AMN107 (nilotinib): a novel and selective inhibitor of BCR-ABL

Chronic myelogenous leukaemia (CML) and Philadelphia chromosome positive (Ph+) acute lymphoblastic leukaemia (ALL) are caused by the BCR-ABL oncogene. Imatinib inhibits the tyrosine kinase activity of the BCR-ABL protein and is an effective, frontline therapy for chronic-phase CML. However, accelerated or blast-crisis phase CML patients and Ph+ ALL patients often relapse due to drug resistance resulting from the emergence of imatinib-resistant point mutations within the BCR-ABL tyrosine kinase domain. This has stimulated the development of new kinase inhibitors that are able to over-ride resistance to imatinib. The novel, selective BCR-ABL inhibitor, AMN107, was designed to fit into the ATP-binding site of the BCR-ABL protein with higher affinity than imatinib. In addition to being more potent than imatinib (IC50< 30 nM) against wild-type BCR-ABL, AMN107 is also significantly active against 32/33 imatinib-resistant BCR-ABL mutants. In preclinical studies, AMN107 demonstrated activity in vitro and in vivo against wild-type and imatinib-resistant BCR-ABL-expressing cells. In phase I/II clinical trials, AMN107 has produced haematological and cytogenetic responses in CML patients, who either did not initially respond to imatinib or developed imatinib resistance. Dasatinib (BMS-354825), which inhibits Abl and Src family kinases, is another promising new clinical candidate for CML that has shown good efficacy in CML patients. In this review, the early characterisation and development of AMN107 is discussed, as is the current status of AMN107 in clinical trials for imatinib-resistant CML and Ph+ ALL. Future trends investigating prediction of mechanisms of resistance to AMN107, and how and where AMN107 is expected to fit into the overall picture for treatment of early-phase CML and imatinib-refractory and late-stage disease are discussed.

A pilot study to assess the effect of three short-term treatments on frequent and/or prolonged bleeding compared to placebo in women using Implanon

BACKGROUND

The major side-effect of progestogen-only contraception is disruption of menstrual bleeding patterns, which can lead to a high incidence of early discontinuation. The aim of this study was to compare three treatments with placebo on the duration and recurrence of frequent and/or prolonged bleeding in Implanon users.

METHOD

Women between the ages of 18 and 45 years, who had used Implanon for > or =3 months and were experiencing prolonged or frequent bleeding patterns, were recruited at four Australian sites. Subjects were randomized to treatment using computer-generated random number table if they met the World Health Organization criteria for prolonged and/or frequent bleeding in the previous 90 days [Belsey, E.M., Pinol, A.P.Y. and Taskforce on Long-Acting Systemic Agents for Fertility Regulation, World Health Organization (1997) Contraception 55,57-65]. Treatments were: (1) mifepristone 25 mg given twice on day 1 followed by 4 days of twice daily placebo; (2) mifepristone 25 mg given twice on day 1 followed by 4 days of ethinyl estradiol (EE) 20 microg in the morning and placebo at night; (3) doxycycline 100 mg twice daily for 5 days; and (4) placebo twice daily for 5 days. Analysis was by intention to treat. The primary endpoint was the number of days of bleeding and spotting immediately following initiation of the 5 day course of each active therapy compared with placebo.

RESULTS

A total of 179 women was assigned to treatment. Both mifepristone in combination with EE and doxycycline alone were significantly more effective in stopping an episode of bleeding {mean 4. 3 days [confidence interval (CI) 3.5-5.2], and 4.8 days (CI 3.9-5.8) respectively} than mifepristone alone or placebo [5.9 days (CI 4.8-7.2) and 7.5 days (CI 6.1-9.1) respectively]. No effect on subsequent bleeding patterns was observed in any treatment group.

CONCLUSION

Both mifepristone plus EE and doxycycline alone were significantly more effective than placebo in terminating an episode of bleeding in women with prolonged and/or frequent bleeding using Implanon. We believe that the observed reduction in the number of bleeding days by almost 50% compared to placebo in both the mifepristone combination group and the doxycycline group demonstrates a clinically significant improvement in bleeding patterns and that further trials are needed to compare different combinations of therapy as well as multiple dosing regimens in order to establish which is the most effective treatment option. The effect of repeat administration or combinations of these preparations on long-term bleeding patterns requires further investigation.

Identification of mTOR as a novel bifunctional target in chronic myeloid leukemia: dissection of growth‐inhibitory and VEGF‐suppressive effects of rapamycin in leukemic cells

The mammalian target of rapamycin (mTOR) has recently been described to be constitutively activated in Bcr-Abl-transformed cells and to mediate rapamycin-induced inhibition of growth in respective cell lines. We have recently shown that rapamycin down-regulates expression of vascular endothelial growth factor (VEGF), a mediator of leukemia-associated angiogenesis, in primary CML cells. In the present study, we analyzed growth-inhibitory in vitro and in vivo effects of rapamycin on primary CML cells and asked whether rapamycin-induced suppression of VEGF in leukemic cells is related to growth inhibition. Rapamycin dose dependently inhibited growth of primary CML cells obtained from patients with imatinib-responsive or imatinib-resistant disease as well as growth of Bcr-Abl-transformed imatinib-resistant cell lines. Moreover, we observed potent cytoreductive effects of rapamycin in a patient with imatinib-resistant Bcr-Abl+ leukemia. The growth-inhibitory effects of rapamycin on CML cells were found to be associated with G1 cell cycle arrest and with induction of apoptosis. In all cell types tested, rapamycin was found to down-regulate expression of VEGF. However, exogenously added VEGF did not counteract the rapamycin-induced decrease in proliferation. In conclusion, rapamycin inhibits growth of CML cells in vitro and in vivo and, in addition, down-regulates expression of VEGF. Both effects may contribute to the antileukemic activity of the drug in CML.

Characterization of AMN107, a selective inhibitor of native and mutant Bcr-Abl

The Bcr-Abl tyrosine kinase oncogene causes chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). We describe a novel selective inhibitor of Bcr-Abl, AMN107 (IC50 <30 nM), which is significantly more potent than imatinib, and active against a number of imatinib-resistant Bcr-Abl mutants. Crystallographic analysis of Abl-AMN107 complexes provides a structural explanation for the differential activity of AMN107 and imatinib against imatinib-resistant Bcr-Abl. Consistent with its in vitro and pharmacokinetic profile, AMN107 prolonged survival of mice injected with Bcr-Abl-transformed hematopoietic cell lines or primary marrow cells, and prolonged survival in imatinib-resistant CML mouse models. AMN107 is a promising new inhibitor for the therapy of CML and Ph+ ALL.

Histone deacetylase inhibitor NVP-LAQ824 has significant activity against myeloid leukemia cells in vitro and in vivo

NVP-LAQ824 is a novel potent hydroxamic acid-derived histone deacetylase inhibitor that induces apoptosis in nanomolar concentrations in myeloid leukemia cell lines and patient samples. Here we show the activity of NVP-LAQ824 in acute myeloid leukemia cells and BCR/ABL-expressing cells of mouse and human origin, both sensitive and resistant to imatinib mesylate (Gleevec, STI-571). Whereas imatinib inhibited overall cellular tyrosine phosphorylation in Ba/F3.p210 cells, NVP-LAQ824 did not inhibit tyrosine phosphorylation, and did not affect BCR/ABL or ABL protein expression. Neither compound was able to inhibit cellular tyrosine phosphorylation in the imatinib-resistant Ba/F3.p210-T315I cell line. These data taken together suggest that BCR/ABL kinase activity is not a direct target of NVP-LAQ824. Synergy between NVP-LAQ824 and imatinib was demonstrated against BCR/ABL-expressing K562 myeloid leukemia cell lines. In addition, we show that NVP-LAQ824 was well tolerated in vivo in a pre-clinical murine leukemia model, with antileukemia activity resulting in significant prolongation of the survival of mice when treated with NVP-LAQ824 compared to control mice. Taken together, these findings provide the framework for NVP-LAQ824 as a novel therapeutic in myeloid malignancies.

Identifying and characterizing a novel activating mutation of the FLT3 tyrosine kinase in AML

The FLT3 receptor is activated by juxtamembrane insertion mutations and by activation loop point mutations in patients with acute myeloid leukemia (AML). In a systematic tyrosine kinase gene exon resequencing study, 21 of 24 FLT3 exons were sequenced in samples from 53 patients with AML, 9 patients with acute lymphoblastic leukemia (ALL), and 3 patients with myelodysplasia samples. Three patients had novel point mutations at residue N841 that resulted in a change to isoleucine in 2 samples and to tyrosine in 1 sample. Introduction of FLT3-N841I cDNA into Ba/F3 cells led to interleukin-3 (IL-3)–independent proliferation, receptor phosphorylation, and constitutive activation of signal transducer and activator of transcription 5 (STAT5) and extracellular regulatory kinase (ERK), suggesting that the N841I mutation confers constitutive activity to the receptor. An FLT3 inhibitor (PKC412) inhibited the growth of Ba/F3-FLT3N841I cells (IC50 10 nM), but not of wild-type Ba/F3 cells cultured with IL-3. PKC412 also reduced tyrosine phosphorylation of the mutant receptor and inhibited STAT5 phosphorylation. Examination of the FLT3 autoinhibited structure showed that N841 is the key residue in a hydrogen-bonding network that likely stabilizes the activation loop. These results suggest that mutations at N841 represent a significant new activating mutation in patients with AML and that patients with such mutations may respond to small-molecule FLT3 inhibitors such as PKC412.

Resistance to imatinib (Glivec): update on clinical mechanisms

Imatinib mesylate, an orally administered 2-phenylaminopyrimidine derivative that inhibits BCR/ABL tyrosine kinase activity, has shown great promise in the treatment of chronic myelogenous leukemia (CML). This small molecule, tyrosine kinase inhibitor, has also been shown to be effective against metastatic gastrointestinal stromal tumors (GISTs) expressing the stem cell factor (SCF) receptor kit. However, the threat of resistance in patients has prompted investigators to uncover the mechanisms whereby malignant cells develop resistance to imatinib, and has also led to the establishment of strategies designed to over-ride imatinib resistance. Here, we provide a comprehensive overview of the effectiveness of imatinib in the treatment of chronic, accelerated and blast crisis-phase CML, Philadelphia chromosome-positive (Ph+) acute lymphoid leukemia (ALL) and metastatic GIST. Established mechanisms of resistance to imatinib are discussed, as are novel therapeutic approaches to improving drug responsiveness by reversing development of imatinib resistance in patients.

Aminopeptidase inhibitors inhibit proliferation and induce apoptosis of K562 and STI571-resistant K562 cell lines through the MAPK and GSK-3beta pathways

A tyrosine kinase inhibitor, STI571, has been demonstrated to be effective for the treatment of chronic myelogenous leukemia (CML). STI571 inhibits tyrosine kinase activity of ABL and induces apoptosis of CML cells. However, drug resistance develops commonly in patients with blast phase CML, and has become a significant therapeutic problem. We examined the effects of aminopeptidase inhibitors on CML cell line (K562) and a STI571-resistant subline of K562. Ubenimex and the more potent aminopeptidase inhibitor, actinonin, inhibited proliferation of both K562 cells and STI571-resistant K562 cells and also induced their apoptosis in dose- and time-dependent manners. Ubenimex and actinonin induced the activation of caspase-3, and the induction of apoptosis was inhibited by pan-caspase inhibitor, indicating this apoptosis is caspase-dependent. We found that serine phosphorylation of both MAPK and glycogen synthase kinase-3beta were suppressed by aminopeptidase inhibitors in parent K562 and STI571-resistant K562 cells. The expression level of cyclin D1 protein was also reduced by ubenimex and actinonin in both cell lines. These results indicated STI571-resistance does not confer the cross-resistance to aminopeptidase inhibitors in K562 cells and revealed the new findings of aminopeptidase inhibitor-induced intracellular signaling pathways.

Cloning and functional characterization of the murine mastermind-like 1 (Maml1) gene

The Notch signaling pathway controls cell fate decisions and plays a critical role in normal development and diseases. The human mastermind-like (MAML) family members (MAML1, 2 and 3) encode critical transcriptional co-activators for Notch receptors. In this study, we cloned a murine cDNA that is highly homologous to the human MAML1 gene, Maml1. Mouse Maml1 encodes a nuclear protein, binds to the ankyrin repeat domain of Notch receptors, forms a ternary complex with the intracellular domain of Notch (ICN) and the DNA binding protein CSL, and enhances Notch-induced transcription of the target gene, HES-1. Therefore, Maml1 is the murine homologue for human MAML1 and functions as a transcriptional co-activator for Notch signaling. We also characterized the organization of the mouse Maml1 gene: It spans at least 35 kilobases (kb) on chromosome 11 and contains five exons and four introns. Analysis of the 5' flanking region revealed that the promoter is TATA-less, and contains consensus binding sites for transcription factors such as Sp1, glucocorticoid receptor (GR), activating transcription factor (ATF) and cAMP response element-binding protein (CREB). Moreover, we examined Maml1 expression during early mouse development and found that Maml1 gene is expressed widely but selectively in several tissues. There seems to be close correlation of the spatial and temporal expression among Maml1, Notch1 and Hes1 in the central nervous system (CNS) during early development, implicating a role for the Maml1 gene in neurogenesis.

Mutated tyrosine kinases as therapeutic targets in myeloid leukemias

Tyrosine kinases are commonly mutated and activated in both acute and chronic myeloid leukemias. Here, we review the functions, signaling activities, mechanism of transformation, and therapeutic targeting of two prototypic tyrosine kinase oncogenes, BCR-ABL and FLT3, associated with chronic myeloid leukemia (CML) and acute myeloid leukemia (AML), respectively. BCR-ABL is generated by the Philadelphia chromosome translocation between chromosomes 9 and 22, creating a chimeric oncogene in which the BCR and c-ABL genes are fused. The product of this oncogene, BCR-ABL, has elevated ABL tyrosine kinase activity and transforms hematopoietic cells by exerting a wide variety of biological effects, including reduction in growth factor dependence, enhanced viability, and altered adhesion of chronic myelocytic leukemia (CML) cells. Elevated tyrosine kinase activity of BCR-ABL is critical for activating downstream signalling cascades and for all aspects of transformation, explaining the remarkable clinical efficacy of the tyrosine kinase inhibitor, imatinib mesylate (STI571). By comparison, FLT3 is mutated in about one third of all cases of AML, most often through a mechanism that involves an internal tandem duplication (ITD) of a small number of amino acid residues in the juxtamembrane domain of the receptor. As is the case for BCR-ABL, these mutations activate the kinase activity constitutively, activate multiple signaling pathways, and result in an augmentation of proliferation and viability. Transformation by FLT3-ITD can readily be observed in murine models, and FLT3 cooperates with other types of oncogenes to create a fully transformed acute leukemia. FLT3 tyrosine kinase inhibitors are currently being evaluated in clinical trials and may be very useful therapeutic agents in AML.

NVP-LAQ824 is a potent novel histone deacetylase inhibitor with significant activity against multiple myeloma

Histone deacetylase (HDAC) inhibitors are emerging as a promising new treatment strategy in hematologic malignancies. Here we show that NVP-LAQ824, a novel hydroxamic acid derivative, induces apoptosis at physiologically achievable concentrations (median inhibitory concentration [IC50] of 100 nM at 24 hours) in multiple myeloma (MM) cell lines resistant to conventional therapies. MM.1S myeloma cell proliferation was also inhibited when cocultured with bone marrow stromal cells, demonstrating ability to overcome the stimulatory effects of the bone marrow microenvironment. Importantly, NVP-LAQ824 also inhibited patient MM cell growth in a dose- and time-dependent manner. NVP-LAQ824-induced apoptotic signaling includes up-regulation of p21, caspase cascade activation, and poly (adenosine diphosphate [ADP]) ribose (PARP) cleavage. Apoptosis was confirmed with cell cycle analysis and annexin-propidium iodide staining. Interestingly, treatment of MM cells with NVPLAQ824 also led to proteasome inhibition, as determined by reduced proteasome chymotrypsin-like activity and increased levels of cellular polyubiquitin conjugates. Finally, a study using NVP-LAQ824 in a preclinical murine myeloma model provides in vivo relevance to our in vitro studies. Taken together, these findings provide the framework for NVP-LAQ824 as a novel therapeutic in MM.

PKC412 overcomes resistance to imatinib in a murine model of FIP1L1-PDGFRα-induced myeloproliferative disease

FIP1L1-PDGFRalpha causes hypereosinophilic syndrome (HES) and is inhibited by the tyrosine kinase inhibitor imatinib (Gleevec). Imatinib is a potent inhibitor of ABL, ARG, PDGFRalpha, PDGFRbeta, and KIT and induces durable hematologic responses in HES patients. However, we observed relapse with resistance to imatinib as consequence of a T674I mutation in FIP1L1-PDGFRalpha, analogous to the imatinib-resistant T315I mutation in BCR-ABL. We developed a murine bone marrow transplant model of FIP1L1-PDGFRalpha-induced myeloproliferative disease to evaluate the efficacy of PKC412, an alternative inhibitor of PDGFRalpha, for the treatment of HES. PKC412 is effective for treatment of FIP1L1-PDGFRalpha-induced disease and of imatinib-induced resistance due to the T674I mutation. Our data establish PKC412 as molecularly targeted therapy for HES and other diseases expressing activated PDGFRalpha and demonstrate the potential of alternative kinase inhibitors to overcome resistance in target tyrosine kinases.

The vascular endothelial growth factor receptor tyrosine kinase inhibitor PTK787/ZK222584 inhibits growth and migration of multiple myeloma cells in the bone marrow microenvironment

Our prior studies show that multiple myeloma (MM) cell lines and patient cells express high-affinity vascular endothelial growth factor (VEGF) receptor (VEGFR) Flt-1 but not Flk-1/KDR. Moreover, these studies have shown that VEGF induces proliferation and migration of MM cells, and we have begun to delineate the signaling cascades mediating those sequelae. In this study, we examined the activity of PTK787/ZK 222584 (PTK787), a molecule designed to bind specifically to the tyrosine kinase domain of VEGFR and inhibit angiogenesis. We show that PTK787 acts both directly on MM cells and in the bone marrow microenvironment. Specifically, PTK787 (1-5 micro M) inhibits proliferation of MM cells by 50%, as assayed by [(3)H]thymidine uptake. This effect of PTK787 is dose dependent in both MM cell lines and patient cells that are both sensitive and resistant to conventional therapy. PTK787 enhances the inhibitory effect of dexamethasone on growth of MM cells and can overcome the protective effect of interleukin 6 (IL-6) against dexamethasone-induced apoptosis. PTK787 (1 micro M) also blocks VEGF-induced migration of MM cells across an extracellular matrix. Importantly, PTK787 also inhibits the increased MM cell proliferation and increased IL-6 and VEGF secretion in cultures of MM cells adherent to bone marrow stem cells. These findings therefore demonstrate that PTK787 both acts directly on MM cells and inhibits paracrine IL-6-mediated MM cell growth in the bone marrow milieu. The demonstrated anti-MM activity of PTK787, coupled with its antiangiogenic effects, provides the framework for clinical trials of this agent to overcome drug resistance and improve outcome in MM.

Inhibition of mutant FLT3 receptors in leukemia cells by the small molecule tyrosine kinase inhibitor PKC412

Constitutively activating FLT3 receptor mutations have been found in 35% of patients with acute myeloblastic leukemia (AML). Here we report the identification of a small molecule FLT3 tyrosine kinase inhibitor PKC412, which selectively induced G1 arrest and apoptosis of Ba/F3 cell lines expressing mutant FLT3 (IC(50) < 10 nM) by directly inhibiting the tyrosine kinase. Ba/F3-FLT3 cell lines made resistant to PKC412 demonstrated overexpression of mutant FLT3, confirming that FLT3 is the target of this drug. Finally, progressive leukemia was prevented in PKC412-treated Balb/c mice transplanted with marrow transduced with a FLT3-ITD-expressing retrovirus. PKC412 is a potent inhibitor of mutant FLT3 and is a candidate for testing as an antileukemia agent in AML patients with mutant FLT3 receptors.

Effects of the Bcr/abl kinase inhibitors STI571 and adaphostin (NSC 680410) on chronic myelogenous leukemia cells in vitro

The adenosine triphosphate binding-site-directed agent STI571 and the tyrphostin adaphostin are undergoing evaluation as bcr/abl kinase inhibitors. The current study compared the effects of these agents on the survival of K562 cells, bcr/abl-transduced FDC-P1 cells, and myeloid progenitors from patients with chronic myelogenous leukemia (CML) compared with healthy donors. Treatment of K562 cells with 10 microM adaphostin resulted in decreased p210(bcr/abl) polypeptide levels in the first 6 hours, followed by caspase activation and accumulation of apoptotic cells in less than 12 hours. By 24 hours, 90% of the cells were apoptotic and unable to form colonies. In contrast, 20 microM STI571 caused rapid inhibition of bcr/abl autophosphorylation without p210(bcr/abl) degradation. Although this was followed by the inhibition of Stat5 phosphorylation and the down-regulation of Bcl-x(L) and Mcl-1, only 7% +/- 3% and 25% +/- 9% of cells were apoptotic at 16 and 24 hours, respectively. Instead, the cytotoxic effects of STI571 became more pronounced with prolonged exposure, with IC90 values greater than 20 microM and 1.0 +/- 0.6 microM after 24 and 48 hours, respectively. Consistent with these results, 24-hour adaphostin exposure inhibited CML granulocyte colony-forming units (CFU-G) (median IC50, 12 microM) but not normal CFU-G (median IC50, greater than 20 microM), whereas 24-hour STI571 treatment had no effect on CML or normal CFU-G. Additional experiments revealed that STI571-resistant K562 cells remained sensitive to adaphostin. Moreover, the combination of STI571 + adaphostin induced more cytotoxicity in K562 cells and in CML CFU-G than either agent alone did. Collectively, these results identify adaphostin as a mechanistically distinct CML-selective agent that retains activity in STI571-resistant cell lines.

A randomised controlled trial comparing a dilating vaginal speculum with a conventional bivalve speculum

Cervical smears are traditionally taken with the aid of a metal or disposable plastic bivalve speculum. Many women complain of discomfort with these specula. This study compares the efficacy and women's experiences of a new 'dilating speculum' called the Veda-scope, with a conventional metal bivalve speculum (Pederson). The aims of this study were: to determine whether the Veda-scope provides adequate visualisation of the cervix and vaginal walls and an adequate cervical cytology specimen; and to compare user acceptability and women's levels of comfort between the Veda-scope and the bivalve speculum. Sixty-four women were randomised to be examined with the Veda-scope and 60 with the bivalve speculum, by one of two operators. Each woman completed a questionnaire that included subjective views of their previous cervical smear experiences, and acceptability of the examination at the study consultation. Cytologists were blinded as to which speculum was used for cervical sampling. Of women examined, 7-83% of women found Veda-scope examinations comfortable, compared to 38-62% of women who found examinations with the bivalve comfortable; 94% of the women preferred the 'comfort' of the Veda-scope. The Veda-scope was as good as the bivalve speculum in providing samples for cytological analysis following the initial learning curve, and also provided markedly superior magnified views of the cervix and vaginal fornices.

ARG tyrosine kinase activity is inhibited by STI571

The tyrosine kinase inhibitor STI571 inhibits BCR/ABL and induces hematologic remission in most patients with chronic myeloid leukemia. In addition to BCR/ABL, STI571 also inhibits v-Abl, TEL/ABL, the native platelet-derived growth factor (PDGF)beta receptor, and c-KIT, but it does not inhibit SRC family kinases, c-FMS, FLT3, the epidermal growth factor receptor, or multiple other tyrosine kinases. ARG is a widely expressed tyrosine kinase that shares substantial sequence identity with c-ABL in the kinase domain and cooperates with ABL to regulate neurulation in the developing mouse embryo. As described here, ARG has recently been implicated in the pathogenesis of leukemia as a fusion partner of TEL. A TEL/ARG fusion was constructed to determine whether ARG can be inhibited by STI571. When expressed in the factor-dependent murine hematopoietic cell line Ba/F3, the TEL/ARG protein was heavily phosphorylated on tyrosine, increased tyrosine phosphorylation of multiple cellular proteins, and induced factor-independent proliferation. The effects of STI571 on Ba/F3 cells transformed with BCR/ABL, TEL/ABL, TEL/PDGFbetaR, or TEL/ARG were then compared. STI571 inhibited tyrosine phosphorylation and cell growth of Ba/F3 cells expressing BCR/ABL, TEL/ABL, TEL/PDGFbetaR, and TEL/ARG with an IC(50) of approximately 0.5 microM in each case, but it had no effect on untransformed Ba/F3 cells growing in IL-3 or on Ba/F3 cells transformed by TEL/JAK2. Culture of TEL/ARG-transfected Ba/F3 cells with IL-3 completely prevented STI571-induced apoptosis in these cells, similar to what has been observed with BCR/ABL- or TEL/ABL-transformed cells. These results indicate that ARG is a target of the small molecule, tyrosine kinase inhibitor STI571.

Mechanisms of resistance imatinib (STI571) in preclinical models and in leukemia patients

The tyrosine kinase inhibitor imatinib (STI571, Glivec) blocks the activity of the BCR/ABL oncogene and induces hematologic remissions in the majority of patients with chronic myeloid leukemia (CML). Glivec is an aminopyrimidine derivative that interacts with the ATP-binding site within the kinase domain of ABL and several other tyrosine kinases, including c-KIT, PDGF beta receptor, and ARG. The compound is currently in phase III clinical trials. Although patients with chronic phase CML have been found to develop drug resistance only rarely so far, patients in more advanced phases of the leukemia develop resistance frequently. The available information on Glivec resistance will be reviewed.

Serotonin-dependent collagenase transcription in myometrial cells requires extended AP-1 site

Primary cultures of uterine smooth muscle cells from post-partum rats express interstitial collagenase in response to serotonin and the serotonin-dependent production of interleukin-1 (IL-1) [Wilcox, B.D., Dumin, J.A. and Jeffrey, J.J. Serotonin regulation of interleukin-1 messenger RNA in rat uterine smooth muscle cells. Relationship to the production of interstitial collagenase J. Biol. Chem., 269, (1994a), 29658]. Transient transfections of these cells indicate that rat collagenase transcription is regulated via a proximal consensus AP-1 site within an extended palindrome. Mutation of either the AP-1 site or extended palindrome (EP) decreases promoter activity to approximately 30% of the wild-type. Electrophoretic mobility shift assays reveal the binding of smooth muscle cell nuclear proteins to the AP-1 EP. This binding is barely detectable after mutation of the EP and is completely eliminated by mutation of the AP-1 heptamer. Competition experiments demonstrate that binding to the AP-1 EP is specific and of higher affinity than binding to oligonucleotides containing a mutated EP. Binding to the AP-1 EP is higher when smooth muscle cells are cultured in the presence of serotonin than in its absence. Although IL-1 is required for collagenase transcription, binding to the AP-1 EP appears to be IL-1-independent. FosB, Fra-2, c-Jun, JunB and, most abundantly, JunD bind the AP-1 EP in the absence and presence of serotonin. In contrast, Fra-1 expression and binding are serotonin-dependent suggesting that the activation of Fra-1 may be a key component of collagenase transcriptional activation.

Preliminary safety and acceptability of a carrageenan gel for possible use as a vaginal microbicide

OBJECTIVE

We sought to determine the safety and acceptability of vaginal gel formulation PC-503 among low risk, abstinent women. The active ingredient was 2% pharmaceutical grade lambda carrageenan, a sulphated polymer that is generally recognised as safe by the US Food and Drug Administration.

METHODS

35 women in five sites applied 5 ml of the PC-503 gel vaginally once a day for 7 days while abstaining from sexual intercourse. Visual vaginal examinations were performed on days 1, 4, and 8. STI testing and vaginal pool Gram stain preparations were done on days 1 and 8. Participants were asked about product acceptability.

RESULTS

34 of the 35 women enrolled completed 7 days' use. Following product use, five reported mild symptoms including "bladder fullness," "genital warmth," or discomfort, and lower abdominal pain, and one had moderate pale yellow cervical discharge. Using the Nugent criteria, three women had bacterial vaginosis (BV) before and after use; three had BV before but not after, and two had BV after but not before. Most of the women found PC-503 to be pleasant or neutral in feel and smell and considered extra lubrication to be an advantage; however, one third found it to be messy.

CONCLUSIONS

Vaginal use of PC-503 gel did not cause significant adverse effects in a small number of low risk, sexually abstinent women. Further testing in larger numbers of sexually active women is planned. A smaller volume of gel may be more acceptable to some women.

A multifaceted mental health training program in reducing burnout among occupational social workers

This article looks at ways of reducing stress through a multifaceted training program involving the acquisition of mental health knowledge and skills and experiential training in a group of occupational social workers. The training group of 13 occupational workers was compared to a group of occupational social workers not attending the program. Post-training revealed statistically significant increases in professional self-efficacy associated with awareness of psychological and psychopathological issues and professional social support. Reduction in cognitive weariness and listlessness associated with burnout was also found. Gaining competence in mental health issues relating to the occupational setting coupled with emotional sharing helped to reduce professional burnout.

A randomized comparison of the effects on vaginal and cervical epithelium of a placebo vaginal ring with non-use of a ring

Little is known about the effects of contraceptive vaginal rings on the vaginal surface epithelium, although most studies have not demonstrated any significant deleterious effect. However, one study found that some medium-to-long-term levonorgestrel-releasing ring users developed chronic erythematous and ulcerative lesions in the posterior vaginal fornix. Subsequently, this ring was completely redesigned (IVR-2) with different dimensions and much greater flexibility. The first version of IVR-2 was designed as a placebo ring to explore effects on the vagina and cervix without addition of a progestogen. One-hundred-sixty-six healthy sexually active women volunteers were recruited in four centers and randomly assigned for 6 months to either placebo ring use or control (non-use) using a predetermined randomization code generated by WHO in a 2:1 ratio. Careful inspections of the vaginal and cervical epithelium were performed with a colposcope at admission and at 2-month intervals. No clinically significant lesions were detected in any center either among ring users or controls. However, a number of minor changes in appearance of the vaginal and cervical epithelium (erythema, petechiae, ecchymosis, and minor aceto-white changes) were described from the Sydney Center, some of which were present on admission and some of which were found on subsequent examination. Ten of eleven "red" changes on the cervix and vagina were noted in IVR-2 users, and only one in the controls, suggesting a contribution by the IVR-2 to minor epithelial surface changes. Five of ten resolved completely with continued ring use. There was no correlation in this study between epithelial changes and cigarette smoking or frequency of intercourse in the 14 days prior to colposcopic examination but a significant relationship between tampon use in the last 7 days and all epithelial changes (p = 0.05) and especially red changes (p = 0. 027) was noted. Red changes were significantly less likely to be found among condom users (p = 0.007). The IVR-2 placebo ring did not produce clinically significant changes in the vaginal epithelium and cervical mucosa and a carefully controlled and randomized study should be considered to compare the epithelial appearances in women using a placebo IVR-2 and one releasing 20 microg levonorgestrel.

Mechanism of resistance to the ABL tyrosine kinase inhibitor STI571 in BCR/ABL-transformed hematopoietic cell lines

The tyrosine kinase activity of the Bcr/Abl oncogene is required for transformation of hematopoietic cells. The tyrosine kinase inhibitor STI571 (formerly called CGP57148B, Novartis Pharmaceuticals) inhibits BCR/ABL, TEL/ABL, and v-ABL kinase activity and inhibits growth and viability of cells transformed by any of these ABL oncogenes. Here we report the generation of 2 BCR/ABL-positive cell lines that have developed partial resistance to STI571. BCR/ABL-transformed Ba/F3 hematopoietic cells and Philadelphia-positive human K562 cells were cultured in gradually increasing concentrations of STI571 over a period of several months to generate resistant lines. Resistant Ba/F3.p210 cells were found to have an increase in Bcr/Abl messenger RNA, amplification of the Bcr/Abl transgene, and a greater than tenfold increase in the level of BCR/ABL protein. In contrast to Ba/F3.p210 cells, drug-resistant K562 cells did not undergo detectable amplification of the BCR/ABL gene, although they displayed a 2-fold to 3-fold increase in p210BCR/ABL protein. The addition of STI571 to both resistant Ba/F3. p210 and K562 cells resulted in a rapid reduction of tyrosine phosphorylation of cellular proteins, similar to that observed for nonresistant cells. However, the inhibition of kinase activity was transient and partial and was not accompanied by apoptosis. The results suggest that resistance to STI571 may be multifactorial. Increased expression of the target protein BCR/ABL was observed in both lines, and resulted from oncogene amplification in one line. However, altered drug metabolism, transport, or other related mechanisms may also contribute to drug resistance.

A detailed analysis of menstrual blood loss in women using Norplant and Nestorone progestogen-only contraceptive implants or vaginal rings

Changes to the pattern of menstrual bleeding are almost universal in women using progestogen-only methods of contraception, and are an important cause of discontinuation of these methods. The present study was designed to explore the changes in menstrual bleeding patterns and objectively measure menstrual blood loss (MBL) in 110 women before and during one year of use of 4 different progestogen-only contraceptives: Norplant subdermal levonorgestrel implants; Nestorone progestogen 4-cm or 6-cm implants nominally delivering 100 microg or 150 microg daily; or a vaginal ring (CVR) delivering 100 microg of Nestorone (NES) daily (CVR users were limited to only 6 months of use). Groups could not be directly compared because of the differences in numbers of subjects and durations of treatment. The total MBL during each of the three 8-week collection periods during treatment decreased significantly in each group compared to the total blood loss in the two control cycles (greater than 50% decrease in all groups during the first 6 months), although the differences between individual women at the extremes remained considerable. The highest blood loss measured on any single day during the treatment collection periods was significantly reduced (p <0.001) in users of all four devices in all three collection periods compared to the control period (CVR users did not have a 3rd collection period). The Nestorone-releasing CVR was associated with an 88% reduction in mean MBL and a high incidence of amenorrhea at 6 months. There was considerable variation in percentage reduction in total blood loss at 6 and 12 months between individual women ranging from 100% (women with amenorrhea) to a small minority experiencing an increase compared with control cycles. The increases in measured blood loss during treatment were almost entirely in women with light bleeding in the control period and were related to prolonged episodes of light bleeding rather than heavy bleeding. Women contemplating use of a progestogen-only contraceptive method need to be counseled about alterations to the menstrual cycle but can be reassured that total blood loss will usually be much less than with normal cycles.