CHEMOSENSITIZATION OF BLADDER CARCINOMA CELLS BY BCL-xL ANTISENSE OLIGONUCLEOTIDES

Antisense- and siRNA-mediated inhibition of the anti-apoptotic gene Bcl-xL for chemosensitization of bladder cancer cells

Bcl-xL is an apoptosis inhibitor that is upregulated in bladder cancer (BCa) and provides an attractive target for molecular therapies. Treatment with specific antisense oligodeoxynucleotides (AS‑ODNs) or small interfering RNAs (siRNAs) were able to sensitize BCa cells to conventional chemotherapeutics. Ten new Bcl‑xL‑targeting AS‑ODNs were systematically designed by using predicting software. AS‑BX2034 and AS‑BX2100 as well as the previously optimized siRNA construct si‑BX713 were selected for further detailed in vitro analysis in the BCa cell lines UM‑UC‑3 and EJ28. Bcl‑xL mRNA and protein expression levels, cell viability and apoptosis were examined 72 h after transfection. A single treatment with AS‑BX2034 or AS‑BX2100 caused only a low inhibition of the Bcl‑xL mRNA expression with the highest reduction of ≤20% in UM‑UC‑3 cells. In contrast, a single treatment with si‑BX713 strongly decreased Bcl‑xL mRNA expression level by ≤69% in UM‑UC‑3 cells and by ≤86% in EJ28 cells. Both gene expression inhibitor types induced a low to moderate reduction of viability. Depending on the cell line, a combined treatment with AS‑BX2100 or si‑BX713 and cisplatin (CDDP) caused an additional inhibition of cell viability by ~33 and 38%, respectively, compared to the respective control construct combined with CDDP. In comparison to the respective control treatment, combinations of AS‑BX2100 and CDDP led to a stronger induction of apoptosis by 57% in UM‑UC‑3 cells and 44% in EJ28 cells, whereas the combination of si‑BX713 and CDDP enhanced apoptosis by 38 and 118% in UM‑UC‑3 and EJ28 cells, respectively. Our comparative studies showed a stronger knockdown of Bcl‑xL by the siRNA construct compared to AS‑ODN treatment in both BCa cell lines. In combinatory treatments, the Bcl‑xL-directed siRNA markedly enhanced the anti-proliferative and apoptotic effects of CDDP and therefore, may serve as suitable tool for chemosensitization of BCa cells.

Prognostic significance of Bcl-xL expression and efficacy of Bcl-xL targeting therapy in urothelial carcinoma

BACKGROUND

Bcl-xL has an important role in the control of cell death through its inhibition of apoptosis. The aim of this study was to investigate the clinicopathological significance of Bcl-xL in upper urinary tract urothelial carcinoma (UTUC) and the therapeutic effect of targeting Bcl-xL protein in urothelial carcinoma (UC) cells.

METHODS

We evaluated the immunohistochemical expression of Bcl-xL in 175 UTUC patients to determine the clinical role of Bcl-xL expression in clinical outcome. We used bafilomycin A1 (BMA) as a specific inhibitor of Bcl-xL to examine the biological effects in UC cells in vitro and in vivo.

RESULTS

Immunohistochemical analysis of Bcl-xL expression revealed that patients with a high Bcl-xL score had a significantly lower 5-year cancer-specific survival (CSS) rate (53.2%) than those with a low Bcl-xL score (77.2%) (P=0.0011). Multivariate analysis indicated that a high Bcl-xL score was an independent prognostic factor of CSS (P=0.023). BMA inhibited UMUC-3 cell proliferation in vitro by induction of apoptosis. Treatment with BMA significantly inhibited tumour growth in UMUC-3 tumours in this mouse xenograft model accompanied by an elevated apoptosis induction.

CONCLUSION

Bcl-xL appears to be a significant molecular marker for the prognosis of UTUCs. Targeting Bcl-xL may be a promising therapeutic strategy for patients with UC.

Contribution of either YY1 or BclXL-induced inhibition by the NO-donor DETANONOate in the reversal of drug resistance, both in vitro and in vivo. YY1 and BclXL are overexpressed in prostate cancer

Nitric oxide (NO) donors have been shown to activate or inhibit constitutively-activated survival/anti-apoptotic pathways, such as NF-κB, in cancer cells. We report here that treatment of drug-resistant human prostate carcinoma cell lines with high levels (500-1000 μM) of the NO-donor DETANONOate sensitized the resistant tumor cells to apoptosis by CDDP and the combination was synergistic. We hypothesized that DETANONOate inhibits previously identified NF-κB-regulated resistant factors such as Yin Yang 1 (YY1) and Bcl-2/BclXL. Lysates from tumor cells treated with DETANONOate showed inhibition of YY1 and BclXL expressions. Transfection with either YY1 or BclXL siRNA resulted in the inhibition of both YY1 and BclXL expressions and sensitized the cells to CDDP apoptosis. Mice bearing PC-3 tumor xenografts and treated with the combination of DETANONOate and CDDP resulted in significant inhibition of tumor growth; treatment with single agent alone did not have any effect on tumor growth. Analysis of patients TMA tissues with prostatic cancer revealed higher expression of both YY1 and BclXL as a function of tumor grades and their levels were directly correlated. Thus, both YY1 and BclXL are potential prognostic biomarkers. Overall, the above findings suggest that one mechanism of DETANONOate-induced sensitization of resistant tumor cells to CDDP correlated with the inhibition of NF-κB and its targets YY1 and BclXL. The examination of the combination of NO donors and cytotoxic therapy in the treatment of resistant prostate cancer may be warranted.

Emerging apoptosis agonists for bladder cancer

Bladder cancer is a very common and aggressive tumor entity. Unfortunately, common chemotherapy is not able to cure advanced bladder cancer. Therefore, several attempts have been made to improve the response to chemotherapy. Because changes in apoptotic pathways are frequent events in the development of chemoresistance of malignancies, pro-apoptotic treatment seems promising for the improvement of bladder cancer prognosis. Preclinical data show potential ways for a successful combination of apoptosis agonists with conventional chemotherapy. None of these principles has so far successfully been translated into clinical trials for bladder cancer. This review describes actual studies and future perspectives for apoptotic agonists in bladder cancer.

Molecular pathogenesis and diagnostics of bladder cancer

Despite elaborate characterization of the risk factors, bladder cancer is still a major epidemiological problem whose incidence continues to rise each year. Urothelial carcinoma is now recognized as a disease of alterations in several cellular processes. The more prevalent, less aggressive, recurrent, noninvasive tumors are characterized by constitutive activation of the Ras-MAPK pathway. The less common but more aggressive invasive tumors, which have a higher mortality rate, are characterized by alterations in the p53 and retinoblastoma pathways. Several diagnostic tests have attempted to identify these molecular alterations in tumor cells exfoliated in the urine, whereas prognostic tests have tried to identify aberrations so as to predict tumor behavior and identify therapeutic targets. The future of bladder cancer patient management will rely on the use of molecular tests to reliably diagnose the presence of disease, predict individual tumor behavior, and suggest potential targeted therapeutics.

In vivo evaluation of intravesical paclitaxel and combined bcl-xL antisense oligodeoxynucleotide treatment for orthotopic urothelial carcinoma

PURPOSE

To evaluate intravesical paclitaxel monotherapy and combined treatment with antiapoptotic bcl-xL antisense oligodeoxynucleotides (AS-ODNs) on urothelial carcinoma (UC).

METHODS

Forty-eight FoxN(rnu) athymic nude rats with orthotopic human bladder UC were randomized to four treatment groups [1, paclitaxel; 2, paclitaxel/bcl-xL AS-ODNs; 3, bcl-xL AS-ODNs (control); 4, medium (control)]. Three consecutive instillations were applied and weekly endoscopic tumor size measurements were performed.

RESULTS

Significant tumor size reduction was achieved in groups 1 and 2 (each P < 0.0001), whereas continuous UC growth was observed in control animals (groups 3 and 4; P < 0.0001 and P < 0.0020). Complete tumor eradication was achieved in four treated animals (groups 1 and 2). No significant difference in chemoresection effects was found between groups 1 and 2 (P = 0.2251).

CONCLUSIONS

We present an in vivo evaluation of intravesical treatment with paclitaxel and combined bcl-xL AS-ODNs. Despite efficient tumor size reduction, no gain was observed when adding bcl-xL AS-ODNs in this experimental setting.

Optimizing chemotherapy for transitional cell carcinoma by application of bcl-2 and bcl-xL antisense oligodeoxynucleotides

OBJECTIVE

Therapy failure after intravesical and systemic chemotherapy for transitional cell carcinoma (TCC) is still high. Antiapoptotic proteins such as Bcl-2 and Bcl-xL have been reported to promote chemoresistance in TCC. Targeting bcl-2 and bcl-xL messenger ribonucleic acid with antisense oligodeoxynucleotides (AS-ODNs) may enhance the cytotoxic effects of chemotherapeutic agents. Therefore, we investigated the effects of bcl-2 and bcl-xL AS-ODNs in combined treatment with conventional and new chemotherapeutic agents to evaluate the cytotoxic effects in comparison to monotreatment.

METHODS AND MATERIALS

Western blot analysis or immunohistochemistry verified Bcl-2 and Bcl-xL expression in a panel of human TCC cell lines that had been monotreated with cisplatin, gemcitabine, mitomycin C, and paclitaxel. In addition, bcl-2 or bcl-xL AS-ODNs were applied in combination with each chemotherapeutic agent. Cell viability was determined using a standard MTT assay and Neubauer hemocytometry.

RESULTS

All cell lines responded to chemotherapeutic monotreatment in a dose-dependent manner. Maximum cell death rates after monotreatment were 47.4% (cisplatin), 39.0% (gemcitabine), 83.4% (mitomycin C), and 54.8% (paclitaxel). After combined treatment with chemotherapy and bcl-2 or bcl-xL AS-ODNs, cell death rates were significantly higher (e.g., 30.3% vs. 87.2% in HT 1197 cells for monotreatment vs. the combination of paclitaxel and bcl-xL AS-ODNs). Three-way analysis of variance revealed that combined treatment had a significant effect on all cell lines.

CONCLUSIONS

Our study confirms that the addition of bcl-2 and bcl-xL AS-ODNs enhances the cytotoxic potential of chemotherapeutic agents in TCC cell lines as a result of combined effects. Further trials in ex vivo and in vivo models have to be performed to promote clinical application in patients.

Preferential chemosensitization of PTEN-mutated prostate cells by silencing the Akt kinase

BACKGROUND

In prostate cancer, mutations of the phosphatase PTEN can activate the kinase cascade PI3K/Akt/mTOR which induces drug resistance.

METHODS

Chemosensitization by siRNA targeting Akt was studied in HEK293 cells forced to express CA-Akt or kinase-dead DN-Akt. To decrease drug resistance, Akt was silenced with siRNA in human prostate DU-145 cell line expressing the normal PTEN or in LNCaP and PC3 cell lines expressing mutated-PTEN. Taxol was used for the chemosensitization studies.

RESULTS

Silencing Akt in the drug-resistant CA-Akt cells efficiently sensitized cells to antitubule agents, whereas silencing drug-responsive DN-Akt cells did not. Only minor effects were obtained in wild-type HEK293 cells. Potentiation by siRNA of taxol cytotoxicity was significantly greater in mutated-PTEN cells than in prostate cells expressing wild-type PTEN. The apoptotic program induced by taxol was preferentially potentiated by Akt siRNA in PTEN-mutated cell lines as regards the DU-145 cell line.

CONCLUSIONS

Silencing Akt in PTEN-mutated prostate cancer cells enhances the antitumor effects of taxol. No siRNA chemosensitization was obtained in prostate cells with wild type PTEN.

New agents for treatment of advanced transitional cell carcinoma

The prognosis for any patient with progressive or recurrent invasive transitional cell carcinoma remains poor. In this context, the focus of clinical research in these invasive cancers concentrates on identifying systemic treatment options and new agents in order to improve survival of patients. Cisplatin-based chemotherapy is standard treatment of patients with metastatic urothelial cancer; however, despite regimens as the cisplatin-gemcitabine combination, the overall response rates vary between 40% and 65%, with complete response in 15%-25% with survivals up to 16 months. This survival is frequently achieved with severe and life-threatening side effects. None the less, almost all responding patients relapse within the first year; therefore, the need for development of new and tolerable agents is urgent. This review highlights some new active chemotherapeutic as new platinum compounds (oxaliplatin, lobaplatin), gallium nitrate, ifosfamide, the antifolates piritrexim and pemetrexed (Alimta, LY231514), vinflunine and molecular targeting agents such as farnesyltransferase inhibitors (lonafarnib, R115777, SCH66336), ribozyme (RPI.4610), histone deacetylase inhibitor (CI-994) and monoclonal antibodies (epidermal growth factor receptor, Her 2/neu).

Molecular biology of bladder cancer: prognostic and clinical implications

The role of various molecular determinants involved in the genesis, progression, and outcome of bladder cancer has been the focus of investigations for the past 2 decades. Increasingly, the analysis of the interplay between these molecular factors is taking center stage. We review herein the studies examining the effects of deregulation of the various molecules implicated in the cell cycle, apoptosis, and angiogenesis pathways and analyze the central role of p53 in regulating these pathways. Technological advancements enable detection and quantification of gene transcripts and protein products, helping us move toward achieving the goal of establishing diagnostic, prognostic, and therapeutic marker panels. Recent studies have therefore focused on multiple-marker analyses to generate informative panels that can have greater clinical value for bladder cancer management. The use of molecular marker panels can provide a more objective alternative to clinical parameters for diagnosis and treatment decisions. Clinical trials aimed at treating urothelial carcinoma based on a patient's molecular profile can be predicted to empower clinicians to personalize patient management through increased therapeutic efficacy.

Synthetic nucleic acids as potential therapeutic tools for treatment of bladder carcinoma

OBJECTIVES

Abnormal gene activation in human tumours including bladder cancers (bCAs) may cause altered proliferation, maturation, and apoptosis as well as development of resistance to therapeutic interventions. Therefore, silencing of abnormally activated genes appears to be a rational approach for specific target-directed and sensitising therapies.

METHODS

Of the available strategies for gene silencing, antisense-based techniques have attracted much attention and are the focus of this review. Putative target genes should be involved in essential tumour-promoting pathways, such as growth signalling, immortalisation, cell cycle regulation, apoptosis, angiogenesis, and development of therapy resistances. This review gives an overview of selected studies performed on bCA-derived cell lines and xenografts reporting down-regulation of potential target genes by antisense-based synthetic nucleic acids such as antisense oligodeoxynucleotides (AS-ODNs) and small interfering RNAs (siRNAs). Effects on proliferation of bCA cells and enhancement of the cytotoxic action of different chemotherapeutics were evaluated.

RESULTS

Knock-down of the selected target genes frequently caused an impairment of growth of different bCA cell lines originating from cell cycle arrest or increased apoptosis. In numerous studies, the pretreatment with AS-ODNs or siRNAs provoked strong enhancement of subsequent chemotherapies, emphasising the effectiveness of these inhibition approaches.

CONCLUSIONS

The application of antisense-based inhibitors in combination with chemotherapeutics might represent an alternative strategy for the adjuvant treatment of superficial bCA. Nevertheless, translation of this technology to the clinic might be hampered by inestimable off-target effects caused by AS-ODNs and their behaviour after intravesical instillation has to be evaluated in preclinical and clinical trials.

Chemosensitization of bladder cancer cells by survivin-directed antisense oligodeoxynucleotides and siRNA

Survivin is known to be overexpressed in numerous tumor types including human bladder cancer and to cause resistance to radiation and chemotherapy. Therefore, we tested the antisense oligodeoxynucleotide AS-SVV286 and the small interfering RNA si-SVV284 to down-regulate survivin in the BCa cell lines EJ28 and 5637 thereby acting as sensitizers for chemotherapy. Pretreatment with these inhibitors followed by chemotherapy caused an enhanced decrease in cell viability. The observed reduction in cell counts associated with increased rates of apoptosis paralleled the degree of reduction of survivin expression that was achieved more efficiently by the siRNA than by the AS-ODN. Nevertheless, both therapy approaches in combination with all tested chemotherapeutics provoked a remarkable inhibition of viability and may serve as suitable additive tools for chemosensitization of bladder cancer cells.

Antisense oligonucleotides in the treatment of bladder cancer

This review examines the role that antisense oligonucleotides play in the treatment of superficial and muscle-invasive bladder cancer. The unique environment of the urinary bladder allows intravesical instillation of antisense oligonucleotides, and researchers have already demonstrated uptake of antisense oligonucleotides in models of bladder cancer. Second, proof of principle has been established by demonstrating downregulation of the antisense target mRNA and protein. Third, and most importantly from a therapeutic perspective, synergy between chemotherapy and antisense oligonucleotides has been shown in bladder cancer models in vitro and in vivo. The collective evidence points to a role for antisense oligonucleotides in the treatment of superficial and muscle-invasive bladder cancer in combination with existing treatment modalities.

BH3 domain mutation of proapoptotic genes Bad, Bmf and Bcl-G is rare in transitional cell carcinomas of the urinary bladder

AIMS

Mounting evidence indicates that deregulation of apoptosis contributes to the development of human cancers. Bcl-2 family proteins regulate the intrinsic apoptosis pathway. The aim of this study was to explore the possibility that mutation of BH3 domain of proapoptotic Bcl-2 genes Bad, Bmf and Bcl-G might be involved in the development of urinary bladder cancer.

METHODS

We analysed the BH3 domains of Bad, Bmf and Bcl-G genes for the detection of somatic mutations in 43 transitional cell carcinomas (TCCs) of the urinary bladder by a single strand conformation polymorphism assay in this study.

RESULTS

There was no somatic mutation of BH3 domains of Bad, Bmf and Bcl-G genes in the TCC samples.

CONCLUSION

The data presented here indicate that BH3 domain mutation of these genes is rare in TCCs and may not contribute to the pathogenesis of TCCs.

Antisense oligodeoxynucleotide therapy for bladder cancer: recent advances and future prospects

Despite remarkable progress in therapeutic options for the management of bladder cancer, it remains a challenge for urologists to achieve successful outcomes in the treatment of both superficial and invasive bladder cancers. In this review, recent advances in the field of antisense oligodeoxynucleotide therapy targeting several genes playing functionally important roles in the progression and recurrence of bladder cancer are summarized. Data showing the synergistic antitumor activities of antisense oligodeoxynucleotide therapy, combined with several treatments, including cytotoxic chemotherapy, radiation and other molecular targeting therapies, are also presented. Finally, the future direction of antisense oligodeoxynucleotide therapy in the therapeutic strategy of bladder cancer is discussed. These findings may help clarify the significance of antisense oligodeoxynucleotide therapy as an attractive alternative to conventional strategies.

[Cell cycle and apoptosis mechanisms implicated in intravesical chemotherapy resistances in superficial bladder cancer]

It is well documented the effectiveness of intravesical chemotherapy following transurethral resection to prevent recurrences of superficial bladder cancer. But it is also known that efficacy may be limited by tumour cell resistance to one or several of the drugs available for instillation. In addition to the genetically determined unicellular mechanisms classically described in the literature such as glycoprotein P-170 expression (mdr-1), overexpression of Bcl-2 or glutation S-transferase activity, it has been recently shown that multicellular mechanisms may also be involved in drug resistance. Multicellular resistance can only be demonstrated in three-dimensional cultures and fails to be shown in monolayers or cell suspensions. This is explained by the fact that cell-to-cell and cell-to-stroma adhesion limits drug penetration and by the variable susceptibility to cytotoxicity determined by oxygen and tissue proliferation gradients. A better understanding of the molecular mechanisms involved in drug resistance is necessary to increase intravesical chemotherapy effectiveness. Current research includes improving drug penetration, searching resistance reversing agents and developing in vitro chemosensitivity tests to identify drug resistance.

Antisense oligonucleotide therapy in the management of bladder cancer

PURPOSE OF REVIEW

In this paper, we will review the recent advances in antisense oligonucleotide therapy in the treatment of superficial bladder cancer. Bladder cancer has an exciting potential as a model to study antisense oligonucleotide therapy because of the ease of accessibility of treatment, ease of diagnosis through biopsy and urine cytology, and direct observation of treatment efficacy through cystoscopy and posttreatment biopsy.

RECENT FINDINGS

We will elaborate on the recent developments in the delivery of antisense oligonucleotide and the implications of these results on the use of antisense oligonucleotide intravesically. We will also discuss recent preclinical in-vitro results of antisense oligonucleotide therapy in different bladder cancer cell lines.

SUMMARY

Recent developments of the in-vitro and animal in-vivo effectiveness of antisense treatment in bladder cancer provide the foundation to pursue future phase I clinical trials. Antisense oligonucleotide technology is a promising tool that may become an effective method of treating bladder cancer.

Vascular endothelial growth factor antisense pretreatment of bladder cancer cells significantly enhances the cytotoxicity of mitomycin C, gemcitabine and Cisplatin

PURPOSE

Due to unsatisfactory success in the treatment of local and systemic bladder cancer and the low response rates to commonly used chemotherapy (CT) alternative and additive approaches must be found. The function of vascular endothelial growth factor (VEGF) in neo-angiogenesis and, therefore, in solid tumors makes it a promising target for a specific antitumor therapy. We investigated the possibility of sensitizing transitional bladder cancer cell lines to CT by pretreatment with VEGF antisense (AS) oligodeoxynucleotides (AS-ODNs).

MATERIALS AND METHODS

The human bladder cancer cell lines EJ28 and 5637 were transiently transfected with 3 antiVEGF AS-ODNs, followed by incubation with 3 doses of mitomycin C, gemcitabine or cisplatin CT. WST-1 (a sodium salt of 4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate) assay (Roche, Mannheim, Germany) was performed to assess effects on cell viability. Apoptosis was examined by Annexin V staining. In all experiments a nonsense ODN served as a control.

RESULTS

Each cell line responded in a dose dependent manner to all CTs. Combined treatment with VEGF AS-ODNs and CT resulted in decreased viability compared with isolated CT. VEGF857 plus CT significantly decreased the viability of the 2 cell lines compared with nonsense ODN plus CT for all 3 CT agents (p <0.007). This detected chemosensitization was based on an AS mediated increase in apoptosis.

CONCLUSIONS

One of the 3 AS-ODNs tested (VEGF857) significantly sensitizes human transitional cell carcinoma cells to CT. We suggest VEGF as an additional putative target to enhance the therapeutic benefit of, for example mitomycin C and gemcitabine instillation treatment schedules.

Cytotoxicity of cisplatin in bladder cancer is significantly enhanced by application of bcl-2 antisense oligonucleotides

BACKGROUND

The aim of our study was to examine the effects of the combined application of cisplatin and bcl-2 antisense oligonucleotide on human bladder cancer cell lines to determine the possible synergistic effects in cytotoxicity and to estimate its potential value for subsequent in vivo trials.

MATERIALS AND METHODS

Human bladder cancer cell lines (UM-UC 3, RT 112, T24/83 and HT 1197) were treated with bcl-2 antisense oligonucleotide, cisplatin, or a combination of both and incubated for 48 h under standard conditions. Cell survival was determined using a Neubauer haemocytometer or standard MTT assay. BCL-2 expression was verified using western blotting.

RESULTS

The combined treatment resulted in significant lower cell survival rates compared to individual treatment. Additionally, there was a decrease in cell survival rate with an increase in cisplatin concentration in combined treatment that was not observed in cisplatin mono treatment.

CONCLUSIONS

For the combined treatment with oligonucleotides and cisplatin a synergistic effect can be strongly suggested. Therefore, further investigations and in vivo trials have to be done to determine the possible benefits for clinical applications.

Antisense oligonucleotides directed at the bcl-xl gene product augment chemotherapy response in mesothelioma

Objective: Malignant pleural mesothelioma (MPM) is resistant to both conventional chemotherapy and apoptosis. The bcl-2 family proteins are major determinants of apoptotic homeostasis. MPM lines and tumors routinely overexpress the anti-apoptotic protein BCL-XL. We have previously shown that antisense inhibition of BCL-XL in MPM cells leads to apoptosis. We sought to determine whether antisense oligonucleotides directed at the bcl-xl gene product would augment response to a conventional chemotherapeutic agent in human mesothelioma cell lines.

Methods: The human MPM cell lines REN and I-45 were exposed to two bcl-xl antisense oligonucleotides (15999, 16009) and one sense oligonucleotide (113529) construct at varying doses, followed by IC50 cisplatin. Cellular viability was assessed by a calorimetric assay, and apoptosis was evaluated by Hoechst staining, Annexin V staining, and sub-G1 fluorescence-activated cell sorter analysis. Western blot analysis of BCL-2 family proteins was performed following single agent and combined treatment. Isobologram mathematical analysis was used to determine whether or not combination therapies were additive or synergistic.

Results: Cell viability was most affected with the 15999 antisense oligonucleotides plus IC50 cisplatin combination (70% of I-45 and 90% of REN cells killed), and apoptosis was markedly increased with this combination by all measures. Western blot demonstrated 15999 antisense oligonucleotides construct down-regulation of BCL-XL, but no further effect on expression of BCL-2 proteins with cisplatin. Isobologram analysis demonstrated 15999 + cisplatin synergistic effect.

Conclusions: Exposure of human MPM cells to bcl-xl antisense oligonucleotides sensitizes human mesothelioma cells to the conventional chemotherapeutic agent cisplatin. Similar approaches using a combination of molecular and conventional treatment may have clinical utility for this tumor.

Recent advances in the development of anticancer agents targeting cell death inhibitors in the Bcl-2 protein family

Hematopoietic malignancies frequently are characterized by defects in apoptosis signaling. This renders the malignant cells resistant to endogenous apoptotic stimuli, as well as exogenous stimuli, such as chemotherapy drugs and radiation. The defective apoptosis seen in human cancers often results from overexpression of antiapoptotic proteins in the Bcl-2 protein family, particularly Bcl-2 and Bcl-X(L). A great deal of effort is currently aimed at developing novel agents to inhibit the expression or function of these proteins. Antisense agents directed against Bcl-2 mRNA are showing considerable promise in clinical trials. In addition, detailed knowledge of the structures of Bcl-2 and Bcl-X(L), coupled with high-throughput and computer-assisted screening of chemical libraries, has led to the identification of a number of short peptides and small organic molecules capable of inhibiting Bcl-2 and Bcl-X(L) function. These newly described agents hold considerable promise for enhancing the chemo- and radiation sensitivities of Bcl-2- and Bcl-X(L)-overexpressing cancers. This review will highlight recent advances in the development and testing of agents targeting cell death inhibitors in the Bcl-2 protein family.

Antisense oligonucleotide therapy for urologic tumors

Modulation of gene expression using antisense oligonucleotides has advanced from the laboratory to the clinic. Numerous companies can, at least partially, attribute their success to the development of antisense techniques, and one antisense drug is currently on the market. Antisense compounds have been used in clinical trials that included patients with urologic tumors, mostly directed at proliferation- or apoptosis-related targets. Furthermore, therapeutic inhibition of many new identified genes is being investigated in preclinical tests. This review provides a contemporary overview of current preclinical and clinical antisense oligonucleotide concepts for the treatment of urologic tumors.

Peptides derived from BH3 domains of Bcl-2 family members: a comparative analysis of inhibition of Bcl-2, Bcl-x(L) and Bax oligomerization, induction of cytochrome c release, and activation of cell death

Overexpression of Bcl-2, an anti-apoptotic oncoprotein, is commonly observed in a variety of human malignancies and is associated with resistance to chemotherapy and radiotherapy. Although the precise mechanism of Bcl-2 action remains elusive, current evidence indicates that Bcl-2 inhibits apoptosis by binding and inhibiting pro-apoptotic molecules such as Bax. Therefore, agents that disrupt the ability of Bcl-2, or other anti-apoptotic molecules, to bind to pro-apoptotic molecules may have therapeutic value. Several studies have shown that the BH3 domains of Bcl-2 and Bax are critically important for Bax/Bcl-2 heterodimerization. In this report, we designed and synthesized peptides based on the BH3 domains of three distinct Bcl-2 family members, Bcl-2, Bax and Bad. In vitro interaction assays were used to compare the abilities of the different peptides to inhibit Bax/Bcl-2 and Bax/Bcl-x(L) heterodimerization, as well as Bcl-2 and Bax homodimerization. Bax BH3 peptide (20-amino acids) potently inhibited both Bax/Bcl-2 and Bax/Bcl-x(L) interactions, exhibiting IC(50) values of 15 and 9.5 microM, respectively. The Bad BH3 peptide (21 amino acids) was slightly more potent than Bax BH3 at inhibiting Bax/Bcl-x(L) but failed to disrupt Bax/Bcl-2. Bcl-2 BH3 peptide (20-amino acids) was inactive toward Bax/Bcl-2 and had only a weak inhibitory effect on Bax/Bcl-x(L) heterodimerization. All three BH3 peptides failed to significantly inhibit homodimerization of Bcl-2 or Bax. Consistent with its ability to disrupt Bax/Bcl-2 heterodimerization, Bax BH3 peptide was able to overcome Bcl-2 overexpression and induce cytochrome c release from mitochondria of Bcl-2-overexpressing Jurkat T leukemic cells. Bad BH3 peptide, while potently inducing cytochrome c release in wild-type Jurkat cells, only partially overcame the effects of Bcl-2 overexpression. Bcl-2 BH3 failed to induce cytochrome c release, even in wild-type cells. Delivery of the Bax BH3 and Bad BH3 peptides into wild-type Jurkat cells induced comparable levels of cell death. In cells overexpressing Bcl-2, the potency of Bax BH3 peptide was similar to that seen in wild-type cells, while the efficacy of Bad BH3 peptide was reduced. By contrast, in Bcl-x(L)-overexpressing cells, Bad BH3 exhibited greater cell-killing activity than Bax BH3. The Bcl-2 BH3 peptide and a mutant Bax BH3 peptide had no appreciable effect on Jurkat cells. Together, our data suggest that agents based on the Bax BH3 domain may have therapeutic value in cancers overexpressing Bcl-2, while agents based on the BH3 domain of Bad may be more useful for tumors overexpressing Bcl-x(L).

Analysis of ribosyl-modified, mixed backbone analogs of a bcl-2/bcl-xL antisense oligonucleotide

Progress in oligonucleotide chemistry has provided second-generation antisense oligonucleotides with increased efficacy and reduced non-antisense-related toxicity. The ability of the 2'-O-(2-methoxyethylribose) (2'-MOE)-modified phosphorothioate gapmer oligonucleotide 4625, which matches the bcl-2 mRNA and has three base-mismatches to bcl-xL, to inhibit bcl-2 and bcl-xL expression and induce tumor cell apoptosis has been described. Here we investigated the consequences of adding of 2'-MOE or 2'-Me modifications to ribonucleotides at either the two ends of the sequence, or the center region together with different combinations of phosphodiester/phosphorothioate backbones on the activity of oligonucleotide 4625. The ability of the various 4625 analogs, including the parental first-generation oligonucleotide 3005, to inhibit bcl-2 and bcl-xL expression, and diminish cell growth or induce tumor cell death was assessed in SW2 lung cancer cells using real-time PCR, Western blotting and cell viability assays. Only oligonucleotide 4625 exhibited a potent bispecific antisense activity against bcl-2 and bcl-xL, which effectively reduced tumor cell viability. The other antisense oligonucleotides were either uniquely active against bcl-2 or completely inactive. Our data suggest that the 2'-MOE modification in combination with the phophorothioate gapmer chemistry is the optimal format of the 4625 sequence in terms of antisense activity and biological efficacy.