Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Both paclitaxel and ifosfamide have significant single-agent activity in non-small cell lung cancer. We designed a phase I study combining escalating doses of paclitaxel, administered by 24-hour infusion, with ifosfamide given at a dose of 1.6 g/m2 daily x 3. Paclitaxel dose levels were 135, 170, 200, 250, and 300 mg/m2. The goal of the study was to determine the maximum tolerated dose and dose-limiting toxicities of paclitaxel when used in this combination. Dose escalation was possible because of the use of filgrastim, a granulocyte colony-stimulating factor. Twenty-five patients at three institutions were treated. The dose-limiting toxicity of the combination was granulocytopenia, with other toxicities being generally mild to moderate. The maximum tolerated dose of paclitaxel was 300 mg/m2, and the recommended phase II dose is 250 mg/m2. There was a suggestion of a dose-response curve with paclitaxel as all three partial responses were seen at the 250 mg/m2 dose level. An additional II patients had objective regression or stable disease lasting for 9 to 30 weeks. A phase II study of this combination is currently being planned by the Cancer and Leukemia Group B.
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PMID:Paclitaxel and ifosfamide: a multicenter phase I study in advanced non-small cell lung cancer. 754 26

Paclitaxel is a new anticancer agent showing significant promise as therapy for solid tumours and leukaemia, given alone or in combination with other chemotherapeutic agents. Paclitaxel concentrations in biological specimens can be measured using high performance liquid chromatography, or more recently by immunoassay. Pharmacokinetic studies in which adults have been administered pacliaxel intravenously over 1 to 96 hours have demonstrated the following pharmacokinetic characteristics: extensive tissue distribution; high plasma protein binding (approximately 90 to 95%); variable systemic clearance, with average clearances ranging from 87 to 503 ml/min/m2 (5.2 to 30.2 L/h/m2); and minimal renal excretion of parent drug (< 10%). In vitro and in vivo studies have demonstrated that paclitaxel is extensively metabolised by the liver to 3 primary metabolites. Cytochrome P450 enzymes of the CYP3A and CYP2C subfamilies appear to be involved in hepatic metabolism of paclitaxel. Although early reports suggested that paclitaxel has first-order pharmacokinetics, some recent trials in children and adults suggest that its elimination is saturable. The clinical importance of saturable elimination would be greatest when large dosages are administered and/or the drug is infused over a shorter period of time. In these situations, achievable plasma concentrations are likely to exceed the affinity constant for elimination (Km). Thus, small changes in dosage or infusion duration may result in disproportionately large alterations in paclitaxel systemic exposure, potentially influencing patient response. A pharmacokinetic analysis of the combination of cisplatin and paclitaxel has demonstrated that paclitaxel clearance is apparently sequence dependent. Patients administered cisplatin prior to paclitaxel had lower clearances and greater clinical toxicity than patients receiving paclitaxel before cisplatin. Additional pharmacodynamic analyses have shown nonhaematological and haematological toxicity to correlate better with parameters of paclitaxel exposure (e.g. area under the plasma concentration-time curve, duration of plasma concentrations exceeding 0.1 mumol/L) than with the administered dosage.
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PMID:Clinical pharmacokinetics of paclitaxel. 783 63

Paclitaxel, a novel diterpenoid compound, has been used by dissolving in Cremophor EL (polyoxyethylene castor oil) due to its poor aqueous solubility. Cremophor EL was shown to reverse multidrug resistant phenotypes of various cell lines as well as to reverse cross-resistance to paclitaxel of a multidrug resistant cell line in vitro. Thus, a study was carried out to determine the modifying activity of Cremophor EL on the antitumor activity of paclitaxel against P388 leukemia, adriamycin-resistant subline (P388/ADM) and vincristine-resistant subline (P388/VCR) in vivo. Dimethyl sulfoxide (DMSO) was used as a counterpart solvent. The results showed that, although no significant antitumor activity was observed by paclitaxel in both solvents against P388/ADM, a significantly higher antitumor activity was induced by paclitaxel dissolved in Cremophor EL-based solvent compared with DMSO-based solvent against P388/VCR. However, more significant difference in the antitumor activity of paclitaxel against P388 parental line was observed between two solvents and both resistant sublines showed an obvious cross-resistance to paclitaxel. Therefore, it appeared that cross-resistance reversing activity of Cremophor EL is not so high as to be detectable at in vivo level.
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PMID:[Study for modifying activity of solvents on antitumor activity of paclitaxel]. 790 93

Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) is an effective drug in the treatment of metastatic breast cancer (MBC). In the salvage setting, 5-fluorouracil (5-FU) and folinic acid have proved to be effective against MBC as well. Recent preclinical data suggest that paclitaxel plus 5-FU has additive cytotoxicity. Given these observations, we initiated a phase II trial in which 38 women with MBC have been treated with a combination of all three drugs. All patients are currently evaluable for toxicity and 34 are evaluable for response. All women had histologically proven and assessable disease. Patients with prior exposure to paclitaxel were ineligible. Patient characteristics include a median age of 51 years (age range, 31 to 73 years) and a median performance status of 1 (range, 0 to 2). Thirty-three patients have received prior chemotherapy, of whom 23 had adjuvant chemotherapy only. Fifty-eight percent of the patients (22 of 38) had received prior doxorubicin or mitoxantrone; four patients had only hormonal therapy. Four patients had bone-only disease, and three patients had lymphangitic spread or cytologically positive pleural effusion as the only evaluable disease. Treatment consisted of paclitaxel 175 mg/m2 over 3 hours (day 1 only), followed by folinic acid 300 mg over 1 hour, followed by 5-FU 350 mg/m2 on days 1 to 3. Patients received standard paclitaxel premedications. To date, 175 cycles have been administered (median cycle length, 29 days; median number of cycles per patient, five). Toxicities included grade 3/4 infections in nine cycles (5%), grade 3/4 mucositis in three cycles, grade 3/4 nausea/vomiting in three cycles, grade 1 paresthesias in 12 patients (32%), alopecia 100%, and 17 cycles (10%) associated with dose reduction. Based on Cancer and Leukemia Group B toxicity criteria, arthralgia/myalgias were modest and graded mild (32 cycles), moderate (nine cycles), or severe (two cycles). There were two major hypersensitivity reactions, prompting removal of those patients from further protocol treatment. Four patients are unassessable for response due to hypersensitivity reactions (two) and unevaluable disease (two). Among the 34 patients evaluable for response, there were three complete responses, 18 partial responses, one minor response, nine stable disease, and three progressive disease (response rate, 62%). Responses were seen in patients who had received prior doxorubicin or mitoxantrone (11 of 22 patients) and in anthracycline/naive patients (10 of 16 patients). Responses were observed in all metastatic sites: soft tissue, viscera, and bone. Paclitaxel/5-FU/folinic acid appears to be an effective and well-tolerated outpatient regimen for women with MBC, even after failure of anthracycline-containing therapy.
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PMID:Paclitaxel and 5-fluorouracil in metastatic breast cancer: the US experience. 862 38

Paclitaxel dose responses in culture have been investigated alone and in association with cytosine arabinoside (ARA-C) and all-trans retinoic acid (ATRA), with the objective of identifying a role for paclitaxel in the treatment of acute myeloblastic leukaemia (AML). Initial studies were done to determine if paclitaxel dose responses of AML blast cell precursors were altered by regulatory compounds known to modify the dose responses of ARA-C. In contrast to ARA-C, paclitaxel dose responses were independent of cell culture method, the growth factors G-CSF and GM-CSF, and the ligands all-trans retinoic acid (ATRA) and hydrocortisone. Most blast cell populations were sensitive to paclitaxel; compared with normal marrow progenitors the dose responses were markedly heterogenous with some more, and others less, sensitive. Remission marrow progenitor paclitaxel responses resembled those of AML blasts in heterogeneity. The cell culture model tested the effect of pacliataxel and ATRA on the ARA-C dose responses of OCI/ AML-5; paclitaxel exposure was either before or after ARA-C to test for an effect of schedule; ATRA was added to the MEC cultures after paclitaxel and ARA-C. Repeat experiments were done to test three dose levels each of paclitaxel and ATRA. When paclitaxel was given after ARA-C, synergism was found for all but one of the dose combinations tested; only three examples of synergy were seen when paclitaxel preceded ARA-C. The studies justify trials combining ARA-C, paclitaxel and ATRA using a schedule suggested by the cell culture findings.
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PMID:A role for paclitaxel in the combination chemotherapy of acute myeloblastic leukaemia: preclinical cell culture studies. 890 92

Paclitaxel, a recently approved antineoplastic agent, is cleared slowly from the peritoneal cavity after i.p. injection, and therefore appears to be promising for intracavitary therapy of malignancies confined to the peritoneal cavity. However the dose-limiting toxicity of Taxol, the clinical formulation of paclitaxel, was severe abdominal pain, likely caused by the excipients (Cremophor EL and ethanol) that are required to overcome low drug solubility. We tested the hypothesis that a liposome-based formulation could modulate paclitaxel toxicity independent of antitumor activity. The dose-dependence of toxicity and antitumor effect of paclitaxel liposomes was evaluated after i.p. administration against i.p. P388 leukemia. Liposomal paclitaxel showed antitumor activity similar to that of free paclitaxel (as Taxol), but was better tolerated by both healthy and tumor-bearing mice.
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PMID:Paclitaxel-liposomes for intracavitary therapy of intraperitoneal P388 leukemia. 894 23

Paclitaxel (Taxol) has been shown to be clinically effective in treatment of patients with breast and ovarian cancer. It has also shown promising results in various other solid tumours. Paclitaxel has induced apoptosis in the G2/M phase of the cell cycle in both HL-60 and U937 human leukaemia cells. A recent study has shown a dose-dependent cytotoxicity for both taxanes: paclitaxel (taxol) and docetaxel (Taxotere) on fresh leukaemia cells in primary culture from 16 ALL and four AML patients and proposed their use in treatment of acute leukaemia patients. AML is a heterogeneous disease in which malignant transformation and disease progression occur at the level of CD34 positive cells. Also, the multi-drug resistance gene product, P-glycoprotein is expressed only in CD34 positive AML cells. Therefore, an in vitro evaluation of the efficacy of paclitaxel, a P-glycoprotein substrate, in CD34 positive AML cells is warranted before considering its clinical use in acute leukaemia patients. Since all in vitro studies of paclitaxel reported so far have involved only CD34 negative (HL-60, U937, K562) human AML cells, the aim of the present study was to evaluate paclitaxel efficacy against CD34 positive AML cells. The IC50 of paclitaxel for apoptosis was significantly higher in MHH225 CD34 positive cells (12 +/- 2 microM) than in U937 CD34 negative cells (1.7 +/- 0.2 microM), P < 0.001. Paclitaxel has a significantly weaker cytotoxic effect on CD34 positive AML cells. One log higher concentration of paclitaxel was required in MHH225 CD34 positive AML cells to achieve the same apoptosis level achieved in U937 CD34 negative leukaemia cells. Also, at the high concentration achievable in vivo: 10 microM paclitaxel, only half the MHH225 CD34 positive AML cells were apoptotic versus 72% of U937 CD34 negative leukaemia cells. Clearly, paclitaxel has only weak or modest in vitro efficacy compared with several conventional anti-leukaemia drugs used in AML treatment. The present results support the poor level of in vivo induction of apoptosis achieved during a phase I clinical study with paclitaxel therapy in 26 leukaemia patients. Also, the present results have shown a significant increase in nitric oxide production during paclitaxel-induced apoptosis in U937 monocytic leukaemia cells, confirming the vital role of nitric oxide in mediating paclitaxel-induced apoptosis by monocytic cells. In conclusion, the present study has demonstrated a clear difference between the effect of paclitaxel on CD34 negative and CD34 positive AML cells. Given its poor performance in the phase I clinical study of 26 acute leukaemia patients and the present weak in vitro cytotoxic effect, it is unlikely that paclitaxel will have a role in the treatment of acute leukaemia. Also, the present study emphasises the need to use CD34 positive AML cells such as MHH225 rather than the unsuitable lineage-specific CD34 negative cells such as HL-60 or U937 for in vitro pre-clinical screening of potential novel effective anti-leukaemia agents.
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PMID:Divergent effect of taxol on proliferation, apoptosis and nitric oxide production in MHH225 CD34 positive and U937 CD34 negative human leukaemia cells. 976 54

Over the past decade, the involvement of tyrosine kinases in signal transduction pathways evoked by cytokines has been intensively investigated. Only relatively recently have the roles of serine/threonine kinases in cytokine-induced signal transduction and anti-apoptotic pathways been examined. Cytokine receptors without intrinsic kinase activity such as interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF) and the interferons were thought to transmit their regulatory signals primarily by the receptor-associated Jak family of tyrosine kinases. This family of tyrosine kinases activates STAT transcription factors, which subsequently transduced their signals into the nucleus to modulate gene expression. Cytokine receptors with intrinsic tyrosine kinase activity such as c-Kit were initially thought to transduce their signals independently of serine/threonine kinase cascades. Recently, both of these types of receptor signaling pathways have been shown to interact with serine/threonine kinase pathways as maximal activation of these tyrosine kinase regulated cascades involve serine/threonine phosphorylation modulated by, for example MAP kinases. A common intermediate pathway initiating from cytokine receptors is the Ras/Raf/MEK/ERK (MAPK) cascade, which can result in the phosphorylation and activation of additional downstream kinases and transcription factors such as p90Rsk, CREB, Elk and Egr-1. Serine/threonine phosphorylation is also involved in the regulation of the apoptosis-controlling Bcl-2 protein, as certain phosphorylation events induced by cytokines such as IL-3 are anti-apoptotic, whereas other phosphorylation events triggered by chemotherapeutic drugs such as Paclitaxel are associated with cell death. Serine/threonine phosphorylation is implicated in the etiology of certain human cancers as constitutive serine phosphorylation of STATs 1 and 3 is observed in chronic lymphocytic leukemia and can be inhibited by the chemotherapeutic drug fludarabine. Serine/threonine phosphorylation also plays a role in the etiology of immunodeficiencies. Activated STAT5 proteins are detected in reduced levels in lymphocytes recovered from HIV-infected individuals and immunocompromised mice. Serine/threonine phosphorylation may be an important target of certain chemotherapeutic drugs which recognize the activated proteins. This meeting report and mini-review will discuss the interactions of serine/threonine kinases with signal transduction and apoptotic molecules and how some of these pathways can be controlled by chemotherapeutic drugs. Leukemia (2000) 14, 9-21.
Leukemia 2000 Jan
PMID:Serine/threonine phosphorylation in cytokine signal transduction. 1063 71

P-glycoprotein (Pgp) mediates drug accumulation defects in malignant cells in vitro. It confers resistance to multiple drugs including paclitaxel, an agent useful in treating malignancies including acute leukemia. Pgp-mediated drug resistance appears to be due to primary active drug-transport as well as other effects on membrane permeability, but the relative contribution of each is unclear. Flow cells are useful for differentiating transport-mediated efflux from altered membrane permeability, but their utility is limited to attached cells. We developed a novel flow cell to study drug efflux kinetics in suspension culture cells and examined paclitaxel efflux in resistant CEM/VLB100 leukemia cells, which overexpress Pgp, compared with its sensitive CEM parent line. Paclitaxel efflux from both cell lines was described by bi-exponential kinetics. The predominant initial rapid component increased linearly with paclitaxel concentration, consistent with passive efflux, and was faster in CEM/VLB100 than CEM cells. The slow terminal component of efflux was also more rapid for CEM/VLB100 than CEM, and was saturable (V(max)= 9.1 +/- 1.1 versus 3.5 +/- 0.3 pmol/min/10(7) cells, respectively) at a lower paclitaxel concentration than the parental CEM cells (k(m) = 63 +/- 46 nM versus 144 +/- 56 nM, respectively). In CEM/VLB100 cells, this saturable component was inhibited by verapamil and was temperature-sensitive, consistent with Pgp-mediated transport. Verapamil also inhibited the rapid component of efflux, suggesting additional effects on membrane permeability. Our studies show that the present technique is useful for studying drug transport and that effects of Pgp on membrane permeability contribute significantly to the net drug-accumulation defect.
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PMID:A flow cell assay for evaluation of whole cell drug efflux kinetics: analysis of paclitaxel efflux in CCRF-CEM leukemia cells overexpressing P-glycoprotein. 1115 98

Paclitaxel is a novel anticancer drug that has demonstrated efficacy toward treating several malignant tumor types. Here, we demonstrate that c-Jun NH(2)-terminal kinase (JNK), but not p38 mitogen-activated protein kinase or extracellular signal-regulated kinase 1/2, was persistently activated by paclitaxel or other microtubule-damaging agents within human leukemia HL-60 cells. Overexpression of a dominant-negative mutant, mitogen-activated protein kinase kinase 1 (MEKK1-DN) or treatment with JNK-specific antisense oligonucleotide prevented paclitaxel-induced JNK activation, Bcl-2 phosphorylation and apoptosis. Furthermore, we found that the full-length MEKK1 was cleaved to a 91-kDa carboxyl-terminal fragment at the earlier time of apoptosis induced by microtubule-damaging agents. This cleavage, however, occurred consistently with JNK activation and Bcl-2 phosphorylation, but preceded DNA fragmentation in cells in response to paclitaxel activity. The caspase inhibitor Ac-Asp-Glu-Val-Asp-CHO (DEVD-CHO), but not Ac-Tyr-Val-Ala-Asp-CHO (Ac-YVAD-CHO), effectively blocked MEKK1 cleavage, JNK activation, Bcl-2 phosphorylation, and subsequent apoptosis. Subcellular fractionation revealed that the 91-kDa C-terminal MEKK1 fragment was translocated to cytosol. Notably, the MEKK1 fragment could be coimmunoprecipitated with anti-JNK antibodies, suggesting that a signaling complex of C-terminal MEKK1/stress-activated protein kinase/extracellular-signal regulated kinase 1/JNK formed during apoptosis induced by microtubule-damaging agents. Taken together, our results suggest that disruption of cytoarchitecture by paclitaxel triggers a novel apoptosis-signaling pathway, wherein an active DEVD-directed caspase (DEVDase) initially cleaves MEKK1to generate a proapoptotic kinase fragment that is able to activate JNK and subsequent Bcl-2 phosphorylation, finally eliciting cell death.
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PMID:Involvement of Asp-Glu-Val-Asp-directed, caspase-mediated mitogen-activated protein kinase kinase 1 Cleavage, c-Jun N-terminal kinase activation, and subsequent Bcl-2 phosphorylation for paclitaxel-induced apoptosis in HL-60 cells. 1116 Aug 61


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