Epigenetic regulation of microRNA expression in renal cell carcinoma.

The underlying mechanisms of microRNA deregulation in cancer cells include epigenetic modifications, which play a crucial role in carcinogenesis. We demonstrate that numerous microRNAs are induced in renal cell carcinoma cell lines after treatment with inhibitors of the DNA-methyltransferase (5-aza-2'-deoxycytidine) and the histone-deacetylase (suberoylanilide hydroxamic acid). We provide evidence that enrichment of H3 and H3K18 acetylation at the miR-9 promoter is causative for re-expression, while DNA hypermethylation remains unchanged. Our experiments show that the treatment with the epigenetic drugs causes re-expression of silenced microRNAs with putative tumor suppressive function in ccRCC cell lines.

Indirubin-3'-monoxime, a CDK inhibitor induces growth inhibition and apoptosis-independent up-regulation of survivin in transitional cell cancer.

In traditional Chinese Medicine, the preparation Danggui Longhui Wan has been used for years in the treatment of chronic myelocytic leukemia. The compound indirubin has been shown to be the active constituent. A cell permeable derivative, indirubin-3'-monoxime, is a selective and potent inhibitor of cyclin-dependent kinases (cdk). The ability of indirubin-3'-monoxime to induce apoptosis and tumor cell death in transitional cell cancer cell lines was investigated here. The growth-inhibitory properties were evaluated by EZ4U, a cytotoxic assay; apoptosis induction was determined by immunoblotting of cleaved PARP and flow cytometry of Annexin-V/PI staining during treatment. To evaluate further the underlying molecular action of indirubin-3'-monoxime on the cell cycle, the levels of cdk-1 and survivin, a mitotic spindle checkpoint and apoptosis-regulating protein, respectively, were additionally determined by flow cytometry and immunoblotting. The results indicated that indirubin-3'-monoxime induced reversible growth arrest in all four cell lines and an increase of apoptosis in two of them. The treatment with indirubin-3'-monoxime increased the expression of survivin almost four times in the RT4 cells and more than doubled it in the RT112 and T24 cells. In the SUP cells, the expression of survivin increased more than seven-fold after 72-h incubation. No clear correlation between the low apoptosis induction rate and extent of survivin expression was found. Cdk expression was not significantly altered by indirubin-3'-monoxime. In summary, indirubin-3'-monoxime might be a promising candidate for targeted cancer therapy, however, its molecular action remains to be further evaluated.

Carboxyamido-triazole (CAI) reverses the balance between proliferation and apoptosis in a rat bladder cancer model.

Carboxyamido-triazole (CAI) is an orally bioavailable calcium influx and signal transduction inhibitor that has been shown to be anti-invasive, anti-angiogenic and anti-metastatic in different human tumors including transitional cell carcinoma. This study was undertaken to further evaluate the activity of CAI in a rat bladder cancer model. A transitional cell carcinoma (TCC) was chemically induced by intravesical installation of methyl-nitrosurea (MNU) in the bladder of female Fischer 344 rats. First, a toxicity study was performed which revealed no side-effects of CAI in the animals up to a dose of 250 mg/kg CAI. For treatment, a dose of 100 mg/kg CAI dissolved in PEG-400 vehicle was chosen. Oral administration of CAI continuously daily for 4 weeks (group A), 3 days/week over 6 weeks (group B), or intravesically twice a week for 6 weeks (group C) caused a reduction of spontaneous development of TCC. Lower stage and grade of tumors were seen in all CAI-treated animals. Under CAI treatment, the apoptotic rate in tumors increased, whereas the proliferation rate decreased, as shown by TUNEL assay and KI-67-immunhistochemistry, respectively. The highest efficacy was seen in group B, with 5 out of 10 animals tumor-free. Intravesical application (group C) resulted in 3 out of 10 animals tumor-free. Normal urothelium was not affected by CAI. This animal model confirms the anti-tumor effect of CAI and shows induction of apoptosis and growth inhibition in bladder cancer by the drug.

Flavopiridol, an inhibitor of cyclin-dependent kinases, induces growth inhibition and apoptosis in bladder cancer cells in vitro and in vivo.

Flavopiridol is a semi-synthetic flavone analog of the alkaloid, rohitukine, a compound from an Indian tree, Dysoxylum binectariferum. It has been shown to inhibit cyclin-dependent kinases (CDKs), causing cell cycle arrest and growth inhibition. Flavopiridol is reported to have cytotoxic activity against a wide range of cancer cell lines and has demonstrated its efficacy in several clinical trials. Flavopiridol seems a well-suited potential new agent for the treatment of bladder cancer. We, therefore, evaluated whether flavopiridol inhibits growth and induces apoptosis in bladder cancer cells and additionally examined the toxicity and efficacy of this drug in vivo in a rat bladder cancer model. The in vitro experiments showed an IC20 of 50-100 nM in all cell lines tested. However, there was a difference in the response with regard to the grading of the tumor cells at higher doses. The IC50 was found to be 150-350 nM in the well-differentiated RT4 and RTI12 cell lines after treatment with flavopiridol, in comparison to a IC50 of 1000 nMfor the poorly-differentiated cell lines T24 and SUP. After exposure to flavopiridol, all tumor cell lines underwent significant apoptosis in comparison to untreated cells, beginning at a dose of 50 nM flavopiridol. At high concentrations (500 nM) of flavopiridol, 80-90% of all cells showed severe apoptotic alterations. The treatment of rat urinary bladder cancer with flavopiridol demonstrated the best efficacy with an intermittent treatment of 0.1 mg/kg, 3 times weekly over a total of 3 weeks, resulting in 7/12 animals tumor-free and a trend for the remaining tumors to have lower stage and grade. There seems to be a small advantage in intermittent versus daily application of flavopiridol. In summary, our results indicated that flavopiridol could be a useful therapeutic agent for bladder cancer, inhibiting tumor growth, malignant progression and inducing apoptosis.

Superantigen-activated mononuclear cells induce apoptosis in transitional cell carcinoma.

BACKGROUND: Superantigens are among the most potent T-cell mitogens known. Since T-cell activation and T-cell-derived cytokines play a role in the immune response associated with intravesical Bacillus Calmette-Guerin (BCG) application, this study was initiated to explore the fundamental aspects of a potential new immunomodulatory therapy for superficial bladder cancer. Since Superantigen-induced cytotoxicity is mediated by apoptosis, the effects of SEB (staphylococcal enterotoxin B)-Superantigen-activated PBMC (peripheral blood mononuclear cells) on bladder cancer cells were evaluated with regard to Fas/Fas-ligand-based interactions. MATERIALS AND METHODS: Whether SEB can induce Fas-ligand expression on PBMC and the extent of cytokine secretion were examined by flow cytometry and specific ELISA. In addition, whether the SEB-activated PBMC are able to induce apoptosis in transitional cell carcinoma cells (TCC) was evaluated in co-culture experiments. RESULTS: It was shown that SEB induced pronounced time- but not dose-dependent specific Fas-ligand expression on PBMC, lasting 1 h to 7 h after initiation of the experiment. Cleaved soluble Fas-ligand was detected in the culture supernatants 24 h after stimulation, but not earlier. Further, a strong time-dependent secretion of cytokines IL-2, IFN-gamma and TNF-alpha released from the SEB-stimulated PBMC was shown. In co-culture experiments, it was demonstrated that SEB-activated PBMC significantly induced apoptosis in TCC cells. The released cytokines from SEB-treated PBMC demonstrated only a minor, not significant, apoptotic response in TCC cells. CONCLUSION: This first evaluation of the possible mode of action of a Superantigen opens the door for extended studies of this interesting approach to the treatment of bladder cancer.

Carboxyamido-triazole (CAI), a signal transduction inhibitor induces growth inhibition and apoptosis in bladder cancer cells by modulation of Bcl-2.

Pro- and anti-apoptotic factors and intracellular signaling pathways are targets for therapeutic development of anticancer agents. Carboxyamido-triazole (CAI) is an inhibitor of transmembrane calcium influx and intracellular calcium-requiring signal transduction pathways. The present study investigates the effects of CAI on human transitional cancer cell (TCC) viability and apoptosis, and evaluates whether apoptotic resistance may be overcome pharmacologically. Both well-differentiated (RT4, RT112/grade 1) and poorly-differentiated (T24/grade 3; SUP/grade 4) human TCC lines were shown to express Fas. Upon exposure to agonistic monoclonal Fas antibody, only well-differentiated TCC lines underwent apoptotic cell death. CAI exposure reduced cell viability and caused an at least additive anti-apoptotic effect in combination with the Fas antibody in the Fas-insensitive TCC lines. Under the same conditions under which CAI treatment augmented Fas-mediated apoptosis, it was shown to reduce intracellular bcl-2 quantity. This response to CAI indicates that apoptotic cell death is enhanced by the reduction of bcl-2 protein expression. We suggest that the antitumor effect of CAI is at least partially based on restoring a pathway of apoptosis. It may cause transformation of cell homeostasis that leads to the alteration of apoptotic mechanisms, thus allowing highly malignant tumor cells to re-enter the physiological course of cell elimination.

Antiproliferative and apoptosis inducing effects of indirubin-3'-monoxime in renal cell cancer cells.

OBJECTIVES: Indirubin-3'-monoxime, which is a selective and potent inhibitor of cyclin-dependent kinases (CDKs) has shown preclinical activity in several human cancer cells. This study investigated if indirubin-3'-monoxime can induce apoptosis and tumor cell death in 3 human (A498, CAKI-1, CAKI-2) and 1 murine renal cell cancer (RENCA) cell line. METHODS: The growth inhibitory and apoptosis induction properties were evaluated by EZ4U, a cytotoxic assay and by flow cytometry of annexin-V/PI staining during treatment with doses ranging from 5.0 to 15.0 µM indirubin-3'-monoxime over 72 hours. To further establish the underlying molecular targets of indirubin-3'-monoxime, survivin, a major anti-apoptotic protein was additionally determined by intracellular flow cytometry. RESULTS: Our results show that indirubin-3'-monoxime induces growth arrest and apoptosis in all renal cell cancer (RCC) cell lines. All RCC lines expressed survivin. However, a clear correlation between apoptosis induction and expression of survivin was not found. CONCLUSIONS: As treatment of metastatic renal cell cancer (mRCC) remains a challenge, and the need for continuing assessment of novel agents in the treatment of this disease is mandatory. Indirubin-3'-monoxime seems to be a candidate for further evaluation.

Preclinical evaluation of superantigen (staphylococcal enterotoxin B) in the intravesical immunotherapy of superficial bladder cancer.

Superantigens are potent activators of T lymphocytes; therefore, their characteristics can be exploited in diseases where immunomodulation is known to be effective. In this study, we evaluated a new approach for the intravesical therapy of superficial bladder cancer. We investigated in coculture experiments if staphylococcal enterotoxin B (SEB)-activated PBMCs are able to induce apoptosis in human transitional cell carcinoma (TCC) cells. Additionally, we tested the toxicity and efficacy of SEB dissolved in NaCl 0.9% administered intravesically once weekly for 6 weeks in a rat bladder cancer model. To validate the coculture in vitro findings, we evaluated tumor stage, grade, apoptotic cells in the urothelium and stroma of the bladder and infiltration of the bladder wall by lymphocytes, macrophages and mononuclear cells. Coculture experiments revealed that SEB-activated PBMCs are able to kill TCC cells by inducing apoptosis. The intravesical toxicity study with a maximum dose of 100 microg/ml SEB demonstrated no side effects. In the intravesically SEB-treated animals (10 microg/ml), only 3 tumors remained vs. 15 persisting tumors in the control group. The remaining tumors of the therapy group showed a significant amount of apoptosis and granulocytes, mainly in the urothelium, whereas no relevant apoptosis or infiltration of the bladder with lymphocytes or macrophages was found in the control group. These preclinical findings suggest that SEB might be an interesting candidate for further clinical evaluation.