The effect of verapamil on a multi-drug resistant bladder carcinoma cell line and its potential as an intravesical chemotherapeutic agent

The expression of cyclooxygenase in transitional cell carcinoma cell lines: its correlation with tumor differentiation, invasiveness and prostanoids production

OBJECTIVE

To evaluate the isozyme activities of COX-1 and COX-2 in TCC cells and correlate with cellular differentiation and tumor behavior.

MATERIAL AND METHODS

Various TCC cell lines were characterized through several aspects: (1). to measure the content and the mRNA amount of COX-1 and COX-2, (2). to characterize the proteins of COX-1 and COX-2 by Western immunoblotting, (3). to measure the production of prostaglandin E2 and thromboxane B2 in culture media, and (4). to correlate these parameters with tumor differentiation and invasiveness.

RESULTS

Seven out of 10 cell lines (70%) had significantly higher COX expression than normal urothelium. Tumors with lower-grade differentiation and less invasiveness had significantly higher content of COX-1 and COX-2 than those tumors with higher-grade differentiation and more invasive behavior (p<0.01). The expression of COX mRNA in TSGH8301, TCC8702 and RT4 were much higher than J82 which has minimal expression of COXs. Similarly, the COX-2 protein was much higher in TSGH8301, TCC8702 and RT4 when compared with J82. TSGH8301, TCC8702, and RT4 had high production of PGE2 and thromboxane B2 in their culture media. Increased secretions of PGE2 and thromboxane B2 were also observed in TCC8701, TCC9101, HT1376, and T24. The production of prostanoids is closely related to cytoplasmic COX expression of tumor cells.

CONCLUSIONS

The expression of COX-1 and COX-2 is a common phenomenon in TCC cells and closely related to cellular differentiation and tumor invasiveness. The COX-2 inhibitors may play an important role in the control of TCC growth.

Intravesical therapy of superficial bladder cancer

The aim of treatment of superficial bladder cancer with intravesical therapy is threefold: (1) Eradicate existing disease. (2) Prevention of recurrence. (3) Prevention of tumor progression. The prognostic factors allow differentiation in different risk groups and this is useful in planning treatment. Studies on pharmacokinetics have proved the efficacy of optimized drug delivery. Comparing resection with and without intravesical chemotherapy a short term approximately 15% decrease in tumor recurrence with chemotherapy can be obtained but no effect on progression was proven. No agent has proved more effective than the other. Single, early instillation of chemotherapy has proven effective but the role of maintenance therapy has been controversial. Immunotherapy in the form of Bacillus Calmette-Guerin generally have proven more efficacious than chemotherapy. The results in comparison to mitomycin C have not been as conclusive. Several new approaches are explored to improve the efficacy of this therapy.

Intravesical pH: a potentially important variable affecting efficacy and the further development of anthracycline chemotherapy for superficial bladder cancer

OBJECTIVE

To assess, using epirubicin-sensitive and multidrug resistant (MDR) derivatives of human bladder cancer cell lines in vitro, the probable effect of intravesical pH changes, with and without the MDR antagonist verapamil, on the uptake, intracellular distribution and cytotoxicity of epirubicin during intravesical chemotherapy.

MATERIALS AND METHODS

Incubations for cytotoxicity testing were carried out in buffered medium containing epirubicin, at pH values of 6.0-8.5, with verapamil where appropriate. The cytotoxicity of epirubicin, with and without verapamil, was determined using the tetrazolium cytotoxicity assay. Intracellular epirubicin fluorescence was assessed using flow cytometry and confocal microscopy. Flow cytometric total intracellular epirubicin fluorescence was measured at pH 6.0, 6.4, 6.8, 7.2, and 7.6, and confocal microscopy was carried out at pH 6.0 and 8.0. The MDR-reversing agent verapamil was added at 100 micro g/mL to some incubations.

RESULTS

Epirubicin cytotoxicity in resistant cell lines appears considerably enhanced by adding verapamil and further improved, especially in MDR cells, by alkalinization of the drug solution to pH 8.0. Flow cytometry results showed striking and consistent differences in epirubicin handling with pH. Sensitive cells can be induced to absorb considerably more drug at alkaline pH, whilst resistant cells show no such behaviour. Nuclear drug fluorescence was greater in sensitive cells at alkaline pH, but cytoplasmic drug fluorescence in the resistant cells was little changed by pH. Adding verapamil to resistant cells restored the sensitive phenotype of drug handling.

CONCLUSION

Buffering epirubicin to an alkaline pH before intravesical application should increase its intrinsic cytotoxicity. The potential for synergy at certain drug combinations will be enhanced by applying these findings. MDR reversal and fatty acid augmentation of drug uptake are discussed as examples.

Immunohistochemical expression of P-glycoprotein in the rat urinary bladder and the effect of verapamil on intravesical chemotherapy

BACKGROUND

The expression of P-glycoprotein (Pgp) is thought to be common in bladder epithelium and the multidrug resistance mediated by Pgp must be considered to improve the efficacy of chemotherapy for bladder tumors.

METHODS

The expression of Pgp in normal and tumor tissue of the rat urinary bladder was first examined immunohistochemically. The effect of verapamil, an expected modulator of Pgp, on intravesical chemotherapy of the rats was then investigated.

RESULTS

Pgp was immunohistochemically detected in normal epithelium and in tumor tissue of the rat urinary bladder. In those normal and tumor-bearing bladders, verapamil promoted the uptake of intravesically instilled pirarubicin, but the efflux of intracellular accumulated pirarubicin was observed subsequently in both conditions with and without verapamil. The drug concentration decreased more rapidly in the verapamil group than in the control group.

CONCLUSIONS

Verapamil is thought to be useful in promoting uptake of intravesically instilled pirarubicin, but it did not appear to be so efficient at limiting the efflux of intracellular accumulated pirarubicin.

Characterization and modulation of transitional cell carcinoma cell lines with acquired multidrug resistance

OBJECTIVES

To characterize in vitro drug-induced multidrug resistance (MDR) in transitional cell carcinoma (TCC) cell lines, and to elucidate the possible mechanisms of acquired MDR and their modulation.

MATERIALS AND METHODS

Two drug-resistant cell lines, TCC8702/A1000 (adriamycin 1000 ng/mL) and TCC8803/A200 (adriamycin 200 ng/mL), were established after long-term adriamycin treatment for at least 16 months. Their biological characteristics, including growth morphology, doubling time and cell cycle, were analysed. The drug-resistance pattern to various anticancer drugs was measured using a microplate cytotoxicity assay. The modulation of drug sensitivity by calcium-channel blockers and protein kinase C inhibitor was assessed among the different cancer cell lines.

RESULTS

Both MDR sublines had lower growth rates, lower saturation densities and higher nuclear/cytoplasmic ratios than the parent cell lines. DNA staining and cell cycle analysis revealed that both TCC8702/A1000 and TCC8803/A200 cells had a decreased S-phase fraction and the TCC8803/A200 cells a changed stem line; both sublines showed increased expression of membranous glycoprotein gp-170. The cytoplasmic content of glutathione and glucose-6-phosphate dehydrogenase were not related to the MDR development in the sublines. The drug-resistance index of TCC8702/A1000 to adriamycin was 121-fold higher than the native cell line and TCC8803/A200 was 189-fold higher. TCC8803/A200 also had a broader MDR to cisplatin, vinblastine and vincristine. Calcium-channel blockers (verapamil, quinidine) and protein kinase C inhibitors (tamoxifen) inhibited gp-170 activity and slowed the drug-efflux pump, with the acquired-MDR cells subsequently accumulating anticancer drugs. A calcium antagonist-based combination of modulators all presented synergistic cytotoxic enhancement of the anticancer drugs. Parent TCC cell lines had a poorer response to modulator treatment than their MDR sublines.

CONCLUSION

Different MDR mechanisms and subsequent modulator responses exist between native and acquired drug resistance in TCC cells. Acquired MDR seems strongly related to increased gp-170 expression and responds well to calcium antagonists. This phenomenon may be applicable in clinical conditions.

Circumvention of multidrug resistance in genitourinary tumors

Chemotherapy is the principal strategy to systemically challenge metastasized cancers of genitourinary origin. Unfortunately, the efficacy of chemotherapy is often hampered by multidrug resistance, the resistance to a variety of structurally and functionally distinct cytotoxic agents. Multidrug resistance can be either intrinsic or acquired, and can be caused by several mechanisms. The so-called classical multidrug resistance, mediated by the MDR1 gene product P-glycoprotein, has been held mainly responsible for inferring the multidrug resistance phenotype on urologic malignancies. However, several other multidrug resistance pathways have been identified. Multidrug resistance can be caused by the membrane-bound multidrug-resistance-associated protein, the detoxifying glutathione metabolism, the antiapoptotic protein BCL2, and changes in levels or activity of the topoisomerase enzymes. Strategies to overcome multidrug resistance of genitourinary tumors have arisen from the better understanding of the biologic and molecular mechanisms of multidrug resistance, and have been studied in experimental and clinical settings. However, attempts to modulate multidrug resistance in clinical renal cell, bladder, prostate, and testicular cancer have not been very rewarding so far, despite the optimism that had arisen from experimental data. Nevertheless, application of novel therapies to reverse multidrug resistance and to increase efficacy of chemotherapy for urologic cancers should be further pursued, within the setting of controlled clinical trials, to improve on current strategies.

Current recommendations for the management of bladder cancer. Drug therapy

Superficial transitional cell carcinoma of the bladder is a heterogeneous group of tumours, and prediction of disease outcome in an individual patient is still impossible. In low-risk patients the initial treatment [transurethral resection (TUR)] should be followed by no or only one immediate intravesical instillation with a chemotherapeutic drug to prevent a recurrence due to tumour cell implantation during TUR. Drug efficacy has been clearly demonstrated and adverse effects are very limited. Intermediate-risk patients should receive a course of additional intravesical instillations to reduce the recurrence rate with few adverse effects. All drugs seem to be equally effective, but the long term effects remain a question. In high-risk patients intravesical immunotherapy (BCG) should be given. Although toxicity is more pronounced, it is usually mild and adverse effects disappear after cessation of therapy. BCG (maintenance) therapy seems to be able to improve progression and ultimately tumour-related survival. It is important to know the advantages and disadvantages (adverse effects) of these treatment modalities to be able to individualise treatment as much as possible. The choice is difficult because several intravesical bladder cancer trials have not reached consensus on this. For patients with non-metastasised invasive bladder tumours chemotherapy can be given before (neoadjuvant) or immediately after (adjuvant) surgery or radiotherapy. Both strategies have some advantages and disadvantages. For both, however, efficacy still needs to be proven, and results of ongoing trials are needed. For metastasised or recurrent urothelial cell carcinoma MVAC (methotrexate, vinblastine, doxorubicin and cisplatin) chemotherapy remains the most effective treatment modality. Although initial response rates of between 40% and 70% can be achieved, most patients have a recurrence of their cancer. Moreover, toxicity of these drugs also is considerable and limiting. Leucopenia is responsible for the majority of grade III and IV toxicities and subsequent dose modifications. In case of toxic deaths, a leucopenic sepsis is usually the cause. Most other adverse effects are acceptable or can be treated.

Relative cytotoxicities of adriamycin and epirubicin in combination with lonidamine against human bladder cancer cell lines

We have used a panel of bladder cancer cell lines to compare the toxicities of Adriamycin and epirubicin, two drugs used intravesically to treat superficial transitional cell cancer (TCC) of the bladder, alone and in combination with lonidamine, an agent known to be active against anthracycline-resistant disease. Comparing concentrations reducing colony-forming ability by 50%, epirubicin and Adriamycin were similar in their cytotoxicities, although epirubicin was more potent against every line except an Adriamycin-resistant subline. Combinations of the two drugs with a non-cytotoxic concentration (1 microgram/ml) of lonidamine were tested using the Adriamycin-resistant subline MGH-U1R and its sensitive parental line MGH-U1. The addition of lonidamine caused a two-fold increase in the sensitivity of the resistant subline to both drugs, while having no effect on the sensitivity of the parental line. The data indicate that this combination might be of value in anthracycline-resistant disease.

Intravesical instillation chemotherapy of adriamycin with or without verapamil for the treatment of superficial bladder cancer: the final results of a collaborative randomized trial

A collaborative randomized clinical trial on the intravesical administration of Adriamycin (ADM) with or without verapamil (VR), a calcium-channel blocker, as chemotherapy of superficial bladder cancer (Ta, T1) was carried out at two universities, Okayama and Kagoshima, and their affiliated hospitals. Arm A consisted of ADM given at 50 mg/50 ml saline, and arm B consisted of ADM given at 50 mg/40 ml saline plus five ampules (25 mg/10 ml saline) of injectable VR. The drugs were instilled into the bladder for 3 consecutive days, and three such courses were given with a 4-day interval between each course for a total of nine instillations. A total of 96 patients (48 in arm A and 48 in arm B) were entered into this study. The two treatment groups showed no significant difference in background factors. Of the 40 evaluated arm-A patients, 24 (60.0%) showed a response (CR + PR), whereas 19 (48.7%) of the 39 patients in arm B responded. The difference between these response rates was not statistically significant. As for adverse reactions to the intravesical chemotherapy, local inflammatory symptoms were observed in half of the patients, although no systemic reaction was observed. No significant difference was found between arm A and arm B, except for urinary turbidity. In conclusion, at the dose employed in the present clinical trial, there was no clear enhancement of the effect of ADM combined with VR in patients with superficial bladder cancer. Further clinical studies are required to determine the optimal doses of ADM and VR for their combination in intravesical chemotherapy.

Evaluation of multiple drug resistance in human bladder cancer cell lines

We evaluated multidrug resistance (MDR) in human bladder cancer cell lines UM-UC-2, UM-UC-6, UM-UC-9 and the UM-UC-6dox subline induced to doxorubicin resistance by in vitro doxorubicin exposure. We compared the profile of multidrug resistance in these cell lines with that of the UM-UC-3 human renal cancer cell line. Of these cell lines, UM-UC-2 was most sensitive to both doxorubicin and etoposide, while UM-UC-6, UM-UC-9 and UM-UC-3 showed 1.5-, 2.1-, and 5.4-fold more resistance to doxorubicin than UM-UC-2 cells. These cell lines were also more resistant to etoposide than UM-UC-2. Addition of verapamil at 10 microM. reduced the doxorubicin resistance in UM-UC-6 and UM-UC-6dox cells, but UM-UC-9 cells showed little change in doxorubicin sensitivity in the presence of verapamil. In a model of intravesical (short-term) treatment verapamil increased the doxorubicin sensitivity of UM-UC-6dox but not that of UM-UC-6 cells. This effect in UM-UC-6dox cells was enhanced by continuously treating with verapamil after doxorubicin had been removed. Western blot analysis with rabbit anti-human P-glycoprotein polyclonal antibody demonstrated a distinct increase in P-glycoprotein in the resistant cell lines as compared with UM-UC-2. P-glycoprotein expression was roughly proportional to the degree of resistance to both doxorubicin and etoposide, but did not always correlate with the effect of verapamil on decreasing doxorubicin resistance. These results suggest that multidrug resistance is an important phenomenon in bladder cancer and that more than one pathway of multidrug resistance may be present in human bladder cancer cell lines.

Intravesical instillation of adriamycin in the presence or absence of verapamil for the treatment of superficial bladder cancer: preliminary report of a collaborative study

A case-controlled collaborative study on the intravesical administration of Adriamycin in the presence or absence of verapamil, a calcium-channel blocker, as chemotherapy of superficial bladder cancer was carried out at two universities, Okayama and Kagoshima, and their affiliated hospitals. Although little is known about the expression of P-glycoprotein in superficial bladder cancer, it may be a cause of multidrug resistance (MDR). Verapamil was used as an inhibitor of P-glycoprotein. Arm A consisted of Adriamycin given at 50 mg/50 ml saline, and arm B constituted Adriamycin given at 50 mg/40 ml saline plus 5 ampules (10 ml) of injectable verapamil. The drugs were instilled into the bladder for 3 consecutive days in each of 3 consecutive weeks for a total of 9 instillations. No significant difference in antitumor effects was observed between arm A and arm B. Recurrent tumors responded better than did primary tumors to both arm-A and arm-B treatments (P = 0.012). In both treatment arms, significant differences (P = 0.031) in the response rate were found between tumors with diameters of less than 1 cm and those measuring 1-3 cm in diameter. Although the number of evaluable patients was limited, recurrent subjects who had previously received Adriamycin instillations responded in both treatment arms.