent studies demonstrated the functional importance of the disordered domains, which differ in length and amino-acid sequence among the 70 different human IF genes. Here, we investigate the biophysical properties of the disordered domains, and review recent findings on the interactions between them. Our analysis highlights key components governing IF functional roles in the cytoskeleton, where the intrinsically disordered domains dictate protein-protein interactions, supramolecular assembly, and macro-scale order.

Autologous human nasal epithelial cell sheet using temperature-responsive culture insert for transplantation after middle ear surgery

Postoperative mucosal regeneration of the middle ear cavity and the mastoid cavity is of great importance after middle ear surgery. However, the epithelialization of the mucosa in the middle ear is retarded because chronic inflammation without epithelialization aggravates gas exchange and clinical function. These environmental conditions in the middle ear lead to postoperative retraction and adhesion of the newly-formed tympanic membrane. Therefore, if the mucosa on the exposed middle ear bone surface can be rapidly regenerated after surgery, the surgical treatments for cholesteatoma and adhesive middle ear disease can potentially be improved. In this study, we successfully generated a cell sheet designed for the postoperative treatment of cholesteatoma. We used nasal cells to create an artificial middle ear mucosal cell sheet with a three-dimensional (3D) configuration similar to that of the middle ear mucosa. The sheets consisted of multi-layered mucosal epithelia and lower connective tissue and were similar to normal middle ear mucosa. This result indicates that tissue-engineered mucosal cell sheets would be useful to minimize complications after surgical operations in the middle ear and future clinical applications are expected. Copyright © 2015 John Wiley & Sons, Ltd.

Contribution of proteomics to the study of the role of cytokeratins in disease and physiopathology

Cytokeratins (CKs), the most abundant group of cytoskeletal intermediate filaments, and proteomics are strongly connected. On the one hand, proteomics has been extremely useful to uncover new features and functions of CKs, on the other, the highly abundant CKs serve as an exceptional tool to test new technological developments in proteomics. As a result, proteomics has contributed to finding valuable associations of CKs with diseases as diverse as cancer, cystic fibrosis, steatohepatitis, viral and bacterial infection, keratoconus, vitreoretinopathy, preeclampsia or the chronic fatigue syndrome, as well as to characterizing their participation in a number of physiopathological processes, including drug resistance, response to toxicants, inflammation, stem cell differentiation, embryo development, and tissue repair. In some cases, like in cystic fibrosis, CKs have been described as potential therapeutic targets. The development of a specific field of proteomics where CKs become the main subject of research aims and hypotheses is suggested.

Keratin 14-null cells as a model to test the efficacy of gene therapy approaches in epithelial cells

Skin fragility disorders caused by keratin mutations are incurable, and a better understanding of their etiology is needed to find new ways to improve and treat these conditions. The best-studied skin fragility disorder is epidermolysis bullosa simplex (EBS), an autosomal dominant condition caused by mutations in keratin 5 (K5) or K14. To analyze disease mechanisms and develop gene therapy strategies, we have used keratinocyte cell lines derived from EBS patients as model systems. Here, we describe two cell lines established from EBS patients with K14-null mutations. We analyze the responses of these cells to stress assays previously shown to discriminate between wild-type and keratin-mutant keratinocytes, to directly evaluate the efficacy of rescuing K14-null cells by supplementation with wild-type K14 complementary DNA (cDNA). The K14-null cells show elevated levels of stress correlating with reduced normal keratin function. By transfecting wild-type K14 into these cells, we demonstrate "proof of principle" that an add-back approach can significantly rescue the normal keratinocyte behavior profile. These K14-null cell lines provide a disease model for studying the effects of keratin ablation in EBS patients and to test the efficacy of gene add-back and other therapy approaches in keratinocytes.

Stem cell therapies for recessive dystrophic epidermolysis bullosa

Human epidermis is composed of a stratified squamous epithelium that provides a mechanical barrier against the external environment and which is renewed every 3-4 weeks by resident stem cells in the epidermis. However, in the inherited skin fragility disorder, recessive dystrophic epidermolysis bullosa (RDEB), there is recurrent trauma-induced subepidermal blistering that disrupts epidermal homeostasis and is likely to deplete the epidermal stem cell pool. This review article discusses the nature of epidermal stem cells and other stem cell populations in the skin, as well as other possible extracutaneous sources of stem cells, that might have physiological or therapeutic relevance to cell therapy approaches for RDEB. Strategies to identify, create and use cells with multipotent or pluripotent properties are explored and current clinical experience of stem cell therapy in RDEB is reviewed. There is currently no single optimal therapy for patients with RDEB, but cell therapy technologies are evolving and hold great potential for modifying disease severity and improving quality of life for people living with RDEB.

Expression of cytokeratins 10, 13, 14 and 19 in oral lichen planus

OLP is a chronic inflammatory disease of unknown etiology that may develop into squamous-cell carcinoma. Cytokeratins, which are important components of the cytoskeleton, are excellent epithelial differentiation markers used to study neoplastic and inflammatory diseases. To study the profile of cytokeratins in OLP and their possible association with dysplastic alterations, monoclonal antibodies were used for cytokeratins 10, 13, 14 and 19, in 26 samples of OLP. The streptavidin-biotin technique was employed in paraffin-embedded tissue sections. Sample analysis revealed suprabasal expression of cytokeratin 10 in 16/17 samples, 14 of them with reduced expression; suprabasal expression of cytokeratin 13 in 18/23, 16 of them with delay; basal and suprabasal expression of cytokeratin 14 in all samples; and focal basal expression of cytokeratin 19 in 4/21. Expression of cytokeratins 10, 13 and 14 was altered in OLP lesions. The inflammatory process and hyperkeratosis or parakeratosis seem to have interfered with the expression of these CKs. Cytokeratin 19 was expressed in the lesions, in a pattern similar to that mentioned in the literature for the non-keratinized oral mucosa. The presence of mild dysplasia did not change the expression of the cytokeratins studied. No differences in pattern of expression were observed between keratinized and non-keratinized areas in the lesions caused by OLP.

Identification of markers for newly formed beta-cells in the perinatal period: a time of recognized beta-cell immaturity

Markers of beta-cell maturity would be useful in staging the differentiation of stem/progenitor cells to beta-cells whether in vivo or in vitro. We previously identified markers for newly formed beta-cells in regenerating rat pancreases after 90% partial pancreatectomy. To test the generality of these markers of newly formed beta-cells, we examined their expression during the perinatal period, a time of recognized beta-cell immaturity. We show by semiquantitative RT-PCR and immunostaining over the time course from embryonic day 18/20 to birth, 1 day, 2 days, 3 days, 7 days, and adult that MMP-2, CK-19, and SPD are truly markers of new and immature beta-cells and that their expression transiently peaks in the perinatal period and is not entirely synchronous. The shared expression of these markers among fetal, newborn, and newly regenerated beta-cells, but not adult, strongly supports their use as potential markers for new beta-cells in the assessment of both the maturity of stem cell-derived insulin-producing cells and the presence of newly formed islets (neogenesis) in the adult pancreas.

Cytokeratin expression during mouse embryonic and early postnatal mammary gland development

Cytokeratins are intermediate filament proteins found in most epithelial cells including the mammary epithelium. Specific cytokeratin expression has been found to mark different epithelial cell lineages and also to associate with putative mammary stem/progenitor cells. However, a comparative analysis of the expression of cytokaratins during embryonic and postnatal mammary development is currently lacking. Moreover, it is not clear whether the different classes of putative mammary stem/progenitor cells exist during embryonic development. Here, we use double/triple-label immunofluorescence and immunohistochemistry to systematically compare the expression of cytokeratin 5 (K5), cytokeratin 6 (K6), cytokeratin 8 (K8), cytokeratin 14 (K14) and cytokeratin 19 (K19) in embryonic and early postnatal mouse mammary glands. We show that K6(+) and K8(+)/K14(+) putative mammary progenitor cells arise during embryogenesis with distinct temporal and spatial distributions. Moreover, we describe a transient disconnection of the expression of K5 and K14, two cytokeratins that are often co-expressed, during the first postnatal weeks of mammary development. Finally, we report that cytokeratin expression in cultured primary mammary epithelial cells mimics that during the early stages of postnatal mammary development. These studies demonstrate an embryonic origin of putative mammary stem/progenitor cells. Moreover, they provide additional insights into the use of specific cytokeratins as markers of mammary epithelial differentiation, or the use of their promoters to direct gene overexpression or ablation in genetic studies of mouse mammary development.

Decreased poly(ADP-ribosyl)ation of CTCF, a transcription factor, is associated with breast cancer phenotype and cell proliferation

PURPOSE

There is compelling evidence of a relationship between poly(ADP-ribosyl)ation and tumorigenesis; however, much less is known about the role of specific targets of poly(ADP-ribosyl)ation in tumor development. Two forms of the multifunctional transcription factor, CTCF, were previously identified: a 130-kDa protein (CTCF-130), characteristic for cell lines, and a 180-kDa protein (CTCF-180), modified by poly(ADP-ribosyl)ation. This study was aimed to investigate differential poly(ADP-ribosyl)ation of CTCF in normal and tumor breast tissues.

EXPERIMENTAL DESIGN

Western blot analysis, mass spectrometry, and immunohistochemical and immunofluorescent stainings were used to characterize CTCF-130 and CTCF-180 in breast cell lines, primary cultures, and normal and tumor breast tissues. The immunoreactivity score was used for CTCF-130 quantification in tissues.

RESULTS

We discovered that only CTCF-180 is detected in the normal breast tissues, whereas both CTCF-130 and CTCF-180 are present in breast tumors. Using an antibody specific for CTCF-130, we observed that 87.7% of breast tumors were positive for CTCF-130. A negative correlation existed between the levels of CTCF-130, tumor stage, and tumor size. Significantly, a transition from CTCF-180 to CTCF-130 was discovered in primary cultures generated from normal breast tissues, indicating a link between CTCF-130 and proliferation. Conversely, the appearance of CTCF-180 was observed following growth arrest in breast cell lines.

CONCLUSIONS

Collectively, our data suggest that the loss of CTCF poly(ADP-ribosyl)ation is associated with cell proliferation and breast tumor development. We propose the use of CTCF-130 as a marker for tumor breast cells and lower levels of CTCF-130 as an indicator of unfavorable prognosis.

Contrasting expression of keratins in mouse and human embryonic stem cells

RNA expression data reveals that human embryonic stem (hES) cells differ from mouse ES (mES) cells in the expression of RNAs for keratin intermediate filament proteins. These differences were confirmed at the cellular and protein level and may reflect a fundamental difference in the epithelial nature of embryonic stem cells derived from mouse and human blastocysts. Mouse ES cells express very low levels of the simple epithelial keratins K8, K18 and K19. By contrast hES cells express moderate levels of the RNAs for these intermediate filament proteins as do mouse stem cells derived from the mouse epiblast. Expression of K8 and K18 RNAs are correlated with increased c-Jun RNA expression in both mouse and human ES cell cultures. However, decreasing K8 and K18 expression associated with differentiation to neuronal progenitor cells is correlated with increasing expression of the Snai2 (Slug) transcriptional repression and not decreased Jun expression. Increasing K7 expression is correlated with increased CDX2 and decreased Oct4 RNA expression associated with the formation of trophoblast derivatives by hES cells. Our study supports the view that hES cells are more similar to mouse epiblast cells than mouse ES cells and is consistent with the epithelial nature of hES cells. Keratin intermediate filament expression in hES cells may modulate sensitivity to death receptor mediated apoptosis and stress.

Cytokeratin-related loss of cellular integrity is not a major driving force of human intrinsic skin aging

The contribution of extracellular matrix components to intrinsic skin aging has been investigated thoroughly, however, there is little information as to the role of the cytoskeletal proteins in this process. Therefore, we compared the expression of the constituents of the cytoskeleton, keratins 1-23 (K1-K23) as well as junction-plakoglobin (JUP), alpha-tubulin (TUBA), and beta-actin (ACTB) in human foreskins of both young (mean 6.4 years) and aged (mean 54.3 years) individuals. By applying RNA expression analysis to intrinsically aged human skin, we demonstrated that the mRNA levels of the genes for K1, K3, K4, K9, K13, K15, K18, K19 and K20 are downregulated in aged skin, K5 and K14 are unchanged, and K2, K16 and K17 are upregulated in aged skin. The mRNA data were confirmed on the protein level. This diverse picture is in contrast to other cytoskeletal proteins including components of the desmosome (JUP), microtubuli (TUBA) and microfilaments (ACTB) - often regarded as house-keeping genes - that were all reduced in aged skin. These cytoskeletal features of intrinsic aging highlight the importance of the cellular compartment in this process and demonstrate that special attention has to be given to RNA as well as protein normalization in aging studies.

The human keratins: biology and pathology

The keratins are the typical intermediate filament proteins of epithelia, showing an outstanding degree of molecular diversity. Heteropolymeric filaments are formed by pairing of type I and type II molecules. In humans 54 functional keratin genes exist. They are expressed in highly specific patterns related to the epithelial type and stage of cellular differentiation. About half of all keratins—including numerous keratins characterized only recently—are restricted to the various compartments of hair follicles. As part of the epithelial cytoskeleton, keratins are important for the mechanical stability and integrity of epithelial cells and tissues. Moreover, some keratins also have regulatory functions and are involved in intracellular signaling pathways, e.g. protection from stress, wound healing, and apoptosis. Applying the new consensus nomenclature, this article summarizes, for all human keratins, their cell type and tissue distribution and their functional significance in relation to transgenic mouse models and human hereditary keratin diseases. Furthermore, since keratins also exhibit characteristic expression patterns in human tumors, several of them (notably K5, K7, K8/K18, K19, and K20) have great importance in immunohistochemical tumor diagnosis of carcinomas, in particular of unclear metastases and in precise classification and subtyping. Future research might open further fields of clinical application for this remarkable protein family.

Epidermal repair results from activation of follicular and epidermal progenitor keratinocytes mediated by a growth factor cascade

Reepithelialization of human suction blister wounds was examined in five normal human volunteers over a period of 14 days postwounding to understand the control of keratinocyte migration, proliferation, and differentiation in acute wound healing in a controlled model. The hypothesis that morphological changes and progenitor activation result from altered cytokines and growth factor expression [in particular interleukin-1 beta (IL-1beta), interleukin-6 (IL-6), transforming growth factor alpha (TGF-alpha), TGF-beta 1, and keratinocyte growth factor] was tested using semiquantitative immunohistochemistry combined with reverse transcriptase-polymerase chain reaction of samples from the blister roof, edge, and base. Parallel changes in keratin expression were examined using a wide range of well-established antibodies to multiple keratins and in situ hybridization for keratin 16 (K16), a marker of the hyperproliferative (mucoregenerative) phenotype. Longitudinal morphological, semiquantitative cytokine and growth factor expression, and histometric histone and cytokeratin profiles suggest three phases to reepithelialization: phase 1, or the acute activation phase, early in the first 24 hours postwounding is characterized by epidermal expression of IL-1beta and IL-6, and dermal expression of TGF-beta1, as basal, upper outer root sheath, and putative interfollicular transit amplifying keratinocytes become committed to mitosis; phase 2, or the early activation phase, late in the second 24 hours postwounding, characterized by epidermal expression of TGF-alpha and IL-6 with concurrent suprabasal K16 expression and migration with continued proliferation, and dermal expression of keratinocyte growth factor and IL-6; and phase 3 or restitution over the following 2 weeks, characterized by the return of normal homeostasis, including bulge activation as evidenced by K19 expression.

Of microenvironments and mammary stem cells

In most adult tissues there reside pools of stem and progenitor cells inside specialized microenvironments referred to as niches. The niche protects the stem cells from inappropriate expansion and directs their critical functions. Thus guided, stem cells are able to maintain tissue homeostasis throughout the ebb and flow of metabolic and physical demands encountered over a lifetime. Indeed, a pool of stem cells maintains mammary gland structure throughout development, and responds to the physiological demands associated with pregnancy. This review discusses how stem cells were identified in both human and mouse mammary glands; each requiring different techniques that were determined by differing biological needs and ethical constraints. These studies together create a robust portrait of mammary gland biology and identify the location of the stem cell niche, elucidate a developmental hierarchy, and suggest how the niche might be manipulated for therapeutic benefit.

Neuronal-epithelial interactions in mammalian gustatory epithelium

There are two neurally controlled morphogenetic programmes in the fungiform papillae of the rodent tongue. When gustatory axons are present they not only promote the expression of taste receptor cells but also simultaneously suppress the outgrowth of an ectopic filiform spine. Innervation during development is essential for the initial formation of taste buds. Consequently, denervation during development irreversibly prevents the establishment of a permanent line of stem cells for taste buds, in contrast to the reliable re-emergence of taste buds after the reinnervation of denervated adult gustatory epithelium. Monoclonal antibodies to keratins selectively recognize cells in particular differentiated states and may contribute to an understanding of the cell lineages and cell-cell interactions that lead to taste buds and filiform spines. Regeneration may recapitulate the late steps in taste development but not the early steps, which are slower and subject to irreversible alteration with denervation. Arguments are set forth that the nerve dependence of taste buds and some other cutaneous receptor cells provides an important selective advantage. Nerve dependence ensures that a more protective integumental covering will replace any superficial, secondary sensory cells rendered useless by denervation.

Evidence for a stem cell hierarchy in the adult human breast

Cellular pathways that contribute to adult human mammary gland architecture and lineages have not been previously described. In this study, we identify a candidate stem cell niche in ducts and zones containing progenitor cells in lobules. Putative stem cells residing in ducts were essentially quiescent, whereas the progenitor cells in the lobules were more likely to be actively dividing. Cells from ducts and lobules collected under the microscope were functionally characterized by colony formation on tissue culture plastic, mammosphere formation in suspension culture, and morphogenesis in laminin-rich extracellular matrix gels. Staining for the lineage markers keratins K14 and K19 further revealed multipotent cells in the stem cell zone and three lineage-restricted cell types outside this zone. Multiparameter cell sorting and functional characterization with reference to anatomical sites in situ confirmed this pattern. The proposal that the four cell types are indeed constituents of an as of yet undescribed stem cell hierarchy was assessed in long-term cultures in which senescence was bypassed. These findings identify an adult human breast ductal stem cell activity and its earliest descendants.

Differential proteome analysis of colon carcinoma cell line SW480 after reconstitution of the tumour suppressor Smad4

The tumour suppressor gene Smad4 is frequently inactivated in gastrointestinal carcinomas. Smad4 plays a pivotal role in transducing signals of the transforming growth factor-beta (TGF-beta) superfamily of proteins. Inactivation of Smad4 seems to occur late during tumour progression when tumours acquire invasive and metastatic properties. Identification of proteins directly or indirectly regulated by Smad4 would, therefore, ease the future design of new diagnostic and therapeutic strategies for gastrointestinal carcinoma. We have used human colon carcinoma cell line SW480 stably transfected with Smad4 as an in-vitro model system to identify Smad4-regulated proteins by applying two-dimensional gel electrophoresis (2DE) then MALDI-PMF/PFF-MS. We identified a total of 47 protein species with a Smad4-dependent expression. From the functions of the candidate proteins we obtained new insights into Smad4's participation in processes, for example apoptosis, differentiation, and proliferation.

Identification of a stem cell candidate in the normal human prostate gland

Stem cells of the human prostate gland have not yet been identified utilizing a structural biomarker. We have discovered a new prostatic epithelial cell phenotype-expressing cytokeratin 6a (Ck6a+ cells). The Ck6a+ cells are present within a specialized niche in the basal cell compartment in fetal, juvenile and adult prostate tissue, and within the stem cell-enriched urogenital sinus. In adult normal prostate tissue, the average abundance of Ck6a+ cells was 4.9%. With proliferative stimuli in the prostate organ culture model, in which the epithelial-stromal interaction was maintained, a remarkable increase of Ck6a expression was noticed to up to 64.9%. The difference in cytokeratin 6a expression between the normal adult prostate and the prostate organ culture model was statistically significant (p<0.0001). Within the prostate organ culture model the increase of cytokeratin 6a-expressing cells significantly correlated with increased proliferation index (r = 0.7616, p = 0.0467). The Ck6a+ cells were capable of differentiation as indicated by their expression of luminal cell markers such as ZO-1 and prostate specific antigen (PSA). Our data indicate that Ck6a+ cells represent a prostatic epithelial stem cell candidate possessing high potential for proliferation and differentiation. Since the development of benign prostatic hyperplasia and prostate carcinogenesis are disorders of proliferation and differentiation, the Ck6a+ cells may represent a major element in the development of these diseases.

Keratins and skin disorders

The association of keratin mutations with genetic skin fragility disorders is now one of the best-established examples of cytoskeleton disorders. It has served as a paradigm for many other diseases and has been highly informative for the study of intermediate filaments and their associated components, in helping to understand the functions of this large family of structural proteins. The keratin diseases have shown unequivocally that, at least in the case of the epidermal keratins, a major function of intermediate filaments is to provide physical resilience for epithelial cells. This review article reflects on the variety of phenotypes arising from mutations in keratins and the reasons for this variation.

Differential expression of CD44 during human prostate epithelial cell differentiation

CD44 is a polymorphic transmembrane glycoprotein that binds hyaluronan and growth factors. Multiple isoforms of the protein can be generated by alternative splicing but little is known about the expression and function of these isoforms in normal development and differentiation. We have investigated the expression of CD44 during normal prostate epithelial cell differentiation. A conditionally immortalized prostate epithelial cell line, Pre2.8, was used as a model system. These cells proliferate at 33C but at 39C stop dividing and undergo changes consistent with early stages of cell differentiation. During the differentiation of these cells, the expression of the CD44 isoform v3-v10 was upregulated. Two layers of epithelial cells can clearly be distinguished in the human prostate, a basal layer expressing keratins 5/14 and a luminal layer expressing keratins 8/18. In prostate tissue the v3-v10 isoform was found predominantly in basal cells but also in keratin 14-negative, keratin 19-positive cells intermediate between the two layers. CD44 v3-v10 was also expressed in other keratin 14-negative prostate tissues, the ejaculatory ducts and prostatic urethra. Therefore, CD44 v3-v10 may be important as a cell surface marker for differentiating cells in the prostate epithelium.

Expression profiling of human keratinocyte response to ultraviolet A: implications in apoptosis

Ultraviolet A radiation from sunlight is a major human health concern, as it is not absorbed by the ozone layer and can deeply penetrate into the skin causing skin damage. To study the molecular mechanism involved in the ultraviolet A effect, human HaCaT keratinocytes were exposed to ultraviolet A at doses of 10 J per cm2 and 30 J per cm2. Ultraviolet A irradiation caused dose- and time-dependent apoptotic cell death, as evidenced by DNA fragmentation, flow cytometry, and the activation of caspase-3. To study the genes altered by ultraviolet A at an apoptosis-inducing dose (30 J per cm2), cells were harvested immediately after ultraviolet A treatment (0 h), and 6 h and 24 h after ultraviolet A exposure. Total RNA was extracted for microarray and real-time RT-PCR analysis, and cellular proteins were extracted for western blot analysis. Of the selected critical genes/proteins, the induction of c-Jun, c-myc, and p33ING1, and the repression of epidermal growth factor receptor, inhibitor of apoptosis protein, and survivin pathways, could be involved in ultraviolet-A-induced apoptosis. On the other hand, the late induction of cyclin D1 and cyclin-dependent kinase 4 was indicative of possible cell cycle recovery in surviving cells. Real-time RT-PCR analysis confirmed these results and a majority of the protein levels paralleled their corresponding RNA levels. In addition, ultraviolet A treatment altered the expression of genes involved in signal transduction, RNA processing, structural proteins, and metabolism in a time-dependent manner. This initial microarray analysis could advance our understanding of cellular responses to ultraviolet A exposure, and provide a platform from which to further study ultraviolet-A-induced apoptosis and carcinogenesis.

Epidermal and Hair Follicle Progenitor Cells Express Melanoma-Associated Chondroitin Sulfate Proteoglycan Core Protein

Basal keratinocytes in the epidermis and hair follicle are biologically heterogeneous but must include a stable subpopulation of epidermal stem cells. In animal models these can be identified by their retention of radioactive label due to their slow cycle (label-retaining cells) but human studies largely depend on in vitro characterization of colony forming efficiency and clonogenicity. Differential integrin expression has been used to detect cells of increased proliferative potential but further stem cell markers are urgently required for in vivo and in vitro characterization. Using LHM2, a monoclonal antibody reacting with a high molecular weight melanoma-associated proteoglycan core protein, a subset of basal keratinocytes in both the interfollicular epidermis and the hair follicle has been identified. Coexpression of melanoma-associated chondroitin sulfate proteoglycan with keratins 15 and 19 as well as beta 1 and alpha 6 integrins has been examined in adult and fetal human skin from hair bearing, nonhair bearing, and palmoplantar regions. Although melanoma-associated chondroitin sulfate proteoglycan coexpression with a subset of beta 1 integrin bright basal keratinocytes within the epidermis suggests that melanoma-associated chondroitin sulfate proteoglycan colocalizes with epidermal stem cells, melanoma-associated chondroitin sulfate proteoglycan expression within the hair follicle was more complex and multiple subpopulations of basal outer root sheath keratinocytes are described. These data suggest that epithelial compartmentalization of the outer root sheath is more complex than interfollicular epidermis and further supports the hypothesis that more than one hair follicle stem cell compartment may exist.

Establishment and characterization of a cell line from smokeless tobacco associated oral squamous cell carcinoma

A cell line, AMOS-III has been established from the surgically resected specimen of an untreated primary human oral squamous cell carcinoma of the floor of mouth from a chronic smokeless tobacco consumer. Immunocytochemical analysis showed epithelial specific antigen, cytokeratins 5, 10, 13 and 16 and integrin alpha(6) markers in AMOS-III cells, confirming the epithelial lineage of the cell line. Analyses of morphology, ultrastructure, karyotype, anchorage independent growth and immunocytochemical properties of the cell line demonstrated the transformed phenotype of epithelial cells. AMOS-III cells have doubling time of 42-44 h. Giemsa-banding patterns of chromosomes confirmed the human origin of the AMOS-III cells. Molecular analysis of cancer-related gene products, p53 and p21(cip1/waf1) showed the presence of wild type p21(cip1/waf1) and truncated p53 proteins. The molecular mechanism underlying the action of retinoids in preventing the occurrence of second primary tumors in oral cancer patients remain to be clearly defined. Treatment of AMOS-III cells with all-trans retinoic acid (ATRA) at 10(-4) microM resulted in 81% cell death. ATRA treatment resulted in enhanced expression of p21(cip1/waf1), nuclear translocation of retinoic acid receptors and apoptotic cell death. Thus, this cell line provides an in vitro model for elucidating the mechanism involving p53 inactivation and p21(cip1/waf1) overexpression in smokeless tobacco-induced oral cancer. Furthermore, the ATRA responsiveness of the cell line underscores its potential utility in identifying the retinoid responsive molecular targets in oral cancer cells.

Basal cells of second trimester fetal breasts: immunohistochemical study of myoepithelial precursors

The molecular characterization of human mammary myoepithelial cells is incomplete, hindering our understanding of its importance in breast physiology and pathology. Because data on the precursors of this cell lineage remain scarce and often contradictory, basal epithelial cells of second trimester fetal breasts were studied by light microscopy (LM) and immunohistochemistry (IHC). Up to 20 wk of gestational age, the mammary rudiments only comprised roundish primary outgrowths, "primary buds," more likely to represent immature nipples than true mammary tissue. At 21 wk secondary outgrowths, "projections," extended from enlarged primary buds into well-vascularized layers of dense mesenchyme. Basal projection cells had a partial myoepithelial-like phenotype: they reacted with CD29, CD49f, CD104, keratin 14, vimentin, S100beta protein, and p63; furthermore, many became positive for keratin 17, alpha-smooth muscle actin, and CD10 (but not for keratin 19) between wk 21 and 25. The continuous basement membrane associated with the fetal mammary rudiments was strongly positive for collagens type IV and VII, and for laminin 5. Consistently strong and basally polarized staining for hemidesmosomal components suggested that although incompletely differentiated, most second trimester myoepithelial precursors might already mediate local epithelial-mesenchymal interactions, i.e., complex signaling pathways which are crucial for both orderly growth during development and maintenance of homeostasis during adult life. Because they are likely implicated in the phenomenon of menstrual cycle-related growth spurts in the adult resting breast, the strategically positioned cells of the myoepithelial lineage might constitute critical protagonists in defective epithelial-mesenchymal signaling associated with cancer progression.

The quest for the function of simple epithelial keratins

Simple epithelial keratins K8 and K18 are components of the intracellular cytoskeleton in the cells of the single-layered sheet tissues inside the body. As members of the intermediate filament family of proteins, their function has been a matter for debate since they were first discovered. Whilst there is an indisputable case for a structural cell-reinforcing function for keratins in the mutilayered squamous epithelia of external barrier tissues, some very different stress-protective features now seem to be emerging for the simple epithelial keratins. Even the emerging evidence of pathological mutations in K8/K18 looks very different from mutations in stratified epithelial keratins. K8/K18-like keratins were probably the first to evolve and, whilst stratified epithelial (keratinocyte) keratins have diversified into a large group of keratins highly specialised for providing mechanical stability, the simple epithelial keratins have retained early features that may protect the internal epithelia from a broader range of stresses, including osmotic stress and chemical toxicity.

Requirement of STAT3 activation for differentiation of mucosal stratified squamous epithelium

STAT3, a member of the signal transducers and activators of transcription (STAT) family, has been shown to play a key role in promoting proliferation, differentiation, or cell cycle progression, depending on cell type. A number of signaling pathways are altered in laryngeal papillomas, benign tumors induced by human papillomavirus 6/11. Papillomas overexpress the epidermal growth factor receptor and display enhanced MAP kinase and PI-3-kinase activity. They also show reduced activation of Akt and reduced levels of tyrosine-phosphorylated STAT3, due to overexpression of the tumor suppressor, PTEN. As papillomas show abnormalities in terminal differentiation, we examined the potential role of STAT3 in regulating epithelial differentiation. Laryngeal epithelial cells were suspended in supplemented serum-free medium. Differentiation was measured by Western blot analysis of keratin 13. Normal laryngeal epithelial cells were transfected with a constitutively active STAT3 or a dominant negative STAT3. Cells were transferred to suspension culture 24 h after transfection. Increased expression of keratin 13 was accompanied by the activation of STAT3 when differentiation was induced, and expression of a constitutively active STAT3 (STAT3C) enhanced the expression of keratin 13. In contrast, expression of a dominant negative STAT3 (Y705F) inhibited the expression of keratin 13. We conclude that activation of STAT3 is required for the differentiation of normal human stratified squamous epithelium.

Epidermal stem cells

The clinical implications of understanding epidermal stem cell biology abound. Thousands of burns victims across the world have benefited from early research into the proliferation of epidermal keratinocytes in vitro. Advances now indicate there are a number of stem cell repositories within the epidermis, two of which, the interfollicular epidermis and the bulge region of the hair follicle, may supply each other when damaged. This review details the progress made in the identification and characterisation of stem cells within the epidermis and discusses the molecules involved in the epidermal stem cell's choice of fate. Finally, the skin, like bone marrow, could be a readily accessible source of stem cells for therapeutic intervention and evidence of skin stem cell plasticity is highlighted.

Keratin expression in human tissues and neoplasms

Keratin expression in human tissues and neoplasms Keratin filaments constitute type I and type II intermediate filaments (IFs), with at least 20 subtypes named keratin 1-20. Since certain keratin subtypes are only expressed in some normal human tissues but not others, and vice versa, various tissues have been subclassified according to the pattern of keratin staining. Simple epithelia generally express the simple epithelial keratins 7, 18, 19, and 20, while complex epithelia express complex epithelial keratins 5/6, 10, 14, and 15. When an epithelium undergoes malignant transformation, its keratin profile usually remains constant. The constitution and expression patterns of keratin filaments in human epithelial neoplasms are complex and often distinctive. In this article, we first briefly review the molecular and cell biology of keratin filaments. We then focus on the expression patterns of keratin filaments in various human neoplasms.

Immunohistochemical and ultrastructural observations of desmoplastic trichoepithelioma with a special reference to a morphological comparison with normal apocrine acrosyringeum

BACKGROUND

Desmoplastic trichoepithelioma is a benign neoplasm considered to have follicular differentiation. Its sweat gland- or sebaceous-lines of differentiation have been also reported. There have been, however, only a few reports regarding extensive immunohistochemical and ultrastructural investigations of this neoplasm.

METHODS

Histopathological and immunohistochemical studies were performed on three cases of desmoplastic trichoepithelioma, comparing it with normal skin. One of these cases was ultrastructurally investigated.

RESULTS

The cord-like basaloid nests were reacted with the anti-cytokeratin (CK)1/5/10/14, -CK5/8, -CK14 and -CK15 antibodies, but not with the anti-CK6 antibody. Similar findings were observed in the outer layers of the normal follicular outer root sheath. Basaloid cell nests in one case, which showed ductal structures in the nests, also expressed CK7, CK8/18 and CK19. These keratins were also detected in the normal sweat glands. In addition, CK8/18 and CK19 were expressed in the basal cells of the outer root sheath. Keratinous cysts had inner reactions with the anti-CK10/11 and -CK6 antibodies, and outer reactions with anti-CK5/8 and -CK14 antibodies. Ultrastructurally, the cells in the cord-like nests were basically immature and basaloid in appearance. A few cells contained Odland bodies, which were also observed in the normal apocrine acrosyringeum. The ductal structure was lined by the cells which bore numerous microvilli in the luminal surface.

CONCLUSION

The cells in desmoplastic trichoepithelioma are suggested to be in close association with the basal cells in the outer root sheath, which can differentiate into various parts of the folliculosebaceous apocrine unit.

Regulation of keratin expression by ultraviolet radiation: differential and specific effects of ultraviolet B and ultraviolet a exposure

Skin, the most superficial tissue of our body, is the first target of environmental stimuli, among which is solar ultraviolet radiation. Very little is known about the regulation of keratin gene expression by ultraviolet radiation, however, although (i) it is well established that ultraviolet exposure is involved in skin cancers and photoaging and (ii) keratins represent the major epidermal proteins. The aim of this study was to analyze the regulation of human keratin gene expression under ultraviolet B (290-320 nm) or ultraviolet A (320-400 nm) irradiation using a panel of constructs comprising different human keratin promoters cloned upstream of a chloramphenicol acetyl transferase reporter gene and transfected into normal epidermal keratinocytes. By this approach, we demonstrated that ultraviolet B upregulated the transcription of keratin 19 gene and to a lesser extent the keratin 6, keratin 5, and keratin 14 genes. The DNA sequence responsible for keratin 19 induction was localized between -130 and +1. In contrast to ultraviolet B, ultraviolet A irradiation induced only an increase in keratin 17, showing a differential gene regulation between these two ultraviolet ranges. The induction of keratin 19 was confirmed by studying the endogenous protein in keratinocytes in classical cultures as well as in skin reconstructed in vitro and normal human skin. These data show for the first time that keratin gene expression is regulated by ultraviolet radiation at the transcriptional level with a specificity regarding the ultraviolet domain of solar light.

The nonhelical tail domain of keratin 14 promotes filament bundling and enhances the mechanical properties of keratin intermediate filaments in vitro

Keratin filaments arise from the copolymerization of type I and II sequences, and form a pancytoplasmic network that provides vital mechanical support to epithelial cells. Keratins 5 and 14 are expressed as a pair in basal cells of stratified epithelia, where they occur as bundled arrays of filaments. In vitro, bundles of K5-K14 filaments can be induced in the absence of cross-linkers, and exhibit enhanced resistance to mechanical strain. This property is not exhibited by copolymers of K5 and tailless K14, in which the nonhelical tail domain has been removed, or copolymers of K5 and K19, a type I keratin featuring a short tail domain. The purified K14 tail domain binds keratin filaments in vitro with specificity (kD approximately 2 microM). When transiently expressed in cultured cells, the K14 tail domain associates with endogenous keratin filaments. Utilization of the K14 tail domain as a bait in a yeast two-hybrid screen pulls out type I keratin sequences from a skin cDNA library. These data suggest that the tail domain of K14 contributes to the ability of K5-K14 filaments to self-organize into large bundles showing enhanced mechanical resilience in vitro.