Progressive renal papillary calcification and ureteral stone formation in mice deficient for Tamm-Horsfall protein

Mammalian urine contains a range of macromolecule proteins that play critical roles in renal stone formation, among which Tamm-Horsfall protein (THP) is by far the most abundant. While THP is a potent inhibitor of crystal aggregation in vitro and its ablation in vivo predisposes one of the two existing mouse models to spontaneous intrarenal calcium crystallization, key controversies remain regarding the role of THP in nephrolithiasis. By carrying out a long-range follow-up of more than 250 THP-null mice and their wild-type controls, we demonstrate here that renal calcification is a highly consistent phenotype of the THP-null mice that is age and partially gene dosage dependent, but is gender and genetic background independent. Renal calcification in THP-null mice is progressive, and by 15 mo over 85% of all the THP-null mice develop spontaneous intrarenal crystals. The crystals consist primarily of calcium phosphate in the form of hydroxyapatite, are located more frequently in the interstitial space of the renal papillae than intratubularly, particularly in older animals, and lack accompanying inflammatory cell infiltration. The interstitial deposits of hydroxyapatite observed in THP-null mice bear strong resemblances to the renal crystals found in human kidneys bearing idiopathic calcium oxalate stones. Compared with 24-h urine from the wild-type mice, that of THP-null mice is supersaturated with brushite (calcium phosphate), a stone precursor, and has reduced urinary excretion of citrate, a stone inhibitor. While less frequent than renal calcinosis, renal pelvic and ureteral stones and hydronephrosis occur in the aged THP-null mice. These results provide direct in vivo evidence indicating that normal THP plays an important role in defending the urinary system against calcification and suggest that reduced expression and/or decreased function of THP could contribute to nephrolithiasis.

Temporally and spatially controllable gene expression and knockout in mouse urothelium

Urothelium that lines almost the entire urinary tract performs important functions and is prone to assaults by urinary microbials, metabolites, and carcinogens. To improve our understanding of urothelial physiology and disease pathogenesis, we sought to develop two novel transgenic systems, one that would allow inducible and urothelium-specific gene expression, and another that would allow inducible and urothelium-specific knockout. Toward this end, we combined the ability of the mouse uroplakin II promoter (mUPII) to drive urothelium-specific gene expression with a versatile tetracycline-mediated inducible system. We found that, when constructed under the control of mUPII, only a modified, reverse tetracycline trans-activator (rtTA-M2), but not its original version (rtTA), could efficiently trans-activate reporter gene expression in mouse urothelium on doxycycline (Dox) induction. The mUPII/rtTA-M2-inducible system retained its strict urothelial specificity, had no background activity in the absence of Dox, and responded rapidly to Dox administration. Using a reporter gene whose expression was secondarily controlled by histone remodeling, we were able to identify, colocalize with 5-bromo-2-deoxyuridine incorporation, and semiquantify newly divided urothelial cells. Finally, we established that, when combined with a Cre recombinase under the control of the tetracycline operon, the mUPII-driven rtTA-M2 could inducibly inactivate any gene of interest in mouse urothelium. The establishment of these two new transgenic mouse systems enables the manipulation of gene expression and/or inactivation in adult mouse urothelium at any given time, thus minimizing potential compensatory effects due to gene overexpression or loss and allowing more accurate modeling of urothelial diseases than previously reported constitutive systems.

Abstract 1475: Molecular mechanisms of “SNAIL” activation in invasive bladder cancer of p53/Rb double knockout mice exposed to chemical carcinogen BBN

Epithelial-mesenchymal transition (EMT) plays a central role in empowering tumor cells to acquire invasive properties. It appears that EMT is not a random process but is highly regulated by transcription regulators. Of particular interests are the transcription repressors that inhibit the expression of cell-cell junction proteins, such as E-cadherin. Recent in vitro studies indicate that increased signaling of “Snail” the transcription repressor per se is sufficient to confer an invasive phenotype on otherwise non-invasive cells. Despite these recent advances, relatively little is known about the mechanisms of Snail activation in invasive bladder cancer. In this study, using p53 and Rb double knockout mice exposed the carcinogen BBN, we examined the expression levels of “Snail” and E-cadherin protein in bladder cancer tissues. Findings from both immunohistochemical and immunofluorescence staining revealed overexpression of Snail in the stromal as well as in the tumor regions. Although a complete loss of E-cadherin was not evident in all the tumors examined, most of the sections analyzed showed a moderate to weak expression of E-cadherin. This is consistent with the findings from Western blot analysis of the protein lysate from human bladder cancer cells with varying status of p53 and Rb. To explore the mechanism of Snail activation leading invasive bladder cancer, we transfected the human bladder cancer cells with siRNAs for Snail, p53 and Rb. Our findings were consistent with the in vivo studies, in that Western blot analysis revealed only a moderate inhibition of E-cadherin in p53 or Rb knockout cells. However, the Snail knockout cells showed less invasiveness (migration) compared to the control, and was associated with a significant inhibition of E-cadherin expression. To investigate further on the possible role of TGFβ on Snail activation, we treated the bladder cancer cells with TGFβ for 12h and examined the effect on Smad 4 and 7, Snail and E-cadherin expression. Activation of Snail was associated the expression of vimentin, a typical marker of mesenchymal cells, and cytokeratins of epithelial cells suggesting TGFβ mediated Snail activation. Finally, we extended our analysis to determine the role of noncoding microRNAs that act as post-transcriptional repressors. To this end we performed microRNA profiling of J82 and HT1376 bladder cancer cells using human miRNA arrays. Findings on differential expression of potential microRNA network involved in the regulation of TGFβ, Snail and E-cadherin expression associated with urothelial tumor plasticity are discussed. Overall findings from these studies suggest possible mechanism(s) of Snail activation and E-cadherin regulation in invasive bladder cancer for the first time and may pave the way for novel therapeutic approaches.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1475.

Deficiency of pRb family proteins and p53 in invasive urothelial tumorigenesis

Defects in pRb tumor suppressor pathway occur in approximately 50% of the deadly muscle-invasive urothelial carcinomas in humans and urothelial carcinoma is the most prevalent epithelial cancer in long-term survivors of hereditary retinoblastomas caused by loss-of-function RB1 mutations. Here, we show that conditional inactivation of both RB1 alleles in mouse urothelium failed to accelerate urothelial proliferation. Instead, it profoundly activated the p53 pathway, leading to extensive apoptosis, and selectively induced pRb family member p107. Thus, pRb loss triggered multiple fail-safe mechanisms whereby urothelial cells evade tumorigenesis. Additional loss of p53 in pRb-deficient urothelial cells removed these p53-dependent tumor barriers, resulting in late-onset hyperplasia, umbrella cell nuclear atypia, and rare-occurring low-grade, superficial papillary bladder tumors, without eliciting invasive carcinomas. Importantly, mice deficient in both pRb and p53, but not those deficient in either protein alone, were highly susceptible to subthreshold carcinogen exposure and developed invasive urothelial carcinomas that strongly resembled the human counterparts. The invasive lesions had a marked reduction of p107 but not p130 of the pRb family. Our data provide compelling evidence, indicating that urothelium, one of the slowest cycling epithelia, is remarkably resistant to transformation by pRb or p53 deficiency; that concurrent loss of these two tumor suppressors is necessary but insufficient to initiate urothelial tumorigenesis along the invasive pathway; that p107 may play a critical role in suppressing invasive urothelial tumor formation; and that replacing/restoring the function of pRb, p107, or p53 could be explored as a potential therapeutic strategy to block urothelial tumor progression.

Biology of urothelial tumorigenesis: insights from genetically engineered mice

Urothelium, one of the slowest cycling epithelia in the body, embodies a unique biological context for cellular transformation. Introduction of oncogenes into or removing tumor suppressor genes from the urothelial cells or a combination of both using the transgenic and/or knockout mouse approaches has provided useful insights into the molecular mechanisms of urothelial transformation and tumorigenesis. It is becoming increasingly clear that over-activation of the receptor tyrosine kinase (RTK) pathway, as exemplified by the constitutively activated Ha-ras oncogene, is both necessary and sufficient to initiate the low-grade, non-invasive urothelial carcinomas. Dosage of the mutated Ha-ras, but not concurrent inactivation of pro-senescence molecules p16Ink4a and p19Arf, dictates whether and when the low-grade urothelial carcinomas arise. Inactivation of both p53 and pRb, a prevailing paradigm previously proposed for muscle-invasive urothelial tumorigenesis, is found to be necessary but insufficient to initiate this urothelial carcinoma variant. Instead, downregulation in p53/pRb co-deficient urothelial cells of p107, a pRb family member, is associated with the genesis of the muscle-invasive bladder cancers. p53 deficiency also seems to be capable of cooperating with that of PTEN in eliciting invasive urothelial carcinomas. The genetically engineered mice have improved the molecular definition of the divergent pathways of urothelial tumorigenesis and progression, helped delineate the intricate crosstalk among different genetic alterations within a urothelium-specific context, identified new prognostic markers and novel therapeutic targets potentially applicable for clinical intervention, and provided in vivo platforms for testing preventive strategies of bladder cancer.

Urothelial expression of neuropilins and VEGF receptors in control and interstitial cystitis patients

Interstitial cystitis (IC) is a chronic and painful bladder syndrome of unknown cause with no reliable biological marker or effective therapy. Vascular endothelial growth factor (VEGF), which plays a key role in bladder inflammation, is closely associated with the vascular alterations observed in patients with IC. However, our recent findings of VEGF receptors (VEGF-Rs) and VEGF coreceptors on nonendothelial cells in human and mouse urothelium suggest that additional VEGF targets and functions are possible in IC bladders. We report here that VEGF-Rs and coreceptors (neuropilins; NRP) are strongly expressed in both the human bladder urothelium and in the human bladder cancer cell line (J82) and that the expression of NRP2 and VEGF-R1 is significantly downregulated in IC compared with control subjects. In addition, treatment of J82 cells with bacillus Calmette-Guérin (BCG), a novel treatment strategy for IC, upregulates the messages for NRPs and VEGF-Rs. Furthermore, intravesical instillation of an internalizable VEGF fluorescent tracer (scVEGF/Cy5.5) into mouse urinary bladders results in a marked ligand accumulation in the urothelium and bladder parenchyma, indicating that urothelial VEGF-Rs are functionally active and capable of ligand interaction and internalization. Our results suggest that the VEGF pathway is altered in IC, that urinary VEGF may gain access to the bladder wall via these receptors, and that BCG treatment may replenish the missing VEGF-Rs/NRP receptors. Together, these results suggest that levels of NRPs, VEGF-Rs, and VEGF are new putative markers for the diagnosis of IC and that modulating these receptors can be exploited as therapeutic strategies.

Tamm-Horsfall protein protects the kidney from ischemic injury by decreasing inflammation and altering TLR4 expression

Tamm-Horsfall protein (THP) is a glycoprotein with unclear functions expressed exclusively in thick ascending limbs (TAL) of the kidney. Its role in ischemic acute kidney injury is uncertain, with previous data suggesting a possible negative effect by enhancing cast formation and promoting inflammation. Using a recently characterized THP knockout mouse (THP-/-), we investigated the role of THP in renal ischemia-reperfusion injury (IRI). In wild-type mice (THP+/+), THP expression was increased by injury. THP-/- mice developed more functional and histological renal damage after IRI compared with THP+/+. THP-/- kidneys showed more inflammation and tubular necrosis. Cast formation correlated with the severity of injury and was independent of THP presence. THP absence was associated with a more necrotic, rather than apoptotic, phenotype of cell death. The outer medulla was predominantly affected, where significant interstitial neutrophil infiltration was detected in proximity to injured S3 proximal tubular segments and TAL. This coincided with an enhanced expression of the innate immunity receptor Toll-like receptor 4 (TLR4) in S3 segments of THP-/- compared with THP+/+ mice. Specifically, a basolateral S3 expression of TLR4 was more evident in THP-/- kidneys compared with a more apical distribution in THP+/+. Such basolateral location for TLR4 allows a greater interaction with proinflammatory ligands present in the interstitium during ischemia. In conclusion, we are showing a completely novel role for a very old protein in the setting of renal injury. Our data suggest that THP stabilizes the outer medulla in the face of injury by decreasing inflammation, possibly through an effect on TLR4.

VEGF receptors and neuropilins are expressed in the urothelial and neuronal cells in normal mouse urinary bladder and are upregulated in inflammation

Recent evidence supports a role for vascular endothelium growth factor (VEGF) signaling in bladder inflammation. However, it is not clear what bladder cells are targeted by VEGF. Therefore, we determined the nature of cells responding to VEGF in normal and inflamed bladders by tagging such cells in vivo with a targeted fluorescent tracer, scVEGF/Cy, an engineered single-chain VEGF labeled with Cy5.5 dye, which identifies cells with accessible and functionally active VEGF receptors. Inflammation was induced by intravesical instillation of PAR-activating peptides or BCG. In vivo NIRF imaging with intravenously injected scVEGF/Cy revealed accumulation of the tracer in the control mouse bladder and established that inflammation increased the steady-state levels of tracer uptake. Ex vivo colocalization of Cy5.5 dye revealed that in normal and at a higher level in inflamed bladder, accumulation of scVEGF/Cy occurs in both urothelial and ganglial cells, expressing VEGF receptors VEGFR-1 and VEGFR-2, as well as VEGF coreceptors neuropilins (NRP) NRP1 and NRP2. PCR results indicate that the messages for VEGF-Rs and NRPs are present in the bladder mucosa and ChIP/QPCR analysis indicated that inflammation induced upregulation of genes encoding VEGFRs and NRPs. Our results strongly suggest new and blossoming VEGF-driven processes in bladder urothelial cells and ganglia in the course of inflammation. We expect that molecular imaging of the VEGF pathway in the urinary tract by receptor-mediated cell tagging in vivo will be useful for clinical diagnosis and therapeutic monitoring, and will help to accelerate the development of bladder-targeting drugs and treatments.

Molecular networks discriminating mouse bladder responses to intravesical bacillus Calmette-Guerin (BCG), LPS, and TNF-alpha

Background

Despite being a mainstay for treating superficial bladder carcinoma and a promising agent for interstitial cystitis, the precise mechanism of Bacillus Calmette-Guerin (BCG) remains poorly understood. It is particularly unclear whether BCG is capable of altering gene expression in the bladder target organ beyond its well-recognized pro-inflammatory effects and how this relates to its therapeutic efficacy. The objective of this study was to determine differentially expressed genes in the mouse bladder following chronic intravesical BCG therapy and to compare the results to non-specific pro inflammatory stimuli (LPS and TNF-α). For this purpose, C57BL/6 female mice received four weekly instillations of BCG, LPS, or TNF-α. Seven days after the last instillation, the urothelium along with the submucosa was removed from detrusor muscle and the RNA was extracted from both layers for cDNA array experiments. Microarray results were normalized by a robust regression analysis and only genes with an expression above a conditional threshold of 0.001 (3SD above background) were selected for analysis. Next, genes presenting a 3-fold ratio in regard to the control group were entered in Ingenuity Pathway Analysis (IPA) for a comparative analysis in order to determine genes specifically regulated by BCG, TNF-α, and LPS. In addition, the transcriptome was precipitated with an antibody against RNA polymerase II and real-time polymerase chain reaction assay (Q-PCR) was used to confirm some of the BCG-specific transcripts.

Results

Molecular networks of treatment-specific genes generated several hypotheses regarding the mode of action of BCG. BCG-specific genes involved small GTPases and BCG-specific networks overlapped with the following canonical signaling pathways: axonal guidance, B cell receptor, aryl hydrocarbon receptor, IL-6, PPAR, Wnt/β-catenin, and cAMP. In addition, a specific detrusor network expressed a high degree of overlap with the development of the lymphatic system. Interestingly, TNF-α-specific networks overlapped with the following canonical signaling pathways: PPAR, death receptor, and apoptosis. Finally, LPS-specific networks overlapped with the LPS/IL-1 mediated inhibition of RXR. Because NF-kappaB occupied a central position in several networks, we further determined whether this transcription factor was part of the responses to BCG. Electrophoretic mobility shift assays confirmed the participation of NF-kappaB in the mouse bladder responses to BCG. In addition, BCG treatment of a human urothelial cancer cell line (J82) also increased the binding activity of NF-kappaB, as determined by precipitation of the chromatin by a NF-kappaB-p65 antibody and Q-PCR of genes bearing a NF-kappaB consensus sequence. Next, we tested the hypothesis of whether small GTPases such as LRG-47 are involved in the uptake of BCG by the bladder urothelium.

Conclusion

As expected, BCG treatment induces the transcription of genes belonging to common pro-inflammatory networks. However, BCG also induces unique genes belonging to molecular networks involved in axonal guidance and lymphatic system development within the bladder target organ. In addition, NF-kappaB seems to play a predominant role in the bladder responses to BCG therapy. Finally, in intact urothelium, BCG-GFP internalizes in LRG-47-positive vesicles.

These results provide a molecular framework for the further study of the involvement of immune and nervous systems in the bladder responses to BCG therapy.

Renal calcinosis and stone formation in mice lacking osteopontin, Tamm-Horsfall protein, or both

Although often supersaturated with mineral salts such as calcium phosphate and calcium oxalate, normal urine possesses an innate ability to keep them from forming harmful crystals. This inhibitory activity has been attributed to the presence of urinary macromolecules, although controversies abound regarding their role, or lack thereof, in preventing renal mineralization. Here, we show that 10% of the mice lacking osteopontin (OPN) and 14.3% of the mice lacking Tamm-Horsfall protein (THP) spontaneously form interstitial deposits of calcium phosphate within the renal papillae, events never seen in wild-type mice. Lack of both proteins causes renal crystallization in 39.3% of the double-null mice. Urinalysis revealed elevated concentrations of urine phosphorus and brushite (calcium phosphate) supersaturation in THP-null and OPN/THP-double null mice, suggesting that impaired phosphorus handling may be linked to interstitial papillary calcinosis in THP- but not in OPN-null mice. In contrast, experimentally induced hyperoxaluria provokes widespread intratubular calcium oxalate crystallization and stone formation in OPN/THP-double null mice, while completely sparing the wild-type controls. Whole urine from OPN-, THP-, or double-null mice all possessed a dramatically reduced ability to inhibit the adhesion of calcium oxalate monohydrate crystals to renal epithelial cells. These data establish OPN and THP as powerful and functionally synergistic inhibitors of calcium phosphate and calcium oxalate crystallization in vivo and suggest that defects in either molecule may contribute to renal calcinosis and stone formation, an exceedingly common condition that afflicts up to 12% males and 5% females.

Lymphatic vessel density and function in experimental bladder cancer

BACKGROUND

The lymphatics form a second circulatory system that drains the extracellular fluid and proteins from the tumor microenvironment, and provides an exclusive environment in which immune cells interact and respond to foreign antigen. Both cancer and inflammation are known to induce lymphangiogenesis. However, little is known about bladder lymphatic vessels and their involvement in cancer formation and progression.

METHODS

A double transgenic mouse model was generated by crossing a bladder cancer-induced transgenic, in which SV40 large T antigen was under the control of uroplakin II promoter, with another transgenic mouse harboring a lacZ reporter gene under the control of an NF-kappaB-responsive promoter (kappaB-lacZ) exhibiting constitutive activity of beta-galactosidase in lymphatic endothelial cells. In this new mouse model (SV40-lacZ), we examined the lymphatic vessel density (LVD) and function (LVF) during bladder cancer progression. LVD was performed in bladder whole mounts and cross-sections by fluorescent immunohistochemistry (IHC) using LYVE-1 antibody. LVF was assessed by real-time in vivo imaging techniques using a contrast agent (biotin-BSA-Gd-DTPA-Cy5.5; Gd-Cy5.5) suitable for both magnetic resonance imaging (MRI) and near infrared fluorescence (NIRF). In addition, IHC of Cy5.5 was used for time-course analysis of co-localization of Gd-Cy5.5 with LYVE-1-positive lymphatics and CD31-positive blood vessels.

RESULTS

SV40-lacZ mice develop bladder cancer and permitted visualization of lymphatics. A significant increase in LVD was found concomitantly with bladder cancer progression. Double labeling of the bladder cross-sections with LYVE-1 and Ki-67 antibodies indicated cancer-induced lymphangiogenesis. MRI detected mouse bladder cancer, as early as 4 months, and permitted to follow tumor sizes during cancer progression. Using Gd-Cy5.5 as a contrast agent for MRI-guided lymphangiography, we determined a possible reduction of lymphatic flow within the tumoral area. In addition, NIRF studies of Gd-Cy5.5 confirmed its temporal distribution between CD31-positive blood vessels and LYVE-1 positive lymphatic vessels.

CONCLUSION

SV40-lacZ mice permit the visualization of lymphatics during bladder cancer progression. Gd-Cy5.5, as a double contrast agent for NIRF and MRI, permits to quantify delivery, transport rates, and volumes of macromolecular fluid flow through the interstitial-lymphatic continuum. Our results open the path for the study of lymphatic activity in vivo and in real time, and support the role of lymphangiogenesis during bladder cancer progression.

The histone deacetylase inhibitor belinostat (PXD101) suppresses bladder cancer cell growth in vitro and in vivo

BACKGROUND

Treatment options for patients with recurrent superficial bladder cancer are limited, necessitating aggressive exploration of new treatment strategies that effectively prevent recurrence and progression to invasive disease. We assessed the effects of belinostat (previously PXD101), a novel histone deacetylase inhibitor, on a panel of human bladder cancer cell lines representing superficial and invasive disease, and on a transgenic mouse model of superficial bladder cancer.

METHODS

Growth inhibition and cell cycle distribution effect of belinostat on 5637, T24, J82, and RT4 urothelial lines were assessed. Ha-ras transgenic mice with established superficial bladder cancer were randomized to receive either belinostat or vehicle alone, and assessed for bladder weight, hematuria, gene expression profiling, and immunohistochemistry (IHC).

RESULTS

Belinostat had a significant linear dose-dependent growth inhibition on all cell lines (IC50 range of 1.0-10.0 microM). The 5637 cell line, which was derived from a superficial papillary tumor, was the most sensitive to treatment. Belinostat (100 mg/kg, intraperitoneal, 5 days each week for 3 weeks) treated mice had less bladder weight (p < 0.05), and no hematuria compared with 6/10 control mice that developed at least one episode. IHC of bladder tumors showed less cell proliferation and a higher expression of p21WAF1 in the belinostat-treated mice. Gene expression profile analysis revealed 56 genes significantly different in the treated group; these included the upregulation of p21WAF1, induction of core histone deacetylase (HDAC), and cell communication genes.

CONCLUSION

Our data demonstrate that belinostat inhibits bladder cancer and supports the clinical evaluation of belinostat for the treatment of patients with superficial bladder cancer.

Persistent uroplakin expression in advanced urothelial carcinomas: implications in urothelial tumor progression and clinical outcome

As the terminal differentiation products of human urothelium, uroplakins (UPs) would be expected to diminish during urothelial tumorigenesis. Surprisingly, recent studies found UPs to be retained even by well-advanced urothelial carcinomas, suggesting that the loss of UPs does not strictly parallel urothelial transformation. Little is known, however, about whether the status of UPs is associated with a particular pathologic parameter, the tumor's biological behavior, or patient outcome. Here we assessed UP expression by immunohistochemistry on tissue arrays from 285 patients with bladder urothelial carcinomas or nontumor conditions. UPs were expressed in all 9 normal urothelial specimens, 63 of 74 (85%) patients with non-muscle-invasive urothelial carcinomas on transurethral resection, 104 of 202 (51.5%) patients who underwent radical cystectomy for advanced urothelial carcinomas, and 33 of 50 (66%) lymph node metastases. Normally associated with urothelial apical surface, UPs were localized aberrantly in tumors, including microluminal, basal-laminal, cytoplasmic, or uniform patterns. In non-muscle-invasive diseases, there was no association between UP expression and disease recurrence, progression, or mortality. In contrast, in invasive diseases, absent UP expression was significantly associated with advanced pathologic stage, lymph node metastases, disease recurrence, and bladder cancer-specific mortality (P = .042, P = .035, P = .023, and P = .022, respectively) in univariate analyses. Furthermore, UP status was independent of key cell-cycle regulators, including p53, pRb, p27, and cyclin D1, thus excluding a functional link between these 2 groups of proteins. Our data demonstrate for the first time that persistent UP expression is associated with a favorable clinical outcome and that UPs may be used as adjunct markers for predicting the prognoses of patients with invasive and metastatic bladder carcinomas. Our results also suggest that UP-positive and -negative carcinomas have different clonal origins or may be derived from different cancer stem cells.

Decreased DOC-2/DAB2 Expression in Urothelial Carcinoma of the Bladder

PURPOSE

DOC-2/DAB2 (differentially expressed in ovarian carcinoma-2/disabled-2), a potential tumor suppressor gene, is underexpressed in several cancers. Little is known about the expression of this gene in urothelial carcinoma of the bladder (UCB). We profiled DOC-2/DAB2 expression in mouse and human normal and neoplastic urothelia.

EXPERIMENTAL DESIGN

Immunohistochemical staining for DOC-2/DAB2 was carried out on tissue specimens from two transgenic mouse models with urothelium-specific molecular alterations and on a tissue microarray containing cores from 9 normal controls, 44 patients who underwent transurethral resection of the bladder tumor (TURBT), 195 patients who underwent radical cystectomy for UCB, and 39 lymph nodes with metastatic UCB.

RESULTS

Normal mouse urothelium stained uniformly with DOC-2/DAB2. Weaker staining was observed in low-grade, superficial papillary bladder tumors from transgenic mice harboring constitutively active Ha-Ras, whereas carcinoma in situ-like lesions and high-grade bladder tumors from transgenic mice expressing a SV40 T antigen completely lacked DOC-2/DAB2 expression. In human tissues, DOC-2/DAB2 expression was decreased in 11% of normal bladder specimens, 59% of TURBT specimens, 65% of radical cystectomy specimens, and 77% of the metastatic lymph node specimens. Decreased DOC-2/DAB2 expression was associated with advanced pathologic stage (P = 0.023), lymph node metastases (P = 0.050), and lymphovascular invasion (P < 0.001). In univariable, but not in multivariable analysis, decreased DOC-2/DAB2 was associated with an increased probability of bladder cancer recurrence (log-rank test, P = 0.020) and bladder cancer-specific mortality (log-rank test, P = 0.023).

CONCLUSIONS

Decreased DOC-2/DAB2 expression seems to occur early in bladder tumorigenesis and becomes more prominent in advanced stages of UCB.

Clinical and molecular survey in 124 Chinese patients with Leigh or Leigh-like syndrome

Leigh syndrome is the most common mitochondrial disorder in children characterized by necrotic lesions in the central nervous system. Both mitochondrial DNA (mtDNA) and nuclear DNA defects in the mitochondrial respiratory chain can lead to this disease. To characterize the clinical and genetic traits of Leigh or Leigh-like syndrome patients in China, 124 unrelated cases were collected between 1992 and 2005. Seventy-seven cases (62.1%) met the typical criteria of Leigh syndrome, including symmetrical bilateral abnormal signals in the basal ganglia, thalamus and brain stem, etc. Other cases (37.9%) belonged to Leigh-like syndrome with atypical clinical or radiological manifestations. Late-onset patients accounted for 20.2%, which is more than previously reported. Movement disorder was the most common symptoms in our patients. Thirty-two patients (25.8%) were confirmed to carry mutant genes. Among them, six cases (4.8%) have been demonstrated to have point mutations in mitochondrial DNA. Two separate patients were detected to have mutations on A8344G and A3243G. The T8993G point mutation was identified in one patient and T8993C in one other patient. SURF1 mutations associated with cytochrome-c oxidase deficiency were identified in 25 patients (20.2%). Four unreported variations have been identified in SURF1 gene from three patients. G604C was found in 22 patients. Only one patient had C214T mutation in the pyruvate dehydrogenase E1alpha subunit gene. In the remaining 92 patients (74.2%), a specific molecular dysfunction or underlying metabolic abnormality could not be identified.

Hyperactivation of Ha-ras oncogene, but not Ink4a/Arf deficiency, triggers bladder tumorigenesis

Although ras is a potent mitogenic oncogene, its tumorigenicity depends on cellular context and cooperative events. Here we show that low-level expression of a constitutively active Ha-ras in mouse urothelium induces simple urothelial hyperplasia that is resistant to progression to full-fledged bladder tumors even in the absence of Ink4a/Arf. In stark contrast, doubling of the gene dosage of the activated Ha-ras triggered early-onset, rapidly growing, and 100% penetrant tumors throughout the urinary tract. Tumor initiation required superseding a rate-limiting step between simple and nodular hyperplasia, the latter of which is marked by the emergence of mesenchymal components and the coactivation of AKT and STAT pathways as well as PTEN inactivation. These results indicate that overactivation of Ha-ras is both necessary and sufficient to induce bladder tumors along a low-grade, noninvasive papillary pathway, and they shed light on the recent findings that ras activation, via point mutation, overexpression, or intensified signaling from FGF receptor 3, occurs in 70%-90% of these tumors in humans. Our results highlight the critical importance of the dosage/strength of Ha-ras activation in dictating its tumorigenicity--a mechanism of oncogene activation not fully appreciated to date. Finally, our results have clinical implications, as inhibiting ras and/or its downstream effectors, such as AKT and STAT3/5, could provide alternative means to treat low-grade, superficial papillary bladder tumors, the most common tumor in the urinary system.

Early detection and measurement of urothelial tumors in mice

OBJECTIVES

To establish reliable noninvasive in vivo methods to detect, measure, and monitor experimentally induced urothelial tumors in mice.

METHODS

UPII-SV40T transgenic mice reliably develop bladder tumors by expression of simian virus 40 large T antigen specifically in bladder urothelium through the use of the uroplakin II promoter. Two wild-type and 10 UPII-SV40T transgenic mice were monitored for microhematuria two to three times weekly using dipstick analysis. A unique flat panel detector-based cone beam computed tomography (FPD-CBCT) system imaged the urinary tracts of anesthetized mice after tail vein injection of an iodinated contrast agent (Omnipaque) that is excreted in urine. Within 10 seconds, the FPD-CBCT system acquired 290 two-dimensional images, which produced three-dimensional volumes with true isotropic resolution (180 microm)3 using a filtered back projection-based modified Feldkamp reconstruction algorithm. Amira, version 3.1.1-1, for MacOSX was used for data analysis and advanced visualization of the three-dimensional reconstructed FPD-CBCT images.

RESULTS

Hematuria was present in UPII-SV40T transgenic mice at 32 days of age; the wild-type animals exhibited no hematuria. Filling defects, associated with histologically confirmed tumors, in the bladders of the UPII-SV40T transgenic mice were visualized in the reconstructed FPD-CBCT images 1 to 45 minutes after contrast agent injection. Longitudinal FPD-CBCT imaging sessions showed the tumor position, volume, and growth.

CONCLUSIONS

The combination of early detection of hematuria and high-resolution in vivo FPD-CBCT imaging of murine bladder tumors enabled accurate longitudinal assessment of tumor growth and progression in individual animals. This approach could provide an important alternative to serial sacrifice experimental designs, while refining statistical power and reducing animal use.

Distinct glycan structures of uroplakins Ia and Ib: structural basis for the selective binding of FimH adhesin to uroplakin Ia

Although it has been shown that mouse uroplakin (UP) Ia, a major glycoprotein of urothelial apical surface, can serve as the receptor for the FimH lectin adhesin of type 1-fimbriated Escherichia coli, the organism that causes a great majority of urinary tract infections, the glycan structure of this native receptor was unknown. Using a sensitive approach that combines in-gel glycosidase and protease digestions, permethylation of released glycans, and mass spectrometry, we have elucidated for the first time the native glycoform structures of the mouse UPIa receptor and those of its non-binding homolog, UPIb, and have determined the glycosylation site occupancy. UPIa presents a high level of terminally exposed mannose residues (located on Man(6)GlcNAc(2) to Man(9)GlcNAc(2)) that are capable of specifically interacting with FimH. We have shown that this property is conserved not only in the mouse uroplakins but also in cattle and, even more importantly, in human UPIa, thus establishing the concept that UPIa is a major urothelial receptor in humans and other mammals for the mannose-specific FimH variant. In contrast, our results indicate that most terminally exposed glycans of mouse UPIb are non-mannose residues, thus explaining the failure of FimH to bind to this UPIb. In cattle, on the other hand, complex carbohydrates constituted only about 20% of the UPIb N-linked glycans. Human UPIa contained exclusively high mannose glycans, and human UPIb contained only complex glycans. The drastically different carbohydrate processing of the UPIa and UPIb proteins, two closely related members of the tetraspanin family, may reflect differences in their folding and masking due to their interactions with their associated proteins, UPII and UPIIIa, respectively. Results from this study shed light on the molecular pathogenesis of urinary tract infections and may aid in the design of glyco-mimetic inhibitors for preventing and treating this disease.