Molecular analysis of PTEN and MXI1 in primary bladder carcinoma

USP13 functions as a tumor suppressor by blocking the NF-kB-mediated PTEN downregulation in human bladder cancer

Background

USP13 has been reported to be involved in the tumorigenesis of human cancers, however, its functional role and regulatory mechanisms in bladder cancer (BC) remain unclear.

Methods

q-RT-PCR was performed to examine the expression of miR-130b-3p, miR-301b-3p and USP13 in BC tissue samples. Western blot, q-RT-PCR, bioinformatic analysis and dual-luciferase reporter assay were conducted to identify the regulatory function of miR-130b-3p/301b-3p for USP13. Co-immunoprecipitation assay was performed to assess the interaction between USP13 and PTEN protein. Cell-counting-kit 8, colony formation assay and transwell assay were performed to value the proliferative, migrative and invasive capacities of BC cells in vitro. Mouse xenograft model of BC cells was established to verify the function of USP13 in vivo. Immunohistochemistry was performed to identify the protein expression of USP13, NF-kB p65 or PTEN in clinical/xenograft tumor tissues.

Results

Our present study reveals that USP13 functions as a tumor suppressor by interacting with PTEN protein and increasing its expression in bladder cancer. We found that loss of USP13 led to the downregulation of PTEN and promoted proliferative, invasive and migrative capacities of bladder cancer cells. Furthermore, we discovered that USP13 was a common target of miR-130b-3p and miR-301b-3p, and the miR-130b/301b cluster, which could be transcriptionally upregulated by NF-kB. Our data demonstrated that NF-kB activation decreased expression level of USP13 and PTEN, and promoted the tumorigenesis phenotypes of BC cells. In addition, reintroduction of USP13 partially rescued PTEN expression as well as the oncogenesis trend caused by NF-kB.

Conclusion

We reported a potential regulatory loop that the NF-kB-induced miR-130b/301b overexpression decreased USP13 expression and subsequently resulted in the downregulation of PTEN protein and promoted tumorigenesis of bladder cancer. Moreover, NF-kB-mediated PTEN downregulation is very likely to facilitate the full activation of NF-kB.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1262-4) contains supplementary material, which is available to authorized users.

The Current Status and Future Role of the Phosphoinositide 3 Kinase/AKT Signaling Pathway in Urothelial Cancer: An Old Pathway in the New Immunotherapy Era

The phosphoinositide 3 kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway is a well studied signaling pathway that regulates diverse cellular functions including proliferation, metabolism, and transcription. Aberrant activation of this pathway has been implicated in multiple cancers. Genomic studies have shown that activating mutations in oncogenes as well as inactivating mutations in tumor suppressor genes are present across a variety of malignancies, including urothelial carcinoma. In bladder cancer, up to 40% of tumors exhibit constitutive activation of the PI3K/AKT/mTOR pathway. Current treatments for non-muscle-invasive disease confer a 5-year cancer-specific survival rate as high as 90%. However, patients with muscle-invasive, recurrent, or metastatic disease have a poor prognosis. Although the introduction of immune checkpoint inhibitors is certainly changing the therapeutic landscape and is a great addition to the platinum-based therapy that was the standard of care for the past 3 decades, it is anticipated that a great number of patients would fail to respond or their disease would progress with either chemotherapy or immunotherapy. Therefore, the use of agents that target members of the PI3K/AKT/mTOR pathway represent an attractive, alternative therapeutic strategy for patients with advanced urothelial carcinoma. In this review we describe the pathway, with a focus on the rationale for targeting the PI3K/AKT/mTOR pathway in patients with advanced urothelial carcinoma and considers the challenges that we face from the current clinical trials. Novel agents such as PI3K inhibitors and microRNA inhibitors that target this pathway might lead to durable responses especially when used in combination with chemotherapy or immune checkpoint inhibitors, however, toxicity remains an obstacle. Finally, in this review we discuss the importance of developing biomarkers to help select appropriate patients and identify optimal treatment options.

Bladder cancer

Bladder cancer is a highly prevalent disease and is associated with substantial morbidity, mortality and cost. Environmental or occupational exposures to carcinogens, especially tobacco, are the main risk factors for bladder cancer. Most bladder cancers are diagnosed after patients present with macroscopic haematuria, and cases are confirmed after transurethral resection of bladder tumour (TURBT), which also serves as the first stage of treatment. Bladder cancer develops via two distinct pathways, giving rise to non-muscle-invasive papillary tumours and non-papillary (solid) muscle-invasive tumours. The two subtypes have unique pathological features and different molecular characteristics. Indeed, The Cancer Genome Atlas project identified genetic drivers of muscle-invasive bladder cancer (MIBC) as well as subtypes of MIBC with distinct characteristics and therapeutic responses. For non-muscle-invasive bladder cancer (NMIBC), intravesical therapies (primarily Bacillus Calmette-Guérin (BCG)) with maintenance are the main treatments to prevent recurrence and progression after initial TURBT; additional therapies are needed for those who do not respond to BCG. For localized MIBC, optimizing care and reducing morbidity following cystectomy are important goals. In metastatic disease, advances in our genetic understanding of bladder cancer and in immunotherapy are being translated into new therapies.

Phosphatidylinositol- 3-kinase inhibitor induces chemosensitivity to a novel derivative of doxorubicin, AD198 chemotherapy in human bladder cancer cells in vitro

BACKGROUND

Doxorubicin (Dox) is widely used to treat progressed bladder cancer after transurethral resection. The use of Dox-chemotherapy has been limited due to induced drug resistance and cumulative cardiotoxic effects. N-benzyladriamycin-14-valerate (AD198), a novel derivative of Dox, has a potential to become a more effective treatment than Dox by overcoming drug resistance and cardio-toxicity as shown in the rodent model of lymphoma in vivo. The purpose of this study was to compare the efficacy of Dox and AD198 and explore their mechanisms in inhibition on human bladder cancer cells in vitro.

METHODS

We evaluated the effects of Dox and AD198 on cell viability of human transitional cell carcinoma (TCC) cell lines T24 and UMUC3 by MTS assay in vitro. The effects of Dox and AD198 on cell apoptosis were determined by caspase 3/7 assay, generation of reactive oxygen species (ROS), and Western Blotting (WB) analysis.

RESULTS

AD198 was more effective than Dox in inhibition of cell viability of T24 and UMUC3 cells in vitro. Both Dox and AD198 significantly increased the generation of ROS and induced apoptosis in caspase-dependent and -independent manner in T24 and UMUC3 cells. AD 198 induced significantly higher production of ROS as compared to Dox in human TCC cells. Dox and AD198 activated the pro-apoptotic p38 MAPK pathway; however, on the other hand also increased phosphorylation of AKT, an anti-apoptotic signaling pathway, in T24 and UMUC3 cells. Combined treatment of PI3K inhibitor (LY294002) with Dox or AD198 inhibited cell viability of T24 and UMUC3 cells more effectively than any of drug treatments alone.

CONCLUSIONS

These data suggest that AD198 as novel derivative of Dox, could be a used as effective treatment for bladder cancer. Dox and AD198 induced PI3K/AKT signaling pathway that is a one of the indicators of pro-survival and possible drug-resistance mechanisms of chemotherapies in bladder cancer. Combined therapies of Dox or AD198 with inhibitors of PI3K/AKT signaling pathway might lead to more effective treatment outcome for patients diagnosed with bladder cancer based on our in vitro experiments.

Molecular markers in bladder cancer: Novel research frontiers

Bladder cancer (BC) is a heterogeneous disease encompassing distinct biologic features that lead to extremely different clinical behaviors. In the last 20 years, great efforts have been made to predict disease outcome and response to treatment by developing risk assessment calculators based on multiple standard clinical-pathological factors, as well as by testing several molecular markers. Unfortunately, risk assessment calculators alone fail to accurately assess a single patient's prognosis and response to different treatment options. Several molecular markers easily assessable by routine immunohistochemical techniques hold promise for becoming widely available and cost-effective tools for a more reliable risk assessment, but none have yet entered routine clinical practice. Current research is therefore moving towards (i) identifying novel molecular markers; (ii) testing old and new markers in homogeneous patients' populations receiving homogeneous treatments; (iii) generating a multimarker panel that could be easily, and thus routinely, used in clinical practice; (iv) developing novel risk assessment tools, possibly combining standard clinical-pathological factors with molecular markers. This review analyses the emerging body of literature concerning novel biomarkers, ranging from genetic changes to altered expression of a huge variety of molecules, potentially involved in BC outcome and response to treatment. Findings suggest that some of these indicators, such as serum circulating tumor cells and tissue mitochondrial DNA, seem to be easily assessable and provide reliable information. Other markers, such as the phosphoinositide-3-kinase (PI3K)/AKT (serine-threonine kinase)/mTOR (mammalian target of rapamycin) pathway and epigenetic changes in DNA methylation seem to not only have prognostic/predictive value but also, most importantly, represent valuable therapeutic targets. Finally, there is increasing evidence that the development of novel risk assessment tools combining standard clinical-pathological factors with molecular markers represents a major quest in managing this poorly predictable disease.

Targeting Hsp90 in urothelial carcinoma

Urothelial carcinoma, or transitional cell carcinoma, is the most common urologic malignancy that carries significant morbidity, mortality, recurrence risk and associated health care costs. Despite use of current chemotherapies and immunotherapies, long-term remission in patients with muscle-invasive or metastatic disease remains low, and disease recurrence is common. The molecular chaperone Heat Shock Protein-90 (Hsp90) may offer an ideal treatment target, as it is a critical signaling hub in urothelial carcinoma pathogenesis and potentiates chemoradiation. Preclinical testing with Hsp90 inhibitors has demonstrated reduced proliferation, enhanced apoptosis and synergism with chemotherapies and radiation. Despite promising preclinical data, clinical trials utilizing Hsp90 inhibitors for other malignancies had modest efficacy. Therefore, we propose that Hsp90 inhibition would best serve as an adjuvant treatment in advanced muscle-invasive or metastatic bladder cancers to potentiate other therapies. An overview of bladder cancer biology, current treatments, molecular targeted therapies, and the role for Hsp90 inhibitors in the treatment of urothelial carcinoma is the focus of this review.

Molecular profiling of infiltrating urothelial carcinoma of bladder and nonbladder origin

BACKGROUND

Infiltrating UC represents the second most common genitourinary malignancy. Advanced UC has a poor prognosis and new treatments are needed. Molecular profiling of UC might identify biomarkers associated with targeted therapies or chemotherapeutics, providing physicians with new treatment options.

MATERIALS AND METHODS

Five hundred thirty-seven cases of locally advanced or metastatic UC of the bladder, 74 nonbladder, and 55 nonurothelial bladder cancers were profiled using mutation analysis, in situ hybridization, and immunohistochemistry assays for biomarkers predictive of therapy response.

RESULTS

Molecular profiling of UC showed high overexpression of topoisomerase 2α, common phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha and/or phosophatase and tensin homolog (PTEN) alterations in nonbladder (27%) and bladder UC (21%), and rare gene mutations across subtypes. Compared with nonbladder, bladder UC consistently exhibited more frequent abnormal protein expression, including HER2 (10% vs. 3%; P = .04), tyrosine protein c-Kit receptor kinases (11% vs. 5%), c-Met proto-oncogene, receptor tyrosine kinases (25% vs. 8%), androgen receptor (16% vs. 6%), O(6)-methylguanine-methyltransferase (63% vs. 43%), ribonucleotide reductase M1 (32% vs. 11%), Serum protein acidic and rich in cysteine (SPARC) (69% vs. 33%), and topoisomerase 1 (63% vs. 39%). Bladder UC also exhibited increased amplification of HER2 (12% vs. 2%; P = .06).

CONCLUSION

Comprehensive molecular profiling of UC identified a large number of biomarkers aberrations that might direct treatment in conventional chemotherapies and targeted therapies, not currently recommended in this population. As a group, bladder UC exhibited higher levels of actionable biomarkers, suggesting that UC from different primary sites and non-UC are driven by different molecular pathways. These differences could have clinical implications resulting in different treatment regimens depending on the site of origin of UC.

Targeting the genetic alterations of the PI3K-AKT-mTOR pathway: its potential use in the treatment of bladder cancers

Urothelial carcinoma of the bladder is the most frequent tumor of the urinary tract and represents the fifth cause of death by cancer worldwide. The current first line chemotherapy is a combination of cisplatin and gemcitabine with median survival not exceeding 15months. Vinflunine is the only drug approved by EMEA as second-line treatment and few progresses have been made for the past 20years to increase the survival of metastatic patients, especially those who are not eligible for cisplatin-based regimen. The recent studies characterizing the genetic background of urothelial cancers of the bladder, revealed chromosomal alterations that are not seen at the same level in other types of cancers. This is especially the case for mutations of genes involved in the PI3K/AKT/mTOR signaling pathway that occupies a major place in the etiology of these tumors. Here, we describe the mutations leading to constitutive activation of the PI3K/AKT/mTOR pathway and discuss the potential use of the different classes of PI3K/AKT/mTOR inhibitors in the treatment of urothelial bladder cancers. Despite the recent pivotal study evidencing specific mutations of TSC1 in bladder cancer patients responding to everolimus and the encouraging results obtained with other derivatives than rapalogs, few clinical trials are ongoing in bladder cancers. Because of the genetic complexity of these tumors, the cross-talks of the PI3K/AKT/mTOR pathway with other pathways, and the small number of eligible patients, it will be of utmost importance to carefully choose the drugs or drug combinations to be further tested in the clinic.

Identification of mutations in distinct regions of p85 alpha in urothelial cancer

Bladder cancers commonly show genetic aberrations in the phosphatidylinositol 3-kinase signaling pathway. Here we have screened for mutations in PIK3R1, which encodes p85α, one of the regulatory subunits of PI3K. Two hundred and sixty-four bladder tumours and 41 bladder tumour cell lines were screened and 18 mutations were detected. Thirteen mutations were in C-terminal domains and are predicted to interfere with the interaction between p85α and p110α. Five mutations were in the BH domain of PIK3R1. This region has been implicated in p110α-independent roles of p85α, such as binding to and altering the activities of PTEN, Rab4 and Rab5. Expression of these mutant BH-p85α forms in mouse embryonic fibroblasts with p85α knockout indicated that all forms, except the truncation mutants, could bind and stabilize p110α but did not increase AKT phosphorylation, suggesting that BH mutations function independently of p110α. In a panel of 44 bladder tumour cell lines, 80% had reduced PIK3R1 mRNA expression relative to normal urothelial cells. This, along with mutation of PIK3R1, may alter BH domain functioning. Our findings suggest that mutant forms of p85α may play an oncogenic role in bladder cancer, not only via loss of ability to regulate p110α but also via altered function of the BH domain.

PTEN deletions are related to disease progression and unfavourable prognosis in early bladder cancer

AIMS

This study aimed to determine the prevalence and clinical significance of deletions of the tumour suppressor gene PTEN in bladder cancer.

METHODS AND RESULTS

A tissue microarray with 686 bladder cancers was analysed for PTEN deletions by fluorescence in-situ hybridization. PTEN mutations were analysed in nine tumours with heterozygous PTEN deletion. Heterozygous PTEN deletions were present in 16.5% of tumours and were associated with grade (P = 0.0024) and p53 status (P = 0.0141), but not linked to stage (P = 0.0965). PTEN deletions were seen in 5.8% of pTaG1, 10.9% of pTaG2, 29.0% of pTaG3, 16.7% of pT1G2, 22.2% of pT1G3, 17.7% of pT2-4G2 and 20.9% of pT2-4G3 tumours (P = 0.0235). PTEN deletions were associated significantly with recurrences in pTa tumours (P = 0.0173), progression in pT1 tumours (P = 0.0016), but not with overall or cancer-specific survival in pT2 tumours. Multivariate analyses including grade and PTEN deletions revealed that PTEN deletions but not grade were associated independently with recurrence in pTa tumours (P = 0.0377) and progression in pT1 tumours (P = 0.0030). No inactivating PTEN mutations were found.

CONCLUSIONS

PTEN is linked to aggressive tumour phenotype and to unfavourable outcome in early bladder cancer. Heterozygous PTEN loss, i.e. reduced PTEN gene dosage, might be sufficient to cause aggressive tumour behaviour in bladder cancer cells.

Network analysis of microRNAs, genes and their regulation in human bladder cancer

Bladder cancer (BC) is the fifth most common malignancy occurring worldwide and a significant cause of cancer-related morbidity and mortality. Although BC is a serious health issue, studies available concerning the relationship of genes, microRNAs (miRNAs) and their host genes has been lacking. In the present study, we assessed experimentally validated data from various sources that reported the effect of miRNA on various diseases, miRNA targeting of mRNAs, and combined these data with initial transcription factor (TF) binding site predictions within miRNA promoter regions. Topology networks obtained in this study included the differentially expressed, BC-associated and global networks. The three networks may be used to assess the effect of miRNAs and their regulation in human BC. By comparing and analyzing the similarities and differences among the three networks, key nodes with the largest potential of affecting the behavior of a particular network were identified. The results also showed potentially substantially influential miRNAs and TFs, which revealed subnetworks demonstrating the mechanisms involved as well as regulatory miRNA network motifs in human BC. Regulatory pathways regarding differentially expressed elements, such as genes and miRNAs, demonstrate self-adapting associations including, self-adapting associations and feedback loops in genes MYC, TP53, PTEN and 10 differentially expressed miRNAs. The differentially expressed network partially identified the BC mechanism. miRNA-targeted human BC genes were also enriched in highly relevant pathways, cell cycle regulation and apoptosis. The present study systematically delineated the pathogenesis of BC and provided theoretical foundations for gene therapy investigators to focu attention on key genes and miRNAs in future studies.

CSTP1, a novel protein phosphatase, blocks cell cycle, promotes cell apoptosis, and suppresses tumor growth of bladder cancer by directly dephosphorylating Akt at Ser473 site

Akt/protein kinase B is a pivotal component downstream of phosphatidylinositol 3-kinase (PI3K) pathway, whose activity regulates the balance between cell survival and apoptosis. Phosphorylation of Akt occurs at two key sites either at Thr308 site in the activation loop or at Ser473 site in the hydrophobic motif. The phosphorylated form of Akt (pAkt) is activated to promote cell survival. The mechanisms of pAkt dephosphorylation and how the signal transduction of Akt pathway is terminated are still largely unknown. In this study, we identified a novel protein phosphatase CSTP1(complete s transactivated protein 1), which interacts and dephosphorylates Akt specifically at Ser473 site in vivo and in vitro, blocks cell cycle progression and promotes cell apoptosis. The effects of CSTP1 on cell survival and cell cycle were abrogated by depletion of phosphatase domain of CSTP1 or by expression of a constitutively active form of Akt (S473D), suggesting Ser473 site of Akt as a primary cellular target of CSTP1. Expression profile analysis showed that CSTP1 expression is selectively down-regulated in non-invasive bladder cancer tissues and over-expression of CSTP1 suppressed the size of tumors in nude mice. Kaplan-Meier curves revealed that decreased expression of CSTP1 implicated significantly reduced recurrence-free survival in patients suffered from non-invasive bladder cancers.

Oncogenic activation of Pak1-dependent pathway of macropinocytosis determines BCG entry into bladder cancer cells

Bacille Calmette-Guerin (BCG) is an attenuated strain of Mycobacterium bovis that is used widely as a vaccine for tuberculosis and is used as an effective treatment for superficial bladder carcinoma. Despite being the most successful cancer biotherapy, its mechanism of action and response determinants remain obscure. Here, we establish a model system to analyze BCG interaction with bladder cancer cells, using it to show that these cells vary dramatically in their susceptibility to BCG infection. Unexpectedly, the uptake of BCG by bladder cancer cells occurs by macropinocytosis rather than phagocytosis. BCG entry into bladder cancer cells relied upon Rac1, Cdc42, and their effector kinase Pak1. The difference in susceptibility between BCG-permissive and -resistant bladder cancer cells was due to oncogenic activation of signaling pathways that activate macropinocytosis, with phosphoinositide 3-kinase inhibitor activation stimulating BCG uptake independently of Akt. Similarly, activated Ras strongly activated Pak1-dependent uptake of BCG. These results reveal that oncogenic activation of macropinocytosis determines BCG uptake by bladder cancer cells, implying that tumor responsiveness to BCG may be governed by the specific mutations present in the treated cancer cell.

High levels of phosphatase and tensin homolog expression are associated with tumor progression, tumor recurrence, and systemic metastases in pT1 urothelial carcinoma of the bladder: a tissue microarray study of 156 patients treated by transurethral resection

OBJECTIVE

To evaluate immunohistochemical expression of phosphatase and tensin homolog (PTEN) and mammalian target of rapamycin (mTOR) pathway members in pT1 urothelial carcinomas treated by transurethral resection and to determine if immunohistochemistry can be used to predict prognosis.

METHODS

Formalin-fixed, paraffin-embedded tissue samples from 156 patients with pT1 urothelial carcinoma treated by transurethral resection were used to build 5 tissue microarrays. Tissue microarray sections were stained for PTEN, phosphorylated (phos)-AKT, phos-mTOR, phos-S6, eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), and phos-4EBP1. Patients were monitored after initial treatment (mean, 22.5; median, 16; range, 3-108 months) to detect tumor recurrence, tumor progression, or systemic metastases.

RESULTS

During follow-up, 101 patients (65%) showed tumor recurrence, 57 showed tumor progression (37%), and 18 showed systemic metastases (12%). Patients with ≥2 lesions at the initial workup had higher proportions and higher hazard ratios of tumor recurrence, tumor progression, and systemic metastases. Complete loss of PTEN expression was observed in 6 patients (4%), and >80% of the mTOR pathway members showed at least focal positivity. Proportions of tumors with higher levels of PTEN immunohistochemical expression were higher in patients with tumor recurrence (P=.001), tumor progression (P=.05), and systemic metastases (P=.001). Proportions of tumors with lower phos-S6 and low phos-4EBP1 levels were higher in patients with tumor recurrence (P≤.05). Proportions were similar for the remaining biomarkers.

CONCLUSION

Higher levels of PTEN immunohistochemical expression were associated with higher rates of tumor recurrence, tumor progression, and systemic metastases in patients with pT1 urothelial carcinomas treated by transurethral resection.

The androgen receptor and stem cell pathways in prostate and bladder cancers (review)

Bladder cancer is three times more common in men than in women. However, the physiological basis of the male predominance of bladder cancer remains poorly understood. A higher than expected association of prostate and bladder cancers has also been reported which may indicate a common mechanism of carcinogenesis. Consistent with this, androgens and the androgen receptor (AR) play essential roles in prostate carcinogenesis and are believed to play a role in bladder carcinogenesis. There is also evidence implicating cancer stem cells in prostate and bladder cancers. Indeed putative prostate and bladder cancer stem cells share some common molecular features. We highlight key proteins (CD49f, CD133, PTEN, CD44) which are implicated in both prostate and bladder cancers and are enriched in putative prostate and bladder cancer stem cells. We examine published chromatin immuno-precipitation studies analyzing the genome-wide distribution of the AR to identify AR association with, and by inference potential AR-regulation of, these loci. We discuss recent evidence indicating a role for the AR in the splicing of the key urological stem cell protein CD44. We propose a model whereby aberrant AR regulation of these putative stem cell proteins contributes to malignant transformation of prostate and bladder cells. For these reasons we propose that the relationship between androgens and cancer stem cell associated proteins warrants further investigation.

Phosphatidylinositol 3'-kinase, mTOR, and glycogen synthase kinase-3β mediated regulation of p21 in human urothelial carcinoma cells

BACKGROUND

The PTEN/Phosphatidylinositol 3'-kinase (PI3-kinase) growth factor signaling pathway plays a critical role in epithelial tumor development in a multitude of tissue types. Deletion of the Pten tumor suppressor gene in murine urothelial cells in vivo results in upregulation of cyclin-dependent kinase inhibitor p21. We have previously shown in mice that p21 expression blocks an increase in urothelial cell proliferation due to Pten deletion. In this study, we utilized human urothelial carcinoma cells UMUC-3 and UMUC-14 to identify the signaling pathways downstream of PI3-kinase that regulate p21.

METHODS

Cells were treated with a combination of PI3-kinase stimulating growth factors and kinase inhibitors, or transfected with exogenous genes in order to identify the signaling events that are necessary for p21 induction. Mice with conditional deletion of Pten in bladder urothelium were also examined for evidence of PI3-kinase pathway signaling events that affect p21 expression.

RESULTS

When cells were treated with PI3-kinase activating growth factors EGF or PDGF, we found that p21 levels increased, in a manner similar to that observed in mice. We used the inhibitors LY294002, Akti-1/2, and rapamycin, to show that p21 induction is dependent upon PI3-kinase and AKT activity, and partially dependent on mTOR. We treated the cells with proteasome inhibitor MG-132 and found that p21 may be degraded in the proteasome to regulate protein levels. Importantly, our findings show that GSK-3β plays a role in diminishing p21 levels in cells. Treatment of cells with the GSK-3β inhibitor SB-216763 increased p21 levels, while exogenous expression of GSK-3β caused a decrease in p21, indicating that GSK-3β actively reduces p21 levels. We found that a combined treatment of LY294002 and SB-216763 improved the cytotoxic effect against UMUC-3 and UMUC-14 carcinoma cells over LY294002 alone, suggesting potential therapeutic uses for GSK-3β inhibitors. Immunohistochemical staining in bladders from wild-type and Pten-deleted mice indicated that GSK-3β inhibitory phosphorylation increases when Pten is deleted.

CONCLUSION

PI3-kinase and AKT cause an upregulation of p21 by suppressing GSK-3β activity and activating mTOR in both cultured human urothelial carcinoma cells and mouse urothelial cells in vivo.

PTEN loss in the continuum of common cancers, rare syndromes and mouse models

PTEN is among the most frequently inactivated tumour suppressor genes in sporadic cancer. PTEN has dual protein and lipid phosphatase activity, and its tumour suppressor activity is dependent on its lipid phosphatase activity, which negatively regulates the PI3K-AKT-mTOR pathway. Germline mutations in PTEN have been described in a variety of rare syndromes that are collectively known as the PTEN hamartoma tumour syndromes (PHTS). Cowden syndrome is the best-described syndrome within PHTS, with approximately 80% of patients having germline PTEN mutations. Patients with Cowden syndrome have an increased incidence of cancers of the breast, thyroid and endometrium, which correspond to sporadic tumour types that commonly exhibit somatic PTEN inactivation. Pten deletion in mice leads to Cowden syndrome-like phenotypes, and tissue-specific Pten deletion has provided clues to the role of PTEN mutation and loss in specific tumour types. Studying PTEN in the continuum of rare syndromes, common cancers and mouse models provides insight into the role of PTEN in tumorigenesis and will inform targeted drug development.

Bladder cancer or bladder cancers? Genetically distinct malignant conditions of the urothelium

Despite the fact that the current histopathologic classification for bladder cancer has led to improved concepts for the clinical management of the disease, key questions with regard to assessment of risk for recurrence and/or progression to invasive disease remain. In addition, response to specific therapies cannot be predicted accurately. Bladder tumors comprise a heterogeneous group with respect to both histopathology and clinical behavior. Thus, it is anticipated that a thorough knowledge and interpretation of the molecular alterations involved in tumor development and progression will lead to greater prognostic and predictive power. This may not only lead to better comprehension of the biology of the disease, but may also lead to the development of novel individualized therapies. Novel means of stratification are urgently needed to provide a new subclassification of urothelial lesions. This review discusses and summarizes the genetic alterations that have been reported in bladder cancer and relates these to the current 2-pathway model for tumor development. The molecular pathogenesis of high-grade noninvasive papillary tumors and of T1 tumors is not yet clear, and possibilities are discussed.

Molecular genetics of bladder cancer: Emerging mechanisms of tumor initiation and progression

Urothelial cancer has served as one of the most important sources of information about the mutational events that underlie the development of human solid malignancies. Although "field effects" that affect the entire bladder mucosa appear to initiate disease, tumors develop along 2 distinct biological "tracks" that present vastly different challenges for clinical management. Recent whole genome methodologies have facilitated even more rapid progress in the identification of the molecular mechanisms involved in bladder cancer initiation and progression. Specifically, whole organ mapping combined with high resolution, high throughput SNP analyses have identified a novel class of candidate tumor suppressors ("forerunner genes") that localize near more familiar tumor suppressors but are disrupted at an earlier stage of cancer development. Furthermore, whole genome comparative genomic hybridization (CGH) and mRNA expression profiling have demonstrated that the 2 major subtypes of urothelial cancer (papillary/superficial and non-papillary/muscle-invasive) are truly distinct molecular entities, and in recent work our group has discovered that muscle-invasive tumors express molecular markers characteristic of a developmental process known as "epithelial-to-mesenchymal transition" (EMT). Emerging evidence indicates that urothelial cancers contain subpopulations of tumor-initiating cells ("cancer stem cells") but the phenotypes of these cells in different tumors are heterogeneous, raising questions about whether or not the 2 major subtypes of cancer share a common precursor. This review will provide an overview of these new insights and discuss priorities for future investigation.

Novel intravesical therapies for non-muscle-invasive bladder cancer refractory to BCG

The definitive treatment for patients with non-muscle-invasive bladder cancer (NMIBC) who fail to respond to intravesical BCG is cystectomy. When a patient is deemed BCG-refractory and cannot or will not undergo cystectomy, alternative intravesical therapy may be the most effective way to minimize recurrence and progression. A number of immunotherapeutic and chemotherapeutic agents have been given intravesically over the years, and several recently and currently investigated novel agents appear to be particularly promising for the management of BCG-refractory NMIBC. The most effective treatments in the future will likely utilize targeted therapies based on the underlying genetic mutations associated with each individual diagnosis of NMIBC.

Differential induction of reactive oxygen species through Erk1/2 and Nox-1 by FK228 for selective apoptosis of oncogenic H-Ras-expressing human urinary bladder cancer J82 cells

PURPOSE

This study sought to reveal mechanisms for differential regulation of reactive oxygen species (ROS) in histone deacetylase inhibitor FK228-induced selective apoptosis of oncogenic H-Ras-expressing human cancer cells.

METHODS

Human urinary bladder cancer J82 and oncogenic H-Ras-expressing J82 cells were used to reveal FK228-induced differential Erk1/2 activation, Nox-1 elevation, ROS production, glutathione (GSH) depletion, caspase activation, and apoptosis. Specific inhibitors were used to suppress Nox-1 activity and ROS production. Mek1/2 inhibitor was used to suppress Erk1/2 activation. Validated-specific siRNAs were used to knock down Nox-1. ROS levels, GSH levels, and caspase-3/7 activities were measured by GSH assay, flow cytometry and luminescence assays, respectively. Western blot analysis determined levels of Erk1/2 and Nox-1.

RESULTS

Erk1/2, Nox-1, ROS, caspase-3/7, and cell death were differentially induced, whereas GSH was differentially depleted by FK228 in oncogenic H-Ras-expressing J82 versus parental cells. Blockage of the ERK pathway resulted in suppressing oncogenic H-Ras- and FK228-induced Nox-1 elevation, ROS production, caspase activation, and cell death. Knockdown of Nox-1 by specific siRNAs reduced FK228-induced ROS production, caspase activation, and cell death.

CONCLUSION

Oncogenic H-Ras expression and FK228 treatment synergistically induced the ERK pathway, resulting in differentially increased Nox-1 elevation, ROS production, and GSH depletion, leading to differential caspase activation and cell death in oncogenic H-Ras-expressing J82 versus parental cells.

Phosphatidylinositol 3-kinase (PI3K) pathway activation in bladder cancer

The phosphatidylinositol 3-kinase (PI3K) pathway is a critical signal transduction pathway that regulates multiple cellular functions. Aberrant activation of this pathway has been identified in a wide range of cancers. Several pathway components including AKT, PI3K and mTOR represent potential therapeutic targets and many small molecule inhibitors are in development or early clinical trials. The complex regulation of the pathway, together with the multiple mechanisms by which it can be activated, make this a highly challenging pathway to target. For successful inhibition, detailed molecular information on individual tumours will be required and it is already clear that different tumour types show distinct combinations of alterations. Recent results have identified alterations in pathway components PIK3CA, PTEN, AKT1 and TSC1 in bladder cancer, some of which are significantly related to tumour phenotype and clinical behaviour. Co-existence of alterations to several PI3K pathway genes in some bladder tumours indicates that these proteins may have functions that are not related solely to the known canonical pathway.

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.

Spectrum of phosphatidylinositol 3-kinase pathway gene alterations in bladder cancer

PURPOSE

The phosphatidylinositol 3-kinase (PI3K) pathway can be activated by alterations affecting several pathway components. For rational application of targeted therapies, detailed understanding of tumor biology and approaches to predict efficacy in individual tumors are required. Our aim was to assess the frequency and distribution of pathway alterations in bladder cancer.

EXPERIMENTAL DESIGN

We examined the pathway components (PIK3CA, PTEN, TSC1, RHEB, and LKB1) and putative upstream regulators (FGFR3 and RAS genes) for mutation, allelic loss, copy number alteration, and expression in bladder tumors and cell lines.

RESULTS

No mutations were found in RHEB and only a single mutation in LKB1. PIK3CA mutations were detected in 25% of tumors and 26% of cell lines with a significant excess of helical domain mutations (E542K and E545K). There was over-representation but not amplification of the gene. Loss of heterozygosity of the PTEN region and homozygous deletion were found in 12% and 1.4% of tumors, and reduced expression in 49%. Forty-six percent of cell lines showed alterations that implicated PTEN. Sixteen percent of tumors and 11% of cell lines showed TSC1 mutation, and 9q loss of heterozygosity was common (57%). Pathway alterations were independently distributed, suggesting that the mutation of two pathway members may have additive or synergistic effects through noncanonical functions.

CONCLUSIONS

PI3K pathway alterations are common in bladder cancer. The lack of redundancy of alterations suggests that single-agent PI3K-targeted therapy may not be successful in these cancers. This study provides a well-characterized series of cell lines for use in preclinical studies of targeted agents.

Alterations of BCCIP, a BRCA2 interacting protein, in astrocytomas

Background

Loss of heterozygosity of chromosome 10q26 has been shown to be associated with the aggressiveness of astrocytic tumors (or astrocytomas), but the responsible gene(s) residing in this region has not been fully identified. The BCCIP gene is located at chromosome 10q26. It encodes a BRCA2 and CDKN1A (p21) interacting protein. Previous studies have shown that down-regulation of BCCIP impairs recombinational DNA repair, G1/S cell cycle checkpoint, p53 trans-activation activity, cytokinesis, and chromosome stability, suggesting a potential role of BCCIP in cancer etiology. In this study, we investigated whether BCCIP is altered in astrocytomas.

Methods

Genomic DNA from 45 cases of grade IV astrocytic tumor (glioblastoma) tissues and 12 cases of normal tissues were analyzed by quantitative PCR. The BCCIP protein expression in 96 cases of grade II–IV astrocytic tumors was detected by immunohistochemistry (IHC). IHC staining of glial fibrillary acid protein (GFAP), a marker for astrocytic cells, was used to identify cells of the astrocytic lineage.

Results

We found that BCCIP protein is expressed in normal cells with positive staining of GFAP. However, BCCIP protein expression was not detectable in ~45% of all astrocytic tumors, and in > 60% in the grade IV glioblastoma. About 45% glioblastoma have significant (p < 0.01) reduction of BCCIP gene copy number when compared to normal DNA. Furthermore, the frequency of lacking BCCIP expression is associated with the aggressiveness of astrocytic tumors.

Conclusion

Our data implicate a role of BCCIP in astrocytic tumorigenesis, and lack of BCCIP may be used as a marker for astrocytomas.

Role of reactive oxygen species in proapoptotic ability of oncogenic H-Ras to increase human bladder cancer cell susceptibility to histone deacetylase inhibitor for caspase induction

PURPOSE

Reveal mechanisms for the novel proapoptotic ability of oncogenic H-Ras to increase cell susceptibility to a histone deacetylase inhibitor (HDACI) FR901228 for inducing caspase activation and selective apoptosis.

METHODS

Human urinary bladder cancer J82 and oncogenic H-Ras-expressing J82 cells were used to reveal differential induction of intracellular reactive oxygen species (ROS), caspase activation, and apoptosis by HDACI FR901228. ROS levels and caspase-8, -9, and -3/7 activities were measured by flow cytometry and luminescence assays, respectively. Specific inhibitors were used to suppress caspases and ROS. Western blot analysis determined modulators of caspase pathways.

RESULTS

ROS, caspase activity, and cell death was differentially increased by FR901228 in oncogenic H-Ras-expressing J82 versus parental cells. Blocking ROS resulted in reduced FR901228-induced cell death and caspase activation. Suppression of caspase-8 resulted in reduced FR901228-activated caspase-9 and -3/7. Suppression of caspase-9 resulted in reduced FR901228-activated caspase-3/7. Although FR901228 induced an ROS-dependent increase of FasL, FasL failed to induce caspase activation and cell death.

CONCLUSION

Increased ROS played an important role in the activation of the extrinsic and intrinsic caspase pathways to cooperatively induce executioner caspase-3/7 through a novel FasL-independent pathway in FR901228-induced selective apoptosis of oncogenic H-Ras-expressing J82 versus parental cells.

The roles of PTEN in development, physiology and tumorigenesis in mouse models: a tissue-by-tissue survey

In 1997, PTEN (phosphatase and tensin homologue deleted on chromosome 10, 10q23.3) was identified as an important tumor suppressor gene that is inactivated in a wide variety of human cancers. Ever since, PTEN's function has been extensively studied, and huge progress has been made in understanding PTEN's role in normal physiology and disease. In this review, we will systematically summarize the important data that have been gained from gene inactivation studies in mice and will put these data into physiological context using a tissue-by-tissue approach. We will cover mice exhibiting complete and constitutive inactivation of Pten as well as a large number of strains in which Pten has been conditionally deleted in specific tissues. We hope to highlight not only the tumor suppressive function of Pten but also its roles in embryogenesis and in the maintenance of the normal physiological functions of many organ systems.

Molecular pathogenesis of bladder cancer

Bladder tumors show widely differing histopathology and clinical behavior. This is reflected in the molecular genetic alterations they contain. Much information has accumulated on somatic genomic alterations in bladder tumors of all grades and stages and when this information is related to the common histopathological appearances, a model for the pathogenesis of two major groups of bladder tumors has emerged. This review summarizes the genetic alterations that have been reported in bladder cancer and relates these to the current two-pathway model for tumor development. The molecular pathogenesis of high-grade noninvasive papillary tumors and of T1 tumors is not yet clear and possibilities are discussed.

Expression and significance of PTEN in canine mammary gland tumours

To explore the expression and clinical importance of the anti-oncogene phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in canine mammary gland tumours, PTEN expression was compared in 50 cases of canine mammary tumour and four examples of normal mammary tissue using real-time quantitative PCR. PTEN expression was similar in benign mammary tumours and normal mammary tissues (P>0.05), but was lower in malignant tumours than in normal mammary tissues or benign mammary tumours (P<0.001). PTEN expression was also low in the lymph node metastases of malignant mammary tumours. The expression profile of PTEN in malignant mammary tumours compared to those without lymph node metastasis varied significantly. Low-level PETN expression might play an important role in carcinogenesis and the progression of canine mammary tumours, and PTEN protein detection might be useful in evaluating tumour development and prognosis.

Hyperplasia and carcinomas in Pten-deficient mice and reduced PTEN protein in human bladder cancer patients

PTEN is a tumor suppressor gene mutated in many human cancers. We used the Cre-loxP system to generate an urothelium-specific null mutation of Pten in mice [FabpCrePten(flox/flox) (FPten(flox/flox)) mice]. Histologic examination revealed that all FPten(flox/flox) mice exhibited urothelial hyperplasia in which component cells showed enlarged nuclei and increased cell size. With time, 10% of FPten(flox/flox) mice spontaneously developed pedicellate papillary transitional cell carcinomas (TCC). This type of tumor also arose in FPten(flox/flox) mice treated with the chemical carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine. FPten(flox/flox) urothelial cells were hyperproliferative and showed increased activation of the survival signaling molecules Akt and extracellular signal-regulated kinase. In humans, 53% of primary bladder cancer patients exhibited decreased or absent expression of PTEN protein in either the cytoplasm or nucleus of tumor cells. In early bladder cancers, PTEN expression was repressed in 42% of superficial papillary TCC but in only 8% of cases of carcinoma in situ (CIS). In advanced bladder cancers, PTEN protein was significantly reduced (particularly in the nucleus) in 94% of cases, and this decrease in PTEN correlated with disease stage and grade. Thus, PTEN deficiency may contribute to bladder cancer both by initiating superficial papillary TCC and by promoting the progression of CIS to advanced invasive and metastatic forms.

Proapoptotic ability of oncogenic H-Ras to facilitate apoptosis induced by histone deacetylase inhibitors in human cancer cells

More than 35% of human urinary bladder cancers involve oncogenic H-Ras activation. In addition to tumorigenic ability, oncogenic H-Ras possesses a novel proapoptotic ability to facilitate the induction of apoptosis by histone deacetylase inhibitors (HDACI). HDACIs are a new class of anticancer agents and are highly cytotoxic to transformed cells. To understand the connection between the selectivity of HDACIs on transformed cells and the proapoptotic ability of oncogenic H-Ras to facilitate HDACI-induced apoptosis, we introduced oncogenic H-Ras into urinary bladder J82 cancer cells to mimic an acquisition of the H-ras gene activation in tumor development. Expression of oncogenic H-Ras promoted J82 cells to acquire tumorigenic ability. Meanwhile, oncogenic H-Ras increased susceptibility of J82 cells to HDACIs, including FR901228 and trichostatin A, for inducing apoptosis. The caspase pathways, the B-Raf and extracellular signal-regulated kinase pathway, p21(Cip1) and p27(Kip1), and core histone contents are regulated differently by FR901228 in oncogenic H-Ras-expressed J82 cells than their counterparts in parental J82 cells, contributing to the increased susceptibility to the induction of selective apoptosis. Our results lead us to a suggestion that HDACIs activate the proapoptotic ability of oncogenic H-Ras, indicating a potential therapeutic value of this new class of anticancer agents in the control of human urinary bladder cancer that has progressed to acquire oncogenic H-Ras.

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.

The Mad side of the Max network: antagonizing the function of Myc and more

A significant body of evidence has been accumulated that demonstrates decisive roles of members of the Myc/Max/Mad network in the control of various aspects of cell behavior, including proliferation, differentiation, and apoptosis. The components of this network serve as transcriptional regulators. Mad family members, including Mad1, Mxi1, Mad3, Mad4, Mnt, and Mga, function in part as antagonists of Myc oncoproteins. At the molecular level this antagonism is reflected by the different cofactor/chromatin remodeling complexes that are recruited by Myc and Mad family members. One important function of the latter is their ability to repress gene transcription. In this review we summarize the current view of how this repression is achieved and what the consequences of Mad action are for cell behavior. In addition, we point out some of the many aspects that have not been clarified and thus leave us with a rather incomplete picture of the functions, both molecular and at the cellular level, of Mad family members.

Pten deficiency activates distinct downstream signaling pathways in a tissue-specific manner

PTEN deficiency predisposes to a subset of human cancers, but the mechanism that underlies such selectivity is unknown. We have generated a mouse line that conditionally deletes Pten in urogenital epithelium. These mice develop carcinomas at high frequency in the prostate but at relatively low frequency in the bladder, despite early and complete penetrance of hyperplasia in both organs. Cell proliferation is initially high in the bladder of newborn Pten-deficient mice but within days is inhibited by p21 induction. In contrast, proliferation remains elevated in Pten-deficient prostate, where p21 is never induced, suggesting that p21 induction is a bladder-specific compensatory mechanism to inhibit proliferation caused by Pten deletion. Furthermore, the AKT/mammalian target of rapamycin growth pathway, which is highly activated in Pten-deficient prostate, is not activated in bladder epithelium. Our results reveal alternative downstream signaling pathways activated by Pten deficiency that lead to tissue-specific susceptibilities to tumorigenesis.

Molecular subtypes of bladder cancer: Jekyll and Hyde or chalk and cheese?

Cancer of the bladder shows divergent clinical behaviour following diagnosis and it has been proposed that two major groups of tumours exist that develop via different molecular pathways. Low-grade, non-invasive papillary tumours recur frequently, but patients with these tumours do not often suffer progression of disease to muscle invasion. In contrast, tumours that are invading muscle at diagnosis are aggressive and associated with significant mortality. Molecular studies have identified distinct genetic, epigenetic and expression changes in these groups. However, it is not yet clear whether there is direct progression of low-grade superficial tumours to become invasive (a Jeckell and Hyde scenario) or whether in those patients who apparently progress from one form of the disease to the other, different tumour clones are involved and that the two tumour groups are mutually exclusive ('chalk and cheese'). If the latter is true, then attempts to identify molecular markers to predict progression of low-grade superficial bladder tumours may be fruitless. Similarly, it is not clear whether other subgroups of tumours exist that arise via different molecular pathways. There is now a large amount of molecular information about bladder cancer that facilitates examination of these possibilities. Some recent studies provide evidence for the existence of at least one further group of tumours, high-grade superficial papillary tumours, which may develop via a distinct molecular pathway. Patients with such tumours do show increased risk of disease progression and for these there may exist a real progression continuum from non-invasive to invasive. If this is the case, definition of the molecular signature of this pathway and improved understanding of the biological consequences of the events involved will be pivotal in disease management.

Differential PTEN protein expression profiles in superficial versus invasive bladder cancers

INTRODUCTION

The prognostic significance of PTEN protein loss in bladder cancer is not well established. The objective of this study was to investigate the PTEN expression profile in superficial noninvasive papillary transitional cell carcinoma (TCC) versus invasive TCC and compared the results with pathological and clinical parameters.

MATERIALS AND METHODS

Bladder tumor samples were obtained from 29 patients who underwent surgery for superficial (n=11) and invasive (n=18) bladder cancers at the Akdeniz University Hospital. The patient profile including sex, age, histological grade and the stage, presence of carcinoma in situ, cystoscopy findings (tumor size, location, multiplicity) were obtained by examining the patients' medical records. No patient received anticancer agents prior to the operation. Western blotting was performed using bladder carcinoma samples in order to determine the level of PTEN protein expression for each patient.

RESULTS

Only 4 (13.7%) patients with bladder carcinoma manifested a decrease in the level of PTEN expression. Regarding the correlation between tumor stage and the PTEN expression, with the exception of patient 23 all patients who displayed a reduction in PTEN expression had muscle-invasive TCC.

CONCLUSION

Future studies with a clinical follow-up will be needed to determine if those superficial tumors with decreased PTEN expression are going to progress to a later stage. Based on our results PTEN by itself does not seem to be a good candidate as an independent marker to predict the behavior of bladder cancers.

The src-family kinase inhibitor PP2 suppresses the in vitro invasive phenotype of bladder carcinoma cells via modulation of Akt

OBJECTIVE

To evaluate PP2 as a modulator of the cadherin/catenin complex in late-stage bladder carcinoma cells, and to assess its potential invasion-suppressor activity in this model.

MATERIALS AND METHODS

A panel of five human bladder carcinoma cells, characterizing late-stage disease, was used to determine the concentration for 50% inhibition of PP2 in cell-proliferation assays. Modulation of cadherin/catenin expression by PP2 was determined in Western blot analysis, with an assessment of the activation status of mitogen-activated protein kinase and Akt signalling pathways. Altered invasive capacity linked to these variables was determined in standard in vitro invasion assays.

RESULTS

PP2 elicited concentration-dependent growth inhibition in all bladder cell lines within the panel, with growth suppression recorded at 10-35 micromol/L PP2. Distinct morphological changes were recorded in cell lines exposed to PP2, accompanied by up-regulation of plakoglobin expression in a subset of lines. Exposure of cells to PP2 resulted in inactivation of Akt in all cells and a concomitant reduction in in vitro invasive capacity.

CONCLUSIONS

These results show that PP2 inhibits bladder carcinoma cell growth and can modulate plakoglobin expression in a subset of cell lines. In addition, PP2 can suppress the in vitro invasive capacity of bladder carcinoma cells by modulating the activation status of Akt.

PTEN can inhibit in vitro organotypic and in vivo orthotopic invasion of human bladder cancer cells even in the absence of its lipid phosphatase activity

Recent studies have found a higher frequency of the PTEN tumor-suppressor gene alterations in invasive bladder carcinoma than in superficial disease, suggesting that PTEN is important in this process. A role of PTEN in bladder cancer invasion is further suggested by the fact that PTEN is a regulator of cell motility, a necessary component of tumor invasion. However, it is unknown whether PTEN is mechanistically involved in 'in vivo' tumor invasion or merely an epiphenomenon and, if the former is true, whether this process is dependent on its protein or lipid phosphatase activities. To address these issues, we stably transfected several commonly used human bladder cancer cell lines with known invasive phenotypes with either wild-type PTEN constructs or those deficient in the lipid phosphatase (G129E) or both protein and lipid phosphatase (G129R) activities. Here we show that chemotaxis was inhibited by both the wild-type and G129E mutant of PTEN but not by G129R-transfected cells. Using a novel organotypic in vitro invasion assay, we evaluated the impact of wild-type and mutant PTEN transgene expression on the invasive ability of T24T, a human bladder cancer cell line with a functionally impaired PTEN. Results indicate that the G129E mutant blocks invasion as efficiently as wild-type PTEN transfection. In contrast to the wild-type gene, this mutant has no effect on cell clonogenicity in agar. To further establish the role of PTEN in tumor invasion, we evaluated vector- and PTEN-transfected T24T cells in an orthotopic in vivo assay that faithfully reproduces human disease. Microscopic examination of murine bladders at the completion of this experiment parallels the results obtained with the organotypic assay. Our results are the first demonstration: (1) that the inhibitory effects of PTEN on cell motility translate into suppression of in vivo invasion; (2) that PTEN can inhibit tumor invasion even in the absence of its lipid phosphatase activity; (3) how organotypic in vitro approaches can be used as surrogates of in vivo invasion allowing rapid dissection of molecular processes leading to this phenotype while reducing the number of animals used in research.

Novel expression of N-cadherin elicits in vitro bladder cell invasion via the Akt signaling pathway

Novel N-cadherin expression has been linked to the invasive phenotype in bladder tumors yet a primary role for N-cadherin in invasion has not been defined in this model. To address this, N-cadherin was stably transfected into E-cadherin expressing bladder carcinoma cells. This resulted in an enhanced invasive capacity in in vitro assays that was blocked by incubation with an N-cadherin function-blocking antibody in a dose-dependent manner. Analysis of the signaling pathway(s) implicated in N-cadherin-mediated invasion in bladder carcinoma cell lines revealed no correlation between MAPK signaling and invasion, in the presence or absence of fibroblast growth factor 2. Also, while MAPK and p38 kinase inhibitors did not alter the invasive behavior of these cells, an increase in the phosphorylation of Akt at serine-473 was detected in N-cadherin transfectants, suggestive of N-cadherin-mediated Akt activation in bladder cell invasion. Incubation of N-cadherin transfectants with either PI3 kinase or Akt inhibitors resulted in a significant decrease in the invasive capacity of these cells. Exposure of cells to PP2, a src family kinase inhibitor, also decreased the invasive potential of N-cadherin transfectants and resulted in reduced phosphorylation of Akt. The involvement of Akt signaling in bladder cell invasion was also supported by the inhibition of bladder cell invasion by cells constitutively expressing an activated Akt kinase, using the PI3 kinase and Akt inhibitors and PP2. These results suggest that activation of PI3/AKT kinase following N-cadherin expression contributes to the increased invasive potential of bladder carcinoma cells.

The phosphatidylinositol-3 kinase pathway regulates bladder cancer cell invasion

OBJECTIVES

To investigate the role of the phosphatidylinositol (PI)-3 kinase pathway in the invasion of bladder cancer cell lines, and to assess the activation of this pathway in primary human bladder tumours.

MATERIALS AND METHODS

Human bladder cancer cells were treated with pathway specific inhibitors or were transfected with PI-3 kinase pathway components. The invasion of cultured bladder cancer cells was analysed by an invasion assay. Bladder cancer cells lines and primary human bladder tumours were analysed for pathway activation by western blotting.

RESULTS

A specific inhibitor of PI-3 kinase enzyme activity, Ly294002, potently suppressed the invasive properties of three highly invasive bladder tumour cell lines. Restoration of the PTEN gene to invasive UM-UC-3 bladder tumour cells or expression of a dominant-negative version of the PI-3 kinase target, Akt, also potently inhibited invasion, indicating a central role for the PI-3 kinase/Akt pathway in this process. In addition, 55% of primary tumours from patients with bladder cancer had markedly high levels of phosphorylated Akt.

CONCLUSION

Pharmacological or biochemical inhibition of the PI-3 kinase pathway drastically reduced the invasive capacity of bladder cancer cell lines; over half of primary human bladder tumours had high Akt phosphorylation, suggesting that the aberrant activation of this pathway may contribute to the invasion of a significant subset of bladder cancers.

The role of Ras superfamily proteins in bladder cancer progression

PURPOSE

The prognosis of patients with bladder cancer is strongly dependent on whether the lesion is superficial or invasive at initial presentation. In addition, a significant fraction of patients presenting with superficial disease have invasive tumor during followup. Understanding how superficial bladder cancer progresses to invasive forms of the disease is of paramount importance for early diagnosis and successful treatment. Molecular mechanisms underlying bladder cancer progression are being elucidated. We reviewed the roles that members of the Ras superfamily of monomeric G proteins, an important class of cellular regulator, have in bladder cancer and its progression.

MATERIALS AND METHODS

We performed MEDLINE searches focusing on members of the Ras superfamily of monomeric G proteins and their involvement in transitional cell carcinoma, which is the most common form of bladder cancer. General involvement in cancer of key superfamily members, focusing on mechanisms and downstream pathways, was also reviewed through MEDLINE and manual bibliographic searches.

RESULTS

With more than 100 members in humans the Ras superfamily is a diverse group of monomeric G proteins. These proteins regulate many cellular processes, such as cell cycle progression, actin cytoskeletal dynamics and membrane traffic. Members of the Ras and Rho family are also known to be involved in human cancer through mutation, over expression and dysregulation. In this review we focus on bladder cancer. In particular we focus on how H-Ras, RalA/B and RhoGDI2, a regulator of Rho family members, participate in bladder cancer progression and how their participation may be related to other molecules associated with bladder cancer progression, such as epidermal growth factor receptor, p53 and PTEN (phosphatase and tensin homologue deleted on chromosome 10).

CONCLUSIONS

The findings discussed offer the hopeful possibility that signaling pathways mediated by Ras superfamily members may offer new opportunities for diagnostic and therapeutic interventions in bladder cancer.

Growth, invasion, metastasis, differentiation, angiogenesis and apoptosis of gastric cancer regulated by expression of PTEN encoding products

AIM: To investigate expression of PTEN in gastric cancer and to explore its roles in tumorigenesis and progression of gastric cancer.

METHODS: Formalin-fixed and paraffin-embedded tissues of adjacent non-tumor mucosa and primary foci from 113 cases of gastric cancers were studied for the expression of PTEN and Caspase-3 and microvessel density (MVD) by streptavidin-peroxidase (S-P) immunohistochemistry with antibodies against PTEN, Caspase-3, and CD34. The relationship between PTEN and Caspase 3 expression and clinicopathological parameters of tumors was compared.

RESULTS: Primary gastric cancer cells expressed PTEN less frequently than adjacent epithelial cells of primary foci (54.9% vs 89.4%; P = 0.000, χ² = 33.474). PTEN expression was significantly associated with invasive depth (P = 0.003, rs = 0.274), metastasis (P = 0.036, rs = 0.197), growth pattern (P=0.008, rs = 0.282), Lauren’s classification (P = 0.000, rs = 0.345), and histological classification (P = 0.005, rs = 0.262) of tumors, but not with tumor size (P = 0.639, rs = 0.045), Borrmann’s classification (P = 0.544, rs = 0.070) or TNM staging (P = 0.172, rs = 0.129). PTEN expression was negatively correlated with MDV in primary gastric cancer (P = 0.020, F = 5.558). Primary gastric cancer cells showed less frequent immunoreactivity to Caspase-3 than adjacent epithelial cells of primary foci (32.7% vs 50.4%; P = 0.007, χ² = 7.286). Caspase-3 expression was dependent of PTEN expression in primary gastric cancer cells (P = 0.000, χ² = 15.266).

CONCLUSION: Down-regulated expression of PTEN plays an important role in tumorigenesis, progression, growth, differentiation and angiogenesis of gastric cancer. Low expression of PTEN can decrease expression of Caspase-3 to disorder apoptosis of tumor cells, which might explain the molecular mechanisms of PTEN contributions to tumorigenesis and progression of gastric cancer.