Methotrexate cross-resistance in a mitoxantrone-selected multidrug-resistant MCF7 breast cancer cell line is attributable to enhanced energy-dependent drug efflux.
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Cellular resistance to the antifolate methotrexate (MTX) is often caused by target amplification, uptake defects, or alterations in polyglutamylation. Here we have examined MTX cross-resistance in a human breast carcinoma cell line (MCF7/MX) selected in the presence of mitoxantrone, an anticancer agent associated with the multidrug resistance (MDR) phenotype. Examination of protein expression and enzyme activities showed that MCF7/MX cells displayed none of the classical mechanisms of MTX resistance. They did, however, exhibit an ATP-sensitive accumulation defect accompanied by reduced polyglutamylation. Although the kinetics of drug uptake was similar between parental and resistant cells, the resistant cells exhibited increased energy-dependent drug efflux. This suggested the involvement of an ATP-binding cassette (ABC) transporter. However, cells transfected with the breast cancer resistance protein (BCRP)-the ABC transporter known to be highly overexpressed in MCF7/MX cells and to confer mitoxantrone resistance (D. D. Ross et al., J. Natl. Cancer Inst. 91: 429-433, 1999)-were not MTX resistant, which suggested that this transporter is not involved in MTX cross-resistance. Moreover, members of the MRP protein family of transport proteins, which had previously been implicated in MTX resistance, were not found to be overexpressed in the MCF7/MX cells. Thus, our data suggest that a novel MTX-specific efflux pump may be involved in this unusual cross-resistance phenotype. (+info)
Increased risk of acute leukemia after adjuvant chemotherapy for breast cancer: a population-based study.
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PURPOSE: To quantify the risk of acute leukemia after adjuvant therapy, especially chemotherapy with topoisomerase II inhibitors. PATIENTS AND METHODS: We performed a population-based study in a cohort of 3,093 women younger than 85 years who resided in the French administrative area of the Cote d'Or, who were given a first diagnosis of primary breast cancer between 1982 and 1996, and who received a curative treatment. Information about therapy and follow-up events was obtained from records of cancer registries that covered this area. RESULTS: Until December 1998, 10 cases of acute leukemia, including nonlymphoid acute leukemia and refractory anemia with excess of blasts, occurred in patients before any local or distant recurrence. All cases developed in the first 4 years of follow-up. Compared with the general female population, the incidence rate of leukemia was significantly increased in women who received radiotherapy and chemotherapy (standardized incidence ratio, 28.5; P <.0001). A dose-dependent increase in the risk of leukemia was observed in women treated with mitoxantrone. Cox regression analysis showed that the risk of leukemia was significantly lower in patients treated with anthracyclines than in those treated with mitoxantrone at cumulative doses >/= 13 mg/m(2). CONCLUSION: The combination of adjuvant radiotherapy and chemotherapy with mitoxantrone induces a high risk of acute leukemia in patients with breast cancer. A leukemogenic effect of chemotherapy with anthracyclines cannot be ruled out with certainty. However, there are some suggestions that these topoisomerase II inhibitors might be less leukemogenic than mitoxantrone and could be preferred in an adjuvant setting. (+info)
The "comparative growth assay": examining the interplay of anti-cancer agents with cells carrying single gene alterations.
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We have developed a "comparative growth assay" that complements current assays of drug effects based on cytotoxicity. A co-culture of two cell lines, one of which is fluorescently labeled, is exposed to a cytotoxic agent and the proportion of fluorescent cells is compared with that of a baseline unexposed co-culture. For demonstration purposes, two HCT116 cell lines (an hMLH1 homozygous and an hMLH1 heterozygous mutant), altered by insertion of vector alone or the same vector carrying an insert for the expression of enhanced green fluorescent protein (EGFP), were exposed to numerous "anti-cancer" agents. The assay was further validated in a system of two cell lines differing only in the expression of the breast cancer resistance protein (BRCP). The assay allowed the estimation of the duration of action of a particular agent. Assessment of the agent's differential activity over a given time in culture could be expressed as a selection rate, which we chose to describe on an "average selection per day" basis. We conclude that this assay: 1) provides insight into the differential dynamic effects of chemotherapeutic agents or radiation; and 2) allows, through the use of matched cell lines, the investigation of critical physiologic features that govern cell sensitivity. (+info)
Topoisomerase II is required for mitoxantrone to signal nuclear factor kappa B activation in HL60 cells.
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Topoisomerase II is a target for a number of chemotherapeutic agents used in the treatment of cancer. Its essential physiological role in modifying the topology of DNA involves the generation of transient double-strand breaks. Anti-cancer drugs, such as mitoxantrone, that target this enzyme interrupt its catalytic cycle and give rise to persistent double strand breaks, which may be lethal to a cell. We investigated the role of such lesions in signaling the activation of the transcription factor nuclear factor kappaB (NFkappaB) by this drug. Mitoxantrone activated NFkappaB and stimulated IkappaBalpha degradation in the promyelocytic leukemia cell line HL60 but not in the variant cells, HL60/MX2 cells, which lack the beta isoform of topoisomerase II and express a truncated alpha isoform that results in an altered subcellular distribution. Treatment of sensitive HL60 cells with mitoxantrone led to a depletion of both isoforms, suggesting the stabilization of transient DNA-topoisomerase II complexes. This depletion was absent in the variant cells, HL60/MX2. Activation of caspase 3 by mitoxantrone was also impaired in the HL60/MX2 cells. NFkappaB activation in response to tumor necrosis factor and bleomycin, the latter causing topoisomerase II-independent DNA damage, was intact in both cell lines. An inhibitor rather than a poison of topoisomerase II, Imperial Cancer Research Fund 187 (ICRF 187) the mechanism of which does not involve the generation of double strand breaks, did not activate NFkappaB, nor did it induce apoptosis in parental HL60 cells. However, ICRF 187 protected against IkappaB degradation in parental HL60 cells in response to mitoxantrone. This protection was also shown with another topoisomerase II inhibitor, merbarone, which is structurally and functionally distinct from ICRF 187. Their effects were specific, as neither protected against tumor necrosis factor-stimulated IkappaB degradation. The poisoning of topoiso- merase II with resultant DNA damage is therefore a critical signal for NFkappaB activation. (+info)
Definition of relapse risk and role of nonanthracycline drugs for consolidation in patients with acute promyelocytic leukemia: a joint study of the PETHEMA and GIMEMA cooperative groups.
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Preliminary independent reports of the Italian GIMEMA and the Spanish PETHEMA trials for newly diagnosed acute promyelocytic leukemia (APL) indicated a similarly high antileukemic efficacy in terms of complete remission and disease-free survival rates. To better investigate these studies and the prognostic factors influencing relapse risk, this study analyzed the updated results of 217 patients with PML/RAR alpha-positive APL enrolled in GIMEMA (n = 108) and PETHEMA (n = 109). All patients received identical induction (AIDA schedule) and maintenance. For consolidation, GIMEMA patients received 3 courses including idarubicin/cytarabine, mitoxantrone/etoposide, and idarubicin/cytarabine/thioguanine, whereas PETHEMA patients received the same drugs and dose schedule of idarubicin and mitoxantrone with the omission of nonintercalating agents. Depending on whether molecular relapses were classified as censored or uncensored events, the 3-year Kaplan-Meier estimates of relapse-free survival (RFS) for the combined series were 90 +/- 2% and 86 +/- 2%, respectively. Minor differences observed between the 2 patient cohorts were negligible. Multivariate regression analysis of RFS showed that initial leukocyte (WBC) and platelet counts were the only variables with independent prognostic value. The resulting predictive model for RFS demonstrated its capability of segregating patients into low-risk (WBC count 40 x 10(9)/L), intermediate-risk (WBC count 10 x 10(9)/L) groups, with distinctive RFS curves (P <.0001). The conclusions are that omission of nonanthracycline drugs from the AIDA regimen is not associated with reduced antileukemic efficacy and a simple predictive model may be used for risk-adapted therapy in this disease. (Blood. 2000;96:1247-1253) (+info)
Etoposide, mitoxantrone and prednisone: a salvage regimen with low toxicity for refractory or relapsed non-Hodgkin's lymphoma.
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BACKGROUND AND OBJECTIVES: Relapsed non-Hodgkin's lymphoma (NHL) is preferably treated with high-dose therapy and stem cell support. However, not all patients qualify for intensive chemotherapy. We evaluated the efficacy and toxicity of a new salvage chemotherapy regimen designed for patients with relapsed or refractory NHL who are not appropriate candidates for high-dose therapy (HDT). DESIGN AND METHODS: Seventy-nine patients received a regimen consisting of etoposide (350 mg/m(2) i.v. day 1), mitoxantrone (14 mg/m(2) i.v. day 1) and prednisone (80 mg/m(2) p.o. days 1-5) (EMP). The majority had aggressive NHL. Twenty-one patients were elderly, i.e. >60 years of age; RESULTS: The overall response rate in the 79 patients was 38% as compared to 67% in the elderly. The progression-free survival was 54% and 30% at 12 months and 24 months, respectively. The toxicity of the regimen was relatively low. No toxic deaths have occurred. In 28 of 231 cycles (12%) a CTC-grade 2-4 infection was encountered. Twenty-one hospital admissions were necessary because of infection or fever. Other toxicity was rare. Toxicity was not greater in the elderly patients. WHO performance status 2-4 and elevated serum lactate dehydrogenase (LDH) concentrationv were adverse prognostic factors for response as well as for overall survival. Another adverse prognostic factor for response was age <60 years. INTERPRETATION AND CONCLUSIONS: EMP is a new salvage regimen with a relatively low toxicity. It should be considered for patients with relapsed or refractory NHL who are not candidates for standard reinduction therapy and stem cell transplantation. (+info)
High-dose chemotherapy (CTM) for breast cancer.
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We designed and implemented a new mitoxantrone-based high-dose chemotherapy regimen to minimize pulmonary injury (seen in carmustine-based regimens) in patients with breast cancer. One hundred and ninety-one breast cancer patients (99 stage II/IIIA; 27 stage IIIB; 65 stage IV responsive to conventional-dose chemotherapy) were treated with high-dose chemotherapy (CTM) delivered over 4 days (cyclophosphamide (6 g/m2), thiotepa (600 mg/m2), and mitoxantrone (24-60 mg/m2)) followed by autologous hematopoietic stem cell rescue. Stage II/III patients received chest wall radiation and tamoxifen (if hormone-receptor positive) after CTM. The 5-year event-free survival (EFS) for stage II/IIIA patients with 10 or more involved axillary lymph nodes (n = 80) was 62 +/- 12%. Hormone receptor-positive patients with 10 or more nodes did significantly better than negative patients. The EFS for stage IIIB patients at 5 years was 44 +/- 19%; for stage IV patients at 5 years was 17 +/- 10%. Stage IV patients achieving complete response in viscera and/or soft tissue prior to CTM did significantly better than those achieving a partial response. There were six (3%) treatment-related deaths including two due to diffuse alveolar hemorrhage. There were no episodes of delayed interstitial pneumonitis. There were six severe cardiac events in 91 patients (6.6%) but none after instituting mitoxantrone dose-adjustment in the final 100 patients. We conclude that CTM is associated with a low treatment-related mortality and little pulmonary toxicity. CTM produces excellent outcomes in stage II/IIIA patients with 10 or more involved axillary lymph nodes. (+info)
A phase II study to evaluate the combination of fludarabine, mitoxantrone and dexamethasone (FMD) in patients with follicular lymphoma.
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BACKGROUND: 'Molecular response' is being investigated as a therapeutic goal in follicular lymphoma (FL). High response rates in FL with the fludarabine combination 'FMD' have been associated with 'molecular remission'. A phase II study of FMD in FL was therefore conducted. PATIENTS AND METHODS: Fifty-four patients, ten of whom were newly diagnosed received FMD. Forty-four percent of the previously treated patients had 'chemoresistant' disease. Treatment comprised: fludarabine 25 mg/m2 days 1-3, mitoxantrone 10 mg/m2 day 1, and dexamethasone 20 mg days 1-5. Blood/bone marrow was collected for quantitation of t(14;18) by 'real-time' PCR. RESULTS: The overall response rate was 37 of 54 (69%), complete responses being seen in 11 patients (20%), with no difference between newly diagnosed and the previously treated patients. However, the response rate in 'chemosensitive' relapse was 84% compared to 44% in patients in whom the last prior regimen had failed. Molecular responses were seen in 17 of 25 and PCR negativity in 8 of 25, although molecular and clinical responses did not always correlate. Toxicity was moderate, 19 patients required admission. However, in 6 of 12 patients, subsequent G-CSF mobilised stem cell harvests failed. CONCLUSIONS: FMD was well tolerated but with a lower than expected response rate. Molecular responses were seen in the majority of responding patients however, 'molecular remission' was rare. (+info)