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

Bladder carcinoma: understanding advanced and metastatic disease with potential molecular therapeutic targets

This article is an expert review of bladder cancer genetics focusing on genetic changes and their significance in the pathogenesis and progression of bladder transitional cell carcinoma, in particular, muscle-invasive disease. Alongside the relevant genetic markers and their products, new therapeutic targets and agents that are being developed are presented.

Lentivirus-mediated shRNA interference targeting vascular endothelial growth factor inhibits angiogenesis and progression of human pancreatic carcinoma

Angiogenesis is known to be essential to the survival, growth, invasion and metastasis of cancer cells. Vascular endothelial growth factor (VEGF) is an important factor regulating tumor angiogenesis. In the present study, we analyzed the effect of lentivirus-mediated shRNA interference targeting vascular endothelial growth factor (VEGF) on angiogenesis and progression in the pancreatic cancer cell line Patu8988 in vitro and in vivo. The study aimed to construct a recombinant lentivirus carrying targeted VEGF shRNA (LV-RNAi) to be used to transfect Patu8988 cells, and we investigated its anti-angiogenic and growth inhibitory effects on pancreatic cancer. VEGF expression was measured by RQ-PCR, western blotting and enzyme-linked immunosorbent assay (ELISA). In subcutaneous transplantation models, tumor volumes were determined, and the expression levels of VEGF and CD34 were assessed by immunohistochemistry. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) was used to determine apoptosis. In the orthotopic transplantation models, tumor volume and liver metastasis were determined. We successfully constructed LV-RNAi and confirmed that it knocked down the VEGF gene at the mRNA and protein levels in Patu8988 cells. In the subcutaneous transplantation models, tumors with low levels of VEGF expression exhibited reduced pancreatic carcinoma angiogenesis and growth, and the apoptotic index was significantly higher. In the orthotopic transplantation models, tumors with low levels of VEGF expression exhibited significantly reduced pancreatic carcinoma growth, but no significant difference was observed between the three mouse groups, LV-RNAi, LV-NC and the control, in regards to liver metastasis. In summary, lentivirus-mediated RNAi silencing of VEGF inhibited tumor angiogenesis and growth, and increased apoptosis of the pancreatic cancer cell line Patu8988. VEGF targeted gene silencing approach has the potential to serve as a novel treatment for pancreatic cancer.

Sunitinib synergizes the antitumor effect of cisplatin via modulation of ERCC1 expression in models of gastric cancer

We evaluated the effects of sunitinib monotherapy and in combination with cisplatin in human gastric cancer cell lines. Sunitinib showed antiproliferative effect in gastric cancer cells line with high PDGFRA expression. Knockdown of PDGFRA showed that sunitinib sensitivity was correlated with the basal expression of PDGFRA. Synergistic growth inhibitory activity in combination with cisplatin was identified. We further explored how sunitinib potentiated the activity of cisplatin. We found that sunitinib treatment resulted in the down-regulation of ERCC1 expression via the modulation of PDGFRA expression in gastric cancer cells. The effect was verified via SNU484 xenograft model. Our data support the rationale of clinical trial using sunitinib in combination of cisplatin in gastric cancer.

Effect of mitomycin C on concentrations of vascular endothelial growth factor and its receptors in bladder cancer cells and in bladders of rats intravesically instilled with mitomycin C

OBJECTIVES

• To examine, using in vitro and in vivo models, the largely unexamined effect of mitomycin C (MMC), an effective intravesical treatment for superficial bladder cancer and carcinoma in situ, on expression of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR-2), which mediates many of the angiogenic properties of VEGF. • To measure, as a positive control, concentrations of the inhibitor of apoptosis, survivin, as an assessment of MMC effectiveness. • To measure MMC-induced changes in proliferation in the presence and absence of VEGF-A small interfering RNA (siRNA).

MATERIALS AND METHODS

• After treatment with increasing MMC concentrations (5-200 µg/mL), we measured proliferation, as well as VEGF, survivin, VEGF receptor-1 (VEGFR-1) and VEGFR-2 concentrations in RT-4 and T-24 bladder cancer cells. • The effect of pre-treatment of VEGF siRNA and survivin siRNA on MMC-induced decreases in proliferation was measured. • Urinary VEGF concentrations and bladder and kidney concentrations of VEGF-A, VEGFR-1, VEGFR-2 and interleukin-6 (IL-6) mRNA were measured in rats intravesically instilled with saline or MMC (200 µg/mL).

RESULTS

• Although MMC treatment inhibited cell proliferation and decreased survivin mRNA expression in T-24 and RT4 cells, MMC (12-50 µg/mL) increased VEGF-A mRNA and VEGFR-2 mRNA and protein expression. • Pre-treatment with VEGF-A siRNA or survivin siRNA before MMC treatment reduced proliferation more than MMC alone. • MMC-induced reductions in proliferation were reduced additively by pre-treatment with survivin siRNA, but were potentiated by pre-treatment with VEGF-A siRNA. • VEGFR-2 mRNA and protein concentrations and urinary VEGF concentrations were increased in bladders of rats instilled with MMC.

CONCLUSIONS

• Intravesically instilled MMC increases urinary VEGF and bladder VEGFR-2 protein and mRNA in rats. • MMC increases VEGF mRNA and VEGFR-2 protein and mRNA concentrations in bladder cancer cells. Therefore, we speculate that MMC could increase the angiogenic potential of both cancer and normal cells. • In cancer cells this effect is largest at lower MMC concentrations. • Combining MMC with agents that reduce EGF concentrations could be of value in treatment of transitional cell carcinoma of the bladder (TCC).

Gemcitabine and paclitaxel suppress the production of vascular endothelial growth factor induced by deferoxamine in human non-small cell lung cancer A549 cells

Vascular endothelial growth factor (VEGF) plays an important role in the process of angiogenesis in many types of cancer, including non-small cell lung cancer (NSCLC), and angiogenesis inhibitors and standard chemotherapy exhibit synergy though an unknown mechanism. We therefore hypothesized that cytotoxic chemotherapy influences VEGF production and analyzed VEGF production in an NSCLC A549 cell line after treatment with standard chemotherapy. Paclitaxel inhibited the production of VEGF in A549 cells, while cisplatin and erlotinib did not. Paclitaxel and gemcitabine inhibited deferoxamine (DFX) (known to mimic hypoxia)-induced VEGF production in A549 cells. Erlotinib also inhibited DFX-induced VEGF production in A549 cells slightly, while cisplatin did not. We subsequently examined the effect of the interaction between paclitaxel or gemcitabine and VEGF protein. Paclitaxel and gemcitabine did not directly affect the binding of VEGF. Since VEGF is known as one of the HIF-1 target genes, we examined the effect of paclitaxel and gemcitabine on HIF-1α levels induced by DFX in A549 cells. Paclitaxel and gemcitabine inhibited DFX-induced HIF-1α in A549 cells. These findings may be useful for future treatment schedules, including anti-cancer agents in NSCLC.

Enzastaurin shows preclinical antitumor activity against human transitional cell carcinoma and enhances the activity of gemcitabine

Enzastaurin, an oral serine/threonine kinase inhibitor, suppresses signaling through protein kinase C (PKC)-beta and the phosphatidylinositol 3-kinase/AKT pathways. We preclinically evaluated enzastaurin alone and in combination with gemcitabine for transitional cell cancer (TCC). Immunohistochemistry (IHC) was done on 105 human samples from a microarray to show the expression of PKC-beta. The preclinical antitumor activity of enzastaurin and gemcitabine as single agents and in combination against aggressive human -lines (-SUP and 5637) and murine subcutaneous xenografts bearing 5637 cells was determined. Western Blot was done on tumor cells in vitro to detect signaling through PKC-beta, GSK-3beta, and AKT. The effect on cell migration was determined in vitro. Modulation of proliferation (Ki-67), apoptosis (cleaved caspase-3), and angiogenesis (CD31) in vivo was determined by IHC. IHC done on human TCC samples from a microarray showed the expression of PKC-beta in 33% of tumors. Enzastaurin induced significant apoptosis and inhibited proliferation in vitro at low micromolar concentrations. The in vitro inhibitory activity of combination enzastaurin and gemcitabine by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay seemed synergistic. Western Blotting revealed down-regulation of Akt, PKC-beta, and GSK-3 beta phosphorylation. Enzastaurin inhibited migration at an earlier time point independent of antiproliferative activity. Combination therapy had significantly superior antitumor activity in murine xenografts compared with untreated controls, whereas single agents did not. IHC showed reduced Ki-67 and CD31 and increased cleaved caspase-3 with combination therapy compared with controls. Enzastaurin showed preclinical antitumor activity against human TCC and enhanced the activity of gemcitabine.

Targeting vasculature in urologic tumors: mechanistic and therapeutic significance

Recent advances toward understanding the molecular mechanisms regulating cancer initiation and progression provide new insights into the therapeutic value of targeting tumor vascularity by interfering with angiogenic signaling pathways. The functional contribution of key angiogenic factors toward increased vascularity characterizing metastatic tumors and their therapeutic exploitation is considered in three major urologic malignancies, renal, bladder, and prostate cancer. With the realization that the success of the therapeutic efficacy of the various anti-angiogenic approaches for the treatment of urologic tumors has yet to be proven clinically, the challenge remains to select critical angiogenesis pathways that can be targeted for an individual tumor. Here we discuss the major mechanisms that support formation of vasculature in renal, bladder, and prostate tumors and the current results of targeting of specific molecules/regulators for therapeutic intervention against metastastic disease.

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.

Effect of vascular endothelial growth factor 165 on apoptosis of human gastric carcinoma cells in vitro and its mechanism

AIM: To investigate the effect of vascular endothelial growth factor 165 (VEGF165) on apoptosis of human gastic adenocarcinoma cell line (BGC-823) in vitro and its underlying mechanism.

METHODS: BGC-823 cells were divided into control group, Ad-GFP group and Ad-VEGF165 group and cultured with GFP (MOI = 20) and Ad-VEGF165. Apoptotic cells were detected by FCM assay. Expression of Bcl-2 mRNA and Bcl-2 protein was determined by RT-PCR and immunocytochemistry, respectively.

RESULTS: FCM showed that the apoptosis rate of BGC-823 cells was significantly lower in the Ad-VEGF165 group than in the Ad-GFP and control groups(4.6% ± 0.31% vs 8.37% ± 1.06%, 7.73% ± 0.86%, P < 0.01). PCR and immunocytochemistry displayed that VEGF165-transfected BGC-823 increased the expression of Bcl-2 mRNA and Bcl-2 protein, which was higher in the Ad-VEGF165 group than in the control and Ad-GFP groups (Bcl-2 mRNA: 0.761 ± 0.05 vs 0.363 ± 0.12, 0.356 ± 0.08; Bcl-2 protein: 1.010 ± 0.08 vs 0.865 ± 0.07, 0.901 ± 0.05; P < 0.01).

CONCLUSION: VEGF165 can inhibit cell apoptosis induced by serum starvation by up-regulating the expression of Bcl-2.

VEGF signaling inhibitors: more pro-apoptotic than anti-angiogenic

The vascular endothelial growth factor (VEGF) family of polypeptide growth factors regulates a family of VEGF receptor (VEGFR) tyrosine kinases with pleiotropic downstream effects. Angiogenesis is the best known of these effects, but additional VEGF-dependent actions include increased vascular permeability, paracrine/autocrine growth factor release, enhancement of cell motility, and inhibition of apoptosis. In theory, therapeutic inhibition of angiogenesis should reduce tumor perfusion and thus increase tumor hypoxia and chemoresistance, but in clinical practice the VEGF antibody bevacizumab acts as a broad-spectrum chemosensitizer. Since VEGFR expression occurs in many tumor types, such chemosensitization is more readily explained by direct inhibition of tumor cell survival signals than by indirect stromal/vascular effects. The emerging model of anti-VEGF drug action being mediated primarily by tumoral (as distinct from endothelial) VEGFRs has clinically important implications for optimizing the anti-metastatic efficacy of this expanding drug class.

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).

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.

Angiogenic and cell survival functions of vascular endothelial growth factor (VEGF)

Vascular endothelial growth factor (VEGF) was originally identified as an endothelial cell specific growth factor stimulating angiogenesis and vascular permeability. Some family members, VEGF C and D, are specifically involved in lymphangiogenesis. It now appears that VEGF also has autocrine functions acting as a survival factor for tumour cells protecting them from stresses such as hypoxia, chemotherapy and radiotherapy. The mechanisms of action of VEGF are still being investigated with emerging insights into overlapping pathways and cross-talk between other receptors such as the neuropilins which were not previously associated with angiogenesis. VEGF plays an important role in embryonic development and angiogenesis during wound healing and menstrual cycle in the healthy adult. VEGF is also important in a number of both malignant and non-malignant pathologies. As it plays a limited role in normal human physiology, VEGF is an attractive therapeutic target in diseases where VEGF plays a key role. It was originally thought that in pathological conditions such as cancer, VEGF functioned solely as an angiogenic factor, stimulating new vessel formation and increasing vascular permeability. It has since emerged it plays a multifunctional role where it can also have autocrine pro-survival effects and contribute to tumour cell chemoresistance. In this review we discuss the established role of VEGF in angiogenesis and the underlying mechanisms. We discuss its role as a survival factor and mechanisms whereby angiogenesis inhibition improves efficacy of chemotherapy regimes. Finally, we discuss the therapeutic implications of targeting angiogenesis and VEGF receptors, particularly in cancer therapy.