Myeloid malignancies induced by alkylating agents in Nf1 mice.
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Therapy-related acute myeloid leukemia and myelodysplastic syndrome (t-AML and MDS) are severe late complications of treatment with genotoxic chemotherapeutic agents. Children with neurofibromatosis type 1 (NF1) are predisposed to malignant myeloid disorders that are associated with inactivation of the NF1 tumor suppressor gene in the leukemic clone. Recent clinical data suggest that NF1 might be also associated with an increased risk of t-AML after treatment with alkyating agents. To test this hypothesis, we administered cyclophosphamide or etoposide to cohorts of wild-type and heterozygous Nf1 knockout mice. Cyclophosphamide exposure cooperated strongly with heterozygous inactivation of Nf1 in myeloid leukemogenesis, while etoposide did not. Somatic loss of the normal Nf1 allele correlated with clinical disease and was more common in 129/Sv mice than in 129/Sv x C57BL/6 animals. Leukemic cells showing loss of heterozygosity at Nf1 retained a structural allele on each chromosome 11 homolog. These studies establish a novel in vivo model of alkylator-induced myeloid malignancy that will facilitate mechanistic and translational studies. (+info)
Cisplatin inhibits paclitaxel-induced apoptosis in cisplatin-resistant ovarian cancer cell lines: possible explanation for failure of combination therapy.
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Combination chemotherapy using paclitaxel with a platinum-based regimen is currently the standard first-line therapy for ovarian cancer after surgical cytoreduction. Whereas cisplatin-paclitaxel combination chemotherapy has shown significant efficacy over previous drug combinations in ovarian cancer, 20-30% of patients fail to respond to this combination. These patients are deemed cisplatin-paclitaxel resistant, although it is unclear whether the tumors are resistant to one or both drugs. Because the options available to ovarian cancer patients for second-line therapy are limited, and knowing that mechanistic differences exist between cisplatin and paclitaxel, we assessed the efficacy of combination drug therapy on cisplatin-resistant (cisplatinR) ovarian cancer cells. We found that paclitaxel induced apoptosis in cisplatinR cells as well as in the cisplatin-sensitive parental cell lines. In cisplatinR C-13 cells, the concomitant addition of cisplatin blocked paclitaxel-induced apoptosis as determined by DNA fragmentation assays, fluorescence microscopy, and flow cytometry. Paclitaxel-induced multimininucleation was also inhibited when the cells were exposed sequentially to paclitaxel and then cisplatin. Cisplatin did not block paclitaxel-induced stabilization of microtubules or prevent paclitaxel-induced loss of Bcl-2 expression in cisplatinR cells. Conversely, paclitaxel did not inhibit p53 protein accumulation by cisplatin. These results suggest that cisplatin blocks paclitaxel-induced apoptosis at a point downstream of Bcl-2 degradation and independent of microtubule stabilization. Our research shows that cisplatin can inhibit the effectiveness of paclitaxel in cispatinR cell lines. Therefore, the establishment of a clinical protocol to evaluate the efficacy of paclitaxel alone versus another second-line regimen in patients with cisplatin-paclitaxel-resistant ovarian cancer is warranted. (+info)
Overexpression of p21(waf1) decreases G2-M arrest and apoptosis induced by paclitaxel in human sarcoma cells lacking both p53 and functional Rb protein.
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We examined the effect of overexpression of p21(waf1) on cytotoxicity of paclitaxel, a microtubule stabilizer, using a tetracycline-inducible expression system in human sarcoma cells (SaOs-2) that lack both functional retinoblastoma protein and p53. Under normal growth conditions, p21(waf1) is not detectable in SaOs-2 cells. Upon p21(waf1) induction by tetracycline withdrawal, we observed a reduced apoptotic response to paclitaxel with a 3- to 6-fold increase in IC50 values compared with that of cells not induced by p21(waf1). We also observed a 5-fold increase in the IC50 value when cytotoxicity to vincristine, another microtubule-disrupting agent, was assessed, whereas we observed a marked decrease in the IC50 value after p21(waf1) induction in response to etoposide, a topoisomerase II inhibitor. After treatment with paclitaxel, less accumulation of G2-M was observed in p21(waf1)-induced cells compared with non-p21(waf1)-induced cells (57% versus 74%). p21(waf1) induction also inhibited the increased cyclin B1-associated kinase activity induced by paclitaxel. Overexpression of p21(waf1) in SaOs-2 cells lacking both p53 and functional retinoblastoma protein may decrease the G2-M arrest induced by paclitaxel due to suppression of the S-G2 checkpoint, resulting in a decreased apoptotic response of cells to paclitaxel. (+info)
Effect of PSC 833, a P-glycoprotein modulator, on the disposition of vincristine and digoxin in rats.
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PSC 833 has been used to overcome the phenomenon of multidrug resistance by inhibiting the P-glycoprotein (P-gp)-mediated efflux of antitumor drugs from tumor cells. Because P-gp expressed in several normal tissues may affect the disposition of its substrates, we examined the dose-dependent effect of PSC 833 on the disposition of vincristine (VCR) and digoxin (DGX) in rats. One-tenth milligram per kilogram PSC 833 was sufficient to significantly reduce the biliary excretion clearance of DGX from 3.0 ml/min/kg to 0.5 ml/min/kg, whereas 3 mg/kg PSC 833 was needed to significantly reduce the biliary excretion clearance of VCR from 36 ml/min/kg to 9 ml/min/kg. Three milligrams per kilogram PSC 833 significantly reduced the renal clearance of VCR by 30% but did not affect that of DGX significantly. The tissue-to-plasma DGX concentration ratio in the brain at 6 h after administration (0.34 versus 1.64), but not that of VCR at 2 h (1.07 versus 1.37), was significantly increased by PSC 833, 3 mg/kg. The differential effect of PSC 833 on the disposition of VCR and DGX may be ascribed to the different degree of contribution of P-gp to the disposition of these ligands. (+info)
Paclitaxel enhances macrophage IL-12 production in tumor-bearing hosts through nitric oxide.
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Tumor-induced macrophages (Mphis) mediate immunosuppression, in part, through increased production of factors that suppress T cell responsiveness and underproduction of positive regulatory cytokines. Pretreatment of tumor-bearing host (TBH) Mphis with the anticancer agent paclitaxel (Taxol) partially reverses tumor-induced Mphi suppressor activity, suggesting that paclitaxel may restore TBH Mphi production of proimmune factors. Because paclitaxel demonstrates LPS-mimetic capabilities and increased production of the LPS-induced immunostimulatory cytokine IL-12 could account for enhanced T cell responsiveness, we investigated whether paclitaxel induces Mphi IL-12 production. Tumor growth significantly down-regulated Mphi IL-12 p70 production through selective dysregulation of IL-12 p40 expression. LPS stimulation failed to overcome tumor-induced dysregulation of p40 expression. In contrast, paclitaxel significantly enhanced both normal host and TBH Mphi IL-12 p70 production in vitro, although TBH Mphi IL-12 production was lower than that of similarly treated normal host Mphis. Paclitaxel enhanced p40 expression in a dose-dependent manner. Through reconstituted Mphi IL-12 expression, paclitaxel pretreatment relieved tumor-induced Mphi suppression of T cell alloreactivity. Blocking Mphi NO suppressed paclitaxel's ability to induce IL-12 production. This suggests that paclitaxel-induced activities may involve a NO-mediated autocrine induction pathway. Collectively, these data demonstrate that paclitaxel restores IL-12 production in the TBH and ascribe a novel immunotherapeutic component to the pleiotropic activities of NO. Through its capacity to induce IL-12 production, paclitaxel may contribute to the correction of tumor-induced immune dysfunction. (+info)
BOMP/EPI intensive alternating chemotherapy for IGCCC poor-prognosis germ-cell tumors: the Spanish Germ-Cell Cancer Group experience (GG)
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BACKGROUND: Patients with poor-prognosis germ-cell tumors according to the IGCCC have a poor long-term survival. This study evaluates the efficacy and toxicity of the intensive alternating chemotherapy regimen BOMP/EPI in these patients. PATIENTS AND METHODS: Patients with IGCCC poor-prognosis germ-cell tumors treated at 13 centres were studied. Treatment consisted of bleomycin 30 mg, vincristine 2 mg, methotrexate 300 mg/m2 and cisplatin 100 mg/m2 (BOMP), alternating after a 14-day interval with etoposide 120 mg/m2 day 1-4, ifosfamide 1.3 g/m2 day 1-4 and cisplatin 25 mg/m2 day 1-4 (EPI). BOMP was administered 21 days after the EPI. Bleomycin was administered weekly per 12 weeks. RESULTS: Thirty-eight patients were treated. The median number of cycles administered was 7 (1-10 cycles). Eighteen patients achieved complete responses with chemotherapy alone (12 had necrosis and 2 mature teratoma at postchemotherapy resection), and four achieved complete responses with chemotherapy and surgical resection of viable cancer. Thus, an overall favorable response was achieved in 22 patients (60%). Four additional patients had marker-negative non-resected residual masses. Eleven patients were considered treatment failures, including one who died early and another who succumbed to granulocytopenic sepsis and renal failure. Hematologic toxicity was the most common, with 26 patients (70%) having grade 4 granulocytopenia. After a median follow-up of 41 months, the actuarial two-year overall survival and progression-free survival were 64% and 58%, respectively. CONCLUSION: BOMP/EPI is active in poor-prognosis germ-cell tumors according to the IGCCC criteria. The results obtained compare favorably with those expected with conventional chemotherapy, and justify further studies. (+info)
Cisplatin-topotecan-paclitaxel weekly administration with G-CSF support for ovarian and small-cell lung cancer patients: a dose-finding study.
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PURPOSE: Paclitaxel (PTX) and topotecan (TPT) have shown promising antitumor activity in both ovarian cancer (OC) and small-cell lung cancer (SCLC) patients. This phase I study was aimed at determining the maximum tolerable dose (MTD) of TPT given weekly over 30 min in combination with fixed doses of cisplatin (CDDP) and (PTX), and with G-CSF support. PATIENTS AND METHODS: Forty-four patients with OC (19) or SCLC (25), either chemo-naive (20) or pretreated (24) received CDDP 40 mg/m2, PTX 85 mg/m2 (one-hour infusion) and escalating TPT doses (starting from 0.75 mg/m2) in a 30-min infusion in weekly administration. Filgrastim 5 mg/kg was administered on days 3 to 5 of each week. RESULTS: Eight different dose levels were tested for a total of 295 delivered cycles. The dose escalation was interrupted at the TPT dose of 2.50 mg/m2. No toxic deaths occurred in this study. Grade 3 to 4 neutropenia, thrombocytopenia, and anemia occurred in 15 patients (36 cycles), seven patients (15 cycles), and four patients (five cycles), respectively. Severe vomiting and diarrhoea occurred in seven and four patients. Peripheral neuropathy was recorded in 11 patients (42 cycles), but it was never severe. An overall 11 of 19 (58%) OC and 11 of 25 (44%) SCLC patients obtained objective responses. Eight patients showed complete responses (three OC and three SCLC). Among the 20 chemo-naive patients, 9 of 11 (82%) OC and seven of nine (78%) SCLC responded. CONCLUSIONS: The CDDP/TPT/PTX weekly administration with filgrastim support represents a well-tolerated and active therapeutic approach in both chemo-naive and pretreated OC and SCLC patients. A weekly dose of TPT of 2.25 mg/m2 is recommended for the phase II study. (+info)
Boswellic acids and malignant glioma: induction of apoptosis but no modulation of drug sensitivity.
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Steroids are essential for the control of oedema in human malignant glioma patients but may interfere with the efficacy of chemotherapy. Boswellic acids are phytotherapeutic anti-inflammatory agents that may be alternative drugs to corticosteroids in the treatment of cerebral oedema. Here, we report that boswellic acids are cytotoxic to malignant glioma cells at low micromolar concentrations. In-situ DNA end labelling and electron microscopy reveal that boswellic acids induce apoptosis. Boswellic acid-induced apoptosis requires protein, but not RNA synthesis, and is neither associated with free radical formation nor blocked by free radical scavengers. The levels of BAX and BCL-2 proteins remain unaltered during boswellic acid-induced apoptosis. p21 expression is induced by boswellic acids via a p53-independent pathway. Ectopic expression of wild-type p53 also induces p21, and facilitates boswellic acid-induced apoptosis. However, targeted disruption of the p21 genes in colon carcinoma cells enhances rather than decreases boswellic acid toxicity. Ectopic expression of neither BCL-2 nor the caspase inhibitor, CRM-A, is protective. In contrast to steroids, subtoxic concentrations of boswellic acids do not interfere with cancer drug toxicity of glioma cells in acute cytotoxicity or clonogenic cell death assays. Also, in contrast to steroids, boswellic acids synergize with the cytotoxic cytokine, CD95 ligand, in inducing glioma cell apoptosis. This effect is probably mediated by inhibition of RNA synthesis and is not associated with changes of CD95 expression at the cell surface. Further studies in laboratory animals and in human patients are required to determine whether boswellic acids may be a useful adjunct to the medical management of human malignant glioma. (+info)