Determination and reversal of resistance to epirubicin intravesical chemotherapy. A confocal imaging study

Cooling-mediated protection from chemotherapy drug-induced cytotoxicity in human keratinocytes by inhibition of cellular drug uptake

Chemotherapy-induced alopecia (CIA) represents the most distressing side-effect for cancer patients. Scalp cooling is currently the only treatment to combat CIA, yet little is known about its cytoprotective effects in human hair follicles (HF). We have previously established in vitro human keratinocyte models to study the effects of taxanes and anthracyclines routinely-used clinically and reported that cooling markedly-reduced or even completely-prevented cytotoxicity in a temperature dependent manner. Using these models (including HF-derived primary keratinocytes), we now demonstrate that cooling markedly attenuates cellular uptake of the anthracyclines doxorubicin and epirubicin to reduce or prevent drug-mediated human keratinocyte cytotoxicity. We show marked reduction in drug uptake and nuclear localization qualitatively by fluorescence microscopy. We have also devised a flow cytometry-based methodology that permitted semi-quantitative analysis of differences in drug uptake, which demonstrated that cooling can reduce drug uptake by up to ~8-fold in comparison to normal/physiological temperature, an effect that was temperature-dependent. Our results provide evidence that attenuation of cellular drug uptake represents at least one of the mechanisms underpinning the ability of cooling to rescue human keratinocytes from chemotherapy drug-cytotoxicity, thus supporting the clinical efficacy of scalp cooling.

Coenzyme Q10 for Prevention of Anthracycline-Induced Cardiotoxicity

Preclinical and clinical studies suggest that anthracycline-induced cardiotoxicity can be prevented by administering coenzyme Q10 during cancer chemotherapy that includes drugs such as doxorubicin and daunorubicin. Studies further suggest that coenzyme Q10 does not interfere with the antineoplastic action of anthracyclines and might even enhance their anticancer effects. Preventing cardiotoxicity might allow for escalation of the anthracycline dose, which would further enhance the anticancer effects. Based on clinical investigation, although limited, a cumulative dose of doxorubicin of up to 900 mg/m2, and possibly higher, can be administered safely during chemotherapy as long as coenzyme Q10 is administered concurrently. The etiology of the dose-limiting cardiomyopathy that is induced by anthracyclines can be explained by irreversible damage to heart cell mitochondria, which differ from mitochondria of other cells in that they possess a unique enzyme on the inner mitochondrial membrane. This enzyme reduces anthracyclines to their semiquinones, resulting in severe oxidative stress, disruption of mitochondrial energetics, and irreversible damage to mitochondrial DNA. Damage to mitochondrial DNA blocks the regenerative capability of the organelle and ultimately leads to apoptosis or necrosis of myocytes. Coenzyme Q10, an essential component of the electron transport system and a potent intracellular antioxidant, appears to prevent damage to the mitochondria of the heart, thus preventing the development of anthracycline-induced cardiomyopathy.

Multidrug resistance in a urothelial cancer cell line after 3, 1-hour exposures to mitomycin C

PURPOSE

The development of multidrug resistance is a problem in chemotherapy for many tumors. In vitro models of multidrug resistance require adapted cell strains that are conventionally produced from parental lines by chronic low dose drug exposure. Because adjunctive intravesical chemotherapy for superficial bladder cancer uses short courses of high dose treatment, we investigated whether such exposure of the RT112 cell line (Catalogue No. ACC 418, Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany) to mitomycin C, which is a common intravesical agent, would elicit multidrug resistance.

MATERIALS AND METHODS

Three 1-hour exposures to graded concentrations were done at 3-week intervals. The highest mitomycin C concentrations permitting recovery in cultures and, therefore, available for examination were 3.13 and 1.06 microg/ml. Cross-resistance to epirubicin in surviving cultures was visualized by confocal microscopy and quantified by MTT residual viable biomass assay. Spheroids were made by the agarose technique and exposed to high dose mitomycin C to assess the probability that the relevant concentrations might be found clinically in some cell layers of a superficial lesion.

RESULTS

Resistance was induced by 3 short drug exposures. The evidence for this was functional (MTT assay) and by intracellular localization. Toxicity to an alternative multidrug resistance class drug was lowered in surviving clones and nuclear exclusion of the drug was noted. Spheroid experiments showed sharp gradients of incorporated drug across the outermost layers of cells, suggesting that a proportion of cells in clinical superficial bladder cancer would be exposed to drug at concentrations that generated the resistant clones in these experiments.

CONCLUSIONS

We report multidrug resistance induction using 2 independent methodologies. The results have implications for the development of experimental models and the likelihood of resistance resulting from clinical regimens. Brief exposure can elicit detectable resistance. It is arguable that selective rather than instructive mechanisms are involved, and the levels of drug required are likely to exist in a superficial transitional cell carcinoma frond exposed at its surface to high drug concentrations.

Furosemide reverses multidrug resistance status in bladder cancer cells in vitro

BACKGROUND

Multidrug resistance (MDR) has a potentially serious influence on cancer treatment and should be taken into consideration in the design and application of therapeutic regimens. It is mediated through the activity of cellular pumps.

AIM

To investigate whether furosemide, itself a pump-blocker, reverses MDR in an in vitro model.

MATERIALS AND METHODS

An MDR bladder cancer cell line (MGH-u 1R) and its parental (drug sensitive) clone were exposed to epirubicin and furosemide, with the concentration of one drug fixed and that of the other serially diluted in a 96-well plate format. Both drugs formed the variable component in separate experiments. After a 1-h exposure, the cells were washed and replenished with fresh medium. To examine the toxicity of epirubicin and furosemide separately and in combination, monotetrazolium-based assays were carried out. Intracellular epirubicin distribution was assessed by confocal microscopy as a second index of resistance status after in vitro exposure.

RESULTS

MGH-u 1R cells incubated with furosemide showed distribution of drug similar to that in the parental cells (MGH-u 1 sensitive). Controls (without furosemide) continued to show a resistant pattern of fluorescence. In cytotoxicity assays furosemide appeared substantially non-toxic. Resistant cells in the toxicity titration experiments showed increased resistance to levels of furosemide over 500 mug/ml. Parental cells were made only marginally more sensitive against increased background toxicity.

CONCLUSION

Furosemide is effective in reversing MDR status in bladder cancer cell lines in vitro. It may also have an increment of intrinsic cytotoxicity, but only at higher concentrations. We propose a potential for further investigation of furosemide as an adjunct to chemotherapy for superficial bladder cancer.

[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.

The nuclear membrane in multidrug resistance: microinjection of epirubicin into bladder cancer cell lines

OBJECTIVE

To assess whether microinjecting epirubicin into cells showing multidrug resistance (MDR, common to many cancers, including bladder cancer, with resistance to, e.g. anthracyclines and mitomycin C) spares the nucleus, as when these drugs accumulate, distribution in MDR cells characteristically spares the nucleus, suggesting that the nuclear membrane is responsible for excluding cytotoxic drugs from MDR nuclei.

MATERIALS AND METHODS

Nuclear exclusion of drugs is an important feature of resistance in MDR cells, as many MDR-susceptible drugs have cytotoxic actions within the nucleus. Drug accumulation in 'classical' P-glycoprotein-mediated MDR cells is greatly reduced by efflux. Microinjection of epirubicin into the cytoplasm of MDR cells bypasses the P-glycoprotein efflux pump on the plasma membrane. Nuclear sparing would directly implicate the nuclear membrane in this phenomenon. Because of their fluorescence properties, which allow study by confocal microscopy and flow cytometry, anthracyclines have also been used extensively to investigate MDR. Thus sensitive (MGH-U1 and RT112) and MDR (MGH-U1R and MGH-U1-MMC) bladder cancer cell lines were used. Adherent cells from each cell line were individually microinjected with epirubicin (0.5 mg/mL) and a 77 kDa fluorescein isothiocyanate (FITC)-dextran (0.5 mg/mL). The pattern of nuclear epirubicin uptake in injected cells was then evaluated by confocal microscopy. The 77 kDa FITC-dextran allowed easier identification of injected cells and was also excluded from their nuclei.

RESULTS

Sensitive bladder cancer cell lines all showed a nuclear accumulation pattern of epirubicin, consistent with their normal uptake after exposure to epirubicin. The MDR cell lines showed the characteristic nuclear-sparing pattern of epirubicin uptake, similar to the normal uptake pattern after epirubicin exposure. The 77 kDa FITC-dextran showed clearly which cells had been microinjected, and was excluded from the nuclei of all injected cells. Cell viability was confirmed by acridine-orange staining after initial visualization of injected cells.

CONCLUSION

The nuclear membrane is responsible for the nuclear exclusion of epirubicin in MDR cells. Further work is necessary to determine the mechanisms involved.

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.

Intracellular localisation studies of doxorubicin and Victoria Blue BO in EMT6-S and EMT6-R cells using confocal microscopy

The subcellular localisation of doxorubicin and Victoria Blue BO (VBBO) in a murine mammary tumour cell line EMT6-S, and the resistant sub-lineEMT6-R was studied, using confocal microscopy, in order to investigate their sites of action. In cells treated with doxorubicin (10 mu M) for 90 min, the pattern of intracellular drug distribution differed between the two cell lines. Doxorubicin was found to localise mainly in the nucleus of the sensitive cell line, whereas weak fluorescence was observed in the cytoplasm of the resistant cells, in a punctuate pattern, with no nuclear involvement. The drug also appeared to be effluxed more rapidly by the resistant cell line. The accumulation of doxorubicin at various time intervals over 1h in EMT6-S cells showed that the drug clearly interacted with both the plasma membrane and the nucleus. In contrast to doxorubicin, the intracellular distribution of VBBO in both EMT6-S and EMT6-R was similar, VBBO was clearly localised throughout the cytoplasm, in a punctuate pattern, which may be consistent with the widespread distribution of mitochondria. A more apical pattern of accumulation was noted in the EMT6-R cell line. No interaction with the plasma membrane was evident. These results indicate that the main modes of action for the two drugs differ markedly, suggesting involvement of both the membrane and the nucleus in the case of doxorubicin, but mitochondrial involvement for VBBO.

Cellular resistance to mitomycin C is associated with overexpression of MDR-1 in a urothelial cancer cell line (MGH-U1)

OBJECTIVE

To compare multidrug resistance (MDR)-1 and MDR-3 gene expression in a new urothelial cancer cell line (MGHU-1, with resistance to mitomycin C) against controls and the established (epirubicin-resistant) MDR clone, and to correlate MDR with cytotoxicity data.

MATERIALS AND METHODS

Resistance to mitomycin C was induced by the long-term exposure of wild-type MGHU-1 cells to increasing concentrations (20-400 nmol/L) of mitomycin C. The cytotoxicity of mitomycin C or epirubicin was then compared in MGHU-1, MGHU-MMC (mitomycin C-resistant) and MGHU-1R (established MDR) cells, using the tetrazolium biomass assay. The expression of MDR-1 and -3 was investigated by the reverse transcriptase-polymerase chain reaction, using cDNA-specific primers after titration, and compared with DNA and negative controls.

RESULTS

MDR-1 and -3 were significantly and equally overexpressed in MGHU-1R, and associated with a dramatic increase in the 50% inhibitory drug concentration (P < 0.001) for mitomycin C and epirubicin against controls. In MGHU-MMC, the overexpression of MDR-1 was three times greater than that of MDR-3. The cytotoxicity profile for both agents was very similar to that of MGHU-1R. Trace amounts of MDR-1, but not MDR-3, were identified in the MGHU-1 wild-type.

CONCLUSIONS

Urothelial cancer cell resistance to mitomycin C is associated with cross-resistance to epirubicin and overexpression of MDR-1, suggesting that mitomycin C falls within the MDR category. Clinical application of this methodology may allow patients to be identified who are unlikely to benefit from intravesical chemotherapy.

Epirubicin: a review of its intravesical use in superficial bladder cancer

The anthracycline epirubicin has been investigated for intravesical use in patients with superficial bladder cancer. In multicentre, randomised trials, prophylaxis with intravesical epirubicin 30 to 80 mg after transurethral resection (TUR) was more effective than no prophylaxis in the prevention of disease recurrence. Intravesical prophylaxis with epirubicin was as effective as that with equivalent dosages of doxorubicin after TUR. Data are conflicting concerning the relative efficacy of intravesical epirubicin and bacillus Calmette-Guerin (BCG) in patients at intermediate risk of recurrence after TUR, but epirubicin was less effective than BCG in those at high risk. The efficacy and tolerability of prophylaxis with epirubicin relative to that with mitomycin is not yet established. The efficacy of epirubicin as prophylaxis after TUR in combination with BCG or interferon-alpha-2b, or as treatment in patients with superficial bladder cancer has been evaluated in small, noncomparative trials, but requires clarification. Adverse events associated with intravesical epirubicin were generally mild and transient. The most common adverse events were localised to the bladder (cystitis, haematuria and urinary tract infection). Systemic adverse events (cardiac, haematological or related to hypersensitivity) were not reported in many trials of intravesical epirubicin, and when reported generally occurred in < or =5% of patients who received the drug. Intravesical epirubicin was generally tolerated as well as intravesical doxorubicin and was associated with a lower incidence of mild chemical cystitis in 1 clinical trial. The incidence of adverse events associated with intravesical epirubicin was markedly lower than that associated with intravesical BCG.

CONCLUSIONS

Intravesical epirubicin has shown efficacy in preventing disease recurrence after TUR of superficial bladder cancer. In comparison with equivalent dosages of doxorubicin, the efficacy of epirubicin for this indication is generally similar, and the tolerability profile may be more favourable. Epirubicin is less effective than BCG as intravesical prophylaxis in patients at high risk of recurrence after TUR; the relative efficacy of epirubicin and BCG after TUR in patients at intermediate risk is not yet clear. Intravesical epirubicin is generally tolerated better than BCG. Intravesical epirubicin may be used as prophylaxis after TUR in patients who are at low or intermediate risk of recurrence of superficial bladder cancer.

Effect of gamma-linolenic acid on cellular uptake of structurally related anthracyclines in human drug sensitive and multidrug resistant bladder and breast cancer cell lines

This study investigated the effect on drug uptake in multidrug resistant cells by the incorporation of the essential fatty acid gamma-linolenic acid (GLA). The cell lines used were the MCF-7/R resistant human breast cancer and MGH-U1/R bladder cancer. Uptake of drug (doxorubicin, epirubicin, mitoxantrone and idarubicin) after the incorporation of GLA was investigated quantitatively by flow cytometry and qualitatively by confocal microscopy. There was no observable overall increase in drug uptake due to GLA incorporation into the cells as shown by flow cytometry. However, an increase in uptake of the chemotherapeutic agent idarubicin was observed in GLA-treated resistant cells compared with untreated cells using the confocal microscope. This overall increase in cellular drug uptake was not accompanied by a change in cellular drug distribution. Only one drug, mitoxantrone, displayed a change in intracellular drug distribution due to GLA incorporation into MCF-7/R cells. This suggests that essential fatty acid incorporation into the cellular membranes of some resistant cells may cause a shift in the intracellular distribution of certain chemotherapeutic drugs.

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.

Confocal microscopy of idarubicin localisation in sensitive and multidrug-resistant bladder cancer cell lines

Idarubicin is a highly lipophilic anthracycline and appears effective against tumours resistant to conventional anthracyclines. Confocal microscopy demonstrates predominantly cytoplasmic idarubicin accumulation. This distribution is unaltered by resistance status or the resistance reversing agent verapamil. Our results contrast with studies on conventional anthracyclines and suggest that nuclear accumulation may not be a prerequisite for anthracycline cytotoxicity.