The use of histone deacetylase inhibitor FK228 and DNA hypomethylation agent 5-azacytidine in human bladder cancer therapy

New Approaches to Targeting Epigenetic Regulation in Bladder Cancer

Epigenetics is a growing field and in bladder cancer, it is of particular interest in advanced or metastatic disease. As opposed to genetic mutations in which the nucleotide sequence itself is altered, epigenetic alterations refer to changes to the genome that do not involve nucleotides. This is of great interest in cancer research because epigenetic alterations are reversible, making them a promising target for pharmacological agents. While chemoimmunotherapy is the mainstay for metastatic disease, there are few alternatives for patients who have progressed on first- or second-line treatment. By targeting reversible epigenetic alterations, novel epigenetic therapies are important potential treatment options for these patients. A search of clinical registries was performed in order to identify and collate epigenetic therapies currently in human trials. A literature search was also performed to identify therapies that are currently in preclinical stages, whether this be in vivo or in vitro models. Twenty-five clinical trials were identified that investigated the use of epigenetic inhibitors in patients with bladder cancer, often in combination with another agent, such as platinum-based chemotherapy or pembrolizumab. The main classes of epigenetic inhibitors studied include DNA-methyltransferase (DNMT) inhibitors, histone deacetylase (HDAC) inhibitors, and histone methyltransferase (HMT) inhibitors. At present, no phase 3 clinical trials have been registered. Few trials have published results, though DNMT inhibitors have shown the most promise thus far. Many patients with advanced or metastatic bladder cancer have limited treatment options, particularly when first- or second-line chemoimmunotherapy fails. Epigenetic alterations, which are common in bladder cancer, are potential targets for drug therapies, and these epigenetic agents are already in use for many cancers. While they have shown promise in pre-clinical trials for bladder cancer, more research is needed to assess their benefit in clinical settings.

MEK is a promising target in the basal subtype of bladder cancer

While many resources exist for the drug screening of bladder cancer cell lines in 2D culture, it is widely recognized that screening in 3D culture is more representative of in vivo response. Importantly, signaling changes between 2D and 3D culture can result in changes to drug response. To address the need for 3D drug screening of bladder cancer cell lines, we screened 17 bladder cancer cell lines using a library of 652 investigational small-molecules and 3 clinically relevant drug combinations in 3D cell culture. Our goal was to identify compounds and classes of compounds with efficacy in bladder cancer. Utilizing established genomic and transcriptomic data for these bladder cancer cell lines, we correlated the genomic molecular parameters with drug response, to identify potentially novel groups of tumors that are vulnerable to specific drugs or classes of drugs. Importantly, we demonstrate that MEK inhibitors are a promising targeted therapy for the basal subtype of bladder cancer, and our data indicate that drug screening of 3D cultures provides an important resource for hypothesis generation.

DNA Methylation as a Therapeutic Target for Bladder Cancer

Bladder cancer (BC) is the tenth most frequent cancer worldwide and is associated with high mortality when diagnosed in its most aggressive form, which is not reverted by the current treatment options. Thus, the development of new therapeutic strategies, either alternative or complementary to the current ones, is of major importance. The disruption of normal epigenetic mechanisms, namely, DNA methylation, is a known early event in cancer development. Consequently, DNA methyltransferase (DNMT) inhibitors constitute a promising therapeutic target for the treatment of BC. Although these inhibitors, mainly nucleoside analogues such as 5-azacytidine (5-aza) and decitabine (DAC), cause re-expression of tumor suppressor genes, inhibition of tumor cell growth, and increased apoptosis in BC experimental models and clinical trials, they also show important drawbacks that prevent their use as a valuable option for the treatment of BC. However, their combination with chemotherapy and/or immune-checkpoint inhibitors could aid in their implementation in the clinical practice. Here, we provide a comprehensive review of the studies exploring the effects of DNA methylation inhibition using DNMTs inhibitors in BC, from in vitro and in vivo studies to clinical trials.

Romidepsin Induces G2/M Phase Arrest and Apoptosis in Cholangiocarcinoma Cells

Background:

Cholangiocarcinoma (CCA) is an extremely intractable malignancy since most patients are already in an advanced stage when firstly discovered. CCA needs more effective treatment, especially for advanced cases. Our study aimed to evaluate the effect of romidepsin on CCA cells in vitro and in vivo and explore the underlying mechanisms.

Methods:

The antitumor effect was determined by cell viability, cell cycle and apoptosis assays. A CCK-8 assay was performed to measure the cytotoxicity of romidepsin on CCA cells, and flow cytometry was used to evaluate the effects of romidepsin on the cell cycle and apoptosis. Moreover, the in vivo effects of romidepsin were measured in a CCA xenograft model.

Results:

Romidepsin could reduce the viability of CCA cells and induce G2/M cell cycle arrest and apoptosis, indicating that romidepsin has a significant antitumor effect on CCA cells in vitro. Mechanistically, the antitumor effect of romidepsin on the CCA cell lines was mediated by the induction of G2/M cell cycle arrest and promotion of cell apoptosis. The G2/M phase arrest of the CCA cells was associated with the downregulation of cyclinB and upregulation of the p-cdc2 protein, resulting in cell cycle arrest. The apoptosis of the CCA cells induced by romidepsin was attributed to the activation of caspase-3. Furthermore, romidepsin significantly inhibited the growth of the tumor volume of the CCLP-1 xenograft, indicating that romidepsin significantly inhibited the proliferation of CCA cells in vivo.

Conclusions:

Romidepsin suppressed the proliferation of CCA cells by inducing cell cycle arrest through cdc2/cyclinB and cell apoptosis by targeting caspase-3/PARP both in vitro and in vivo, indicating that romidepsin is a potential therapeutic agent for CCA.

Characterization of Histone Deacetylase Expression Within In Vitro and In Vivo Bladder Cancer Model Systems

Epigenetic aberrations are prominent in bladder cancer (BC) and contribute to disease pathogenesis. We characterized histone deacetylase (HDAC) expression, a family of deacetylation enzymes, in both in vitro and in vivo BC model systems and analyzed expression data from The Cancer Genome Atlas (TCGA). Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting analysis was used to determine the expression status of Class I and II HDACs in ten human BC cell lines, while qRT-PCR was used to determine HDAC expression in 24 human tumor specimens. The TCGA cohort consists of 408 muscle invasive BC (MIBC) clinical samples and analysis of this data set identified expression of HDAC4 and -9 as being associated with basal-squamous disease. These findings agree with qRT-PCR results identifying increased expression of HDAC4, -7, and -9 in basal BC cell lines (p < 0.05; Kruskal-Wallis test) and in clinical specimens with invasive bladder cancer (not statistically significant). We also observed increased expression in Hdac4, -7, and -9 in commonly used BC mouse models. Here, we identify suitable preclinical model systems for the study of HDACs, and show increased expression of Class IIa HDACs, specifically HDAC4 and HDAC9, in basal BC cell lines and in invasive clinical specimens. These results suggest this class of HDACs may be best suited for targeted inhibition in patients with basal BC.

Revisiting Histone Deacetylases in Human Tumorigenesis: The Paradigm of Urothelial Bladder Cancer

Urinary bladder cancer is a common malignancy, being characterized by substantial patient mortality and management cost. Its high somatic-mutation frequency and molecular heterogeneity usually renders tumors refractory to the applied regimens. Hitherto, methotrexate-vinblastine-adriamycin-cisplatin and gemcitabine-cisplatin represent the backbone of systemic chemotherapy. However, despite the initial chemosensitivity, the majority of treated patients will eventually develop chemoresistance, which severely reduces their survival expectancy. Since chromatin regulation genes are more frequently mutated in muscle-invasive bladder cancer, as compared to other epithelial tumors, targeted therapies against chromatin aberrations in chemoresistant clones may prove beneficial for the disease. “Acetyl-chromatin” homeostasis is regulated by the opposing functions of histone acetyltransferases (HATs) and histone deacetylases (HDACs). The HDAC/SIRT (super-)family contains 18 members, which are divided in five classes, with each family member being differentially expressed in normal urinary bladder tissues. Since a strong association between irregular HDAC expression/activity and tumorigenesis has been previously demonstrated, we herein attempt to review the accumulated published evidences that implicate HDACs/SIRTs as critical regulators in urothelial bladder cancer. Moreover, the most extensively investigated HDAC inhibitors (HDACis) are also analyzed, and the respective clinical trials are also described. Interestingly, it seems that HDACis should be preferably used in drug-combination therapeutic schemes, including radiation.

Combinatorial Antitumor Activity of Oxaliplatin with Epigenetic Modifying Agents, 5-Aza-CdR and FK228, in Human Gastric Cancer Cells

Epigenetic silencing is considered to be a major mechanism for loss of activity in tumor suppressors. Reversal of epigenetic silencing by using inhibitors of DNA methyltransferase (DNMT) or histone deacetylases (HDACs) such as 5-Aza-CdR and FK228 has shown to enhance cytotoxic activities of several anticancer agents. This study aims to assess the combinatorial effects of gene-silencing reversal agents (5-Aza-CdR and FK228) and oxaliplatin in gastric cancer cells, i.e., Epstein-Barr virus (EBV)-negative SNU-638 and EBV-positive SNU-719 cells. The doublet combinatorial treatment of 5-Aza-CdR and FK228 exhibited synergistic effects in both cell lines, and this was further corroborated by Zta expression induction in SNU-719 cells. Three drug combinations as 5-Aza-CdR/FK228 followed by oxaliplatin, however, resulted in antagonistic effects in both cell lines. Simultaneous treatment with FK228 and oxaliplatin induced synergistic and additive effects in SNU-638 and SNU-719 cells, respectively. Three drug combinations as 5-Aza-CdR prior to FK228/oxaliplatin, however, again resulted in antagonistic effects in both cell lines. This work demonstrated that efficacy of doublet synergistic combination using DNMT or HDACs inhibitors can be compromised by adding the third drug in pre- or post-treatment approach in gastric cancer cells. This implies that the development of clinical trial protocols for triplet combinations using gene-silencing reversal agents should be carefully evaluated in light of their potential antagonistic effects.

Histone deacetylase inhibitors interrupt HSP90•RASGRP1 and HSP90•CRAF interactions to upregulate BIM and circumvent drug resistance in lymphoma cells

Histone deacetylase (HDAC) inhibitors, which are approved for the treatment of cutaneous T cell lymphoma and multiple myeloma, are undergoing evaluation in other lymphoid neoplasms. How they kill susceptible cells is incompletely understood. Here we show that trichostatin A, romidepsin, and panobinostat induce apoptosis across a panel of malignant B cell lines, including lines that are intrinsically resistant to bortezomib, etoposide, cytarabine, and BH3 mimetics. Further analysis traces the pro-apoptotic effects of HDAC inhibitors to increased acetylation of the chaperone heat shock protein 90 (HSP90), causing release and degradation of the HSP90 client proteins RASGRP1 and CRAF, which in turn leads to downregulation of mitogen activated protein kinase pathway signaling and upregulation of the pro-apoptotic BCL2 family member BIM in vitro and in vivo. Importantly, these pro-apoptotic effects are mimicked by RASGRP1 siRNA or HSP90 inhibition and reversed by overexpression of constitutively active MEK1 or siRNA-mediated downregulation of BIM. Collectively, these observations not only identify a new HSP90 client protein, RASGRP1, but also delineate a complete signaling pathway from HSP90 acetylation through RASGRP1 and CRAF degradation to BIM upregulation that contributes to selective cytotoxicity of HDAC inhibitors in lymphoid malignancies.

Epigenetic modification suppresses proliferation, migration and invasion of urothelial cancer cell lines

Epigenetic approaches offer additional therapeutic options, including apoptosis induction, modification of cell cycle regulating proteins and the re-expression of pharmaceutical targets, such as hormone receptors. The present study analyzed the effect of the epigenetic modifiers 5-aza-2′-deoxycytidine and Trichostatin A on the proliferative, migratory and invasive behavior of four urinary bladder cancer cell lines (RT-4, RT-112, VMCUB-1 and T-24), and the expression of various matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs). Cell proliferation, migration and invasion assays revealed that treatment with the two epigenetic modifiers resulted in proliferation inhibition in all cell lines, and migration and invasion inhibition in RT-4, RT-112 and T-24 cell lines. Quantitative polymerase chain reaction demonstrated that the mRNA expression of a broad selection of MMPs and their TIMPs was induced in all cell lines, and MMP-14 mRNA expression was suppressed in all cell lines, with the exception of RT-4. In conclusion, epigenetic modifications suppressed the motility and invasiveness of three out of four urothelial cancer cell lines. The inhibitory effect on cell motility appears to be crucial for reduced invasive properties. However, even a broad spectrum of mRNA analysis does not sufficiently explain the loss of invasiveness, as it does not allow for functional conclusions. Further complex urothelial tumour models should be applied to investigate whether epigenetic therapeutic approaches may be an option in urothelial cancer.

Histone deacetylase inhibitor, Romidepsin (FK228) inhibits endometrial cancer cell growth through augmentation of p53-p21 pathway

OBJECTIVE

Romidepsin (FK228), a Histone Deacetylase (HDAC) inhibitor, has been used for anti-cancer therapies. However, the anti-cancer effect of FK228 and its underlying mechanism in endometrial carcinoma (EC) have not been studied. The aime of this study was to investigate the anti-cancer effects of FK228 and the associated mechanism(s) in EC.

METHODS

Ishikawa and HEC-1-A endometrial cancer cells were treated with 8nM concentration of FK228 and cell growth was measured by XTT assay. The cell cycle distribution and cell death were measured by flow cytometry, immunofluorescence, respectively. The mNRA and protein expressions were analyzed by quantitative RT-PCR and western blot, respectively.

RESULTS

Based on assays carried out in EC cell lines, it was observed that FK228 inhibited EC cell proliferation in a dose and time-dependent manner. Furthermore, following treatment with FK228 for 48h, there were significant induction of apoptosis and cell cycle arrest at G0/G1 phase in EC cells. Moreover, FK228 treatment significantly increased the mRNA and protein expressions of p53, p21, cleaved caspases such as 3, 7 and 8 and PARP. Further, FK228 treatment increased the levels of acetylated histone H3 and H4 that confirms the HDAC inhibition.

CONCLUSION

In conclusion, FK228 inhibits EC tumor cell proliferation and induces apoptosis by activation caspase/PARP via the induction of p53/p21 signaling cascades, suggesting that FK228 is a potential therapeutic agent for EC.

DNMT1 and EZH2 mediated methylation silences the microRNA-200b/a/429 gene and promotes tumor progression

Aberrant expression of the microRNA-200 (miR-200) family has been linked to the occurrence and development of various types of malignant tumors, including hepatocellular carcinoma (HCC), colon cancer and breast cancer. However, little is known about the precise mechanism by which miR-200 expression is downregulated. The intricate relationship between DNA methylation and histone modifications has become a subject of increasing interest. The expression of miR-200 family members is modified by similar or complementary epigenetic mechanisms in MGC-803 and BGC-823 gastric cancer cells and U87 MG glioma cells. Chromatin immunoprecipitation assays revealed that DNA methyltransferase 1 (DNMT1) bound to miR-200b/a/429 promoter regions, indicating an interaction between DNMT1 and the miR-200b/a/429 promoter. Furthermore, Co-Immunoprecipitation (Co-IP) detection showed that DNMT1, together with the PcG protein Enhancer of Zeste homolog 2 (EZH2), a histone methyltransferase, contributed to the transcriptional repression of microRNA-200 family members. Knockdown of EZH2 not only impacted H3K27 trimethylation but also reduced DNMT1 presence on the miR-200b/a/429 promoter. EZH2 appeared to be essential for DNMT1 recruitment to the promoter region. Silencing EZH2 and DNMT1 using drugs or RNA interference dramatically reduced the levels of miR-200b/a/429 expression. Collectively, these results indicated that EZH2 and DNMT1-mediated epigenetic silencing contributed to the progression of gastric cancer and glioblastoma, and therefore represents a novel therapeutic target for malignant tumors.

Dynamic bioluminescence and fluorescence imaging of the effects of the antivascular agent Combretastatin-A4P (CA4P) on brain tumor xenografts

Combretastatin A-4 (CA4) is a natural product isolated from Combretum caffrum that inhibits tubulin polymerization by binding to the colchicine-binding site. A corresponding water soluble pro-drug (referred to as CA4P), has undergone extensive clinical trials and has been evaluated in pre-clinical studies using multiple modalities. We previously reported a novel assay based on dynamic bioluminescent imaging to assess tumor vascular disruption and now present its application to assessing multiple tumors simultaneously. The current study evaluated the vascular-disrupting activity of CA4P on subcutaneous 9L rat brain tumor xenografts in mice using dynamic bioluminescence imaging. A single dose of CA4P (120 mg/kg, intraperitoneally) induced rapid, temporary tumor vascular shutdown revealed by a rapid and reproducible decrease of light emission from luciferase-expressing 9L tumors following administration of luciferin as a substrate. A time-dependent reduction of tumor perfusion after CA4P treatment was confirmed by immunohistological assessment of the perfusion marker Hoechst 33342 and the tumor vasculature marker CD31. The vasculature showed distinct recovery within 24 h post therapy. Multiple tumors behaved similarly, although a size dependent vascular inhibition was observed. In conclusion, CA4P caused rapid, temporary tumor vascular shutdown and led to reduction of tumor perfusion in rat brain tumor xenografts and the multiple tumor approach should lead to more efficient studies requiring fewer animals and greater consistency.

5-Azacytidine enhances the radiosensitivity of CNE2 and SUNE1 cells in vitro and in vivo possibly by altering DNA methylation

The radioresistance of tumor cells remains a major cause of treatment failure in nasopharyngeal carcinoma (NPC). Recently, several reports have highlighted the importance of epigenetic changes in radiation-induced responses. Here, we investigated whether the demethylating agent 5-azacytidine (5-azaC) enhances the radiosensitivity of NPC cells. The NPC cell lines CNE2 and SUNE1 were treated with 1 μmol/L 5-azaC for 24 h before irradiation (IR); clonogenic survival was then assessed. Tumor growth was investigated in a mouse xenograft model in vivo. The apoptosis, cell cycle progression and DNA damage repair were examined using flow cytometry, immunofluorescent staining and western blotting. Promoter methylation and the expression of four genes epigenetically silenced during the development of NPC were evaluated by pyrosequencing and real-time PCR. We found that pretreatment with 5-azaC significantly decreased clonogenic survival after IR compared to IR alone; the sensitivity-enhancement ratio of 5-azaC was 1.4 and 1.2 for CNE2 and SUNE1 cells, respectively. The combined administration of 5-azaC and IR significantly inhibited tumor growth in the mouse xenograft model, and enhanced radiation-induced apoptosis in vitro compared to 5-azaC alone or IR alone. 5-AzaC also decreased promoter methylation and upregulated the expression of genes which are epigenetically silenced both in vitro and in vivo in NPC. Thus, 5-azaC enhance the radiosensitivity of both the CNE2 and SUNE1 cell lines, possibly by altering DNA methylation levels and increasing the ability of irradiated cells to undergo apoptosis. The use of 5-azaC combined with IR maybe represent an attractive strategy for the treatment of NPC.

Histone deacetylase inhibitor AR-42 enhances E7-specific CD8⁺ T cell-mediated antitumor immunity induced by therapeutic HPV DNA vaccination

We have previously created a potent DNA vaccine encoding calreticulin linked to the human papillomavirus (HPV) oncogenic protein E7 (CRT/E7). While treatment with the CRT/E7 DNA vaccine generates significant tumor-specific immune responses in vaccinated mice, the potency with the DNA vaccine could potentially be improved by co-administration of a histone deacetylase inhibitor (HDACi) as HDACi has been shown to increase the expression of MHC class I and II molecules. Thus, we aimed to determine whether co-administration of a novel HDACi, AR-42, with therapeutic HPV DNA vaccines could improve the activation of HPV antigen-specific CD8(+) T cells, resulting in potent therapeutic antitumor effects. To do so, HPV-16 E7-expressing murine TC-1 tumor-bearing mice were treated orally with AR-42 and/or CRT/E7 DNA vaccine via gene gun. Mice were monitored for E7-specific CD8(+) T cell immune responses and antitumor effects. TC-1 tumor-bearing mice treated with AR-42 and CRT/E7 DNA vaccine experienced longer survival, decreased tumor growth, and enhanced E7-specific immune response compared to mice treated with AR-42 or CRT/E7 DNA vaccine alone. Additionally, treatment of TC-1 cells with AR-42 increased the surface expression of MHC class I molecules and increased the susceptibility of tumor cells to the cytotoxicity of E7-specific T cells. This study indicates the ability of AR-42 to significantly enhance the potency of the CRT/E7 DNA vaccine by improving tumor-specific immune responses and antitumor effects. Both AR-42 and CRT/E7 DNA vaccines have been used in independent clinical trials; the current study serves as foundation for future clinical trials combining both treatments in cervical cancer therapy.

KEY MESSAGE

AR-42, a novel HDAC inhibitor, enhances potency of therapeutic HPV DNA vaccines AR-42 treatment leads to strong E7-specific CD8+ T cell immune responses AR-42 improves tumor-specific immunity and antitumor effects elicited by HPV DNA vaccine AR-42 is more potent than clinically available HDACi in combination with HPV DNA vaccine.

Synergistic induction of cancer cell death and reduction of clonogenic resistance by cisplatin and FK228

Human urinary bladder cancer is the fifth most common cancer in the United States, and the long-term disease-free survival in patients is still suboptimal with current chemotherapeutic regimens. Development of effective chemotherapeutic regimens is crucial to decrease the morbidity and mortality of this cancer. The goal of this study was to investigate the effectiveness of FK228 in increasing cisplatin's ability to induce bladder cancer cell death and reduce drug resistance. Our study revealed that FK228 combined with cisplatin synergistically induced cell death and reduced clonogenic survival of human urinary bladder cancer cells. The Erk-Nox pathway played an important role in mediating signals highly increased by this combined treatment to induce significantly-elevated levels of reactive oxygen species, leading to substantially-induced caspase activation and synergistically-increased death in cancer cells. Cisplatin was able to enhance the ability of FK228 to significantly reduce glutathione, indicating a novel activity of combined FK228 and cisplatin in reducing drug resistance. The ability of combined FK228 and cisplatin to synergistically induce cell death and reduce clonogenic survival was also applicable to colon cancer cells. Hence, combined use of FK228 with cisplatin should be considered in development of therapeutic strategies to control urinary bladder cancer and other cancer development and recurrence.

Trials with 'epigenetic' drugs: an update

Epigenetic inactivation of pivotal genes involved in correct cell growth is a hallmark of human pathologies, in particular cancer. These epigenetic mechanisms, including crosstalk between DNA methylation, histone modifications and non-coding RNAs, affect gene expression and are associated with disease progression. In contrast to genetic mutations, epigenetic changes are potentially reversible. Re-expression of genes epigenetically inactivated can result in the suppression of disease state or sensitization to specific therapies. Small molecules that reverse epigenetic inactivation, so-called epi-drugs, are now undergoing clinical trials. Accordingly, the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for cancer treatment have approved some of these drugs. Here, we focus on the biological features of epigenetic molecules, analyzing the mechanism(s) of action and their current use in clinical practice.

DNMT1: an emerging target in the treatment of invasive urinary bladder cancer

OBJECTIVES

More than 14,000 people die from invasive urothelial carcinoma (iUC) of the urinary bladder each year in the USA, and more effective therapies are needed. Naturally occurring canine iUC very closely resembles the disease in humans and serves as a highly relevant translational model for novel therapy of human iUC. Work was undertaken to identify new targets for anticancer therapy in dogs with the goal of translating successful therapeutic strategies into humans with iUC.

MATERIALS AND METHODS

Microarray expression analyses were conducted on mRNA extracted from canine normal bladder (n = 4) and iUC tissues (n = 4) using Genome Array 1.0 and analyzed by GeneSpring GX 11, with the stringency of P < 0.02 and a ≥ 2-fold change. The genes thus identified were further analyzed for functional and pathway analysis using Protein ANalysis THrough Evolutionary Relationships (PANTHER) Classification System. In selecting genes for further study, consideration was given for evidence of a role of the gene in human iUC. From these analyses, DNA methyltransferase 1 (DNMT1) was selected for further study. Immunohistochemistry (IHC) of canine normal bladder and iUC tissues was performed to confirm the microarray expression analyses. The effects of targeting DNMT1 in vitro was assessed through MTT assay and Western blot of canine iUC cells treated with 5-azacitidine (5-azaC) and trichostatin A (TSA).

RESULTS

DNMT1 was expressed in 0 of 6 normal canine bladder samples and in 10 of 22 (45%) canine iUC samples. The proliferation of canine iUC cells was inhibited by 5-azaC (at concentrations ≥ 5 μm) and by TSA (at concentrations ≥ 0.1 μm). Western blot results were supportive of DNMT1-related effects having a role in the antiproliferative activity.

CONCLUSIONS

Microarray expression analyses on canine tissues identified DNMT1 as a potentially "targetable" gene. Expression of DNMT1 in canine iUC was confirmed by IHC, and in vitro studies confirmed that drugs that inhibit DNMT1 have antiproliferative effects. These findings are similar to those recently reported in human iUC and are also in line with results of a preclinical (prehuman) trial of 5-azaC in dogs with naturally occurring iUC. DNMT1 has excellent potential as a target for iUC therapy in humans.

Analysis of the Hox epigenetic code

Archetypes of histone modifications associated with diverse chromosomal states that regulate access to DNA are leading the hypothesis of the histone code (or epigenetic code). However, it is still not evident how these post-translational modifications of histone tails lead to changes in chromatin structure. Histone modifications are able to activate and/or inactivate several genes and can be transmitted to next generation cells due to an epigenetic memory. The challenging issue is to identify or “decrypt” the code used to transmit these modifications to descent cells. Here, an attempt is made to describe how histone modifications operate as part of histone code that stipulates patterns of gene expression. This papers emphasizes particularly on the correlation between histone modifications and patterns of Hox gene expression in Caenorhabditis elegans. This work serves as an example to illustrate the power of the epigenetic machinery and its use in drug design and discovery.

Epigenetic regulation of vascular endothelial growth factor a dynamic expression in transitional cell carcinoma

Vascular endothelial growth factor A (VEGF-A) is a key mediator in the neovascularization of cancers. We have found that VEGF-A was expressed at significantly higher levels in high-grade transitional cell carcinoma (TCC) cells than low-grade TCC cells in our previous study. In the present study, promoter methylation pattern was assessed and quantified by bisulfite genomic sequencing (BGS) and specific VEGF-A CpG sites in low-grade, but not in high-grade, TCC cells were observed. Reporter assays indicated that hypermethylation of nine CpG sites can inhibit the transcriptional activity of the VEGF-A gene. Subsequent chromatin immunoprecipitation (ChIP) assay revealed down-regulation of transcription activity of VEGF-A with increasing binding of methyl-CpG-binding protein 2 (MBD2) and trimethyl-histone H3 (Lys9) proteins to these CpG sites in low-grade TCC cells during hypermethylation. Furthermore, treatment of low-grade TCC cells with DNA methyltransferase inhibitor and histone deacetylase inhibitor can restore the expression of VEGF-A and promote the invasive ability of low-grade TCC cells. Hypermethylation with lower expression levels of VEGF-A in low-grade TCC tumors than high-grade TCC tumors was also confirmed in clinical specimens by reverse transcriptase-PCR and pyrosequencing analyses. Our findings are the first results indicating that VEGF-A expression is suppressed in low-grade TCC tumors by promoter hypermethylation. This offers a new perspective on the role of VEGF-A in TCC tumor behavior.

Subcutaneous 5-azacitidine treatment of naturally occurring canine urothelial carcinoma: a novel epigenetic approach to human urothelial carcinoma drug development

PURPOSE

We determined the efficacy, biological activity, pharmacokinetics and safety of the hypomethylating agent 5-azacitidine (Celgene Corp., Summit, New Jersey) in dogs with naturally occurring invasive urothelial carcinoma.

MATERIALS AND METHODS

We performed a preclinical phase I trial in dogs with naturally occurring invasive urothelial carcinoma to examine once daily subcutaneous administration of 5-azacitidine in 28-day cycles at doses of 0.10 to 0.30 mg/kg per day according to 2 dose schedules, including days 1 to 5 (28-day cohort) or days 1 to 5 and 15 to 19 (14-day cohort). Clinical efficacy was assessed by serial cystosonography, radiography and cystoscopy. Urinary 5-azacitidine pharmacokinetic analysis was also done. Pretreatment and posttreatment peripheral blood mononuclear cell and invasive urothelial carcinoma DNA, respectively, was analyzed for global and gene specific [CDKN2A (p14ARF)] methylation changes.

RESULTS

Enrolled in the study were 19 dogs with naturally occurring invasive urothelial carcinoma. In the 28-day cohort the maximum tolerated dose was 0.20 mg/kg per day with higher doses resulting in grade 3 or 4 neutropenia in 4 of 6 dogs. In the 14-day cohort the maximum tolerated dose was 0.10 mg/kg per day with grade 3 or 4 neutropenia seen in 2 of 3 dogs treated at higher doses. No grade 3 or 4 nonhematological toxicity was observed during either dosing schedule. Of 18 dogs evaluable for tumor response partial remission, stable disease and progressive disease were observed in 4 (22.2%), 9 (50.0%) and 4 (22.2%), respectively. Consistent 5-azacitidine levels (205 to 857 ng/ml) were detected in urine. Pretreatment and posttreatment methylation analysis revealed no significant correlation with clinical response.

CONCLUSIONS

Subcutaneous 5-azacitidine showed promising clinical activity in a canine invasive urothelial carcinoma model, thus meriting further development in humans with urothelial carcinoma.

Hypomethylating agents for urologic cancers

Silencing of tumor suppressor genes by promoter-region methylation as an epigenetic mechanism of gene regulation is increasingly recognized as beneficial in cancer. Initially developed as cytotoxic high-dose therapies, azacitidine and decitabine are now being reinvestigated in lower-dose cancer treatment regimens with a different paradigm - hypomethylation. Recent evidence for benefit in myelodysplastic syndromes and acute myeloid leukemias has renewed interest in hypomethylation as a therapeutic option in epithelial cancers. In this article, we describe the mechanistic aspects of DNA methylation, which alters gene expression, and review the evidence for hypomethylation as a therapeutic option in urologic cancers. Potential correlative studies that may assist in developing tailored therapy with hypomethylating agents are reviewed. Given that the population with urologic cancers is typically elderly with multiple comorbidities, the excellent tolerability of lower-dose hypomethylating agents provides a high therapeutic index and rational development is warranted, bearing in mind that the cytostatic and delayed activity present challenges in the choice of appropriate trial end points.

DNA hypermethylation as a chemotherapy target

Epigenetics refers to partially reversible, somatically inheritable, but DNA sequence-independent traits that modulate gene expression, chromatin structure, and cell functions such as cell cycle and apoptosis. DNA methylation is an example of a crucial epigenetic event; aberrant DNA methylation patterns are frequently found in human malignancies. DNA hypermethylation and the associated expression silencing of tumor suppressor genes represent a hallmark of neoplastic cells. The cancer methylome is highly disrupted, making DNA methylation an excellent target for anti-cancer therapies. Several small synthetic and natural molecules, are able to reverse the DNA hypermethylation through inhibition of DNA methyltransferase (DNMT). DNMT is the enzyme catalyzing the transfer of methyl groups to cytosines in genomic DNA. These reagents are studied intensively in cell cultures, animal models, and clinical trials for potential anti-cancer activities. It was found that accompanying DNA demethylation is a dramatic reactivation of the silenced genes and inhibition of cancer cell proliferation, promotion of cell apoptosis, or sensitization of cells to other chemotherapeutic reagents. During the last few decades, an increasing number of DNMT inhibitors (DNMTi) targeting DNA methylation have been developed to increase efficacy with reduced toxicity. This review provides an update on new findings on cancer epigenetic mechanisms, the development of new DNMTi, and their application in the clinical setting. Current challenges, potential solutions, and future directions concerning the development of DNMTi are also discussed in this review.

Bladder cancer: translating molecular genetic insights into clinical practice

Transitional cell (urothelial) carcinoma of the bladder is the second most common urologic malignancy and is one of the best understood neoplasms, with relatively well-defined pathogenetic pathways, natural history, and tumor biology. Conventional clinical and pathologic parameters are widely used to grade and stage tumors and to predict clinical outcome of transitional cell carcinoma; but the predictive ability of these parameters is limited, and there is a lack of indices that could allow prospective assessment of risk for individual patients. In the last decade, a wide range of candidate biomarkers representing key pathways in carcinogenesis have been reported to be clinically relevant and potentially useful as diagnostic and prognostic molecular markers, and as potential therapeutic targets. The use of molecular markers has facilitated the development of novel and more accurate diagnostic, prognostic, and therapeutic strategies. FGFR3 and TP53 mutations have been recognized as key genetic pathways in the carcinogenesis of transitional cell carcinoma. FGFR3 appears to be the most frequently mutated oncogene in transitional cell carcinoma; its mutation is strongly associated with low tumor grade, early stage, and low recurrence rate, which confer a better overall prognosis. In contrast, TP53 mutations are associated with higher tumor grade, more advanced stage, and more frequent tumor recurrences. These molecular markers offer the potential to characterize individual urothelial neoplasms more completely than is possible by histologic evaluation alone. Areas in which molecular markers may prove valuable include prediction of tumor recurrence, molecular staging of transitional cell carcinoma, detection of lymph node metastasis and circulating cancer cells, identification of therapeutic targets, and prediction of response to therapy. With accumulating molecular knowledge of transitional cell carcinoma, we are closer to the goal of bridging the gap between molecular findings and clinical outcomes. Assessment of key genetic pathways and expression profiles could ultimately establish a set of molecular markers to predict the biological nature of tumors and to establish new standards for molecular tumor grading, classification, and prognostication. The main focus of this review is to discuss clinically relevant biomarkers that might be useful in the management of transitional cell carcinoma and to provide approaches in the analysis of molecular pathways that influence the clinical course of bladder cancer.

Upregulation of TRAG3 gene in urothelial carcinoma of the bladder

Conventional chemotherapy is commonly used for advanced stages of bladder cancer with modest success and high morbidity. Identifying markers of resistance will allow clinicians to tailor treatment to a specific patient population. T24-tumorigenic cell line was grown orthotopically in nude mice and monitored using bioluminescence imaging and microcomputed tomography until they developed metastases. Stable sublines were then developed from primary bladder (T24-P), lung (T24-L) and bone (T24-B) tissues. Chromosomal analysis and DNA microarray were used to characterize these sublines. Real-time quantitative polymerase chain reaction and immunohistochemistry were used for validation. Epigenetic modifiers were used to study gene regulation. The cell viability was quantified with MTT assay. Chromosomal analysis revealed multiple alterations in metastatic cell lines compared to T24-P. DNA microarray analysis showed that taxol resistance-associated gene (TRAG) 3 was the most upregulated gene. From real-time quantitative polymerase chain reaction and immunohistochemistry, TRAG3 was significantly higher in T24-L and T24-B than T24-P. TRAG3 gene expression is likely controlled by DNA methylation but not histone acetylation. Interestingly, T24-B and T24-L cells were more resistant than T24-P to treatment with antimicrotubule agents such as docetaxel, paclitaxel and vinblastine. TRAG3 mRNA expression was higher in 20% of patients with ≤ pT2 (n = 10) and 60% of patients with ≥ pT3 (n = 20) compared to normal adjacent tissue (p = 0.05). In addition, the median TRAG3 expression was 6.7-fold higher in ≥ pT3 tumors compared to ≤ pT2 tumors. Knowing the status of TRAG3 expression could help clinicians tailor treatment to a particular patient population that could benefit from treatment, while allocating patients with resistant tumors to new experimental therapies.

S110, a 5-Aza-2'-deoxycytidine-containing dinucleotide, is an effective DNA methylation inhibitor in vivo and can reduce tumor growth

Methylation of CpG islands in promoter regions is often associated with gene silencing and aberrant DNA methylation occurs in most cancers, leading to the silencing of some tumor suppressor genes. Reversal of this abnormal hypermethylation by DNA methylation inhibitors is effective in reactivating methylation-silenced tumor suppressor genes both in vitro and in vivo. Several DNA methylation inhibitors have been well studied; the most potent among them is 5-aza-2'-deoxycytidine (5-Aza-CdR), which can induce myelosuppression in patients. S110 is a dinucleotide consisting of 5-Aza-CdR followed by a deoxyguanosine, which we previously showed to be effective in vitro as a DNA methylation inhibitor while being less prone to deamination by cytidine deaminase, making it a promising alternative to 5-Aza-CdR. Here, we show that S110 is better tolerated than 5-Aza-CdR in mice and is as effective in vivo in inducing p16 expression, reducing DNA methylation at the p16 promoter region, and retarding tumor growth in human xenograft. We also show that S110 is effective by both i.p. and s.c. deliveries. S110 therefore is a promising new agent that acts similarly to 5-Aza-CdR and has better stability and less toxicity.

Impact of genomic methylation on radiation sensitivity of colorectal carcinoma

PURPOSE

To investigate the influence of demethylation with 5-aza-cytidine (AZA) on radiation sensitivity and to define the intrinsic radiation sensitivity of methylation deficient colorectal carcinoma cells.

METHODS AND MATERIALS

Radiation sensitizing effects of AZA were investigated in four colorectal carcinoma cell lines (HCT116, SW480, L174 T, Co115), defining influence of AZA on proliferation, clonogenic survival, and cell cycling with or without ionizing radiation. The methylation status for cancer or DNA damage response-related genes silenced by promoter methylation was determined. The effect of deletion of the potential target genes (DNMT1, DNMT3b, and double mutants) on radiation sensitivity was analyzed.

RESULTS

AZA showed radiation sensitizing properties at >or=1 micromol/l, a concentration that does not interfere with the cell cycle by itself, in all four tested cell lines with a sensitivity-enhancing ratio (SER) of 1.6 to 2.1 (confidence interval [CI] 0.9-3.3). AZA successfully demethylated promoters of p16 and hMLH1, genes associated with ionizing radiation response. Prolonged exposure to low-dose AZA resulted in sustained radiosensitivity if associated with persistent genomic hypomethylation after recovery from AZA. Compared with maternal HCT116 cells, DNMT3b-defcient deficient cells were more sensitive to radiation with a SER of 2.0 (CI 0.9-2.1; p = 0.03), and DNMT3b/DNMT1-/- double-deficient cells showed a SER of 1.6 (CI 0.5-2.7; p = 0.09).

CONCLUSIONS

AZA-induced genomic hypomethylation results in enhanced radiation sensitivity in colorectal carcinoma. The mediators leading to sensitization remain unknown. Defining the specific factors associated with radiation sensitization after genomic demethylation may open the way to better targeting for the purpose of radiation sensitization.

Bioluminescent imaging: a critical tool in pre-clinical oncology research

Bioluminescent imaging (BLI) is a non-invasive imaging modality widely used in the field of pre-clinical oncology research. Imaging of small animal tumour models using BLI involves the generation of light by luciferase-expressing cells in the animal following administration of substrate. This light may be imaged using an external detector. The technique allows a variety of tumour-associated properties to be visualized dynamically in living models. The increasing use of BLI as a small-animal imaging modality has led to advances in the development of xenogeneic, orthotopic, and genetically engineered animal models expressing luciferase genes. This review aims to provide insight into the principles of BLI and its applications in cancer research. Many studies to assess tumour growth and development, as well as efficacy of candidate therapeutics, have been performed using BLI. More recently, advances have also been made using bioluminescent imaging in studies of protein-protein interactions, genetic screening, cell-cycle regulators, and spontaneous cancer development. Such novel studies highlight the versatility and potential of bioluminescent imaging in future oncological research.

Double stranded-RNA-mediated activation of P21 gene induced apoptosis and cell cycle arrest in renal cell carcinoma

Small double stranded RNAs (dsRNA) are a new class of molecules which regulate gene expression. Accumulating data suggest that some dsRNA can function as tumor suppressors. Here, we report further evidence on the potential of dsRNA mediated p21 induction. Using the human renal cell carcinoma cell line A498, we found that dsRNA targeting the p21 promoter significantly induced the expression of p21 mRNA and protein levels. As a result, dsP21 transfected cells had a significant decrease in cell viability with a concomitant G1 arrest. We also observed a significant increase in apoptosis. These findings were associated with a significant decrease in survivin mRNA and protein levels. This is the first report that demonstrates dsRNA mediated gene activation in renal cell carcinoma and suggests that forced over-expression of p21 may lead to an increase in apoptosis through a survivin dependent mechanism.

High-throughput quantitative bioluminescence imaging for assessing tumor burden

Bioluminescence imaging (BLI) has emerged during the past 5 years as the preeminent method for rapid, cheap, facile screening of tumor growth and spread in mice. Both subcutaneous and orthotopic tumor models are readily observed with high sensitivity and reproducibility. User-friendly commercial instruments exist and, increasingly, luciferase-expressing tumor cells are available in academic institutions or commercially. There is an increasing literature on routine use of BLI for assessing chemotherapeutic efficacy, drug combinations, dosing, and timing. In addition, BLI may be applied to more sophisticated questions of molecular biology by including specific promoter sequences. This chapter will describe routine methods used to support multiple investigators in our small animal imaging resource.

Epigenetics in bladder cancer

Bladder cancer (BC) is the second most common malignancy of the genitourinary tract and the second leading cause of cancer death in patients with urinary tract malignancies. DNA methylation and histone modifications are important epigenetic mechanisms of gene regulation and play essential roles both independently and cooperatively in tumor initiation and progression. Aberrant epigenetic events such as DNA hypermethylation and altered histone acetylation have both been observed in bladder cancer, in which they affect a large number of genes. Although the list of aberrantly epigenetically regulated genes continues to grow, combination analysis including several candidate genes has given promising results of potential tumor biomarkers for the early diagnosis and risk assessment of bladder cancer. Thus, large-scale screening of aberrant epigenetic events such as DNA hypermethylation is needed to identify bladder cancer-specific epigenetic fingerprints. The reversibility of epigenetic aberrations has made them attractive targets for cancer treatment with modulators that demethylate DNA and inhibit histone deacetylases, leading to the reactivation of silenced genes. In this review, we examine the current literature on epigenetic changes in bladder cancer and discuss the clinical potential of cancer epigenetics for the diagnosis and treatment of this disease.

The Impact of Genomics in Understanding Human Melanoma Progression and Metastasis

Background

Recent technological advances in the analysis of the human genome have opened the door to improving our primitive understanding of the gene expression patterns in cancer. For the first time, we have an overview of the complexities of tumorigenesis and metastatic progression of cancer. The examination of the phenotypic and (epi)genetic changes in cutaneous melanoma has identified several genes deemed central to the development and progression of melanoma.

Methods

A review of the recent literature was performed to determine the role of array-based high-throughput gene expression analysis in understanding the specific genes involved as well as the pathways and the comparative gene expression patterns of primary and metastatic melanoma.

Results

Most studies utilizing gene microarray analysis and other whole genome approaches reveal a wide array of genes and expression patterns in human melanoma. Furthermore, several of the same genes have been found in comparative studies, with some studies attempting correlation with clinical outcome. Several genes have been identified as potential prognostic markers of tumor progression and overall clinical outcome.

Conclusions

High-throughput gene expression analysis has had a major impact in melanoma research. Several gene expression platforms have provided insight into the gene expression patterns in melanoma. Such data will provide the foundations for the future development of prognostic markers and improved targeted therapies for patients with melanoma.

Antitumor effect of dsRNA-induced p21(WAF1/CIP1) gene activation in human bladder cancer cells

We recently reported that synthetic dsRNAs targeting promoter regions can induce gene expression in a phenomenon referred to as dsRNA-induced gene activation/RNA activation (RNAa) [Li et al. Proc Natl Acad Sci U S A 2006;103:17337-42]. The present study investigates the in vitro antitumor activity RNAa can elicit through triggering the expression of cell cycle repressor protein p21(WAF1/CIP1) (p21) in human bladder cancer cells. Transfection of a 21-nucleotide dsRNA targeting the p21 promoter (dsP21) was used to induce p21 expression in T24 and J82 bladder cancer cell lines. Reverse transcription-PCR and Western blot analysis accessed the increase p21 mRNA and protein levels, respectively, in transfected cells. In association to p21 induction, dsP21 transfection significantly inhibited bladder cancer cell proliferation and clonogenicity. Further analysis of cell viability and cell cycle distribution revealed that dsP21 transfection also enhanced apoptotic cell death and caused an accumulation in the G(1) phase in both cell lines. In conclusion, p21 activation by RNAa has antitumor activity in vitro in bladder cancer cells. These results suggest that RNAa could be used for cancer treatment by targeted activation of tumor suppressor genes.

Intravesical chemotherapy of high-grade bladder cancer with HTI-286, a synthetic analogue of the marine sponge product hemiasterlin

PURPOSE

HTI-286 is a fully synthetic analogue of the natural tripeptide hemiasterlin that inhibits tubulin polymerization and has strong cytotoxic potential. In this study, we evaluate the inhibitory effects of HTI-286 on human bladder cancer growth, both in vitro and as an intravesical agent in an orthotopic murine model.

EXPERIMENTAL DESIGN

Various bladder cancer cell lines were treated with HTI-286 and mitomycin C (MMC) in vitro. Human KU-7 bladder tumor cells that stably express firefly luciferase were inoculated in female nude mice by intravesical instillation and quantified using bioluminescence imaging. Mice with established KU-7-luc tumors were given HTI-286 or MMC intravesically twice a week for 2 h. Pharmacokinetic data was obtained using high-performance liquid chromatography-mass spectrometry analyses.

RESULTS

In vitro, HTI-286 was a potent inhibitor of proliferation in all tested cell lines and induced marked increases in apoptosis of KU-7-luc cells even after brief exposure. In vivo, HTI-286 significantly delayed cancer growth of bladder tumors in a dose-dependent fashion. HTI-286, at a concentration of 0.2 mg/mL, had comparable strong cytotoxicity as 2.0 mg/mL of MMC. The estimated systemic bioavailability of intravesically given HTI-286 was 1.5% to 2.1% of the initial dose.

CONCLUSIONS

Intravesical HTI-286 instillation therapy showed promising antitumor activity and minimal toxicity in an orthotopic mouse model of high-grade bladder cancer. These findings provide preclinical proof-of-principle for HTI-286 as an intravesical therapy for nonmuscle-invasive bladder cancer and warrant further evaluation of efficacy and safety in early-phase clinical trials.

The efficacy of combination therapy using adeno-associated virus--interferon beta and trichostatin A in vitro and in a murine model of neuroblastoma

PURPOSE

Trichostatin A (TSA) is a potent histone deacetylase inhibitor and has demonstrated significant antitumor activity against a variety of cancer cell lines. Type I interferons have also shown significant antitumor as well as antiangiogenic activity. In this study, we examined the effectiveness of combination therapy of TSA and interferon beta (IFN-beta) on human neuroblastoma cells in vitro and in vivo using a murine model of retroperitoneal neuroblastoma.

MATERIALS AND METHODS

For in vitro experiments, plated human neuroblastoma cells (NB-1643 and NB-1691) were treated with vehicle or with IFN-beta, TSA, or both for 24 hours. Cytotoxicity was assessed by counting cells and expressing the results as a percentage of controls. Expression of the tumor suppressor p21(Waf1) was assessed by Western blot. For in vivo experiments, retroperitoneal neuroblastomas were established in severe combined immune deficiency (SCID) mice. Interferon beta was given using a gene therapy approach, administering 1.5 x 10(10) particles of an adeno-associated virus vector encoding human IFN-beta (AAV hIFN-beta) via tail vein as a single dose per mouse. Trichostatin A was given at a dose of 5 mg/kg every 48 hours subcutaneously. Treatment groups included controls, AAV hIFN-beta alone, TSA alone, and AAV hIFN-beta together with TSA. Tumor volume was assessed 2 weeks after the treatment began.

RESULTS

After 24 hours, treatment with IFN-beta, TSA, and a combination of both resulted in a 45.3%, 68.1%, and 75% reduction in cell count relative to controls in the NB-1691 cell line. In the NB-1643 line, cell counts were reduced by 23%, 58%, and 62.3% respectively. In addition, NB-1691 cells treated with TSA showed increased expression of p21(Waf1) on Western blot. For in vivo experiments, control-, AAV hIFN-beta-, TSA-, and combination-treated tumors had the following final volumes: 1577.7 +/- 264.2 mm(3) (n = 3); 128.5 +/- 74.4 mm(3) (n = 4; P = .0001); 1248.7 +/- 673.9 mm(3) (n = 4; P = .48); and 127.5 +/- 36.8 mm(3) (n = 4; P = .0007), respectively.

CONCLUSION

Neuroblastoma, because of its unique biology, continues to be a challenging tumor to treat, and many times these tumors are refractory to standard chemotherapeutic regimens. These data show that both TSA and IFN-beta inhibit neuroblastoma growth and that the combination may potentially provide a unique way to treat this difficult disease.

A validated mouse model for orthotopic bladder cancer using transurethral tumour inoculation and bioluminescence imaging

OBJECTIVES

To describe a technique for transurethral tumour inoculation, bioluminescence imaging (BLI) and validation of this approach using ex vivo magnetic resonance imaging (MRI), as a reproducible and quantifiable model of orthotopic bladder cancer is required to enable preclinical pharmacological studies of intravesically administered anticancer agents and the use of BLI provides a sensitive method to monitor tumour growth over time.

MATERIALS AND METHODS

Human KU-7 bladder tumour cells were transduced with a lentiviral construct to stably express the firefly luciferase gene. These cells were then inoculated in female nude mice by intravesical instillation. BLI was performed weekly and the mice were killed after 4 weeks. Ex vivo MRI and whole-mount step-sections were obtained to assess bladder tumour volume.

RESULTS

KU-7 tumour cells were highly tumorigenic and were successfully inoculated in 96% of mice. After 4 weeks, all tumours were confined to the mucosa and submucosa (</=pT1). There was an excellent correlation between tumour volume and BLI for both ex vivo bladder MRI (R(2) = 0.929) and end-point histological measurements (R(2) = 0.836).

CONCLUSIONS

We have established and validated a reliable model of orthotopic bladder cancer that can be used to evaluate various methods of intravesical therapy. BLI allows excellent longitudinal surveillance and quantification of tumour burden.