Chemotherapy in advanced androgen-independent prostate cancer 1990-1999: a decade of progress?
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BACKGROUND AND PURPOSE: A great number of clinical research studies have been reported in the field of chemotherapy for advanced androgen-independent prostate cancer during the last ten years. The aims of the present review were to assess their impact on management of the disease and on survival of patients. METHODS: The review of full published reports was facilited by the use of a MEDLINE computer search. RESULTS: Clinical research studies have focused on defining guidelines for eligibility criteria and accurate endpoints for patients to be enrolled onto clinical trials and developing new agents or combination of drugs including estramustine phosphate. Any combination of current chemotherapy has no impact on overall survival of patients. Among drugs in development, only the promising activity observed with docetaxel deserves randomized trials to assess its impact on survival. The major innovative advance of the 90s is the demonstration of the impact of chemotherapy (mitoxantrone + prednisone) on quality of life as compared to prednisone alone. A greater and longer-lasting improvement in quality of life along with a concomitant decrease in costs was observed. CONCLUSIONS: At the present time, chemotherapy should be considered as a palliative treatment in patients with symptomatic androgen-independent disease. The enrollment of patients into clinical trials dealing with quality of life as primary endpoint is strongly solicited. A standard methodology should be used in phase II trials with a primary goal of selection of agents which should progress to randomized trials using survival as an endpoint. Hopefully new specific strategies targeted to reverse the molecular changes that underlie prostate tumorigenesis should rapidly impact the multimodality management of AIPC in the third millenium. (+info)
Overexpression of the ATP-binding cassette half-transporter, ABCG2 (Mxr/BCrp/ABCP1), in flavopiridol-resistant human breast cancer cells.
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We sought to characterize the interactions of flavopiridol with members of the ATP-binding cassette (ABC) transporter family. Cells overexpressing multidrug resistance-1 (MDR-1) and multidrug resistance-associated protein (MRP) did not exhibit appreciable flavopiridol resistance, whereas cell lines overexpressing the ABC half-transporter, ABCG2 (MXR/BCRP/ABCP1), were found to be resistant to flavopiridol. Flavopiridol at a concentration of 10 microM was able to prevent MRP-mediated calcein efflux, whereas Pgp-mediated transport of rhodamine 123 was unaffected at flavopiridol concentrations of up to 100 microM. To determine putative mechanisms of resistance to flavopiridol, we exposed the human breast cancer cell line MCF-7 to incrementally increasing concentrations of flavopiridol. The resulting resistant subline, MCF-7 FLV1000, is maintained in 1,000 nM flavopiridol and was found to be 24-fold resistant to flavopiridol, as well as highly cross-resistant to mitoxantrone (675-fold), topotecan (423-fold), and SN-38 (950-fold), the active metabolite of irinotecan. Because this cross-resistance pattern is consistent with that reported for ABCG2-overexpressing cells, cytotoxicity studies were repeated in the presence of 5 microM of the ABCG2 inhibitor fumitremorgin C (FTC), and sensitivity of MCF-7 FLV1000 cells to flavopiridol, mitoxantrone, SN-38, and topotecan was restored. Mitoxantrone efflux studies were performed, and high levels of FTC-reversible mitoxantrone efflux were found. Northern blot and PCR analysis revealed overexpression of the ABCG2 gene. Western blot confirmed overexpression of ABCG2; neither P-glycoprotein nor MRP overexpression was detected. These results suggest that ABCG2 plays a role in resistance to flavopiridol. (+info)
Herbimycin A enhances apoptotic effect of chemotherapeutic drugs on K562 cells.
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OBJECTIVES: To explore the anti-apoptotic mechanism and the effective apoptosis-inducing method in chronic myelogenous leukemia (CML) cells. METHODS: K562 cell line was used to observe the effect of combination of herbimycin A (HMA), a tyrosine kinase inhibitor, and chemotherapeutic agents on the induction of apoptosis. RESULTS: HMA or chemotherapeutic agents could inhibit the proliferation but not significantly induce apoptosis of K562 cells. However, HMA significantly enhanced apoptosis when combined with chemotherapeutic agents. Addition of sulfhydryl compound to the cultures to conjugate HMA completely abrogated this enhancing effect on K562 cells. CONCLUSIONS: HMA increases the sensitivity of CML cells to chemotherapeutic agents by inactivating tyrosine kinase activity. It is promising that combination of HMA with conventional chemotherapeutic drugs may be a new strategy in the treatment of CML. (+info)
Fludarabine in combination with cyclophosphamide or with cyclophosphamide plus mitoxantrone for relapsed or refractory low-grade non-Hodgkin's lymphoma.
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BACKGROUND AND OBJECTIVES: We report the activity of two combinations of fludarabine (FLU), one with cyclophosphamide (FLU/CY) and the second with CY plus mitoxantrone (FLU/CY/MITO). The aim of the study was to evaluate the activity and toxicity of these two schedules in patients with non-Hodgkin's lymphoma (NHL). DESIGN AND METHODS: Twenty-two patients with recurrent low grade non-Hodgkin's lymphoma (LGL) received FLU/CY (FLU 25 mg/m(2) days 1 to 3, CY 300 mg/m(2) days 1 to 3), and 31 patients received FLU/CY/MITO (FLU 25 mg/m(2) days 1 to 3, CY 300 mg/m(2) days 1 to 3, mitoxantrone 10 mg/m(2) day 1). Patients received antibiotic oral prophylaxis during all treatments and growth factors (G-CSF) when grade III granulocytopenia (WHO scale) occurred. RESULTS: Of the 53 patients, 31 achieved complete remission (CR) (58%) and 16 partial remission (PR) (30%). Response was similar in both arms of the study. After 3 courses, 77% of patients who achieved CR showed a complete disappearance of disease. Seventy-nine per cent of patients experienced granulocytopenia. Few patients had fever, all without infection. One patient died with fever of unknown origin three months after completion of six courses of treatment. INTERPRETATION AND CONCLUSIONS: Both treatments were seen to be effective in recurrent low-grade NHL. Antibiotic prophylaxis with G-CSF support seems to reduce treatment-related infection. (+info)
Optimal timing and dosage of chemotherapy as a combined treatment with androgen withdrawal in the human prostate LNCaP tumour model.
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Although numerous chemotherapeutic agents have been evaluated for patients with advanced prostate cancer, none have demonstrated improved survival benefits. Here, in order to determine whether the efficacy of chemotherapy can be enhanced by changing the regimen, we evaluated the effect of the varied timing and dosage of chemotherapy in combination with androgen withdrawal on time to androgen-independent (AI) progression in the human androgen-dependent LNCaP tumour model. We first demonstrated the synergistic effect of mitoxantrone on induction of apoptosis in LNCaP cells maintained in the steroid hormone-depleted charcoal-stripped media (CSM) compared to those in the standard media. In addition, this synergy was most remarkable during the simultaneous treatment of LNCaP cells with mitoxantrone and CSM compared to the pre- or post-use of mitoxantrone with CSM. LNCaP tumour growth in athymic nude mice and their increase in serum PSA levels were significantly inhibited by the simultaneous injection of mitoxantrone with castration, compared to the administration of mitoxantrone 2 weeks before or after castration. The TUNEL staining revealed that apoptotic cell death was extensively induced in LNCaP tumours treated with simultaneous castration and mitoxantrone compared to tumours treated with the other schedules. Furthermore, nude mice bearing LNCaP tumours were injected with a total of 0.5 mg mitoxantrone divided into 2, 5 and 10 days, with the most significant therapeutic effect and delayed AI progression observed in mice given injection of mitoxantrone for 2 days. These findings suggest that this might be the optimal way to perform cytotoxic chemotherapy and androgen withdrawal simultaneously in patients with advanced prostate cancer and to administer chemotherapeutic agents at high dosage within short intervals. (+info)
Cytosine methylation enhances mitoxantrone-DNA adduct formation at CpG dinucleotides.
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Recently, we have shown that mitoxantrone can be activated by formaldehyde in vitro to form DNA adducts that are specific for CpG and CpA sites in DNA. The CpG specificity of adduct formation prompted investigations into the effect of cytosine methylation (CpG) on adduct formation, since the majority of CpG dinucleotides in the mammalian genome are methylated and hypermethylation in subsets of genes is associated with various neoplasms. Upon methylation of a 512-base pair DNA fragment (containing the lac UV5 promoter) using HpaII methylase, three CCGG sites downstream of the promoter were methylated at C5 of the internal cytosine residue. In vitro transcription studies of mitoxantrone-reacted DNA revealed a 3-fold enhancement in transcriptional blockage (and hence adduct formation) exclusively at these methylated sites. In vitro cross-linking assays also revealed that methylation enhanced mitoxantrone adduct formation by 2-3-fold, and methylation of cytosine at a single potential drug binding site on a duplex oligonucleotide also enhanced adduct levels by 3-fold. Collectively, these results indicate preferential adduct formation at methylated CpG sites. However, adducts at these methylated sites exhibited the same stability as nonmethylated sites, suggesting that cytosine methylation increases drug accessibility to DNA rather than being involved in kinetic stabilization of the adduct. (+info)
Atp-bound topoisomerase ii as a target for antitumor drugs.
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Topoisomerase II (TOP2) poisons interfere with the breakage/reunion reaction of TOP2 resulting in DNA cleavage. In the current studies, we show that two different classes (ATP-sensitive and -insensitive) of TOP2 poisons can be identified based on their differential sensitivity to the ATP-bound conformation of TOP2. First, in the presence of 1 mm ATP or the nonhydrolyzable analog adenosine 5'-(beta,gamma-imino)triphosphate, TOP2-mediated DNA cleavage induced by ATP-sensitive TOP2 poisons (e.g. doxorubicin, etoposide, mitoxantrone, and 4'-(9-acridinylamino)methanesulfon-m-anisidide) was 30-100-fold stimulated, whereas DNA cleavage induced by ATP-insensitive TOP2 poisons (e.g. amonafide, batracylin, and menadione) was only slightly (less than 3-fold) affected. In addition, ADP was shown to strongly antagonize TOP2-mediated DNA cleavage induced by ATP-sensitive but not ATP-insensitive TOP2 poisons. Second, C427A mutant human TOP2alpha, which exhibits reduced ATPase activity, was shown to exhibit cross-resistance to all ATP-sensitive but not ATP-insensitive TOP2 poisons. Third, using ciprofloxacin competition assay, TOP2-mediated DNA cleavage induced by ATP-sensitive but not ATP-insensitive poisons was shown to be antagonized by ciprofloxacin. These results suggest that ATP-bound TOP2 may be the specific target of ATP-sensitive TOP2 poisons. Using Lac repressor-operator complexes as roadblocks, we show that ATP-bound TOP2 acts as a circular clamp capable of entering DNA ends and sliding on unobstructed duplex DNA. (+info)
High-dose mitoxantrone and cyclophosphamide without stem cell support in high-risk and advanced solid tumors: a phase I trial.
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This phase I study was designed to develop a high-dose combination of two cycles of mitoxantrone and cyclophosphamide in patients with solid tumors, as an alternative to single-cycle high-dose regimens that use only alkylating agents. Treatment was delivered with granulocyte colony-stimulating factor (G-CSF), but without stem cell support, in order to avoid potential tumor cell reinfusion. Thirty-one patients with advanced solid tumors received two cycles of high-dose mitoxantrone (20-30 mg/m2) plus high-dose cyclophosphamide (3000-4000 mg/m2). All patients received G-CSF until hematologic recovery. Dose-escalation was performed when less than 50% of cycles per level had dose-limiting toxicity (DLT). The maximum tolerated dose (MTD) achieved was mitoxantrone 25 mg/m2 and cyclophosphamide 4000 mg/m2. Main dose-limiting toxicities (DLTs) were hematological: grade IV neutropenia lasting more than 7 days and thrombopenia below 20 x 10(9)/l requiring more than one platelet transfusion. Non-hematological DLT consisted predominantly of grade III emesis and asthenia. Follow-up after each cycle was performed in an outpatient setting and there were no toxic deaths. In conclusion, the administration of two cycles of high-dose mitoxantrone and cyclophosphamide with G-CSF support is safe and feasible. MTD was mitoxantrone 25 mg/m2 and cyclophosphamide 4000 mg/m2. Evaluation of this regimen is being done in a phase II trial. (+info)