Evaluation of the antitumor activity of dacomitinib in models of human bladder cancer.

Members of the human epidermal growth factor receptor (HER) family play a significant role in bladder cancer progression and may underlie the development of chemotherapy resistance. Dacomitinib is an irreversible tyrosine kinase inhibitor with structural specificity for the catalytic domains of epidermal growth factor receptor (EGFR), HER2 and HER4 that has exhibited vigorous efficacy against other solid tumors. We evaluated the antitumor activity of dacomitinib in human bladder cancer cell lines expressing varying levels of HER family receptors. These cell lines also were established as bladder cancer xenografts in nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice to assess dacomitinib activity in vivo. Significant cytotoxic and cytostatic effects were noted in cells expressing elevated levels of the dacomitinib target receptors with apoptosis and cell cycle arrest being the predominant mechanisms of antitumor activity. Cells expressing lower levels of HER receptors were much less sensitive to dacomitinib. Interestingly, dacomitinib was more active than either trastuzumab or cetuximab in vitro, and exhibited increased growth inhibition of bladder tumor xenografts compared with lapatinib. Pharmacodynamic effects of dacomitinib included decreased E-cadherin (E-cad) expression, reduction of EGFR and extracellular signal-regulated kinase (ERK) phosphorylation and reduced mitotic count. Dacomitinib also inhibited tumor growth in a chemotherapy-resistant xenograft and, when combined with chemotherapy in a sensitive xenograft, exhibited superior antitumor effects compared with individual treatments. Evaluation in xenograft-bearing mice revealed that this combination was broadly feasible and well tolerated. In conclusion, dacomitinib exhibited pronounced activity both as a single agent and when combined with chemotherapy in human bladder cancer models. Further investigation of dacomitinib in the preclinical and clinical trial settings is being pursued.

Loss of 15-hydroxyprostaglandin dehydrogenase expression contributes to bladder cancer progression.

Prostaglandin E2, which is known to contribute to cancer progression, is inactivated by the catabolic enzyme, 15-hydroxyprostaglandin dehydrogenase (PGDH), which has tumor-suppressor activity in lung, colon, breast, and gastric cancers. Therefore, we evaluated the expression of PGDH in human bladder cancer tissue specimens and cell lines. Immunoperoxidase staining of bladder cancer tissues demonstrated that (1) PGDH is highly expressed by normal urothelial cells but (2) reduced in many low stage (Ta/Tis) bladder cancers, and (3) PGDH is completely lost in most invasive bladder cancers. Of eight cancer cell lines tested, only two relatively well-differentiated bladder cancer cell lines, RT4 and UM-UC9, expressed PGDH. Moreover, inhibition of PGDH expression in well-differentiated RT4 cells using small inhibitory RNA or short hairpin RNA resulted in a more aggressive phenotype with increased motility and anchorage-independent growth. Additionally, PGDH knockdown affected prostaglandin E2 signaling as measured by cAMP generation. These data indicate that loss of PGDH expression contributes to a more malignant bladder cancer phenotype and may be necessary for bladder cancer development and/or progression.

Interleukin-8 is essential for normal urothelial cell survival.

Interleukin-8 (IL-8; CXCL8) has been shown to play a role in multiple cellular processes. Here, we report an additional role of IL-8 as a growth and essential survival factor for normal human urothelial cells. Supplementing exogenous recombinant human IL-8 to normal urothelial cells promoted cell growth through the Akt pathway. Inhibition of IL-8 expression by small inhibitory RNA (siRNA) caused normal urothelial cells to die. Addition of recombinant human IL-8 rescued the normal urothelial cells treated with IL-8 siRNA. This rescue effect could be blocked by antibodies to the IL-8 receptor CXCR1 but not by CXCR2, suggesting that normal urothelial cells normally have IL-8 autocrine or paracrine activity for survival and growth mediated by CXCR1. IL-8 mRNA levels were lower in samples from patients with interstitial cystitis, a urinary bladder disorder associated with urothelial cell dysfunction and/or loss. Taken together, these results suggest that IL-8 is an important normal urothelial growth factor and is necessary for normal urothelial cell survival in vitro and in vivo. Lower IL-8 expression levels in the urinary bladder may contribute to pathophysiology of interstitial cystitis.

A surgical orthotopic approach for studying the invasive progression of human bladder cancer.

The invasion of bladder cancer into the sub-urothelial muscle and vasculature are key determinants leading to lethal metastatic progression. However, the molecular basis is poorly understood, partly because of the lack of uncomplicated and reliable models that recapitulate the biology of locally invasive disease. We developed a surgical grafting technique, characterized by a simple, rapid, reproducible and high-efficiency approach, to recapitulate the pathobiological events of human bladder cancer invasion in mice. This technique consists of a small laparotomy and direct implantation of human cancer cells into the bladder lumen. Unlike other protocols, it does not require debriding of the urothelial lining, injection into the bladder wall, specialized imaging equipment, bladder catheterization or costly surgical equipment. With minimal practice, the procedure can be executed in <10 min. Tumors develop with a high take rate, and most cell lines exhibit local invasion within 4 weeks of implantation.

Molecular Correlates of In Vitro Responses to Dacomitinib and Afatinib in Bladder Cancer.

BACKGROUND: The HER family of proteins (EGFR, HER2, HER3 and HER4) have long been thought to be therapeutic targets for bladder cancer, but previous clinical trials targeting these proteins have been disappointing. Second generation agents may be more effective. OBJECTIVE: The aim of this study was to evaluate responses to two second-generation irreversible tyrosine kinase inhibitors, dacomitinib and afatinib, in bladder cancer cell lines. METHODS: Cell lines were characterized by targeted next generation DNA sequencing, RNA sequencing, western blotting and flow cytometry. Cell survival responses to dacomitinib or afatinib were determined using (3-[4,5-dimethylthioazol-2-yl]-2,5-diphenyl tetrazolium bromide) (MTT) or [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and phenazine methosylfate (PMS) cell survival assays. RESULTS: Only two cell lines of 12 tested were sensitive to afatinib. Sensitivity to afatinib was significantly associated with mutation in either HER2 or HER3 (p < 0.05). The two cell lines sensitive to afatinib were also responsive to dacomitinib ralong with an additional 4 other cell lines out of 16 tested. No characteristic was associated with dacomitinib sensitivity. Molecular profiling demonstrated that only two genes were high in both afatinib and dacomitinib sensitive cells. Further rhigher expression of RAS pathway genes was noted for dacomitinib responsive cells. CONCLUSIONS: This study confirms that cell line screening can be useful in pre-clinical evaluation of targeted small molecule inhibitors and suggests that compounds with similar structure(s) and target(s) may have distinct sensitivity profiles. Further rcombinational targeting of additional molecularly relevant pathways may be important in enhancing responses to HER targeted agents in bladder cancer.

Targeted DNA and RNA Sequencing of Paired Urothelial and Squamous Bladder Cancers Reveals Discordant Genomic and Transcriptomic Events and Unique Therapeutic Implications.

BACKGROUND: Integrated molecular profiling has identified intrinsic expression-based bladder cancer molecular subtypes. Despite frequent histological diversity, robustness of subtypes in paired conventional (urothelial) and squamous components of the same bladder tumor has not been reported. OBJECTIVE: To assess the impact of histological heterogeneity on expression-based bladder cancer subtypes. DESIGN, SETTING, AND PARTICIPANTS: We performed clinically applicable, targeted DNA and/or RNA sequencing (multiplexed DNA and RNA sequencing [mxDNAseq and mxRNAseq, respectively]) on 112 formalin-fixed paraffin-embedded (FFPE) bladder cancer samples, including 12 cases with paired urothelial/squamous components and 21 bladder cancer cell lines. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Unsupervised hierarchical and consensus clustering of target gene expression enabled derivation of basal/luminal molecular subtyping. RESULTS AND LIMITATION: Across 21 bladder cancer cell lines, our custom mxRNAseq panel was highly concordant with whole transcriptome sequencing, and assessed targets robustly determined expression-based basal/luminal subtypes from The Cancer Genome Atlas data (in silico) and internally sequenced FFPE tissues. Frequent deleterious TP53 (56%) and activating hotspot PIK3CA (30%) somatic mutations were seen across 69 high-quality tissue samples. Potentially targetable focal ERBB2 (6%) or EGFR (6%) amplifications were also identified, and a novel subgene copy-number detection approach is described. Combined DNA/RNA analysis showed that focally amplified samples exhibit outlier EGFR and ERBB2 expression distinct from subtype-intrinsic profiles. Critically, paired urothelial and squamous components showed divergent basal/luminal status in three of 12 cases (25%), despite identical putatively clonal prioritized somatic genomic alterations. Limitations include lack of profiled paired normal tissues for formal somatic alteration determination, and the need for formal analytical and clinical validation. CONCLUSIONS: Our results support the feasibility of clinically relevant integrative bladder cancer profiling and challenge the intrinsic nature of expression subtypes in histologically diverse bladder cancers. PATIENT SUMMARY: A targeted RNA sequencing assay is capable of assessing gene expression-based subtypes in individual components of clinical bladder cancer tissue specimens. Different histological components of the same tumor may yield divergent expression profiles, suggesting that expression-based subtypes should be interpreted with caution in heterogeneous cancers.

Comparing the effect of ATRA, 4-HPR, and CD437 in bladder cancer cells.

Clinical trials have explored the use of natural and synthetic retinoids for the prevention of bladder cancer recurrence. Natural retinoids have been shown to inhibit bladder cancer growth. Here, we compared the effects of natural and synthetic retinoids in bladder cancer cells. Bladder cancer cell lines were treated with all-trans-retinoid acid (ATRA), N-4-hydroxyphenyl-retinamide (4-HPR) and 6-[3-(1-adamantyl)-4 hydroxyphenyl]-2-naphthalene carboxylic acid (CD437). Their effects on cell growth, apoptosis, cell cycle, gene expression, and retinoid acid receptors (RARs) and the JWA-retinoid response gene were assessed. Most of the bladder cancer cells were resistant to ATRA (1 and 10 microM). 4-HPR inhibited cell growth by 90% at 10 microM; however, CD437 showed the same effect at 1 microM. 4-HPR and CD437 increased G1 and decreased S phase. The three retinoids differentially affected p53, RARs, and JWA. Only CD437 increased Caspase 3 expression. The results demonstrated that 4-HPR and CD437 were more potent growth inhibitors and apoptosis inducers than ATRA. However, 4-HPR was effective at a concentration at least 10 microM. The in vitro results suggested the higher dose of 4-HPR in chemoprevention trial be considered.

ADAM15 Is Functionally Associated with the Metastatic Progression of Human Bladder Cancer.

ADAM15 is a member of a family of catalytically active disintegrin membrane metalloproteinases that function as molecular signaling switches, shed membrane bound growth factors and/or cleave and inactivate cell adhesion molecules. Aberrant metalloproteinase function of ADAM15 may contribute to tumor progression through the release of growth factors or disruption of cell adhesion. In this study, we utilized human bladder cancer tissues and cell lines to evaluate the expression and function of ADAM15 in the progression of human bladder cancer. Examination of genome and transcriptome databases revealed that ADAM15 ranked in the top 5% of amplified genes and its mRNA was significantly overexpressed in invasive and metastatic bladder cancer compared to noninvasive disease. Immunostaining of a bladder tumor tissue array designed to evaluate disease progression revealed increased ADAM15 immunoreactivity associated with increasing cancer stage and exhibited significantly stronger staining in metastatic samples. About half of the invasive tumors and the majority of the metastatic cases exhibited high ADAM15 staining index, while all low grade and noninvasive cases exhibited negative or low staining. The knockdown of ADAM15 mRNA expression significantly inhibited bladder tumor cell migration and reduced the invasive capacity of bladder tumor cells through MatrigelTM and monolayers of vascular endothelium. The knockdown of ADAM15 in a human xenograft model of bladder cancer inhibited tumor growth by 45% compared to controls. Structural modeling of the catalytic domain led to the design of a novel ADAM15-specific sulfonamide inhibitor that demonstrated bioactivity and significantly reduced the viability of bladder cancer cells in vitro and in human bladder cancer xenografts. Taken together, the results revealed an undescribed role of ADAM15 in the invasion of human bladder cancer and suggested that the ADAM15 catalytic domain may represent a viable therapeutic target in patients with advanced disease.

ATDC/TRIM29 Drives Invasive Bladder Cancer Formation through miRNA-Mediated and Epigenetic Mechanisms.

Bladder cancer is a common and deadly malignancy but its treatment has advanced little due to poor understanding of the factors and pathways that promote disease. ATDC/TRIM29 is a highly expressed gene in several lethal tumor types, including bladder tumors, but its role as a pathogenic driver has not been established. Here we show that overexpression of ATDC in vivo is sufficient to drive both noninvasive and invasive bladder carcinoma development in transgenic mice. ATDC-driven bladder tumors were indistinguishable from human bladder cancers, which displayed similar gene expression signatures. Clinically, ATDC was highly expressed in bladder tumors in a manner associated with invasive growth behaviors. Mechanistically, ATDC exerted its oncogenic effects by suppressing miR-29 and subsequent upregulation of DNMT3A, leading to DNA methylation and silencing of the tumor suppressor PTEN. Taken together, our findings established a role for ATDC as a robust pathogenic driver of bladder cancer development, identified downstream effector pathways, and implicated ATDC as a candidate biomarker and therapeutic target.

N-(4-hydroxyphenyl)retinamide (4-HPR) modulates GADD45 expression in radiosensitive bladder cancer cell lines.

We previously demonstrated that N-(4-hydroxyphenyl)retinamide (4-HPR) and gamma-irradiation, when used in combination, had a synergistic effect in inducing apoptosis in bladder cancer cells, suggesting that 4-HPR may increase radiosensitivity in bladder cancer cells. To unravel molecular correlates in this radiosensitizing effect of 4-HPR, we examined the baseline and 4-HPR-induced expression of GADD45 to elucidate possible mechanisms by which 4-HPR enhanced the effect of gamma-irradiation in three bladder cancer cell lines. To investigate the role of p53 in mediating the radiosensitizing effect of 4-HPR, we also examined mutations in exons 5-9 by using direct sequencing and the levels of p53 expression by using RT-PCR and Western blot, before and after treatment with 4-HPR in these bladder cancer cell lines. Two cell lines had low expression of GADD45, and a dose-dependent increase in GADD45 expression induced by 4-HPR was found in bladder cancer cell lines without p53 mutations in exons 5-9. A combination of gamma-irradiation and 4-HPR showed a significantly greater effect in enhancing GADD45 expression than either agent used alone. The results indicate that the combined treatment with 4-HPR and gamma-irradiation has a stronger effect on GADD45 expression than the treatment with either agent alone, which suggests that the two agents may have an additive/synergistic effect. However, a normal p53 function appears to be necessary for the dose-dependent induction of GADD45 by 4-HPR. Once our results are verified and replicated by other investigators, 4-HPR may have a potential clinical implication in effectively treating bladder cancer in combination with low-gamma-irradiation therapy.

Current preclinical models for the advancement of translational bladder cancer research.

Bladder cancer is a common disease representing the fifth most diagnosed solid tumor in the United States. Despite this, advances in our understanding of the molecular etiology and treatment of bladder cancer have been relatively lacking. This is especially apparent when recent advances in other cancers, such as breast and prostate, are taken into consideration. The field of bladder cancer research is ready and poised for a series of paradigm-shifting discoveries that will greatly impact the way this disease is clinically managed. Future preclinical discoveries with translational potential will require investigators to take full advantage of recent advances in molecular and animal modeling methodologies. We present an overview of current preclinical models and their potential roles in advancing our understanding of this deadly disease and for advancing care.

Loss of 15-hydroxyprostaglandin dehydrogenase expression disrupts urothelial differentiation.

OBJECTIVES: Urothelial differentiation is essential for the maintenance of urinary bladder function. We explored the expression and function of 15-hydroxyprostaglandin dehydrogenase (PGDH) during urothelial differentiation. METHODS: We evaluated expression of PGDH by Northern and Western blotting and immunostaining in human urothelial cultures, cell lines, and tissues. We determined enzymatic function using enzyme-linked immunosorbent assay. Small inhibitory ribonucleic acids were used to inhibit PGDH expression in human bladder cancer cells. RESULTS: We found PGDH messenger ribonucleic acid was increased in an in vitro model of human urothelial differentiation by Northern blotting. Western blotting of human bladder cancer cell lines showed expression in the well-differentiated RT4 cells and no expression in poorly differentiated UC3 cells. Immunostaining showed that PGDH expression increased with differentiation in normal bladder urothelium. The enzyme was functional in the well-differentiated RT4 human bladder cancer cell line. Inhibition of PGDH expression resulted in disruption of E-cadherin expression at cell-cell contacts in well-differentiated RT4 bladder cancer cells. CONCLUSIONS: These studies indicate that PGDH expression is associated with urothelial differentiation, and loss of PGDH expression results in disruption of urothelial differentiation.

Urology residency and research: round table discussion and plea for innovation.

OBJECTIVES: To evaluate the current and future states of resident research experience in urology residencies in the United States. METHODS: Round table discussion with leading educators and Urology faculty from a university urology residency. RESULTS: Research exposure has rapidly diminished in urology residencies for a variety of reasons. There are multiple barriers to resident research and only a small number of residencies will be able to provide protected time. Nevertheless, an understanding of research methodology and biostatistics is required to be a successful clinician. CONCLUSIONS: Some barriers to resident research can be addressed by better integration of residency and fellowships. Flexibility in the format of resident education may allow introduction of new methods to encourage resident research scholarship. An education program with a research curriculum is needed for all residencies.

Erectile function outcome reporting after clinically localized prostate cancer treatment.

PURPOSE: In conjunction with the assignment to update the Guidelines for Management of Clinically Localized Prostate Cancer, the American Urological Association Prostate Cancer Guideline Update Panel performed a side analysis of the reporting of erectile function outcomes in this clinical context as published in the medical literature. MATERIALS AND METHODS: Four National Library of Medicine PubMed(R) Services literature searches targeting articles published from 1991 through early 2004 were done to derive outcome reporting (efficacy or side effects) for the treatment of clinical stage T1 or T2 N0M0 prostate cancer. A database was constructed containing descriptions relating to erectile function as well as numerical frequency rates of complete erectile dysfunction, and partial and intact erectile function for various treatments. A literature review was also done, consisting of a PubMed Services search of current measures and protocols used for assessing erectile function outcomes and a survey of consensus opinion sources on the management of male sexual dysfunctions. RESULTS: Based on inclusion criteria 436 articles were selected. Of these articles database extraction from 100 pertaining to radical prostatectomy garnered various characterizations of erectile function, including qualitative descriptions, generic terminology and rating systems. Database extraction from 31 articles, in which results for at least 50 patients were reported, yielded ranges of rates for complete erectile dysfunction, partial erectile function and intact erectile function that were 26% to 100%, 16% to 48% and 9% to 86% for radical prostatectomy, 8% to 85%, 21% to 47% and 36% to 63% for external beam radiation, and 14% to 61%, 21% and 18% for interstitial radiation, respectively. The literature review showed an evolution in standards for studying and reporting erectile function outcomes. CONCLUSIONS: Clinical studies reporting erectile function outcomes after localized prostate cancer treatment often demonstrate poorly interpretable and inconsistent manners of assessment as well as widely disparate rates of erectile dysfunction and erectile function. Future studies must apply scientifically rigorous methodology and standard outcomes measures to advance this field of study.

Proceedings of the Baltimore smooth muscle meeting: identifying research frontiers and priorities for the lower urinary tract.

PURPOSE: The myocyte is a major parenchymal cell of the lower urinary tract (LUT) in men and women. Significant phenotypic diversity ensures that myocytes subserve their important role in the physiologically distinct tissues and organs of the LUT, including the ureters, bladder, urethra, prostate, penis, vagina and myometrium. Coordinated contraction and relaxation of myocytes is required for normal organ function, while alterations in myocyte structure/function are implicated in the etiology of various LUT diseases/disorders. LUT diseases/disorders will continue to increase in an ever aging American population. The purpose of the Baltimore Smooth Muscle Meeting was to begin to identify some research frontiers and priorities. MATERIALS AND METHODS: A 1-day conference of some of the leading world experts in smooth muscle research was held at American Urological Association headquarters. These experts gave presentations in their areas of expertise and extensively discussed their work. This report details those interactions. RESULTS: There is astonishing diversity in the contribution of the myocyte to LUT physiology and dysfunction. Novel tools, technologies and ideas have produced increased understanding and identified new frontiers. CONCLUSIONS: An improved understanding of urogenital myocyte physiology, function and dysfunction is required better to elucidate disease mechanisms and develop novel therapeutics. The First Annual Baltimore Smooth Muscle Meeting provided the first step in this direction. More coordinated LUT myocyte funding initiatives, the further development of research resources, tools and technologies, and exploration of the urogenital system as a model system for studying systems biology and integrative physiology are among the highest research priorities.

Effect of retinoic acid and interferon alpha-2a on transitional cell carcinoma of bladder.

PURPOSE: Retinoids modulate the growth and differentiation of normal and malignant epithelial cells in vitro and in vivo. Retinoids and their analogues have been used in animal models and clinical trials of chemoprevention and superficial bladder cancer treatment. Interferons are cytokines that have antiviral, antiproliferative and immunomodulatory function. They are used in many clinical trials for the treatment of different cancers. To identify new effective agents and develop novel approaches for the chemoprevention and treatment of superficial bladder cancer we investigated the effects of a combination of retinoids and interferon alpha-2a (IFN) on growth and apoptosis in bladder cancer cell lines. MATERIALS AND METHODS: The 4 bladder cancer cell lines UM-UC-6, UM-UC-9, UM-UC-10 and UM-UC-13 were treated with 2 retinoids, namely all-trans-retinoic acid (ATRA) and 9-cis retinoic acid (9cRA), as well as with IFN or with combinations of retinoids and IFN. The ability of these agents used alone and in combination to inhibit growth, induce apoptosis and modulate gene expression was investigated. The effects of retinoids on an INF related gene were also examined. RESULTS: Most bladder cancer cell lines were resistant to growth inhibition and apoptosis induction by ATRA and 9cRA, even at a high concentration. The effects of these retinoids on cell growth and apoptosis were enhanced by IFN. The combination of ATRA and IFN induced retinoic acid receptor beta, and signal transducer and activator of transcription 1 expression in 3 bladder cancer cell lines, as detected by reverse transcriptase-polymerase chain reaction and Western blot analysis. Retinoids increased IFN-related gene expression detected by microarray analysis and real-time reverse transcriptase-polymerase chain reaction. CONCLUSIONS: The results demonstrate that IFN acts synergistically with ATRA and 9cRA in the growth and apoptosis of bladder cancer cells in vitro and suggest that this combination has a potential for the treatment of transitional cell carcinoma of the bladder.

Suppression of 15-hydroxyprostaglandin dehydrogenase messenger RNA concentration, protein expression, and enzymatic activity during human ureteral obstruction.

Prostanoids produce significant effects in the ureter, particularly in response to obstruction. Ureteral obstruction is associated with increased prostanoid synthesis via cyclooxygenase induction; however, prostaglandin degradation mediated by 15-hydroxyprostaglandin dehydrogenase (PGDH) has not been evaluated in the ureter. The purpose of this study was to determine whether PGDH steady-state mRNA, protein, and enzyme activity are altered in the human ureter during obstruction. Human ureteral segments from patients undergoing donor nephrectomy (normal segments) or ureteral stricture repair (obstructed segments) were obtained with proper informed consent. We evaluated PGDH steady-state mRNA relative to ribosomal protein S26 reference gene by reverse transcription-polymerase chain reaction and Vistra Green fluoroimaging. We determined PGDH protein content relative to glyceraldehyde-3-phosphate dehydrogenase by immunoblotting and PGDH localization by immunohistochemistry. PGDH enzymatic activity was determined by measurement of conversion of 15-hydroxy- to 15-keto-prostaglandin using thin layer chromatography separation. We found that PGDH mRNA and protein were decreased 4- to 6-fold, and enzyme activity was decreased >3-fold in obstructed human ureter relative to normal controls. PGDH was localized to the urothelial cells, with little or no expression in smooth muscle. Our results indicate that PGDH mRNA, protein, and enzyme activity are suppressed in the human ureter during obstruction. Increased concentrations of prostanoids subsequent to ureteral obstruction seem to be due to decreased degradation as well as increased synthesis. Modulation of prostanoid degradation may have therapeutic relevance in obstructive disorders of the ureter.

Growth inhibition and apoptosis induction by retinoic acid and interferon combined use on transitional cell carcinoma of bladder / 中华泌尿外科杂志

Objective To investigate the effects of combination of retinoids and interferon ?-2a on growth inhibition and apoptosis induction in bladder cancer cell lines. Methods Four bladder cancer cell lines and two retinoids,all-trans-retinoic acid (ATRA),9-cis retinoic acid (9cRA),combined with interferon ?-2a(IFN),were used in the study.The abilities of these agents to inhibit growth,induce apoptosis were compared and the expression of nuclear retinoid receptors,Stat1 protein were measured by means of TUNEL,FCM,RT-PCR and Western blot. Results Most of the bladder cancer cell lines were resistant to the effect of ATRA and 9cRA on growth inhibition and apoptosis induction.The effects of ATRA and 9cRA on cell growth and apoptosis were enhanced by IFN ?-2a.Combination of ATRA and IFN ?-2a induced RAR? and Stat 1 expression in three bladder cancer cell lines. Conclusions INF ?-2a synergizes with the inhibitory effect of ATRA and 9cRA on the growth inhibition and apoptosis of bladder cancer cells in vitro,up-regutation of Stat1 gene expression could be the main molecular mechanism.