Chronic myelogenous leukemia

Exploiting the potential of the ubiquitin-proteasome system in overcoming tyrosine kinase inhibitor resistance in chronic myeloid leukemia

The advent of tyrosine kinase inhibitors (TKI) targeting BCR-ABL has drastically changed the treatment approach of chronic myeloid leukemia (CML), greatly prolonged the life of CML patients, and improved their prognosis. However, TKI resistance is still a major problem with CML patients, reducing the efficacy of treatment and their quality of life. TKI resistance is mainly divided into BCR-ABL-dependent and BCR-ABL-independent resistance. Now, the main clinical strategy addressing TKI resistance is to switch to newly developed TKIs. However, data have shown that these new drugs may cause serious adverse reactions and intolerance and cannot address all resistance mutations. Therefore, finding new therapeutic targets to overcome TKI resistance is crucial and the ubiquitin-proteasome system (UPS) has emerged as a focus. The UPS mediates the degradation of most proteins in organisms and controls a wide range of physiological processes. In recent years, the study of UPS in hematological malignant tumors has resulted in effective treatments, such as bortezomib in the treatment of multiple myeloma and mantle cell lymphoma. In CML, the components of UPS cooperate or antagonize the efficacy of TKI by directly or indirectly affecting the ubiquitination of BCR-ABL, interfering with CML-related signaling pathways, and negatively or positively affecting leukemia stem cells. Some of these molecules may help overcome TKI resistance and treat CML. In this review, the mechanism of TKI resistance is briefly described, the components of UPS are introduced, existing studies on UPS participating in TKI resistance are listed, and UPS as the therapeutic target and strategies are discussed.

DNA self-assembly nanoflower reverse P-glycoprotein mediated drug resistance in chronic myelogenous leukemia therapy

Introduction: Chronic myelogenous leukemia (CML) is a clonal myeloproliferative disorder caused by the BCR-ABL chimeric tyrosine kinase. Vincristine (VCR) is widely used in leukemia therapy but is hindered by multidrug resistance (MDR). Methods: We prepared DNA nanoflower via self-assembly for the delivery of VCR and P-glycoprotein small interfering RNA (P-gp siRNA). Results and Discussion: The as-prepared nanoflower had a floriform shape with high loading efficiency of VCR (80%). Furthermore, the nanoflower could deliver VCR and P-gp siRNA into MDR CML cells and induce potent cytotoxicity both in vitro and in vivo, thus overcoming MDR of CML. Overall, this nanoflower is a promising tool for resistant CML therapy.

Expression of GnT-III decreases chemoresistance via negatively regulating P-glycoprotein expression: Involvement of the TNFR2-NF-κB signaling pathway

The phenomenon of multidrug resistance (MDR) is called chemoresistance with respect to the treatment of cancer, and it continues to be a major challenge. The role of N-glycosylation in chemoresistance, however, remains poorly understood. Here, we established a traditional model for adriamycin resistance in K562 cells, which are also known as K562/adriamycin-resistant (ADR) cells. Lectin blot, mass spectrometry, and RT-PCR analysis showed that the expression levels of N-acetylglucosaminyltransferase III (GnT-III) mRNA and its products, bisected N-glycans, are significantly decreased in K562/ADR cells, compared with the levels in parent K562 cells. By contrast, the expression levels of both P-glycoprotein (P-gp) and its intracellular key regulator, NF-κB signaling, are significantly increased in K562/ADR cells. These upregulations were sufficiently suppressed by the overexpression of GnT-III in K562/ADR cells. We found that the expression of GnT-III consistently decreased chemoresistance for doxorubicin and dasatinib, as well as activation of the NF-κB pathway by tumor necrosis factor (TNF) α, which binds to two structurally distinct glycoproteins, TNF receptor 1 (TNFR1) and TNF receptor 2 (TNFR2), on the cell surface. Interestingly, our immunoprecipitation analysis revealed that only TNFR2, but not TNFR1, contains bisected N-glycans. The lack of GnT-III strongly induced TNFR2's autotrimerization without ligand stimulation, which was rescued by the overexpression of GnT-III in K562/ADR cells. Furthermore, the deficiency of TNFR2 suppressed P-gp expression while it increased GnT-III expression. Taken together, these results clearly show that GnT-III negatively regulates chemoresistance via the suppression of P-gp expression, which is regulated by the TNFR2-NF/κB signaling pathway.

Emerging role of exosomes in hematological malignancies

Hematological malignancies are a heterogeneous group of neoplasms in the blood characterized by dysregulated hematopoiesis and classified as leukemia, lymphoma, and myeloma. The occurrence and progression of hematological malignancies depend on transformed hematopoietic stem cells, which refract to chemotherapy and often cause relapse. In recent years, monoclonal antibody therapies are preferred for hematopoietic cancers, owing to their inherent mechanisms of action and improved outcomes. However, efficient drug delivery methods and the establishment of novel biomarkers are currently being investigated and warranted to improve the outcome of patients with hematological malignancies. For instance, non-viral-mediated, natural carriers have been suggested for latent intracellular drug delivery. In this purview, repurposing small vesicles (e.g., exosomes) is considered a latent approach for myeloma therapy. Exosomes (nano-vesicles) have many advantages in that they are secreted by various animals and plants and become sought after for therapeutic and diagnostic purposes. The size of the cellular membrane of exosomes (30-150 nm) facilitates ligand binding and targeted delivery of the loaded molecules. Furthermore, exosomes can be modified to express specific target moiety on their cell membrane and can also be featured with desired biological activity, thereby potentially employed for various convoluted diseases, including hematological malignancies. To advance the current knowledge, this review is focused on the source, composition, function and surface engineering of exosomes pertaining to hematological malignancies.

The progress of small-molecules and degraders against BCR-ABL for the treatment of CML

Chronic myeloid leukemia (CML) is a malignant disease of the hematopoietic system with crucial pathogenic protein named BCR-ABL, which endangers the life of patients severely. As a milestone of targeted drug, Imatinib has achieved great success in the treatment of CML. Nevertheless, inevitable drug resistance of Imatinib has occurred frequently in clinical due to the several mutations in the BCR-ABL kinase. Subsequently, the second-generation of tyrosine kinase inhibitors (TKIs) against BCR-ABL was developed to address the mutants of Imatinib resistance, except T315I. To date, the third-generation of TKIs targeting T315I has been developed for improving the selectivity and safety. Notably, the first allosteric inhibitor has been in market which could overcome the mutations in ATP binding site effectively. Meanwhile, some advanced technology, such as proteolysis-targeting chimeras (PROTAC) based on different E3 ligand, are highly expected to overcome the drug resistance by selectively degrading the targeted proteins. In this review, we summarized the current research progress of inhibitors and degraders targeting BCR-ABL for the treatment of CML.

Burden of tyrosine kinase inhibitor failure in Chinese chronic myeloid leukemia patients: a systematic literature review

Aim: To conduct a systematic literature review of real-world evidence on the burden of tyrosine kinase inhibitor (TKI) failure in Chinese patients with chronic myeloid leukemia (CML). Methods: We identified 155 references in Chinese- and English-language journals from 2001 to 2021. Results: The age-adjusted mortality rate in Chinese CML patients was decreasing. Imatinib treatment had a higher annual treatment failure risk than nilotinib (0.199 vs 0.041). Patients with TKI treatment failure tended to be young (median: 38.6 years), have progressive disease (44.3%) and harbor BCR-ABL1 mutations (51.6%). The disease burden of TKI treatment failure included reduced health outcomes and increased health resource utilization and costs. Conclusion: CML relapse cases could continuously rise in China due to increasing TKI treatment failure over extended survival.

Ponatinib Induces Vascular Toxicity through the Notch-1 Signaling Pathway

Ponatinib, a third-generation tyrosine kinase inhibitor (TKI), is the only approved TKI that is effective against T315I mutations in patients with chronic myeloid leukemia (CML). Specific activation of Notch signaling in CML cells by ponatinib can be considered as the “on-target effect” on the tumor and represents a therapeutic approach for CML. Nevertheless, ponatinib-induced vascular toxicity remains a serious concern, with underlying mechanisms being poorly understood. We aimed to determine the mechanisms of ponatinib-induced vascular toxicity, defining associated signaling pathways and identifying potential rescue strategies. We exposed human umbilical endothelial cells (HUVECs) to ponatinib or vehicle in the presence or absence of the neutralizing factor anti-Notch-1 antibody for exposure times of 0–72 h. Label-free proteomics and network analysis showed that protein cargo of HUVECs treated with ponatinib triggered apoptosis and inhibited vasculature development. We validated the proteomic data showing the inhibition of matrigel tube formation, an up-regulation of cleaved caspase-3 and a downregulation of phosphorylated AKT and phosphorylated eNOS. We delineated the signaling of ponatinib-induced vascular toxicity, demonstrating that ponatinib inhibits endothelial survival, reduces angiogenesis and induces endothelial senescence and apoptosis via the Notch-1 pathway. Ponatinib induced endothelial toxicity in vitro. Hyperactivation of Notch-1 in the vessels can lead to abnormal vascular development and vascular dysfunction. By hyperactivating Notch-1 in the vessels, ponatinib exerts an “on-target off tumor effect”, which leads to deleterious effects and may explain the drug’s vasculotoxicity. Selective blockade of Notch-1 prevented ponatinib-induced vascular toxicity.

The Impact of Recent Generic Drug Price Policies on Pharmaceutical Innovation: A Theoretical Rationale and Proposal of a Method Supporting Innovation in Areas of Unmet Medical Need

New discoveries are a critical priority for the pharmaceutical industry. However, the use of fixed incremental cost-effectiveness (ICER) thresholds for health technology assessment (HTA) may compromise incentives to innovate and affect future treatment options. This paper highlights the impact of generic drug price policies on pharmaceutical innovation in the context of fixed ICER thresholds and proposes a new consideration for the cost-effectiveness analysis (CEA). There is a direct causal relationship between HTA and the market price of a drug; in jurisdictions where HTA agencies apply fixed ICER thresholds as an important reimbursement listing criterion, the incremental cost of a new drug is expected to be proportional to its incremental benefit over the comparator. However, the comparator price is subject to market forces or sudden policies and may change markedly affecting the cost-effectiveness assessment (e.g. where the comparator patent has expired). Since recent generic price regulations increased the price gap between drugs' generic and patented versions, it is harder to achieve a sufficient level of incremental benefits in order to offset incremental prices of new treatments. Consequently, even promising drugs may have challenges to show attractive ICERs and research and development (R&D) investments may become unattractive in certain disease area. In order to promote innovation in therapeutic fields with unmet medical needs, a compromise would be to include the comparator's patented price in the CEA instead of the generic drug. By identifying the relevant disease areas, decision makers and HTA authorities could therefore convey the importance of investing in these therapeutic areas to manufacturers.

Association of The Common CYP1A1*2C Variant (Ile462Val Polymorphism) with Chronic Myeloid Leukemia (CML) in Patients Undergoing Imatinib Therapy

OBJECTIVE

Cytochrome P450 is one of the major drug metabolizing enzyme families and its role in metabolism of cancer drugs cannot be less emphasized. The association be- tween single nucleotide polymorphisms (SNPs) in CYP1A1 and pathogenesis of chronic myeloid leukemia (CML) has been investigated in several studies, but the results observed vary based on varied risk factors. The objective of this study was to investigate the risk factors associated with the CYP1A1*2C [rs1048943: A>G] polymorphism in CML patients and its role in therapeutic response to imatinib mesylate (IM) affecting clinico-pathological parameters, in the Indian population.

MATERIALS AND METHODS

In this case-control study, CYP1A1*2C was analysed in CML patients. After obtaining approval from the Ethics Committee of oncology hospital, we collected blood samples from 132 CML patients and 140 matched controls. Genom- ic DNA was extracted and all the samples were analysed for the presence of the CYP1A1*2C polymorphism using allele-specific polymerase chain reaction, and we examined the relationship of genotypes with risk factors such as gender, age, phase of the disease and other clinical parameters.

RESULTS

We observed a significant difference in the frequency distribution of CYP1A1*2C genotypes AA (38 vs. 16%, P=0.0001), AG (57 vs. 78%, P=0.0002) and GG (5 vs. 6%, P=0.6635) between patients and controls. In terms of response to IM therapy, significant variation was observed in the frequencies of AA vs AG in major (33 vs 67%) and poor (62 vs 31%) hematological responders, and AA vs AG in major (34 vs. 65%) and poor (78 vs. 22%) cytogenetic responders. However, the patients with the GG homozygous genotype did not show any significant therapeutic outcome.

CONCLUSION

The higher frequency of AG in controls indicates that AG may play a protec- tive role against developing CML. We also found that patients with the AG genotype showed favorable treatment response towards imatinib therapy, indicating that this polymorphism could serve as a good therapeutic marker in predicting response to such therapy.

Utility values for specific chronic myeloid leukemia chronic phase health states from the general public in the United Kingdom

This study elicited time trade-off (TTO) and standard gamble (SG) preference values associated with four health states corresponding to response levels in chronic phase chronic myeloid leukemia (CML) from members of the general public in the UK (n = 235). Health states studied were treatment-free remission (TFR), complete molecular response (CMR, i.e. undetectable disease on treatment), molecular response and reappearance of detectable disease (i.e. relapse from TFR to molecular response requiring treatment). TFR was the most preferred health state (mean utility of 0.97 [TTO] and 0.87 [SG]) followed by CMR (mean utility of 0.96 [TTO] and 0.85 [SG]) followed by molecular response (mean utility of 0.94 [TTO] and 0.80 [SG]) followed by reappearance of detectable disease (mean utility of 0.90 [TTO] and 0.72 [SG]). SG values were significantly lower than TTO values (p < 0.001). The study demonstrated that different treatment responses may impact on the health-related quality of life of patients with chronic phase CML.

Clinical investigation of receptor and non-receptor tyrosine kinase inhibitors for the treatment of epithelial ovarian cancer

INTRODUCTION

Epithelial ovarian cancer (EOC) is the second most common gynecologic malignancy and the leading cause of death from gynecologic cancer in the USA. EOC is an exquisitely chemo-sensitive disease with response rates of over 75% in the upfront setting. Despite this, due to high rates of recurrence and development of chemo-resistance, the overall survival of EOC remains about 25%. Thus, there is a great need for new therapeutic approaches to render more durable responses. Based on preclinical and early phase clinical studies, key targeted pathways include targets that drive angiogenesis and chemo-resistance. Receptor tyrosine kinases and non-receptor tyrosine kinases play important roles in these processes and several small molecule tyrosine kinase inhibitors (TKIs) are in clinical development.

AREAS COVERED

This review summarizes clinical rationale, mechanisms of action and clinical data for the TKIs under evaluation in the Phase III setting for EOC.

EXPERT OPINION

Despite reasonable preclinical activity, small molecule TKIs are unlikely to improve patient survival as single agent therapies in an unselected EOC population. Incorporation of tissue evaluation during ongoing clinical trials is required to identify molecularly defined groups that respond to single agents and direct rational combination strategies based on mechanisms of resistance to improve outcomes in EOC.

Trends in chronic myeloid leukemia incidence and survival in the United States from 1975 to 2009

The use of interferon-α and allogeneic stem cell transplant and more recently of tyrosine kinase inhibitors (TKIs) have improved the outcome of patients with chronic myeloid leukemia (CML). We performed a population-based study of CML to evaluate relative survival (RS) trend by treatment eras. All instances of CML diagnosed between 1975 and 2009 reported in the Surveillance, Epidemiology and End Results databases were reviewed. The incidence of CML was 1.75/100 000 persons per year and increased with age. The incidence was highest in Detroit and lowest among Asians. The 5-year RS ratios increased from 0.26 in patients diagnosed in 1975-1989 to 0.36 in 1990-2000 and 0.56 in 2001-2009. There was a significant improvement in 5-year RS ratios in the 2005-2009 calendar period compared to the 2001-2004 period (p < 0.05), corresponding to the introduction of second-generation TKIs. Age was the most important prognostic factor for RS, but the improvement in 5-year RS ratios was observed in all age groups except the group aged < 15 years (p > 0.05), including adolescents and young adults and elderly patient groups. There are ethnic and geographic variations in the incidence of CML. The RS improved with each treatment era, with the greatest improvement in all age groups occurring during the TKI era.

Association of HLA antigens and BCR-ABL transcripts in leukemia patients with the Philadelphia chromosome

Objective

This study aimed to verify the association between human leukocyte antigens and the bcr-abl fusion protein resulting from t(9;22)(q34;q11) in chronic leukemia myeloid and acute lymphoblastic leukemia patients.

Methods

Forty-seven bcr-abl positive individuals were evaluated. Typing was performed bymicrolymphocytotoxicity and molecular biological methods (human leukocyte antigens Class I and Class II). A control group was obtained from the data of potential bone marrow donors registered in the Brazilian Bone Marrow Donor Registry (REDOME).

Results

Positive associations with HLA-A25 and HLA-B18 were found for the b2a2 transcript, as well as a tendency towards a positive association with HLA-B40 and a negative association with HLA-A68. The b3a2 transcript showed positive associations with HLA-B40 and HLA-DRB1*3.

Conclusion

The negative association between human leukocyte antigens and the BCR-ABL transcript suggests that binding and presentation of peptides derived from the chimeric protein are effective to increase a cytotoxic T lymphocyte response appropriate for the destruction of leukemic cells.

Quantitative- and phospho-proteomic analysis of the yeast response to the tyrosine kinase inhibitor imatinib to pharmacoproteomics-guided drug line extension

Imatinib mesylate (IM) is a potent tyrosine kinase inhibitor used as front-line therapy in chronic myeloid leukemia, a disease caused by the oncogenic kinase Bcr-Abl. Although the clinical success of IM set a new paradigm in molecular-targeted therapy, the emergence of IM resistance is a clinically significant problem. In an effort to obtain new insights into the mechanisms of adaptation and tolerance to IM, as well as the signaling pathways potentially affected by this drug, we performed a two-dimensional electrophoresis-based quantitative- and phospho-proteomic analysis in the eukaryotic model Saccharomyces cerevisiae. We singled out proteins that were either differentially expressed or differentially phosphorylated in response to IM, using the phosphoselective dye Pro-Q(®) Diamond, and identified 18 proteins in total. Ten were altered only at the content level (mostly decreased), while the remaining 8 possessed IM-repressed phosphorylation. These 18 proteins are mainly involved in cellular carbohydrate processes (glycolysis/gluconeogenesis), translation, protein folding, ion homeostasis, and nucleotide and amino acid metabolism. Remarkably, all 18 proteins have human functional homologs. A role for HSP70 proteins in the response to IM, as well as decreased glycolysis as a metabolic marker of IM action are suggested, consistent with findings from studies in human cell lines. The previously-proposed effect of IM as an inhibitor of vacuolar H(+)-ATPase function was supported by the identification of an underexpressed protein subunit of this complex. Taken together, these findings reinforce the role of yeast as a valuable eukaryotic model for pharmacological studies and identification of new drug targets, with potential clinical implications in drug reassignment or line extension under a personalized medicine perspective.

Utility values for chronic myelogenous leukemia chronic phase health states from the general public in the United Kingdom

This study estimated time trade-off preference values associated with the four chronic myelogenous leukemia (CML) chronic phase-related health states (i.e. untreated, hematologic response, cytogenetic response and molecular response) among members of the general public in the UK (n = 241). All four health states were associated with decreases in preference values from full health. The molecular response to treatment was the most preferred health state (mean utility of 0.94). The second-most preferred health state was cytogenetic response followed by hematologic response (mean utilities were 0.89 and 0.80, respectively). The least preferred health state was untreated chronic phase CML (mean utility of 0.72). The utility values for each state were significantly different from one another (p < 0.001). This study demonstrated and quantified the impact that more robust treatment responses have on the health-related quality of life of patients with chronic phase CML.

Suboptimal responses in chronic myeloid leukemia: implications and management strategies

The high response rates and increased survival associated with imatinib therapy prompted a paradigm shift in the management of chronic myeloid leukemia. However, 25% to 30% of imatinib-treated patients develop drug resistance or intolerance, increasing the risk of disease progression and poor prognosis. In 2006, the European LeukemiaNet proposed criteria to identify patients with a suboptimal response to, or failure associated with, imatinib; these recommendations were updated in 2009. Suboptimal responders represent a unique treatment challenge. Although they may respond to continued imatinib therapy, their long-term outcomes may not be as favorable as those for optimally responding patients. Validation studies demonstrated that suboptimal responders are a heterogeneous group, and that the prognostic implications of suboptimal response vary by time point. There are few data derived from clinical trials to guide therapeutic decisions for these patients. Clinical trials are currently underway to assess the efficacy of newer tyrosine kinase inhibitors in this setting. Identification of suboptimal responders or patients failing treatment using hematologic, cytogenetic, and molecular techniques allows physicians to alter therapy earlier in the treatment course to improve long-term outcomes.

Managing resistance in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative disorder that affects 5000 new patients per year in the United States. Prior to 10 years ago, durable remission was rare and patients often underwent bone marrow transplantation with substantial morbidity and mortality. Fortunately, CML has been the epicenter of exciting advances in cancer therapy with the discovery of the Bcr-Abl gene fusion and the subsequent development of imatinib mesylate, a small molecule tyrosine kinase inhibitor, to target the kinase activity of the bcr-abl protein product. Despite unprecedented durability for complete hematologic, cytogenetic, and molecular responses seen with front-line imatinib therapy, many patients require alternative therapy because of drug intolerance, suboptimal response, primary resistance, secondary resistance, or progression to advanced phase disease. Further, up to 5% of patients present with advanced disease that does not sustain a durable response to tyrosine kinase inhibitors. Thus, up to one third of CML patients require alternate therapy. Chronic myeloid leukemia has become an exemplary model system for understanding molecular targeting and overcoming mechanisms of drug resistance. This review will discuss potential mechanisms of resistance and ongoing research into novel targets and agents for CML resistant to standard of care.

Use of tyrosine kinase inhibitors for chronic myeloid leukemia: management of patients and practical applications for pharmacy practitioners

OBJECTIVE

To summarize the use of tyrosine kinase inhibitors (TKIs) for treatment of patients with chronic myeloid leukemia (CML) and provide practical information for patient management.

DATA SOURCES

Literature was retrieved from PubMed (2000-January 2011), using the search terms chronic myeloid leukemia and tyrosine kinase inhibitor. Abstracts presented at the 2008-2010 annual meetings of the American Society of Hematology and the American Society of Clinical Oncology, reference citations from identified publications, as well as the manufacturers' full prescribing information for cited drugs, also were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Articles evaluating the efficacy and safety of the TKIs imatinib, nilotinib, and dasatinib were evaluated. Focus was placed on publications supporting management of patients with CML in the chronic phase. Reports presenting clinical trial information of TKIs in development also were included.

DATA SYNTHESIS

The discovery of targeted tyrosine kinase inhibition of BCR-ABL kinase dramatically changed the treatment of CML. Imatinib, the first TKI approved for treatment of patients with Philadelphia chromosome--positive CML, demonstrated significant superiority over the previous standard of care: interferon plus cytarabine. The newer, more potent TKIs, nilotinib and dasatinib, have demonstrated improved efficacy over imatinib as first-line therapy and provide an effective option for patients with resistance or intolerance to imatinib.

CONCLUSIONS

To maximize efficacy of TKI therapy, close patient management, involving frequent monitoring of patient response, is essential. Given the importance of continuing TKI therapy, early recognition and management of adverse events are critical to optimizing outcomes in patients with CML. In addition to the safety profile and considerations of comorbidities, additional factors can affect therapeutic selection, including drug-drug and drug-food interactions. Research investigating new therapies, particularly for patients harboring the T315I mutation-which remains refractory to current TKIs-continues in the quest to improve outcomes in patients with CML.

Contribution of BCR-ABL-independent activation of ERK1/2 to acquired imatinib resistance in K562 chronic myeloid leukemia cells

BCR-ABL tyrosine kinase, generated from the reciprocal chromosomal translocation t(9;22), causes chronic myeloid leukemia (CML). BCR-ABL is inhibited by imatinib; however, several mechanisms of imatinib resistance have been proposed that account for loss of imatinib efficacy in patients with CML. Previously, we showed that overexpression of the efflux drug transporter P-glycoprotein partially contributed to imatinib resistance in imatinib-resistant K562 CML cells having no BCR-ABL mutations. To explain an additional mechanism of drug resistance, we established a subclone (K562/R) of the cells and examined the BCR-ABL signaling pathway in these and wild-type K562 (K562/W) cells. We found the K562/R cells were 15 times more resistant to imatinib than their wild-type counterparts. In both cell lines, BCR-ABL and its downstream signaling molecules, such as ERK1/2, ERK5, STAT5, and AKT, were phosphorylated in the absence of imatinib. In both cell lines, imatinib effectively reduced the phosphorylation of all the above, except ERK1/2, whose phosphorylation was, interestingly, only inhibited in the wild-type cells. We then observed that phospho-ERK1/2 levels decreased in the presence of siRNA targeting BCR-ABL, again, only in the K562/W cells. However, using an ERK1/2 inhibitor, U0126, we found that we could reduce phospho-ERK1/2 levels in K562/R cells and restore their sensitivity to imatinib. Taken together, we conclude that the BCR-ABL-independent activation of ERK1/2 contributes to imatinib resistance in K562/R cells, and that ERK1/2 could be a target for the treatment of CML patients whose imatinib resistance is due to this mechanism.

Healthcare resource utilization and costs associated with non-adherence to imatinib treatment in chronic myeloid leukemia patients

BACKGROUND

Patients with chronic myeloid leukemia (CML) who do not adhere to treatment may experience suboptimal outcomes.

OBJECTIVE

To examine the association between adherence with imatinib and direct healthcare costs and resource utilization in a large group of privately insured CML patients.

PATIENTS AND METHODS

CML patients under age 65 were identified with ICD-9 code 205.1X using MarketScan Commercial Claims data between 1/1/02 and 7/31/08. Patients were required to be continuously enrolled in a private insurance plan during the baseline and study periods, defined respectively as the 4 months prior to and the 12 months following imatinib initiation. Non-adherence was evaluated by the medication possession ratio (MPR), defined as the fraction of days during the study period that patients had filled prescriptions for imatinib, and stratified into two groups (low MPR: <85%, high MPR: > or =85%). Costs, inpatient admissions, and hospital days were compared between high and low adherence groups using Wilcoxon tests. Regression models compared utilization and costs controlling for age, sex, CML severity, Charlson comorbidity index, baseline costs, and other factors.

RESULTS

The study sample consisted of 592 patients, where 242 (40.9%) patients were classified with a low MPR, while 350 (59.1%) had a high MPR. Mean MPR was 79% (95% confidence interval 76-81%). Patients with a low MPR incurred more all-cause inpatient visits (4.1 vs. 0.4; p < 0.001) and all-cause inpatient days (14.8 vs. 1.8; p < 0.001). Regression models demonstrated a 283% increase (US$56 324; p < 0.001) in non-imatinib costs within the low- vs. high-MPR group. The generalizability of this study is limited by the use of a privately insured population under 65 years of age as well as by the limitations common to claims data analyses.

CONCLUSIONS

Imatinib adherence is an important issue for patients and physicians. Better imatinib adherence was associated with significantly lower resource utilization and costs in CML patients, as lower imatinib costs in low MPR patients were more than offset by higher non-imatinib costs mostly driven by inpatient services.

Cost-effectiveness study comparing imatinib with interferon-alpha for patients with newly diagnosed chronic-phase (CP) chronic myeloid leukemia (CML) from the Chinese public health-care system perspective (CPHSP)

OBJECTIVE

Imatinib, a breakthrough oral molecular-targeted therapy, has demonstrated durable responses and significant survival advantage compared with interferon-based treatment. This study compares imatinib with interferon in newly diagnosed chronic-phase chronic myeloid leukemia (CML-CP) patients from the Chinese public health-care system perspective (CPHSP).

METHODS

One-year cost responder and lifetime cost-utility analyses were conducted, respectively. Complete cytogenetic response was used to define a responder. Direct medical costs were included. Response rates as well as survival estimates were obtained from published literature.

RESULTS

The cost per responder for interferon was close to 20 times higher than that for imatinib. The cost per additional responder was RMB36,545. The incremental cost-effectiveness ratio (ICER) comparing imatinib with interferon was RMB73,674 (95% confidence interval RMB67,712-RMB79,637) per quality-adjusted life-year.

CONCLUSION

In newly diagnosed CML-CP, the cost per responder for patients treated with imatinib is much lower than that for patients treated with interferon. In the cost-utility analysis, the ICER is below the cost-effectiveness threshold recommended by the World Health Organization for developing countries. Therefore, imatinib is more cost-effective than interferon from the CPHSP.

Efficacy of various doses and schedules of second-generation tyrosine kinase inhibitors

Imatinib is one of the most potent cancer therapeutic agents identified to date. Before the introduction of this tyrosine kinase inhibitor (TKI), 5-year survival in chronic myeloid leukemia (CML) was approximately 40%-60%, but since the introduction of imatinib, overall survival has increased to approximately 90% for patients with chronic-phase disease. However, nearly one fifth of patients are intolerant or resistant to imatinib, resulting in patients with persistent or progressive disease. Recent research has identified a number of additional compounds that more efficiently inhibit the Abl tyrosine kinase and additional kinases that potentially play a role in imatinib resistance. The advent of dasatinib and nilotinib has provided additional options for patients with progressive disease. A number of phase II clinical trials have recently demonstrated that these second-generation TKIs are well tolerated and effective in patients with Philadelphia chromosome-positive (Ph+) leukemias. Recent clinical trial developments raise questions regarding the proper dosage and schedule of these newer agents as well as the timing of their use in the treatment of patients with CML. Additionally, the development of nonoverlapping resistance patterns with sequential drug exposure argues for the possibility of a drug selection scheme that might limit the development of resistant disease. As the era of personalized medicine has begun to take shape in the 21st century, the addition of newer TKIs might facilitate this trend in the treatment of Ph+ leukemias.

Constitutive overexpression of P-glycoprotein, rather than breast cancer resistance protein or organic cation transporter 1, contributes to acquisition of imatinib-resistance in K562 cells

PURPOSE

The purpose of this study was to investigate the contribution of drug transporters in acquired imatinib-resistance. Specifically, we focused on the efflux transporters, P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), and an influx transporter, organic cation transporter 1 (OCT1).

MATERIALS AND METHODS

We established imatinib-resistant K562 cells (K562/IM). Real-time PCR or Western blot analyses were performed to examine the mRNA or protein levels. Alamar blue method was used in the cytotoxicity assay. The transport activities and intracellular imatinib levels were measured by flow cytometry and HPLC, respectively.

RESULTS

K562/IM displayed a 47-fold increase in resistance to imatinib over the parent K562 cells. Both P-gp and BCRP were overexpressed in K562/IM relative to K562. Furthermore, the intracellular imatinib level was markedly reduced in K562/IM. Interestingly, cyclosporin A, a P-gp inhibitor, but not fumitremorgin C, a BCRP inhibitor, restored both imatinib-sensitivity and the intracellular imatinib level. By contrast, no significant difference in the expression and function of OCT1 was observed between K562/IM and K562.

CONCLUSIONS

P-gp, rather than BCRP or OCT1, is partially responsible for the development of imatinib-resistance due to constitutive and functional overexpression, leading to reduced intracellular accumulation of imatinib in K562/IM.

Imatinib: a review of its use in chronic myeloid leukaemia

Imatinib (Gleevec, Glivec) is a synthetic tyrosine kinase inhibitor used in the treatment of chronic myeloid leukaemia (CML). It is specifically designed to inhibit the breakpoint cluster region (BCR)-Abelson (ABL) fusion protein that results from the chromosomal abnormality known as the Philadelphia chromosome. CML is characterised by this abnormality, which leads to abnormalities of the peripheral blood and bone marrow including an increase in the number of granular leukocytes. Imatinib is approved in numerous countries worldwide for the treatment of newly diagnosed Philadelphia chromosome-positive (Ph+) chronic-phase CML, Ph+ accelerated-phase or blast-crisis CML, and in patients with Ph+ chronic-phase CML who have failed to respond to interferon-alpha therapy. It is also indicated in paediatric patients with newly diagnosed Ph+ chronic-phase CML, in accelerated-phase or blast-crisis CML, or in chronic-phase CML after failure of interferon-alpha therapy or when the disease has recurred after haematopoietic stem cell transplantation (HSCT). Approved indications, however, may vary by country. Imatinib is effective and generally well tolerated in patients with Ph+ CML. In patients with newly diagnosed chronic-phase CML, imatinib was more effective than interferon-alpha plus cytarabine in preventing progression of the disease and in achieving haematological and cytogenetic responses. Overall survival rates remain high after 5 years of follow-up, and historical comparisons with other treatments demonstrate improved overall survival with imatinib in the long term. Patients with accelerated-phase or blast-crisis CML, or those who have not responded to prior interferon-alpha therapy also benefit from imatinib treatment. Some patients become resistant or intolerant to imatinib therapy; management strategies to overcome these problems include dosage adjustment, other treatments, or combination therapy with imatinib and other agents. Allogeneic HSCT is currently the only potentially curative treatment, but it is associated with high rates of morbidity and mortality and is not suitable for all patients. The introduction of imatinib has had a marked impact on outcomes in patients with CML. It remains a valuable treatment for all stages of the disease, especially initial treatment of newly diagnosed Ph+ chronic-phase CML, and is endorsed by European and US treatment guidelines as a first-line option.

Comparative gene expression analysis of a chronic myelogenous leukemia cell line resistant to cyclophosphamide using oligonucleotide arrays and response to tyrosine kinase inhibitors

Acquired imatinib resistance in chronic myelogenous leukemia (CML) can be the consequence of mutations in the kinase domain of BCR-ABL or increased protein levels. However, as in other malignancies, acquired resistance to cytostatic drugs is a common reason for treatment failure or disease progression. As a model for drug resistance, we developed a CML cell line resistant to cyclophosphamide (CP). Using oligonucleotide arrays, we examined changes in global gene expression. Selected genes were also examined by real-time PCR and flow cytometry. Neither the parent nor the resistant lines had mutations in their ATP binding domain. Filtering genes with a low-base line expression, a total of 239 genes showed significant changes (162 up- and 77 down-regulated) in the resistant clone. Most of the up-regulated genes were associated with metabolism, signal transduction, or encoded enzymes. The gene for aldehyde dehydrogenase 1 was over-expressed more than 2000-fold in the resistant clone. BCR-ABL was expressed in both cell lines to a comparable extent. When exposed to the tyrosine kinase inhibitors imatinib and nilotinib, both lines were sensitive. In conclusion, we found multiple genetic changes in a CML cell line resistant to CP related to metabolism, signal transduction or apoptosis. Despite these changes, the resistant cells retained sensitivity to tyrosine kinase inhibitors.

Complex interaction of BCRP/ABCG2 and imatinib in BCR-ABL-expressing cells: BCRP-mediated resistance to imatinib is attenuated by imatinib-induced reduction of BCRP expression

Imatinib, a potent tyrosine kinase inhibitor, is effluxed from cells by the breast cancer resistance protein (BCRP/ABCG2), yet published studies to date fail to demonstrate resistance to imatinib cytotoxicity in BCRP-overexpressing cells in vitro. We investigated cellular resistance to imatinib in BCR-ABL-expressing cells transduced and selected to overexpress BCRP (K562/BCRP-MX10). These cells exhibited a 2- to 3-fold increase in resistance to imatinib (P < .05) and a 7- to 12-fold increase in resistance to mitoxantrone, a known BCRP substrate. Resistance to imatinib was completely abolished by the specific BCRP inhibitor fumitremorgin C. Studies of the mechanism of the diminished resistance to imatinib compared with mitoxantrone revealed that imatinib decreased the expression of BCRP in K562/BCRP-MX10 cells without affecting mRNA levels. BCRP levels in cells that do not express BCR-ABL were not affected by imatinib. Loss of BCRP expression was accompanied by imatinib-induced reduction of phosphorylated Akt in the BCRP-expressing K562 cells. The phosphoinositol-3 kinase (PI3K) inhibitor LY294002 also decreased BCRP levels in K562/BCRP-MX10 cells. These studies show that BCRP causes measurable imatinib resistance, but this effect is attenuated by imatinib-mediated inhibition of BCR-ABL, which in turn downregulates overall BCRP levels posttranscriptionally via the PI3K-Akt pathway.

The development and application of imatinib

The hallmark characteristics of cancer include an unrestrained proliferation involving activation of growth signals, loss of negative regulation and dysfunctional apoptotic pathways. Targeting abnormal cell signalling pathways should provide a more selective approach to cancer treatment than conventional cytotoxic chemotherapy. Tyrosine kinases play an essential role in the signalling pathways involved in the control of cellular proliferation and growth. Imatinib is a small-molecule tyrosine kinase inhibitor of the ABL fusion gene, platelet derived growth factor receptors (PDGFR) and KIT. This agent has demonstrated considerable activity in chronic myeloid leukaemia (CML) by inhibiting the BCR-ABL fusion protein and gastrointestinal stromal tumours (GISTs), which are predominantly driven by activating mutations in KIT. A number of other rare conditions are also responsive, for example, dermatofibrosarcoma protuberans, which is driven by a chromosomal translocation involving PDGF-B and Col1A1, resulting in overexpression of PDGF-B, and hypereosinophillic syndrome, which can be caused by activating PDGFR mutations. The pivotal registration study for newly diagnosed CML was a large randomised trial comparing 400 mg/day of imatinib to a combination of IFN-alpha and cytarabine, which demonstrated a significantly higher complete haematological and cytogenetic response rate in the imatinib arm. In the case of GIST a randomised study in patients with inoperable or metastatic disease explored doses of 400 - 600mg and reported a response rate of > 50% in each arm plus disease stabilisation and an improvement in performance status. Large randomised trials have subsequently been performed, comparing 400 with 800mg/day. The first to report indicates that the larger dose is associated with improved progression-free survival, although it is not yet known whether or not this will translate into a difference in overall survival. The most common KIT mutation involves exon 11 and is associated with a statistically significant better response and prognosis compared with other mutations or no detectable mutations. Mutational analysis is likely to become increasingly important in the selection of patients for neoadjuvant and adjuvant treatment and in helping to understand the nature of acquired resistance.

Clinical correlates of submicroscopic deletions involving the ABL-BCR translocation region in chronic myeloid leukemia

Recent reports indicate a prognostically detrimental effect of submicroscopic abl-bcr deletions associated with the break and fusion points of the derivative chromosome 9 [der(9)] in chronic myeloid leukemia (CML). In a retrospective cohort of 92 patients with CML, the incidence of an atypical D-FISH pattern, that is consistent with a der(9) deletion was 20%. Complete clinical information was available in 82 patients and revealed no significant differences between 18 deleted and 64 non-deleted cases in platelet count, circulating blast percentage, spleen size, or karyotype profile at presentation. However, der(9)-deleted patients presented with significantly lower hemoglobin levels and higher leukocyte counts. At a median follow-up of 31 months, the incidence of disease transformation, drug therapy response, and survival were similar between the two groups. These results are contrary to previous reports that suggested inferior survival as well as poor response to alpha interferon therapy in CML patients carrying der(9) deletions.

Cost effectiveness of imatinib compared with interferon-alpha or hydroxycarbamide for first-line treatment of chronic myeloid leukaemia

OBJECTIVE

To evaluate the cost utility of imatinib compared with interferon (IFN)-alpha or hydroxycarbamide (hydroxyurea) for first-line treatment of chronic myeloid leukaemia.

DESIGN AND SETTING

A cost-utility (Markov) model within the setting of the UK NHS and viewed from a health system perspective was adopted. Transition probabilities and relative risks were estimated from published literature. Costs of drug treatment, outpatient care, bone marrow biopsies, radiography, blood transfusions and inpatient care were obtained from the British National Formulary and local hospital databases. Costs (pound, year 2001-03 values) were discounted at 6%. Quality-of-life (QOL) data were obtained from the published literature and discounted at 1.5%. The main outcome measure was cost per QALY gained. Extensive one-way sensitivity analyses were performed along with probabilistic (stochastic) analysis.

RESULTS

The incremental cost-effectiveness ratio (ICER) of imatinib, compared with IFNalpha, was pound26,180 per QALY gained (one-way sensitivity analyses ranged from pound19,449 to pound51,870) and compared with hydroxycarbamide was pound86,934 per QALY (one-way sensitivity analyses ranged from pound69,701 to pound147,095) [ pound1=$US1.691=euro1.535 as at 31 December 2002].Based on the probabilistic sensitivity analysis, 50% of the ICERs for imatinib, compared with IFNalpha, fell below a threshold of approximately pound31,000 per QALY gained. Fifty percent of ICERs for imatinib, compared with hydroxycarbamide, fell below approximately pound95,000 per QALY gained.

CONCLUSIONS

This model suggests, given its underlying data and assumptions, that imatinib may be moderately cost effective when compared with IFNalpha but considerably less cost effective when compared with hydroxycarbamide. There are, however, many uncertainties due to the lack of long-term data.

Cost-effectiveness of imatinib versus interferon-alpha plus low-dose cytarabine for patients with newly diagnosed chronic-phase chronic myeloid leukemia

BACKGROUND

Despite a lack of long-term data, imatinib has become standard therapy for patients with newly diagnosed chronic-phase chronic myeloid leukemia (CML) who are not candidates for allogeneic stem cell transplantation. In the current study, the authors estimated the incremental cost-effectiveness of imatinib versus interferon-alpha plus low-dose cytarabine (IFN+LDAC) as first-line therapy for these patients.

METHODS

Data from the International Randomized Interferon versus STI571 Study and the literature were used to estimate lifetime costs, survival, and quality-adjusted survival. Survival estimates were based on published survival curves for patients who achieved and those who did not achieve a complete cytogenetic response after treatment with interferon-alpha.

RESULTS

The mean estimated survival with first-line imatinib therapy was 15.30 years, compared with 9.07 years with IFN+LDAC. Undiscounted lifetime costs were approximately $424,600 with imatinib and $182,800 with IFN+LDAC. Using a 3% discount rate, the incremental survival gain with imatinib was 3.93 life-years and 3.89 quality-adjusted life-years (QALYs). Incremental discounted lifetime costs were found to be $168,100 higher with imatinib, resulting in incremental cost-effectiveness ratios of $43,100 per life-year saved (95% confidence interval [95% CI], $37,600-51,100) and $43,300 per QALY (95% CI, $38,300-49,100).

CONCLUSIONS

The results of the current study demonstrate that compared with IFN+LDAC, imatinib is a cost-effective first-line therapy in patients with newly diagnosed chronic-phase CML.

Immunological effects of interferon-alpha on chronic myelogenous leukemia

Treatment with interferon-alpha is effective for chronic myelogenous leukemia in the chronic phase (CML-CP), but the immunological mechanisms of the antileukemic effect of this substance are still unclear. The objective of this study was to investigate the immunological effects of interferon-alpha in CML patients. Markers of cellular activation and apoptosis, natural killer (NK) cell cytotoxicity and production of intracellular cytokines (IFN-gamma, IL-2 and IL-4) were determined by flow cytometry in the peripheral blood mononuclear cells (PBMC) of 26 CML-CP patients before and 3, 6 and 9 months after IFN-alpha treatment. The results were correlated with the hematological response. In the whole group of patients, INF-alpha use was followed by a significant increase of lymphocytes producing IL-2 and IFN-gamma, an increase in NK activity and a decrease in the number of CD34+ cells. Out of 26 CML patients, 15 achieved hematological remission and 7 achieved partial cytogenetic remission after 9 months of IFN-alpha treatment. There was an increase in the percentage of CD8/FasL+, DR/CD3+, DQ/CD3+, CD34/Fas+, DR/CD56+, CD56/FasL+ cells and of IFN-gamma- and IL-2-producing lymphocytes and an increase in NK cytotoxicity only in the group of patients who achieved complete hematological remission. Our results indicate that IFN-alpha use in CML-CP reduces the number of CD34+ cells, activates T cells, enhances stem cell apoptotic markers and increases the production of intracellular IFN-gamma and IL-2 by lymphocytes. Taken together, these results indicate that the therapeutic effect of IFN-alpha in CML-CP is mediated at least in part by immunological mechanisms.

Innovations in the management of leukemia: role of biologic therapies

Chronic myelogenous leukemia (CML) results from clonal proliferation of malignant hematologic progenitor cells and is responsible for 7% to 15% of all adult leukemias. The hallmark of CML is a genetic translocation between chromosomes 9 and 22 (the Philadelphia chromosome), which creates the abnormal bcr-abl gene and a continuously activated Bcr-Abl protein. Bcr-Abl tyrosine kinase activity leads to signal transduction and cell growth. Traditional therapies for CML include allogeneic stem cell transplantation, interferon alfa, and oral chemotherapeutic agents. However, because Bcr-Abl is the causative abnormality in CML, it represents an ideal target for rational biologic therapy. Imatinib mesylate is an orally available tyrosine kinase inhibitor that specifically blocks Bcr-Abl function. Clinical trials have demonstrated that imatinib mesylate produces rapid responses in patients with all stages of CML, including those who were resistant to interferon alfa therapy or intolerant of it. When imatinib mesylate therapy was initiated early in the course of CML, there was a complete hematologic response in 98% of the patients and a complete cytogenetic response in 72% of the patients. Although long-term safety and survival data are not yet available, imatinib mesylate is a promising new treatment option for CML that targets the molecular cause of the disease.

N-Caffeoyltyramine arrests growth of U937 and Jurkat cells by inhibiting protein tyrosine phosphorylation and inducing caspase-3

N-Cinnamoyltyramine, N-caffeoyltyramine, N-feruloyltyramine, and N-sinapoyltyramine were synthesized and investigated to identify the most potent compound with anti-proliferation effect on HL-60, U937 and Jurkat cells. N-Caffeoyltyramine was the most potent with GI(50)=10 microM. The treatment of the cells with N-caffeoyltyramine activated caspase-3 activity, and inhibited the growth of cells via decreasing in protein tyrosine kinase activity including epidermal growth factor receptor. These data indicate that N-caffeoyltyramine is most potent compound, inducing cell death of the cancer cells by inhibiting protein tyrosine kinases and activating caspase-3 activity.

IFN-α promotes the rapid differentiation of monocytes from patients with chronic myeloid leukemia into activated dendritic cells tuned to undergo full maturation after LPS treatment

Chronic myelogenous leukemia (CML) is a malignant myeloproliferative disease arising from the clonal expansion of a stem cell expressing the bcr/abl oncogene. CML patients frequently respond to treatment with interferon-α (IFN-α), even though the mechanisms of the response remain unclear. In the present study, we evaluated the role of IFN-α in differentiation and activity of monocyte-derived dendritic cells (DCs) from CML patients as well as in modulation of the cell response to lipopolysaccharide (LPS). Treatment of CML monocytes with IFN-α and granulocyte-macrophage colony-stimulating factor (GM-CSF) resulted in the rapid generation of activated DCs (CML-IFN-DCs) expressing interleukin-15 (IL-15) and the antiapoptotic bcl-2 gene. These cells were fully competent to induce IFN-γ production by cocultured autologous T lymphocytes and expansion of CD8+ T cells. LPS treatment of CML-IFN-DCs, but not of immature DCs generated in the presence of IL-4/GM-CSF, induced the generation of CD8+ T cells reactive against autologous leukemic CD34+ cells. Altogether, these results suggest that (1) the generation of highly active monocyte-derived DCs could be important for the induction of an antitumor response in IFN-treated CML patients and (2) IFN-α can represent a valuable cytokine for the rapid generation of active monocyte-derived DCs to be utilized for vaccination strategies of CML patients. (Blood. 2004;103:980-987)

Expression of BCR/ABL and BCL-2 in myeloid progenitors leads to myeloid leukemias

Chronic myelogenous leukemia is a myeloproliferative disorder (MPD) that, over time, progresses to acute leukemia. Both processes are closely associated with the t(9;22) chromosomal translocation that creates the BCR/ABL fusion gene in hematopoietic stem cells (HSCs) and their progeny. Chronic myelogenous leukemia is therefore classified as an HSC disorder in which a clone of multipotent HSCs is likely to be malignantly transformed, although direct evidence for malignant t(9;22)+ HSCs is lacking. To test whether HSC malignancy is required, we generated hMRP8p210BCR/ABL transgenic mice in which expression of BCR/ABL is absent in HSCs and targeted exclusively to myeloid progenitors and their myelomonocytic progeny. Four of 13 BCR/ABL transgenic founders developed a chronic MPD, but only one progressed to blast crisis. To address whether additional oncogenic events are required for progression to acute disease, we crossed hMRP8p210BCR/ABL mice to apoptosis-resistant hMRP8BCL-2 mice. Of 18 double-transgenic animals, 9 developed acute myeloid leukemias that were transplantable to wild-type recipients. Taken together, these data indicate that a MPD can arise in mice without expression of BCR/ABL in HSCs and that additional mutations inhibiting programmed cell death may be critical in the transition of this disease to blast-crisis leukemia.

Article Commentary: Improving the US Health Care System: Action Plan to Enhance Efficiency, Reduce Errors, and Improve Quality

The decisions made by stakeholders in the nation's health care system that affect the quality of care experienced by patients are too often made without the benefit of scientific evidence. A multidisciplinary set of investigators conducting health services research have traditionally filled this gap between research findings and clinical decision making, but several barriers are hindering this work. This article offers several recommendations—restructuring organizations, ensuring funding, developing infrastructure, strengthening the community of researchers, and forging new links among stakeholders—to promote high-quality information for health decision makers.

Multifaceted approach to the treatment of bcr-abl-positive leukemias

Bcr-Abl-positive leukemias include chronic myelogenous leukemia (CML), both myeloid and lymphoid blast-phase CML, and some cases of acute lymphoblastic leukemia. The chimeric bcr-abl gene codes for a tyrosine kinase that is constitutively activated in the leukemic cells and plays the central role in leukemogenesis. Hematologic malignancies, including Bcr-Abl-positive leukemias, also frequently have overactivity of the Ras signaling pathway, leading to abnormal transduction of growth and survival signals. New and investigational therapeutic options that target these specific molecular defects of leukemic cells include the tyrosine kinase inhibitor imatinib mesylate (STI571) and farnesyltransferase inhibitors (R115777, SCH66336), which block localization of Ras proteins to the cell membrane. While single-agent therapy with these new agents may produce hematologic and cytogenetic remissions in patients with Bcr-Abl-positive leukemias, molecular remissions are less common, and resistance may develop. Therefore, the development of a multifaceted therapeutic approach to these leukemias is of great interest. Arsenic trioxide (ATO), which has significant activity in patients with relapsed and refractory acute promyelocytic leukemia, is a potential addition to the therapeutic arsenal. While some of the molecular activities of ATO are specific to acute promyelocytic leukemia, arsenicals also have a broad variety of antineoplastic properties that may be useful in combination therapy with agents that target specific molecular defects of Bcr-Abl-positive leukemias.

Synthesis and characterization of N-coumaroyltyramine as a potent phytochemical which arrests human transformed cells via inhibiting protein tyrosine kinases

Numerous phytochemicals are believed to have beneficial effects on human health. N-Coumaroyltyramine accumulates in plants in response to wounding and pathogen attack. Due to the scarcity of N-coumaroyltyramine, its biological activities have not been studied in human cells. In this study, N-coumaroyltyramine was chemically synthesized and then purified by an HPLC with a UV-visible absorbance detector. Retention times of major peaks were 14.3 and 20.7 min, and the peak at 20.7 min was confirmed by LC-MS as N-coumaroyltyramine with a mass/charge (m/z) unit of 284.1. The synthesis procedure was relatively easy and had an acceptable yield (approximately 55%). The compound exhibited a new activity, suppression of growth of human tumor cells such as U937 and Jurkat cells. In addition, the suppressed growth of the cells was strongly associated with an increased percentage of cells in the S phase of the cell cycle progression. Furthermore, N-coumaroyltyramine was able to inhibit the protein tyrosine kinases including epidermal growth factor receptor (EGFR). This is the first report of the growth suppressing activity of N-coumaroyltyramine and its arrest of cells at the S phase of the cell cycle, possibly by inhibition of protein tyrosine kinases.