Stem/progenitor and intermediate cell types and the origin of human prostate cancer

Theories of cell lineage in human prostatic epithelium, based on protein expression, propose that basal and luminal cells: 1) are either independently capable of self-renewal or 2) arise from stem cells expressing a full spectrum of proteins (p63, cytokeratins CK5/14, CK8/18, and glutathione-S-transferase-pi [GST-pi]) similar to cells of the embryonic urogenital sinus (UGS). Such embryonic-like stem cells are thought to give rise to mature basal cells and secretory luminal cells. By single cell cloning of an immortalized, normal human prostate-derived, non-tumorigenic RWPE-1 cell line, we isolated and characterized two epithelial cell types, WPE-stem and WPE-int. WPE-stem cells show: i) strong, sixfold greater nuclear expression of p63; ii) nearly twofold greater expression of CK14; iii) threefold less CK18, and iv) low androgen receptor (AR) expression as compared with WPE-int cells. WPE-stem cells are androgen-independent for growth and survival. WPE-int cells express very low p63 and CK5/14, and high CK18. WPE-int cells are androgen-independent for growth and survival but are highly responsive as shown by androgen induction of AR and prostate specific antigen (PSA). Compared with WPE-int cells, WPE-stem cells are smaller and show more rapid growth. WPE-stem cells can grow in an anchorage-independent manner in agar with 4.5-fold greater cloning efficiency and as free floating "prostaspheres" in liquid medium; and express over 40-fold higher matrix metalloproteinase-2 activity. These results indicate that WPE-stem cells express several features characteristic of stem/progenitor cells present in the UGS and in adult prostatic epithelium. In contrast, WPE-int cells have an intermediate, committed phenotype on the pathway to luminal cell differentiation. We propose that in normal prostatic epithelium, cells exist at many stages in a continuum of differentiation progressing from stem cells to definitive basal and luminal cells. Establishment and characterization of clones of human prostatic epithelial cells provide novel models for determining cell lineages, the origin of prostate cancer, and for developing new strategies for tumor prevention and treatment.     

Cell differentiation lineage in the prostate

Prostatic epithelium consists mainly of luminal and basal cells, which are presumed to differentiate from common progenitor/stem cells. We hypothesize that progenitor/stem cells are highly concentrated in the embryonic urogenital sinus epithelium from which prostatic epithelial buds develop. We further hypothesize that these epithelial progenitor/stem cells are also present within the basal compartment of adult prostatic epithelium and that the spectrum of differentiation markers of embryonic and adult progenitor/stem cells will be similar. The present study demonstrates that the majority of cells in embryonic urogenital sinus epithelium and developing prostatic epithelium (rat, mouse, and human) co-expressed luminal cytokeratins 8 and 18 (CK8, CK18), the basal cell cytokeratins (CK14, CK5), p63, and the so-called transitional or intermediate cell markers, cytokeratin 19 (CK19) and glutathione-S-transferase-pi (GSTpi). The majority of luminal cells in adult rodent and human prostates only expressed luminal markers (CK8, CK18), while the basal epithelial cell compartment contained several distinct subpopulations. In the adult prostate, the predominant basal epithelial subpopulation expressed the classical basal cell markers (CK5, CK14, p63) as well as CK19 and GSTpi. However, a small fraction of adult prostatic basal epithelial cells co-expressed the full spectrum of basal and luminal epithelial cell markers (CK5, CK14, CK8, CK18, CK19, p63, GSTpi). This adult prostatic basal epithelial cell subpopulation, thus, exhibited a cell differentiation marker profile similar to that expressed in embryonic urogenital sinus epithelium. These rare adult prostatic basal epithelial cells are proposed to be the progenitor/stem cell population. Thus, we propose that at all stages (embryonic to adult) prostatic epithelial progenitor/stem cells maintain a differentiation marker profile similar to that of the original embryonic progenitor of the prostate, namely urogenital sinus epithelium. Adult progenitor/stem cells co-express both luminal cell, basal cell, and intermediate cell markers. These progenitor/stem cells differentiate into mature luminal cells by maintaining CK8 and CK18, and losing all other makers. Progenitor/stem cells also give rise to mature basal cells by maintaining CK5, CK14, p63, CK19, and GSTpi and losing K8 and K18. Thus, adult prostate basal and luminal cells are proposed to be derived from a common pleuripotent progenitor/stem cell in the basal compartment that maintains its embryonic profile of differentiation markers from embryonic to adult stages.     

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.     

Generation of active TGF-beta by prostatic cell cocultures using novel basal and luminal prostatic epithelial cell lines

Two prostatic epithelial lines, one of basal origin and one of luminal origin, were established from the dorsolateral prostates of p53 null mice. The cell lines are nontumorigenic when inoculated subcutaneously under the renal capsule or intraprostatically in syngeneic mice. The luminal cell line (PE-L-1) expresses cytokeratins 8 and 18 and the basal cell line (PE-B-1) expresses cytokeratins 5 and 14. The basal cells require serum for growth, whereas the luminal cells grow only in serum-free medium. Both cell lines require the presence of growth factors for optimal growth in culture, with EGF and FGF-2 having the greatest effect on the growth rate. Both lines express androgen receptor (AR) mRNA and protein. Androgen stimulates growth of the basal cell line, indicating that the ARs are functional, whereas growth of the luminal cells is unaffected by androgens. The luminal line is significantly inhibited by exogenous TGF-beta and produces low levels of endogenous TGF-beta. In contrast, the basal cell line produces significant amounts of TGF-beta and its growth is not influenced by this cytokine. Coculture of luminal cells with prostatic smooth muscle cells results in the generation of increased levels of biologically active TGF-beta, indicating a paracrine mechanism of TGF-beta activation that may be involved in the maintenance of normal prostatic function. To our knowledge this is the first report describing both basal and luminal prostatic cell lines from a single inbred animal species and the first indication that prostatic epithelial and stromal cells interact to generate the biologically active form of TGF-beta. These lines will provide an important model for determining basal/luminal interactions in both in vitro and in vivo assays.     

Lactation affects expression of intermediate filaments in human breast epithelium

Abstract The human breast contains two epithelial lineages, luminal epithelial and myoepithelial. Specific patterns of expression of intermediate filaments have previously been demonstrated in the resting breast. To determine how terminal differentiation and lactation influenced expression of intermediate filaments in breast epithelial cells, we used Western blot analysis to measure the levels of vimentin, α-smooth muscle actin, keratin 14, and keratin 18 in the resting and lactating breast. Confocal immunofluorescence was used to determine the subcellular site of localization of the intermediate filaments. Vimentin was localised to myoepithelial cells in both the resting and lactating gland. There was a four-fold increase in vimentin protein levels in lactating tissue relative to resting tissue, and this may be related to increased cellular activity of the myoepithelial cells which surround secretory alveoli. Alpha-smooth muscle actin and keratin 14 were detected in myoepithelial cells, and similar levels of expression were found in lactating and resting tissue. In the resting breast, keratin 18 and keratin 8 were detected in luminal epithelial cells in a filamentous form, whereas in lactating tissue it was present in a punctate form in luminal cells and also seen as granules in the lumen of alveoli. Our results indicate that intermediate filament expression patterns are altered in the lactating human breast, and this may reflect their role in the fully functional gland.     

Lactation affects expression of intermediate filaments in human breast epithelium

The human breast contains two epithelial lineages, luminal epithelial and myoepithelial. Specific patterns of expression of intermediate filaments have previously been demonstrated in the resting breast. To determine how terminal differentiation and lactation influenced expression of intermediate filaments in breast epithelial cells, we used Western blot analysis to measure the levels of vimentin, alpha-smooth muscle actin, keratin 14, and keratin 18 in the resting and lactating breast. Confocal immunofluorescence was used to determine the subcellular site of localization of the intermediate filaments. Vimentin was localised to myoepithelial cells in both the resting and lactating gland. There was a four-fold increase in vimentin protein levels in lactating tissue relative to resting tissue, and this may be related to increased cellular activity of the myoepithelial cells which surround secretory alveoli. Alpha-smooth muscle actin and keratin 14 were detected in myoepithelial cells, and similar levels of expression were found in lactating and resting tissue. In the resting breast, keratin 18 and keratin 8 were detected in luminal epithelial cells in a filamentous form, whereas in lactating tissue it was present in a punctate form in luminal cells and also seen as granules in the lumen of alveoli. Our results indicate that intermediate filament expression patterns are altered in the lactating human breast, and this may reflect their role in the fully functional gland.     

Cytokeratin expression in human thymus: immunohistochemical mapping

Cytokeratin expression in normal postnatal human thymus was studied immunohistochemically by using monoclonal antibodies against various cytokeratin polypeptides. An attempt was made to characterize cell populations giving rise to the cornified structures of Hassal's corpuscles. Monoclonal antibody KB-37, a marker of squamous epithelium basal cells, was applied to distinguish the earliest cells capable of undergoing squamous differentiation. Parts of the subcapsular epithelium were extensively stained with this reagent. This epithelium, like the basal layer of certain squamous epithelia, exibited a high incidence of cytokeratins 13 and 14, and pronounced expression of cytokeratin 19. Simple epithelium cytokeratins 8, 18, and 19 were present in the cortex. Scattered cells reacted with KB-37 antibody. All stellate epithelial cells in the medulla were positive for cytokeratin 19. Most of the medullar epithelial cells were positive for cytokeratins 13, 14 and 17 of complex epithelium, in contrast to the cortex, where only a few cells were positive for these cytokeratins. A significant proportion of the medullar cells was positive for KB-37 antigen. Cytokeratins 8 and 18 were expressed in single cells and in groups of cells surrounding Hassal's corpuscles. The outermost cells of these corpuscles were positive for cytokeratin 19 and KB-37. In the peripheral parts of Hassal's corpuscles, simple epithelium cytokeratins 7, 8, 18, and cytokeratins 4, 13, 14, and 17, characteristic of stratified nonkeratinizing epithelia, were coexpressed with keratinization-specific cytokeratins 10/11. The inner parts of the swirls were uniformly positive for cytokeratins was reduced.     

Changes in Biomarker Expression in the Development of Prostatic Adenocarcinoma

In spite of the prevalence of prostatic adenocarcinoma, the development and natural history of this malignancy is poorly understood. This paper reviews the current knowledge of biomarker expression during the development and progression of prostatic adenocarcinoma. Emphasis is placed on the comparison of biomarker expression in benign prostatic epithelium, intraepithelial neoplasia (PIN), a putative preinvasive lesion, and prostatic adenocarcinoma. Within the benign epithelium, the proliferative potential is restricted to the basal cells as demonstrated by the expression of proliferating cellular nuclear antigen (PCNA). The strong expression of the bcl-2 protein, an inhibitor of apoptosis, supports the concept that the basal cells or a subpopulation of the basal cells represent the stem cell of the epithelium. In addition, the strong expression of growth factor receptors such as the epidermal growth factor receptor (EGFr), p185^erbB-2, p180^erbB-3, and c-met suggests that the growth of the basal cells is regulated by autocrine or paracrine factors. The luminal cells express secretory products such as prostate specific antigen and prostatic acid phosphatase, but demonstrate little expression of PCNA as well as growth factor receptors and proto-oncogene products. These observations are consistent with the theory that the luminal cell population is derived from the differentiation of the basal cells. In contrast to the normal epithelium, PCNA expression is frequently detected in the dysplastic luminal cells of the PIN lesion. Likewise, strong expression of p185^erbB-2, p180^erbB-3 and the c-met proto-oncogene product is also detected in the luminal cells of PIN lesions. Other factors which are strongly expressed by the dysplastic luminal cells include the nm23-Hl gene product, tumor associated glycoprotein-72 (TAG-72), fatty acid synthetase (FASE) and proteolytic enzymes. These findings suggest that PIN lesions are derived from an impairment of the differentiation of basal cells. The majority of biomarkers such as PCNA, p185^erbB-2, p180^erbB-3, TAG-72, nm23-Hl and FASE which are strongly expressed in PIN lesions are also expressed in prostatic adenocarcinoma supporting the concept that PIN is a preinvasive lesion. Mutations of the p53 tumor suppressor gene, as well as strong expression of transforming growth factor a and bcl-2 typically occur in advanced stage prostatic adenocarcinomas and therefore likely represent late events in the development of prostatic adenocarcinoma.     

Estrogens induce malpighian metaplasia of the endocervical junction in female rats immunohistochemistry study

Immature female Wistar rats were treated with 1 mg of estradiol benzoate for 6 days. The injections were started on the 20th day of age; the animals were autopsied every 3 days after the last injection until the age of 45 days. Islets of hyperplastic cells and metaplasia area were seen in the endocervix in the majority of the animals autopsied. We have the expression of cytokeratin polypeptides in reserve cells, in areas exhibiting reserve cell hyperplasia and squamous metaplasia, using a panel of monoclonal cytokeratin antibodies. The reserve cells were positive for antibodies directed against stratified squamous epithelia, type cytokeratins No. 5, 13 and 17. In addition, hyperplastic cells revealed the presence of cytokeratins No. 7, 8, 18 and 19, specific for simple epithelia, but in a variable manner. The Squamous metaplasia cells exhibited cytokeratins No. 13, 18 and 19, but only weakly reactive. Our observations indicate that estrogen-induced endocervix metaplasia results from a transformation of reserve cells towards an epidermoid type epithelium. Hyperplasia would be the intermediate step in the mechanism of induced cervical metaplasia. This transformation is accompanied by the loss of cytoplasmic keratin proteins and the acquisition of new high molecular weight keratin proteins, specific for stratified squamous epithelia. The basal or reserve cells of the cervix can proliferate to produce regions of squamous cell metaplasia. It appears to be a direct effect of estrogen stimulation. Immunohistochemical staining for different molecular weight keratin proteins may be helpful in the evaluation of reserve cell differentiation.     

Proprotein convertases regulate activity of prostate epithelial cell differentiation markers and are modulated in human prostate cancer cells

Prostate derived factor (PDF) is a member of transforming growth factor-beta (TGF-beta) superfamily proteins involved in differentiation of the prostate epithelium. Proprotein convertases (PCs) such as furin are thought to mediate the processing of TGF-beta superfamily. In the present study, we demonstrated for the first time that human prostate cancer cell lines differentially synthesize and secret prostate derived factor (PDF), and that PDF secreted by LNCaP is processed by PCs. Exposure of LNCaP cells to the decanoyl-Arg-Val-Lys-Arg-chloromethylketone (CMK), a synthetic furin-like protease inhibitor, inhibited PDF processing and resulted in the loss of luminal cell phenotype and induction of basal cell phenotype in LNCaP cells as demonstrated by alternations in the expression of cytokeratins 8, 14, 18, and 19, markers of prostate epithelial cell differentiation. These results suggest that proprotein convertases may be involved in the regulation of prostate epithelial cell differentiation, and may be an important target of prostate cancer therapy.     

Expression of simple epithelial type cytokeratins in stratified epithelia as detected by immunolocalization and hybridization in situ

Multi-layered ("stratified") epithelia differ from one-layered ("simple") polar epithelia by various architectural and functional properties as well as by their cytoskeletal complements, notably a set of cytokeratins characteristic of stratified tissue. The simple epithelial cytokeratins 8 and 18 have so far not been detected in any stratified epithelium. Using specific monoclonal antibodies we have noted, in several but not all samples of stratified epithelia, including esophagus, tongue, exocervix, and vagina, positive immunocytochemical reactions for cytokeratins 8, 18, and 19 which in some regions were selective for the basal cell layer(s) but extended into suprabasal layers in others. In situ hybridization with different probes (riboprobes, synthetic oligonucleotides) for mRNAs of cytokeratin 8 on esophageal epithelium has shown, in extended regions, relatively strong reactivity for cytokeratin 8 mRNA in the basal cell layer. In contrast, probes to cytokeratin 18 have shown much weaker hybridization which, however, was rather evenly spread over basal and suprabasal strata. These results, which emphasize the importance of in situ hybridization in studies of gene expression in complex tissues, show that the genes encoding simple epithelial cytokeratins can be expressed in stratified epithelia. This suggests that continual expression of genes coding for simple epithelial cytokeratins is compatible with the formation of squamous stratified tissues and can occur, at least in basal cell layers, simultaneously with the synthesis of certain stratification-related cytokeratins. We also emphasize differences of expression and immunoreactivity of these cytokeratins between different samples and in different regions of the same stratified epithelium and discuss the results in relation to changes of cytokeratin expression during fetal development of stratified epithelia, in response to environmental factors and during the formation of squamous cell carcinomas.     

Extracellular matrix-dependent differentiation of rabbit tracheal epithelial cells in primary culture

Summary The differentiation of tracheal epithelial cells in primary culture was investigated according to the nature of the extracellular matrix used. Cultures obtained by the explant technique were realized on a type I collagen substratum either as a thin, dried coating or as a thick, hydrated gel supplemented with culture medium and serum. These two types of substratum induced distinct cell morphology and cytokeratin expression in the explant derived cells. Where cells are less proliferating (from Day 7 to 10 of culture), differentiation was evaluated by morphologic ultrastructural observations, immunocytochemical detection of cytokeratins, and determination of cytokeratin pattern by biochemical analysis. The epithelium obtained on gel was multilayered, with small, round basal cells under large, flattened upper cells. The determination of the keratin pattern expressed by cells grown on gel revealed an expression of keratin 13, already considered as a specific marker of squamous metaplasia, that diminished with retinoic acid treatment. Present results demonstrated by confocal microscopy that K13-positive cells were large upper cells with a dense keratin network, whereas lower cells were positively stained with a specific monoclonal antibody to basal cells (KB37). Moreover, keratin neosynthesis analysis pointed out a higher expression of K6, a marker of hyperproliferation, on gel than on coating. All these data suggest a differentiation of rabbit tracheal epithelial cells grown on gel toward squamous metaplasia. By contrast, the epithelium observed on coating is nearly a monolayer of very large and spread out cells. No K13-positive cells were observed, but an increase in the synthesis of simple epithelium marker (K18) was detected. These two substrata, similar in composition and different in structure, induce separate differentiation and appear as good tools to explore the mechanisms of differentiation of epithelial tracheal cells.     

Characterization of subcolumnar reserve cells and other epithelia of human uterine cervix. Demonstration of diverse cytokeratin polypeptides in reserve cells

We have analyzed the expression of cytokeratin polypeptides in subcolumnar reserve cells of the human uterine endocervical mucosa and the other epithelial cells using immunoperoxidase and immunofluorescence microscopy as well as by applying two-dimensional gel electrophoresis to microdissected cytoskeletal preparations. Endocervical columnar cells were uniformly positive for antibodies directed against the simple epithelium-type cytokeratins nos. 7, 8, 18, and 19, while a variable proportion of these cells was stained by an antibody against cytokeratin no. 4. Reserve cells were not only positive for cytokeratins nos. 8 (weakly and variably) and 19 but were also decorated by antibody KA 1, which reacts with cytokeratins present in stratified squamous epithelia. This last antibody selectively decorated reserve cells even when they were flat and inconspicuous. Antibody KA 1 uniformly stained the ectocervical squamous epithelium, the basal cells of which were also decorated by antibodies directed against cytokeratins nos. 8 (weakly and variably) and 19. Ectocervical suprabasal cells were positive, to a variable extent, for antibodies against cytokeratins nos. 4, 10/11, and 13. Gel electrophoresis revealed the presence of squamous-type cytokeratins nos. 5 and 17 in reserve cell-rich, but not in reserve cell-free, endocervical mucosa. We also analyzed the distribution pattern of these cells, as revealed by antibody KA 1, in the endocervical mucosa of 26 uteri. In all the specimens examined reserve cells were present, but their numbers exhibited considerable variation. In some cases these cells were confined to small islets localized deep within the cervical canal and lacked any continuity with the squamous epithelium. The expression of cytokeratins nos. 5 and 17 in reserve cells indicates that these cells have undergone a low level of squamous differentiation. The additional expression of cytokeratins nos. 8 and 19 in these cells points to a relationship with simple epithelial cells. The present data would seem to favor the view that reserve cells originate in situ from the columnar epithelium; however, this would imply an acquisition of new differentiation properties.     

Cytokeratins in normal lung and lung carcinomas. I. Adenocarcinomas, squamous cell carcinomas and cultured cell lines

The various epithelial cells of the lower respiratory tract and the carcinomas derived from them differ markedly in their differentiation characteristics. Using immunofluorescence microscopy and two-dimensional gel electrophoresis of cytoskeletal proteins from microdissected tissues we have considered whether cytokeratin polypeptides can serve as markers of cell differentiation in epithelia from various parts of the human and bovine lower respiratory tract. In addition , we have compared these protein patterns with those found in the two commonest types of human lung carcinoma and in several cultured lung carcinoma cell lines. By immunofluorescence microscopy, broad spectrum antibodies to cytokeratins stain all epithelial cells of the respiratory tract, including basal, ciliated, goblet, and alveolar cells as well as all tumor cells of adenocarcinomas and squamous cell carcinomas. However, in contrast, selective cytokeratin antibodies reveal cell type-related differences. Basal cells of the bronchial epithelium react with antibodies raised against a specific epidermal keratin polypeptide but not with antibodies derived from cytokeratins characteristic of simple epithelia. When examined by two-dimensional gel electrophoresis, the alveolar cells of human lung show cytokeratin polypeptides typical of simple epithelia (nos. 7, 8, 18 and 19) whereas the bronchial epithelium expresses, in addition, basic cytokeratins (no. 5, small amounts of no. 6) as well as the acidic polypeptides nos. 15 and 17. Bovine alveolar cells also differ from cells of the tracheal epithelium by the absence of a basic cytokeratin polypeptide. All adenocarcinomas of the lung reveal a "simple-epithelium-type" cytokeratin pattern (nos. 7, 8, 18 and 19). In contrast, squamous cell carcinomas of the lung contain an unusual complexity of cytokeratins. We have consistently found polypeptides nos. 5, 6, 8, 13, 17, 18 and 19 and, in some cases, variable amounts of cytokeratins nos. 4, 14 and 15. Several established cell lines derived from human lung carcinomas (SK-LU-1, Calu -1, SK-MES-1 and A-549) show a uniform pattern of cytokeratin polypeptides (nos. 7, 8, 18 and 19), similar to that found in adenocarcinomas. In addition, vimentin filaments are produced in all the cell lines examined, except for SK-LU-1.(ABSTRACT TRUNCATED AT 400 WORDS)     

Alterations in cytokeratin expression precede histological changes in epithelia of vitamin A-deficient rats

Summary Normal epithelial cell differentiation is charactezied by the production of distinct cytokeratin proteins. It is well known that epithelia of several organs show squamous metaplasia in a vitamin A-deficient status. It is not yet known whether these histological changes are concomitant with a change in cytokeratin expression. Therefore, 3-week-old female rats (BN/BiRij) were fed a vitamin A-deficient diet for 8 weeks. The cytokcratin expression in epithelia of various organs was monitored immunohistochemically during the induction of vitamin A deficiency. Therefore, monoclonal antibodies specific for human cytokeratin 4, 5, 5+8, 7, 10, 14, 18 and 19 were used. In a normal vitamin A status, the distributional pattern for the different cytokeratins in rats was similar to that reported for human tissue. No change in cytokeratin expression was seen in trachea, skin, liver and colon at any time point studied. Squamous metaplasia in urinary bladder and salivary glands was observed after six weeks on the vitamin A-deficient diet. This was concomitant with a substitution of cytokeratins 4, 5+8, 7, 18 and 19 by cytokeratin 10. The latter cytokeratin is specific for keratinzed squamous epithelium. A change in cytokeratin expression was observed in bladder, ureter, kidney, salivary glands, uterus and conjunctiva before histological alterations appeared. In conclusion, the changes in cytokeratin expression observed under vitamin A deficiency in epithelia in vivo are in agreement with those described in other studies for epithelial cells in vitro. The changes in cytokeratin expression and the subsequent differentiation into squamous cells occurs in basal cells of the bladder but not in transitional cells. Furthermore, histological alterations are preceded by changes in cytokeratin expression indicating that vitamin A status controls cytokeratin expression in vivo.     

Immunohistochemical investigation of different cytokeratins and vimentin in the human epididymis from the fetal period up to adulthood

Summary The anatomical distribution of cytokeratins and vimentin was investigated by means of immunohistochemistry in the human epididymis. Epithelial cells of the ductuli efferentes and the corpus epididymidis were positive for cytokeratins and vimentin. The expression of epithelial vimentin decreased toward the cauda epididymidis, whereas cytokeratins remained unchanged. The epithelium of the ductus deferens was negative when antibodies against vimentin were used. With monoclonal antibodies to individual cytokeratins, the presence of cytokeratins 7, 8, 18, and 19 was demonstrated histochemically throughout the epithelium of the epididymis. Monoclonal antibodies specific for cytokeratin 17 allowed immunohistochemical differentiation between the ductuli efferentes and the ductus epididymidis.     

Differentiation of mouse embryonic palatal epithelium in culture: selective cytokeratin expression distinguishes between oral, medial edge and nasal epithelial cells

During normal murine palatogenesis, regional specific differentiation of the epithelium results in three cell phenotypes: nasal (ciliated pseudostratified columnar cells), oral (stratified squamous cells) and medial edge (migratory, epithelio-mesenchymally transformed cells). We have developed a defined, serum-free, culture system which supports the growth and differentiation of isolated murine embryonic palatal epithelia in vitro. Using immunofluorescence microscopy, an established panel of antibodies was used to characterise the cytokeratin intermediate filament profile of palatal epithelial sheets at a precise developmental stage, following culture in serum-free medium with and without either transforming growth factor alpha (TGF alpha) or 10% donor calf serum (DCS). The morphologically discernable oral, medial edge and nasal phenotypes exhibited distinctive cytokeratin profiles, which remained consistent for all culture conditions, and which correlated with the known differentiation states of the epithelial types. The oral epithelia stained positively for cytokeratin 19 and cytokeratins characteristic of multilayered epithelia (1, 5, 14). Nasal epithelia stained similarly but in addition expressed the simple-epithelial cytokeratin pair, 8 and 18. Medial edge epithelia also expressed cytokeratins 1, 5 and 14 but with the exception of a few isolated cells there was no staining for cytokeratins 8 and 18. Cytokeratin 19 was absent specifically from the medial edge epithelial cells: this result may be related to the loss of cytokeratin expression observed during epithelial-mesenchymal transformations. By exhibiting a complexity of expression linked to differentiation state and independent of culture conditions, cytokeratins constitute useful markers of palatal epithelial differentiation in vitro as well as in vivo.     

A conditionally immortalized cell line model for the study of human prostatic epithelial cell differentiation

In the normal human prostate, undifferentiated proliferative cells reside in the basal layer and give rise to luminal secretory cells. There are, however, few epithelial cell lines that have a basal cell phenotype and are able to differentiate. We set out to develop a cell line with these characteristics that would be suitable for the study of the early stages of prostate epithelial cell differentiation. We produced a matched pair of conditionally immortalized prostate epithelial and stromal cell lines derived from the same patient. The growth of these cells is temperature dependent and differentiation can be induced following a rise in culture temperature. Three-dimensional co-cultures of these cell lines elicited gland-like structures reminiscent of prostatic acini. cDNA microarray analysis of the epithelial line demonstrated changes in gene expression consistent with epithelial differentiation. These genes may prove useful as markers for different prostate cell types. The cell lines provide a model system with which to study the process of prostatic epithelial differentiation and stromal-epithelial interactions. This may prove to be useful in the development of differentiation-targeted prostate cancer therapies.