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T T Sun

Publications and source records attributed to T T Sun.

At least 19 recordsLinked to original sources
PubMed2001

Uroplakin as a marker for typing metastatic transitional cell carcinoma on fine-needle aspiration specimens.

BACKGROUND: Immunohistological markers specific for a single type of epithelium are rare. Recently, urothelium tissue-specific genes were cloned. The genes encoded a family of transmembrane proteins, uroplakins, that are expressed only in urothelial mucosa. Using uroplakin antibodies on paraffin-embedded tissue, a previous study demonstrated positive staining in 66% of metastatic transitional cell carcinoma (TCC) cases and negative staining in all other tumors (including breast, ovarian, lung, and gastrointestinal carcinomas) tested. The current study addresses the diagnostic value of uroplakins in conventional fine-needle aspiration (FNA) material in establishing a diagnosis of metastatic TCC. METHODS: Representative slides from 27 FNA cases of metastatic TCC and 52 non-TCC carcinomas were collected. The avidin-biotin-peroxidase method was utilized, using polyclonal antiuroplakin as the primary antibody on 95% ethanol-fixed, Papanicoloau-stained direct smears. RESULTS: Twenty-five of 27 metastatic TCC cases (93%) were found to stain positively for uroplakin with a superficial membrane/microluminal staining pattern. A few cells with diffuse membranous staining also were noted in 48% of the positive metastatic TCC cases. The superficial membrane/microluminal staining pattern was not observed in any of the non-TCC carcinomas. However, approximately 6% of these cases (3 of 52 cases) did show rare tumor cells with diffuse membranous staining. CONCLUSIONS: The application of uroplakin antibodies to 95% ethanol-fixed FNA direct smears has improved the sensitivity of the antibody for metastatic TCC while maintaining a specificity comparable to that of paraffin-embedded tissue. The authors believe that these antibodies have diagnostic potential in cytopathology in the evaluation of metastatic TCC.

Adult↗
PubMed2001

Role of Ha-ras activation in superficial papillary pathway of urothelial tumor formation.

Urothelial tumors develop along two distinctive phenotypic pathways (superficial papillary non-invasive tumors versus flat carcinoma in situ lesions), with markedly different biological behavior and prognosis. Although multiple genetic alterations have been identified in human bladder cancer, their cause-effect relationship with the two pathways has not been firmly established. Using a urothelium-specific promoter of the uroplakin II gene, we showed earlier in transgenic mice that the urothelial expression of SV40T antigen, which inactivates p53 and pRb, induced carcinoma in situ and invasive and metastatic bladder cancer. In striking contrast, we demonstrate here that the urothelial expression of an activated Ha-ras in transgenic mice caused urothelial hyperplasia and superficial papillary non-invasive bladder tumors. These results provide strong, direct experimental evidence that the two phenotypical pathways of bladder tumorigenesis are caused by distinctive genetic defects. Our results indicate that Ha-ras activation can induce urothelial proliferation in vivo; and that urothelial hyperplasia is a precursor of low-grade, superficial papillary bladder tumors. Our transgenic models provide unique opportunities to study the detailed molecular events underlying different types of bladder neoplasms, and can serve as useful preclinical models for evaluating the in vivo efficacy of preventive and therapeutic agents that act on various signaling pathways in bladder cancer.

Animals↗
PubMed2001

Organization of uroplakin subunits: transmembrane topology, pair formation and plaque composition.

The apical surfaces of urothelial cells are almost entirely covered with plaques consisting of crystalline, hexagonal arrays of 16 nm uroplakin particles. Although all four uroplakins, when SDS-denatured, can be digested by chymotrypsin, most uroplakin domains in native urothelial plaques are resistant to the enzyme, suggesting a tightly packed structure. The only exception is the C-terminal, cytoplasmic tail of UPIII (UPIII) which is highly susceptible to proteolysis, suggesting a loose configuration. When uroplakins are solubilized with 2% octylglucoside and fractionated with ion exchangers, UPIa and UPII were bound as a complex by a cation exchanger, whereas UPIb and UPIII were bound by an anion exchanger. This result is consistent with the fact that UPIa and UPIb are cross-linked to UPII and UPIII, respectively, and suggests that the four uroplakins form two pairs consisting of UPIa/II and UPIb/III. Immunogold labelling using a new mouse monoclonal antibody, AU1, revealed that UPIII is present in all urothelial plaques, indicating that the two uroplakin pairs are not segregated into two different types of urothelial plaque and that all plaques must have a similar uroplakin composition. Taken together, these results indicate that uroplakins form a tightly packed structure, that the four uroplakins interact specifically forming two pairs, and that both uroplakin pairs are required for normal urothelial plaque formation.

Amino Acid Sequence↗
PubMed2001

Urothelial function reconsidered: a role in urinary protein secretion.

Mammalian bladder epithelium functions as an effective permeability barrier. We demonstrate here that this epithelium can also function as a secretory tissue directly involved in modifying urinary protein composition. Our data indicate that normal bovine urothelium synthesizes, as its major differentiation products, two well-known proteases: tissue-type plasminogen activator and urokinase, as well as a serine protease inhibitor, PP5. Moreover, we demonstrate that the urothelium secretes these proteins in a polarized fashion into the urine via a cAMP- and calcium-regulated pathway. Urinary plasminogen activators of ruminants are therefore urothelium derived rather then kidney derived as in some other species; this heterogeneity may have evolved in response to different physiological or dietary factors. In conjunction with our recent finding that transgenic mouse urothelium can secrete ectopically expressed human growth hormone into the urine, our data establish that normal mammalian urothelium can function not only as a permeability barrier but also as a secretor of urinary proteins that can play physiological or pathological roles in the urinary tract.

3T3 Cells↗
PubMed2001

Brenner tumors but not transitional cell carcinomas of the ovary show urothelial differentiation: immunohistochemical staining of urothelial markers, including cytokeratins and uroplakins.

To determine whether Brenner tumors and transitional cell carcinomas (TCCs) of the ovary are urothelial in type, the immunoprofiles of 14 Brenner tumors, including three malignant examples, and eight ovarian TCCs were compared with those of Walthard nests, urothelium, 12 urinary bladder TCCs and 17 ovarian adenocarcinomas (serous, endometrioid, mucinous, and undifferentiated type). The immunohistochemical stains used included those for cytokeratins CKs 5/6, CK7, CK8, CK13, and CK20, vimentin, CA125, and the specific urothelial differentiation marker uroplakin III. CK7 and CK8 were broadly expressed in most tumors of ovary and bladder examined, while vimentin was focally present in some ovarian TCCs and adenocarcinomas. As in normal and neoplastic bladder urothelium, urothelial markers, including uroplakin III, CK13, and CK20, were detected in the epithelial nests of Brenner tumors. Brenner tumor cells also expressed uroplakins Ia and II. CA125 was observed focally in some Brenner tumors. In contrast, TCCs of the ovary and Walthard nests lacked uroplakins and were essentially negative for CK20 and CK13 but quite strongly expressed CA125. This immunophenotype closely resembled that found in ovarian adenocarcinomas. Thus, it appears that the only true urothelial-type ovarian neoplasm is the Brenner tumor, whereas ovarian TCC most likely represents a poorly differentiated adenocarcinoma with a morphologic transitional cell pattern. These results may explain the controversies as expressed in the recent literature concerning TCC of the ovary and establish its place among the ovarian adenocarcinomas of müllerian type.

Adenocarcinoma↗
PubMed2000

Ablation of uroplakin III gene results in small urothelial plaques, urothelial leakage, and vesicoureteral reflux.

Urothelium synthesizes a group of integral membrane proteins called uroplakins, which form two-dimensional crystals (urothelial plaques) covering >90% of the apical urothelial surface. We show that the ablation of the mouse uroplakin III (UPIII) gene leads to overexpression, defective glycosylation, and abnormal targeting of uroplakin Ib, the presumed partner of UPIII. The UPIII-depleted urothelium features small plaques, becomes leaky, and has enlarged ureteral orifices resulting in the back flow of urine, hydronephrosis, and altered renal function indicators. Thus, UPIII is an integral subunit of the urothelial plaque and contributes to the permeability barrier function of the urothelium, and UPIII deficiency can lead to global anomalies in the urinary tract. The ablation of a single urothelial-specific gene can therefore cause primary vesicoureteral reflux (VUR), a hereditary disease affecting approximately 1% of pregnancies and representing a leading cause of renal failure in infants. The fact that VUR caused by UPIII deletion seems distinct from that caused by the deletion of angiotensin receptor II gene suggests the existence of VUR subtypes. Mutations in multiple gene, including some that are urothelial specific, may therefore cause different subtypes of primary reflux. Studies of VUR in animal models caused by well-defined genetic defects should lead to improved molecular classification, prenatal diagnosis, and therapy of this important hereditary problem.

Animals↗
PubMed2000

CLED: a calcium-linked protein associated with early epithelial differentiation.

Although it has been well established that Ca(2+) plays a key role in triggering keratinocyte differentiation, relatively little is known about the molecules that mediate this signaling process. By analyzing a bovine corneal epithelial subtraction cDNA library, we have identified a novel gene that we named CLED (calcium-linked epithelial differentiation), which encodes a messenger RNA present in all stratified squamous epithelia, hair follicle, the bladder transitional epithelium, and small intestinal epithelium. The deduced amino acid sequence of CLED, based on a bovine partial cDNA and its full-length, human and mouse homologues that have been described only as ESTs, contains 2 EF-hand Ca(2+)-binding domains, a myristoylation motif, and several potential protein kinase phosphorylation sites; the CLED protein is therefore related to the S100 protein family. In all stratified squamous epithelia, the CLED message is associated with the intermediate cell layers. Similar CLED association with cells that are above the proliferative compartment but below the terminally differentiated compartment is seen in hair follicle, bladder, and small intestinal epithelia. The only exception is corneal epithelium, where CLED is expressed in both basal and intermediate cells. The presence of CLED in corneal epithelial basal cells, but not in the adjacent limbal basal (stem) cells, provides additional, strong evidence for the unique lateral heterogeneity of the limbal/corneal epithelium. These results suggest that CLED, via Ca(2+)-related mechanisms, may play a role in the epithelial cell's commitment to undergo early differentiation, and that its down-regulation is required before the cells can undergo the final stages of terminal differentiation.

Animals↗
PubMed2000

Involvement of follicular stem cells in forming not only the follicle but also the epidermis.

The location of follicular and epidermal stem cells in mammalian skin is a crucial issue in cutaneous biology. We demonstrate that hair follicular stem cells, located in the bulge region, can give rise to several cell types of the hair follicle as well as upper follicular cells. Moreover, we devised a double-label technique to show that upper follicular keratinocytes emigrate into the epidermis in normal newborn mouse skin, and in adult mouse skin in response to a penetrating wound. These findings indicate that the hair follicle represents a major repository of keratinocyte stem cells in mouse skin, and that follicular bulge stem cells are potentially bipotent as they can give rise to not only the hair follicle, but also the epidermis.

Animals↗
PubMed2000

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.

Animals↗
PubMed2000

Transforming growth factor-beta is an autocrine mitogen for a novel androgen-responsive murine prostatic smooth muscle cell line, PSMC1.

A prostatic smooth muscle cell line (PSMC1) was established from the dorsolateral prostate of p53 null mice. The cell line is nontumorigenic when inoculated subcutaneously, under the renal capsule or intraprostatically in syngeneic mice. These cells express alpha-smooth muscle actin (alpha-SMA), indicating their smooth muscle origin, and TGF-beta significantly enhances expression of alpha-SMA. The cells express both androgen receptor (AR) mRNA and protein, and respond mitogenically to physiological concentrations of androgens. PSMC1 cells produce significant amounts of TGF-beta, which stimulates growth by an autocrine mechanism. Dihydrotestosterone (DHT) increases proliferation of PSMC1 cells by promoting TGF-beta secretion. Considering the significant inhibitory effect of TGF-beta on prostatic epithelial cells and its stimulatory effect on the PSMC1 cells, we postulate that TGF-beta produced by prostatic smooth muscle cells may have a paracrine effect on the prostatic epithelium. We also postulate that TGF-beta may be involved in the etiology of benign prostatic hyperplasia (BPH) by stimulating excessive stromal proliferation. Line PSMC1 is the first reported androgen-responsive murine smooth muscle cell line. It will be useful for in vivo and in vitro experiments to study the mechanisms of androgen action on prostatic stroma and for delineating the interactions that occur between prostatic smooth muscle and epithelium that may lead to prostatic diseases such as BPH.

Androgens↗
PubMed2000

Serpins in the human hair follicle.

Proteinases and their inhibitors are very likely to function as mediators or regulators of the hair growth cycle. Very little information is currently available, however, regarding the specific inhibitors present in human hair follicles at defined stages of their growth cycle. In this study we have analyzed two proteinase inhibitors, plasminogen activator inhibitor type 2 and protease nexin 1, in human hair follicles using in situ hybridization and/or immunohistochemistry. Protease nexin 1 mRNA was found only in the mesenchymal population of the hair follicle, i.e., the follicular papilla cells, during the anagen but not the catagen phase. In contrast, plasminogen activator inhibitor type 2 was localized to several epithelial populations in the follicle: the more differentiated cells of the infundibulum; the companion layer in anagen follicles; and the single layer of outer root sheath cells directly abutting the club hair in telogen follicles. At least some of the plasminogen activator inhibitor type 2 in human follicles appears to be in the relaxed form, as evidenced by strong staining with an antibody that is specific for this form of the inhibitor. This suggests that plasminogen activator inhibitor type 2 interacts with and is cleaved by an endogenous follicular proteinase and supports a constitutive role for this inhibitor in human follicular epithelia.

Amyloid beta-Protein Precursor↗
PubMed1999

Urothelium-specific expression of an oncogene in transgenic mice induced the formation of carcinoma in situ and invasive transitional cell carcinoma.

Although many genetic alterations are known to be associated with human transitional cell carcinoma (TCC) of the urinary bladder, relatively little is known about the roles of these molecular defects, singular or in combination, in bladder tumorigenesis. We have developed a transgenic mouse model of bladder tumorigenesis using a 3.6-kb promoter of uroplakin II gene to drive the urotheliums-specific expression of oncogenes. In this study, we demonstrate that transgenic mice bearing a low copy number of SV40T transgene developed bladder carcinoma in situ (CIS), whereas those bearing high copies developed CIS as well as invasive and metastatic TCCs. These results indicate that the SV40T inactivation of p53 and retinoblastoma gene products, defects frequently found in human bladder CIS and invasive TCCs, can cause the aggressive form of TCC. Our results also provide experimental proof that CIS is a precursor of invasive TCCs, thus supporting the concept of two distinct pathways of bladder tumorigenesis (papillary versus CIS/invasive TCC). This transgenic system can be used for the systematic dissection of the roles of individual or combinations of specific molecular events in bladder tumorigenesis.

Animals↗
PubMed1999

Identification of a cytosolic NADP+-dependent isocitrate dehydrogenase that is preferentially expressed in bovine corneal epithelium. A corneal epithelial crystallin.

Recently, metabolic enzymes have been observed in both the lens and corneal epithelium at levels greatly exceeding what is necessary for normal metabolic functions. These proteins have been termed taxon-specific crystallins and are thought to play a role in maintaining tissue transparency. We report here that cytosolic NADP+-dependent isocitrate dehydrogenase (ICDH) represents a new corneal crystallin. Using suppression subtractive hybridization, we identified a gene (with a deduced amino acid sequence that showed 94% identity to rat cytosolic NADP+-dependent ICDH) that is preferentially expressed in bovine corneal epithelium. Northern blots established that its mRNA level in the corneal epithelium was 31-, 39-, 133-, 230-, and 929-fold more than in the liver, bladder epithelium, stomach epithelium, brain, and heart, respectively. This mRNA was detected primarily in corneal epithelial basal cells by in situ hybridization. SDS-polyacrylamide gel electrophoresis, two-dimensional gel analysis, and Western blotting showed that this protein was overexpressed in the corneal epithelium, constituting approximately 13% of the total soluble bovine corneal epithelial proteins. Enzyme assays showed a corresponding overabundance of this protein in bovine corneal epithelium. Taken together, these data indicate that bovine cytosolic ICDH fulfills the criteria for a corneal epithelial crystallin and may be involved in maintaining corneal epithelial transparency.

Amino Acid Sequence↗
PubMed1999

Primary uroepithelial cultures. A model system to analyze umbrella cell barrier function.

Despite almost 25 years of effort, the development of a highly differentiated and functionally equivalent cell culture model of uroepithelial cells has eluded investigators. We have developed a primary cell culture model of rabbit uroepithelium that consists of an underlying cell layer that interacts with a collagen substratum, an intermediate cell layer, and an upper cell layer of large (25-100 micrometer) superficial cells. When examined at the ultrastructural level, the superficial cells formed junctional complexes and had an asymmetric unit membrane, a hallmark of terminal differentiation in bladder umbrella cells. These cultured "umbrella" cells expressed uroplakins and a 27-kDa uroepithelial specific antigen that assembled into detergent-resistant asymmetric unit membrane particles. The cultures had low diffusive permeabilities for water (2.8 x 10(-4) cm/s) and urea (3.0 x 10(-7) cm/s) and high transepithelial resistance (>8000 Omega cm2) was achieved when 1 mM CaCl2 was included in the culture medium. The cell cultures expressed an amiloride-sensitive sodium transport pathway and increases in apical membrane capacitance were observed when the cultures were osmotically stretched. The described primary rabbit cell culture model mimics many of the characteristics of uroepithelium found in vivo and should serve as a useful tool to explore normal uroepithelial function as well as dysfunction as a result of disease.

Animals↗
PubMed1999

Three-dimensional analysis of the 16 nm urothelial plaque particle: luminal surface exposure, preferential head-to-head interaction, and hinge formation.

The luminal surface of mouse urothelium in contact with the urine is almost entirely covered with plaques consisting of uroplakin-containing particles that form p6 hexagonal crystals with a center-to-center distance of 16 nm. A combination of quick-freeze/deep-etch images and our previous negative staining data indicate that the head domain of the uroplakin particle, which is exposed without an extensive glycocalyx shield, interacts closely with the head domains of the neighboring particles, while the membrane-embedded tail domains are farther apart; and that urothelial particles and plaques are not rigid structures as they can change their configuration in response to mechanical perturbations. Based on these data, we have constructed three-dimensional models depicting the structural organization of urothelial particles and plaques. Our models suggest that the head-to-head interaction may play a key role in determining the shape and size of the urothelial plaques. These models can explain many properties of urothelial plaques including their unique shape, detergent-insolubility, and morphological changes during vesicle maturation.

Animals↗