Allogeneic hematopoietic cell transplantation in intermediate risk acute myeloid leukemia negative for FLT3-ITD, NPM1- or biallelic CEBPA mutations.

BACKGROUND: The value of allogeneic hematopoietic cell transplantation (alloHCT) as postremission treatment is not well defined for patients with intermediate-risk acute myeloid leukemia (AML) without FLT3-ITD, biallelic CEBPA-, or NPM1 mutations (here referred to as NPM1mut-neg/CEBPAdm-neg/FLT3-ITDneg AML) in first complete remission (CR1). PATIENTS AND METHODS: We addressed this question using data from two prospective randomized controlled trials on intensive induction- and risk-stratified postremission therapy. The NPM1mut-neg/CEBPAdm-neg/FLT3-ITDneg AML subgroup comprised 497 patients, aged 18-60 years. RESULTS: In donor versus no-donor analyses, patients with a matched related donor had a longer relapse-free survival (HR 0.5; 95% CI 0.3-0.9, P = 0.02) and a trend toward better overall survival (HR 0.6, 95% CI 0.3-1.1, P = 0.08) compared with patients who received postremission chemotherapy. Notably, only 58% of patients in the donor group were transplanted in CR1. We therefore complemented the donor versus no-donor analysis with multivariable Cox regression analyses, where alloHCT was tested as a time-dependent covariate: overall survival (HR 0.58, 95% CI 0.37-0.9, P = 0.02) and relapse-free survival (HR 0.51, 95% CI 0.34-0.76; P = 0.001) for patients who received alloHCT compared with chemotherapy in CR1 were significantly longer. CONCLUSION: Outside clinical trials, alloHCT should be the preferred postremission treatment of patients with intermediate risk NPM1mut-neg/CEBPAdm-neg/FLT3-ITDneg AML in CR1. CINICALTRIALS.GOV IDENTIFIER: NCT00180115, NCT00180102.

A prospective randomised phase-II trial with gemcitabine versus gemcitabine plus sunitinib in advanced pancreatic cancer: a study of the CESAR Central European Society for Anticancer Drug Research-EWIV.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is one of the most common malignant tumours and is still associated with a poor prognosis in advanced disease. To improve the standard therapy with gemcitabine, we initiated a prospective randomised phase-II trial with gemcitabine (GEM) versus gemcitabine plus sunitinib (SUNGEM) based on data of in vitro trials and phase-I data for the combination treatment. The rational of adding sunitinib was its putative antiangiogenic mechanism of action. METHODS: A total of 106 eligible patients with locally advanced, unresectable or metastatic PDAC without previous system therapy were randomised to receive GEM at a dosage of 1.000mg/m(2) d1, 8, 15 q28 versus a combination of SUNGEM at a dosage of GEM 1.000mg/m(2) d1+8 and sunitinib 50mg p.o. d1-14, q21d. The primary end-point was progression free survival (PFS), secondary end-points were overall survival (OS), toxicity and overall response rate (ORR). RESULTS: The confirmatory analysis of PFS was based on the intend-to-treat (ITT) population (N=106). The median PFS was 13.3 weeks (95% confidence interval (95%-CI): 10.4-18.1 weeks) for GEM and 11.6 weeks for SUNGEM (95%-CI: 7.0-18.0 weeks; p=0.78 one-sided log-rank). The ORR was 6.1% (95%-CI: 0.7-20.2%) for GEM and for 7.1% (95%-CI: 0.9-23.5%) for SUNGEM (p=0.87). The median time to progression (TTP) was 14.0 weeks (95%-CI: 12.4-22.3 weeks) for GEM and 18.0 weeks (95%-CI: 11.3-19.3 weeks) for SUNGEM (p=0.60; two-sided log-rank). The median OS was 36.7 weeks (95%-CI: 20.6-49.0 weeks) for the GEM arm and 30.4 weeks (95%-CI: 18.1-37.6 weeks) for the SUNGEM (p=0.78, one-sided log-rank). In regard to toxicities, suspected SAEs were reported in 53.7% in the GEM arm and 71.2% in the SUNGEM arm. Grade 3 and 4 neutropenia was statistically significantly higher in the SUNGEM arm with 48.1% versus 27.8% in the GEM arm (p=0.045, two sided log-rank). CONCLUSIONS: The combination SUNGEM was not sufficient superior in locally advanced or metastatic PDAC compared to GEM alone in regard to efficacy but was associated with more toxicity.

Hematopoietic cell transplantation in patients with intermediate and high-risk AML: results from the randomized Study Alliance Leukemia (SAL) AML 2003 trial.

The optimal timing of allogeneic hematopoietic stem cell transplantation (HCT) in acute myeloid leukemia (AML) is controversial. We report on 1179 patients with a median age of 48 years who were randomized upfront. In the control arm, sibling HCT was scheduled in the first complete remission for intermediate-risk or high-risk AML and matched unrelated HCT in complex karyotype AML. In the experimental arm, matched unrelated HCT in first remission was offered also to patients with an FLT3-ITD (FMS-like tyrosine kinase 3-internal tandem duplication) allelic ratio >0.8, poor day +15 marrow blast clearance and adverse karyotypes. Further, allogeneic HCT was recommended in high-risk AML to be performed in aplasia after induction chemotherapy. In the intent-to-treat (ITT) analysis, superiority of the experimental transplant strategy could not be shown with respect to overall survival (OS) or event-free survival. As-treated analyses suggest a profound effect of allogeneic HCT on OS (HR 0.73; P=0.002) and event-free survival (HR 0.67; P<0.001). In high-risk patients, OS was significantly improved after allogeneic HCT in aplasia (HR 0.64; P=0.046) and after HCT in remission (HR 0.74; P=0.03). Although superiority of one study arm could not be demonstrated in the ITT analysis, secondary analyses suggest that early allogeneic HCT is a promising strategy for patients with high-risk AML.

RITA can induce cell death in p53-defective cells independently of p53 function via activation of JNK/SAPK and p38.

Significant advances have been made in the development of small molecules blocking the p53/MDM2 interaction. The Mdm2 inhibitor Nutlin-3 is restricted to tumors carrying wtp53. In contrast, RITA, a compound that binds p53, has recently been shown also to restore transcriptional functions of mtp53. As more than 50% of solid tumors carry p53 mutations, RITA promises to be a more effective therapeutic strategy than Nutlin-3. We investigated effects of RITA on apoptosis, cell cycle and induction of 45 p53 target genes in a panel of 14 cell lines from different tumor entities with different p53 status as well as primary lymphocytes and fibroblasts. Nine cell strains expressed wtp53, four harbored mtp53, and three were characterized by the loss of p53 protein. A significant induction of cell death upon RITA was observed in 7 of 16 cell lines. The nonmalignant cells in our panel were substantially less sensitive. We found that in contrast to Nultin-3, RITA is capable to induce cell death not only in tumor cells harboring wtp53 and mtp53 but also in p53-null cells. Importantly, whereas p53 has a central role for RITA-mediated effects in wtp53 cells, neither p53 nor p63 or p73 were essential for the RITA response in mtp53 or p53-null cells in our panel demonstrating that besides the known p53-dependent action of RITA in wtp53 cells, RITA can induce cell death also independently of p53 in cells harboring defective p53. We identified an important role of both p38 and JNK/SAPK for sensitivity to RITA in these cells leading to a typical caspase- and BAX/BAK-dependent mitochondrial apoptosis. In conclusion, our data demonstrate that RITA can induce apoptosis through p38 and JNK/SAPK not only in tumor cells harboring wtp53 and mtp53 but also in p53-null cells, making RITA an interesting tumor-selective drug.

Discrepant NOXA (PMAIP1) transcript and NOXA protein levels: a potential Achilles' heel in mantle cell lymphoma.

Mantle cell lymphoma (MCL) is an aggressive lymphoid neoplasm with transient response to conventional chemotherapy. We here investigated the role of the Bcl-2 homology domain 3-only protein NOXA for life-death decision in MCL. Surprisingly, NOXA (PMAIP1) mRNA and NOXA protein levels were extremely discrepant in MCL cells: NOXA mRNA was found to be highly expressed whereas NOXA protein levels were low. Chronic active B-cell receptor signaling and to a minor degree cyclin D1 overexpression contributed to high NOXA mRNA expression levels in MCL cells. The phoshatidyl-inositol-3 kinase/AKT/mammalian target of rapamycin pathway was identified as the major downstream signaling pathway involved in the maintenance of NOXA gene expression. Interestingly, MCL cells adapt to this constitutive pro-apoptotic signal by extensive ubiquitination and rapid proteasomal degradation of NOXA protein (T½âˆ¼15-30 min). In addition to the proteasome inhibitor Bortezomib, we identified the neddylation inhibitor MLN4924 and the fatty acid synthase inhibitor Orlistat as potent inducers of NOXA protein expression leading to apoptosis in MCL. All inhibitors targeted NOXA protein turnover. In contrast to Bortezomib, MLN4924 and Orlistat interfered with the ubiquitination process of NOXA protein thereby offering new strategies to kill Bortezomib-resistant MCL cells. Our data, therefore, highlight a critical role of NOXA in the balance between life and death in MCL. The discrepancy between NOXA transcript and protein levels is essential for sensitivity of MCL to ubiquitin-proteasome system inhibitors and could therefore provide a druggable Achilles' heel of MCL cells.

A randomised phase II trial of the Polo-like kinase inhibitor BI 2536 in chemo-naïve patients with unresectable exocrine adenocarcinoma of the pancreas - a study within the Central European Society Anticancer Drug Research (CESAR) collaborative network.

BACKGROUND: BI 2536, a novel Polo-like kinase 1 inhibitor, was assessed in patients with unresectable advanced exocrine adenocarcinoma of the pancreas. METHODS: The study employed a two-stage design. Randomised first-line patients received BI 2536 200 mg on day 1 (n=43) or 60 mg on days 1-3 (n=43) every 21 days. Recruitment of second-line patients was planned for a second stage dependent on an interim analysis demonstrating ≥ 2 responses in the first 18 evaluable patients following 12 weeks of treatment and/or tumour control ≥ 12 weeks in 5 patients per schedule. Primary end point was objective response rate (ORR). RESULTS: By independent review, ORR was 2.3% (all partial) and 24.4% had stable disease as confirmed best response. The second stage was not initiated. Median overall and progression-free survivals were 149 (95% confidence interval (CI), 91-307) and 46 days (95% CI, 44-56). Most common drug-related adverse events were neutropenia (37.2%), leukopenia (29.1%), fatigue (29.1%) and nausea (22.1%); most common grade 3/4-related events were neutropenia (36.0%), leukopenia (27.9%) and thrombocytopenia (8.1%). CONCLUSION: Given the low ORR and poor survival, further development of BI 2536 monotherapy is not warranted in this population.

Risk stratification using a new prognostic score for patients with secondary acute myeloid leukemia: results of the prospective AML96 trial.

Patients with secondary acute myeloid leukemia (sAML) are generally thought to have a poor prognosis. As there are no prognostic risk stratification models for patients with sAML available, the aim of this study was to obtain a scoring system. Prognostic factors influencing overall survival (OS) and event-free survival (EFS) were analyzed in 305 sAML patients treated in the prospective AML96 trial. The obtained prognostic scoring system was then validated in an independent patient cohort included in the AML2003 and AML60+ trials. In addition to the known risk factors for AML, age and karyotype, we identified the absolute platelet count and the Nucleophosmin 1 mutational status at diagnosis as prognostic factors of sAML patients. A pronounced distribution of sAML patients into three score groups was achieved showing a 2-year OS/EFS of 52/44% for patients in the low-risk group, 21/12% in the intermediate-risk group and 7/3% in the high-risk group (both P<0.001). Validation of this scoring system in a second independent set of sAML patients revealed similar significantly different survival results. In conclusion, for the first time, a prognostic scoring system is provided for sAML patients, allowing differential treatment strategies in the future.

Pharmacological inhibition of c-Abl compromises genetic stability and DNA repair in Bcr-Abl-negative cells.

Imatinib inhibits the kinase activity of Bcr-Abl and is currently the most effective drug for treatment of chronic myeloid leukemia (CML). Imatinib also blocks c-Abl, a physiological tyrosine kinase activated by a variety of stress signals including damaged DNA. We investigated the effect of pharmacological inhibition of c-Abl on the processing of irradiation-induced DNA damage in Bcr-Abl-negative cells. Cell lines and peripheral blood mononuclear cells (PBMCs) from healthy volunteers were treated with imatinib or dasatinib before gamma-irradiation. Inhibition of c-Abl caused an enhanced irradiation-induced mutation frequency and slowdown of DNA repair, whereas imatinib was ineffective in cells expressing a T315I variant of c-Abl. Mutation frequency and repair kinetics were also studied in c-Abl-/- murine embryonic fibroblasts (MEFs) retransfected with wild-type c-Abl (wt-Abl) or a kinase-defect variant of Abl (KD-Abl). Enhanced mutation frequency as well as delayed DNA repair was observed in cells expressing KD-Abl. These data indicate that pharmacological inhibition of c-Abl compromises DNA-damage response.

Recurrent finding of the FIP1L1-PDGFRA fusion gene in eosinophilia-associated acute myeloid leukemia and lymphoblastic T-cell lymphoma.

The FIP1L1-PDGFRA fusion gene has been described in patients with eosinophilia-associated myeloproliferative disorders (Eos-MPD). Here, we report on seven FIP1L1-PDGFRA-positive patients who presented with acute myeloid leukemia (AML, n=5) or lymphoblastic T-cell non-Hodgkin-lymphoma (n=2) in conjunction with AML or Eos-MPD. All patients were male, the median age was 58 years (range, 40-66). AML patients were negative for common mutations of FLT3, NRAS, NPM1, KIT, MLL and JAK2; one patient revealed a splice mutation of RUNX1 exon 7. Patients were treated with imatinib (100 mg, n=5; 400 mg, n=2) either as monotherapy (n=2), as maintenance treatment after intensive chemotherapy (n=3) or in overt relapse 43 and 72 months, respectively, after primary diagnosis and treatment of FIP1L1-PDGFRA-positive disease (n=2). All patients are alive, disease-free and in complete hematologic and complete molecular remission after a median time of 20 months (range, 9-36) on imatinib. The median time to achievement of complete molecular remission was 6 months (range, 1-14). We conclude that all eosinophilia-associated hematological malignancies should be screened for the presence of the FIP1L1-PDGFRA fusion gene as they are excellent candidates for treatment with tyrosine kinase inhibitors even if they present with an aggressive phenotype such as AML.

Sequential high dose chemotherapy as initial treatment for aggressive sub-types of non-Hodgkin lymphoma: results of the international randomized phase III trial (MISTRAL).

INTRODUCTION: Sequential high dose (SHiDo) chemotherapy with stem cell support has been shown to prolong the event-free survival in patients with diffuse large B-cell lymphoma. METHODS: To confirm this result in a multicenter trial, we randomized patients with aggressive NHL, to receive either eight cycles of CHOP or SHiDo. The primary endpoint was overall survival. RESULTS: 129 evaluable patients were randomized to receive either CHOP or SHiDo: median age, 48 years; 62% male; stage III+IV: 73%; age adjusted International Prognostic Index 1/2/3: 21%/52%/27%. Toxicity grades 3+4 were more pronounced in the SHiDo-arm with 13% versus 3% of patients with fever; 34% versus 13% with infections; 13% versus 2% with esophagitis/dysphagia/gastric ulcer. The remission rates were similar in SHiDo and CHOP arms with 34%/37% complete remissions and 31%/31% partial remissions, respectively. After a median observation time of 48 months, there was no difference in overall survival at 3 years, with 46% for SHiDo and 53% for CHOP (P = 0.48). CONCLUSION: In this multicenter trial, early intensification with SHiDo did not confer any survival benefit in previously untreated patients with aggressive NHL and was associated with a higher incidence of grades 3/4 toxicity.

Role of poly(ADP-ribose) polymerase activity in imatinib mesylate-induced cell death.

Imatinib targets Bcr-Abl, the causative event of chronic myelogenous leukemia (CML), and addresses leukemic cells to growth arrest and cell death. The exact mechanisms responsible for imatinib-induced cell death are still unclear. We investigated the role of poly(ADP-ribose) polymerase (PARP) activity in imatinib-induced cell death in Bcr-Abl-positive cells. Imatinib leads to a rapid increase of poly(ADP-ribosyl)ation (PAR) preceding loss of integrity of mitochondrial membrane and DNA fragmentation. The effect of imatinib on PAR can be mimicked by inhibition of phosphatidylinositol 3-kinase (PI3-K) implicating a central role of the PI3-K pathway in Bcr-Abl-mediated inhibition of PAR. Importantly, inhibition of PAR in imatinib-treated cells partially prevented cell death to an extent comparable to that observed after caspase inhibition. Simultaneous blockade of both caspases and PAR revealed additive cytoprotective effects indicating that both pathways function in parallel. In conclusion, our results suggest that in addition to the well-documented caspase-dependent pathway, imatinib also induces a PARP-mediated death process.

[Immunotherapy for advanced renal cell carcinoma]. / Immuntherapie des fortgeschrittenen Nierenzellkarzinomos.

Significant advances have been achieved in the surgical treatment of localized renal cell carcinoma over recent years. However, despite significant research efforts, the prognosis is still dismal in the majority of patients with advanced disease. Treatment with IFN-ac leads to moderately increased survival. In addition, survival can be prolonged by tu-mor nephrectomy in patients with synchronous metastases. Combined treatment with IFN-a, IL-2 and 5-FU has demonstrated a survival benefit in a single randomized controlled trial. High dose IL-2 causes long-term regression in a small fraction of patients. All of these treatments, however, frequently cause significant morbidity and therefore the potential benefit has to be weighed carefully against toxicity in each individual patient. Although, in general, the results of immunotherapeutic approaches have been dis-appointing, studies using allogeneic stem cells, allogeneic mononuclear cells and vaccines clearly demonstrate, that tumor control can be achieved by means of immunological intervention. Future research will hopefully lead to the development of strategies helpful for a greater proportion of patients with this disease.

Successful antiviral treatment for fulminant reactivated hepatitis B after autologous stem cell transplantation and prophylaxis during subsequent allogeneic stem cell transplantation.

The risk of severe hepatic damage due to reactivation of hepatitis B virus (HBV) infection after intensive myelosuppressive chemotherapy is well known. Two of the most evolved nucleotide analogues showing good activity against the hepatitis B virus are lamivudine and famciclovir. We report the successful therapeutic use of lamivudine and famciclovir for fulminant reactivated hepatitis B after autologous peripheral blood stem cell transplantation (PBSCT) and the subsequent prophylactic use of lamivudine during allogeneic blood stem cell transplantation (alloSCT) for chronic lymphocytic leukemia (CLL) in a 40-year-old patient. Antiviral therapy was well tolerated and no hematotoxicity occurred. Our observation warrants further investigation of antiviral therapy with famciclovir and lamivudine in HBV carriers receiving intensive myelosuppressive chemotherapy.

Requirement for Mdm2 in the survival effects of Bcr-Abl and interleukin 3 in hematopoietic cells.

The p53/Mdm2 pathway plays an important role in the induction of cell cycle arrest or apoptosis in response to genotoxic stress. Both the oncogene Bcr-Abl and physiological growth factors such as interleukin (IL)-3 can modulate the outcome of cellular exposure to DNA damage. To determine whether Bcr-Abl and growth factors can affect the p53/Mdm2 pathway, we studied the expression of Mdm2 in the IL-3-dependent pre-B cell line BaF3 and its bcr-abl-transfected derivative BaF3p185 after IL-3 deprivation or treatment with the c-Abl tyrosine kinase inhibitor STI571. We found that both growth factor withdrawal and inhibition of Bcr-Abl kinase lead to a down-regulation of Mdm2 preceding the induction of apoptosis. Apoptotic cell death induced by STI571 is partially dependent on p53. The early decrease of Mdm2 protein was not attributable to transcriptional regulation or to caspase-mediated cleavage. On the other hand, it could be completely blocked by the proteasomal inhibitor lactacystin. Targeted down-regulation of Mdm2 protein by antisense oligodeoxynucleotides overcame the survival effects of IL-3 and Bcr-Abl and resulted in accelerated apoptosis. Taken together, survival signals provided either by physiological growth factors or by oncogenic Bcr-Abl can positively regulate Mdm2, whereas Mdm2 ablation can reduce cell survival. These findings imply that, similarly to physiological growth factors such as IL-3, Bcr-Abl can promote cell survival through modulating the p53-Mdm2 pathway.

Adhesion to fibronectin selectively protects Bcr-Abl+ cells from DNA damage-induced apoptosis.

The phenotype of Bcr-Abl-transformed cells is characterized by a growth factor-independent survival and a reduced susceptibility to apoptosis. Furthermore, Bcr-Abl kinase alters adhesion features by phosphorylating cytoskeletal and/or signaling proteins important for integrin function. Integrin-mediated adhesion to extracellular matrix molecules is critical for the regulation of growth and apoptosis. However, effects of integrin signaling on regulation of apoptosis in cells expressing Bcr-Abl are largely unknown. The influence of adhesion on survival and apoptosis in Bcr-Abl+ and Bcr-Abl- BaF3 cells was investigated. p185bcr-abl-transfected BaF3 cells preadhered to immobilized fibronectin had a significant survival advantage and reduced susceptibility to apoptosis following gamma-irradiation when compared with the same cells grown on laminin, on polylysin, or in suspension. Both inhibition of Bcr-Abl kinase by STI571 and inhibition of specific adhesion reversed the fibronectin-mediated antiapoptotic effect in BaF3p185. The DNA damage response of Bcr-Abl- BaF3 cells was not affected by adhesion to fibronectin. In contrast to parental BaF3 cells, BaF3p185 adherent to fibronectin did not release cytochrome c to the cytosol following irradiation. The fibronectin-mediated antiapoptotic mechanism in Bcr-Abl-active cells was not mediated by overexpression of Bcl-XL or Bcl-2 but required an active phosphatidylinositol 3-kinase (PI-3K). Kinase-active Bcr-Abl in combination with fibronectin-induced integrin signaling led to a hyperphosphorylation of AKT. Thus, cooperative activation of PI-3K/AKT by Bcr-Abl and integrins causes synergistic protection of Bcr-Abl+ cells from DNA damage-induced apoptosis.

Second malignancies after ewing tumor treatment in 690 patients from a cooperative German/Austrian/Dutch study.

BACKGROUND: Ewing tumor treatment involves high cumulative doses of alkylating agents and topoisomerase inhibitors, drugs capable of inducing second cancers. We analyzed the second cancer risk in a large cohort of consistently treated patients. PATIENTS AND METHODS: Six hundred ninety Ewing tumor patients were treated between 1992 and 1999 with local therapy and vincristine. doxorubicin, ifosfamide and/or cyclophosphamide, and antinomycin D, with or without etoposide as a randomized question. Second cancer incidences were estimated by competing risk analyses; standardized incidence ratios (SIR) in comparison to registry data were compiled. RESULTS: After a median observation time of 56 months (32 months for survivors), 6 of 690 patients had developed second cancers: MDS/AML, two, ALL/NHL, two, squamous cell carcinoma, one, liposarcoma, one. SIR were increased 20-30 fold in comparison to the general population. The cumulative second cancer risk five years after diagnosis of the Ewing tumor was 0.0093 for the total group, zero for patients without etoposide, and 0.0118 with etoposide. Additional phase II high-dose therapy increased the risk to 0.0398 after five years. CONCLUSIONS: The second cancder risk observed was in the range to be expected in cancer survivors. High-dose therapy, and less markedly, etoposide, may contribute to the overall second cancer risk.

Bcr-Abl kinase down-regulates cyclin-dependent kinase inhibitor p27 in human and murine cell lines.

Chronic myeloid leukemia (CML) is a malignant stem cell disease characterized by an expansion of myeloid progenitor cells expressing the constitutively activated Bcr-Abl kinase. This oncogenic event causes a deregulation of apoptosis and cell cycle progression. Although the molecular mechanisms protecting from apoptosis in CML cells are well characterized, the cell cycle regulatory event is poorly understood. An inhibitor of the cyclin-dependent kinases, p27, plays a central role in the regulation of growth factor dependent proliferation of hematopoietic cells. Therefore, we have analyzed the influence of Bcr-Abl in the regulation of p27 expression in various hematopoietic cell systems. An active Bcr-Abl kinase causes down-regulation of p27 expression in murine Ba/F3 cells and human M07 cells. Bcr-Abl blocks up-regulation of p27 after growth factor withdrawal and serum reduction. In addition, p27 induction by transforming growth factor-beta (TGF-beta) is completely blocked in Bcr-Abl positive M07/p210 cells. This deregulation is directly mediated by the activity of the Bcr-Abl kinase. A Bcr-Abl kinase inhibitor completely abolishes p27 down-regulation by Bcr-Abl in both Ba/F3 cells transfected either with a constitutively active Bcr-Abl or with a temperature sensitive mutant. The down-regulation of p27 by Bcr-Abl depends on proteasomal degradation and can be blocked by lactacystin. Overexpression of wild-type p27 partially antagonizes Bcr-Abl-induced proliferation in Ba/F3 cells. We conclude that Bcr-Abl promotes cell cycle progression and activation of cyclin-dependent kinases by interfering with the regulation of the cell cycle inhibitory protein p27. (Blood. 2000;96:1933-1939)

The tyrosine kinase inhibitor CGP 57148 (ST1 571) induces apoptosis in BCR-ABL-positive cells by down-regulating BCL-X.

CGP 57148 is a potent inhibitor of the ABL protein tyrosine kinase and a promising new compound for the treatment of a variety of BCR-ABL-positive leukemias. We used this enzyme inhibitor to characterize the biological effects of BCR-ABL in primary cells and two growth factor-dependent BCR-ABL-transfected cell lines. The effect of CGP 57148 on primary cells is dependent on the stage of differentiation. The growth of maturing chronic myeloid leukemia cells is independent of BCR-ABL in the presence of growth factors. However, the proliferation of leukemic immature cobblestone-forming area cells is almost completely blocked after the inhibition of the BCR-ABL kinase. In the BCR-ABL-transfected cell lines, M07/ p210 and Ba/F3/p185, CGP 57148 induces apoptosis by releasing cytochrome c, activating caspase 3, and cleavage of PARP. No alteration of the expression level of the apoptosis regulator BCL-2 was observed. In contrast, BCL-X was down-regulated after exposure to CGP 57148. Inhibitors of signal transduction proteins such as PI-3 kinase, mitogen-activated protein/extracellular signal-regulated kinase kinase, and Janus-activated kinase 2 pathways were not capable of a comparable down-regulation of BCL-X. The Fas/Fas ligand system was not involved either in the induction of apoptosis by CGP 57148. We conclude that the inhibition of the BCR-ABL kinase by CGP 57148 (a) preferentially inhibits the growth of immature leukemic precursor cells, (b) efficiently reverts the antiapoptotic effects of BCR-ABL by down-regulation of BCL-X, and (c) is more effective than the inhibition of the downstream signal transduction pathways of PI-3 kinase, mitogen-activated protein/extracellular signal-regulated kinase kinase, and Janus-activated kinase 2.

Fractionated administration of high-dose cyclophosphamide: influence on dose-dependent changes in pharmacokinetics and metabolism.

PURPOSE: The alkylating agent cyclophosphamide (CP) is a prodrug that is metabolized to both cytotoxic and inactive compounds. We have previously shown that following dose escalation from conventional-dose (CD) to high-dose (HD) levels; the fraction of the dose cleared by bioactivation is significantly decreased (66% versus 48.5%) in favor of inactivating elimination pathways when the HD is given as a single 1-h infusion. Based on the concept of bioactivating enzyme saturation with increasing doses, we investigated the influence of fractionated application of HD-CP on dose-dependent changes in metabolism. PATIENTS AND METHODS: Plasma concentrations of CP (measured by high-performance liquid chromatography, HPLC) and urinary concentrations of CP and its major metabolites (quantified by [31P]-nuclear magnetic resonance spectroscopy; [31P]-NMR spectroscopy), were determined in four patients with high-risk primary breast cancer who received adjuvant chemotherapy including both CD-CP (500 mg/ m2 infused over 1 h) and split HD-CP (50 mg/kg infused over 1 h on each of 2 consecutive days (d): d1 and d2. RESULTS: (Data are given as mean values for CD and d1/d2 of HD, respectively). Systemic clearance (CL) of CP was similar during CD and d1 of HD, but significantly increased on d2 of HD (CL: 83 and 78/115 ml/min; P < 0.01 for d1 versus d2). The latter was translated into an increase in formation CL of both active (+ 16.4 ml/min) and inactive metabolites (+ 17.6 ml/ min) and reflects autoinduction of metabolism. As compared with CD-CP, no statistically significant decrease was observed in the relative contribution of bioactivation CL to overall CL during both days of HD (63% versus 57%/53%). Recovery of intact CP in 24-h urine corresponded to 24%, 29%, 22% of the dose (P < 0.05 for d1 versus d2 of HD). CONCLUSIONS: Following dose escalation of CP, dividing the high dose over 2 days instead of one single infusion may favorably impact the metabolism of CP in terms of bioactivation. In addition, on day 2 of a split regimen, renal elimination of CP is decreased, which implies that more drug is available for metabolism.