Novel therapies for chronic myelogenous leukemia

Successful Treatment of Chronic Myeloid Leukemia With Dasatinib After Kidney Transplantation: A Case Report

OBJECTIVE

Chronic myeloid leukemia (CML) is a rare malignancy in kidney transplant (KT) recipients. Although dasatinib is the first-line treatment for CML, it has inhibitory activity against CYP3A4; this might increase the blood concentration of tacrolimus (administered to KT patients for immune suppression). Furthermore, tacrolimus can also increase blood concentrations of dasatinib through P-glycoprotein inhibition.

METHODS

Here, we report a case of sustained molecular remission of CML with prolonged first-line dasatinib therapy in a KT recipient being treated with tacrolimus. A 61-year-old woman developed CML-chronic phase (CML-CP) 38 months post KT. Her maintenance immunosuppressive therapy consisted of tacrolimus, mycophenolate mofetil, and methylprednisolone. Considering the potential drug interaction with tacrolimus, dasatinib was administered at a low dose of 50 mg/day. Her immune status was evaluated regularly by assessing the mixed lymphocyte reaction (MLR) using an intracellular carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeling technique; immunosuppressive therapy was adjusted accordingly.

RESULTS

The patient achieved complete hematologic remission (CHR) after 1 month of dasatinib treatment. Six months after dasatinib treatment, she achieved a major molecular response. During the observation period, neither antibody-mediated nor acute cellular rejection were encountered in the patient. She remained in CHR with a major molecular response 12 months after the diagnosis of CML-CP.

CONCLUSION

Data obtained from immune monitoring assays using CFSE-MLR helped us to successfully manage a KT recipient with CML-CP being treated with dasatinib. Drug-drug interactions are a key consideration while designing treatment regimens; such strategies would ensure that drug-drug interactions do not negatively affect the treatment outcomes.

Neferine in the Lotus Plumule Potentiates the Antitumor Effect of Imatinib in Primary Chronic Myeloid Leukemia Cells In Vitro

Imatinib, the prototype BCR-ABL tyrosine kinase inhibitor (TKI), is the first-line treatment for Philadelphia chromosome-positive chronic myeloid leukemia (CML) in the chronic phase. However, a subgroup of patients exhibit poor response or experience relapse. This issue may be overcome by combination therapy using natural compounds. Neferine, a major bisbenzylisoquinoline alkaloid extracted from "lotus plumule" (seed embryo of lotus) commonly used in traditional Chinese medicine and tea, was used herein in the combination treatment of CML. The MTT assay showed that neferine exerted cytotoxicity in primary CML cells in a dose-dependent manner. Moreover, low concentrations of neferine (4 and 8 µM) sensitized primary CML cells to imatinib (CI < 1), and significantly decreased its IC₅₀ from 0.70 ± 0.10 to 0.32 ± 0.06 µM and 0.16 ± 0.02 µM, respectively. Cotreatment of neferine and imatinib significantly decreased the expression of BCR-ABL protein and its molecular chaperone heat shock protein 90 (Hsp90) mRNA and protein levels, and further decreased phospho-extracellular regulated protein kinase 1/2 (p-Erk1/2) and myeloid cell leukemia (Mcl-1) expression. These results suggest that neferine might be a potential imatinib sensitizer in CML treatment. PRACTICAL APPLICATION: In China, Lotus plumule, the green embryo of lotus, is used as a tea and as a source of herbal medicine in the treatment of anxiety, insomnia, spermatorrhea, and thirst. Additional, neferine, a bisbenzylisoquinoline alkaloid extracted from lotus plumule has been shown to have antitumor potential. Herein, the effect of neferine and imatinib cotreatment on primary CML cells obtained from CML patients was assessed, with a synergistic effect being observed between the two compounds. Therefore, neferine might be a promising natural compound to potentiate imatinib in CML patients.

MYB is a novel regulator of pancreatic tumour growth and metastasis

BACKGROUND

MYB encodes for a transcription factor regulating the expression of a wide array of genes involved in cellular functions. It is reported to be amplified in a sub-set of pancreatic cancer (PC) cases; however, its pathobiological association has remained unclear thus far.

METHODS

Expression of MYB and other cellular proteins was analysed by immunoblot or qRT-PCR analyses. MYB was stably overexpressed in non-expressing (BxPC3) and silenced in highly expressing (MiaPaCa and Panc1) PC cells. Effect on growth was analysed by automated cell counting at 24-h interval. Cell-cycle progression and apoptotic indices of PC cells with altered MYB expression were measured through flow cytometry upon staining with respective biomarkers. Cell motility/invasion was examined in a Boyden's chamber assay using non-coated or Matrigel-coated membranes. Effect on tumorigenicity and metastatic potential was examined by non-invasive imaging and through end-point measurements of luciferase-tagged MYB-altered PC implanted in the pancreas of nude mice.

RESULTS

MYB was aberrantly expressed in all malignant cases of pancreas, whereas remained undetectable in normal pancreas. All the tested established PC cell lines except BxPC3 also exhibited MYB expression. Forced expression of MYB in BxPC3 cells promoted their growth, cell-cycle progression, survival and malignant behaviour, whereas its silencing in MiaPaCa and Panc1 cells produced converse effects. More importantly, ectopic MYB expression was sufficient to confer tumorigenic and metastatic capabilities to non-tumorigenic BxPC3 cells, while its silencing resulted in significant loss of the same in MYB-overexpressing cells as demonstrated in orthotopic mouse model. We also identified several MYB-regulated genes in PC cells that might potentially mediate its effect on tumour growth and metastasis.

CONCLUSIONS

MYB is aberrantly overexpressed in PC cells and acts as a key determinant of pancreatic tumour growth and metastasis.

Multipotent adult progenitor cell-loaded demineralized bone matrix for bone tissue engineering

Multipotent adult progenitor cells (MAPCs) from bone marrow have been shown to be capable of forming bone, cartilage and other connective tissues. In addition, MAPCs differentiate into lineages that are different from their germ layers of origin. Previous studies showed the ability of MAPCs to improve cardiac function and control allogenic-reactive responses associated with acute graft versus host disease. In the current study, we evaluated the ability of MAPCs to produce bone matrix on demineralized bone allograft substrates. Specifically, MAPCs expressed alkaline phosphatase, produced extracellular matrix proteins and deposited calcium-containing mineral on demineralized bone matrices. Furthermore, the addition of MAPCs on demineralized bone matrix (DBM) scaffolds enhanced osteoinductivity of the carrier in a rat ectopic pouch model. These results demonstrated the potential of MAPCs as a new approach for bone repair in tissue-engineering applications.

Growth arrest of BCR-ABL positive cells with a sequence-specific polyamide-chlorambucil conjugate

Chronic myeloid leukemia (CML) is characterized by the presence of a constitutively active Abl kinase, which is the product of a chimeric BCR-ABL gene, caused by the genetic translocation known as the Philadelphia chromosome. Imatinib, a selective inhibitor of the Bcr-Abl tyrosine kinase, has significantly improved the clinical outcome of patients with CML. However, subsets of patients lose their response to treatment through the emergence of imatinib-resistant cells, and imatinib treatment is less durable for patients with late stage CML. Although alternative Bcr-Abl tyrosine kinase inhibitors have been developed to overcome drug resistance, a cocktail therapy of different kinase inhibitors and additional chemotherapeutics may be needed for complete remission of CML in some cases. Chlorambucil has been used for treatment of B cell chronic lymphocytic leukemia, non-Hodgkin's and Hodgkin's disease. Here we report that a DNA sequence-specific pyrrole-imidazole polyamide-chlorambucil conjugate, 1R-Chl, causes growth arrest of cells harboring both unmutated BCR-ABL and three imatinib resistant strains. 1R-Chl also displays selective toxicities against activated lymphocytes and a high dose tolerance in a murine model.

Small molecules targeting histone H4 as potential therapeutics for chronic myelogenous leukemia

We recently identified a polyamide-chlorambucil conjugate, 1R-Chl, which alkylates and down-regulates transcription of the human histone H4c gene and inhibits the growth of several cancer cell lines in vitro and in a murine SW620 xenograft model, without apparent animal toxicity. In this study, we analyzed the effects of 1R-Chl in the chronic myelogenous leukemia cell line K562 and identified another polyamide conjugate, 6R-Chl, which targets H4 genes and elicits a similar cellular response. Other polyamide conjugates that do not target the H4 gene do not elicit this response. In a murine model, both 1R-Chl and 6R-Chl were found to be highly effective in blocking K562 xenograft growth with high-dose tolerance. Unlike conventional and distamycin-based alkylators, little or no cytotoxicities and animal toxicities were observed in mg/kg dosage ranges. These results suggest that these polyamide alkylators may be a viable treatment alternative for chronic myelogenous leukemia.

Development of adult pluripotent stem cell therapies for ischemic injury and disease

Over the past 5 years, adult pluripotent stem cell lines have been isolated from multiple organs and tissues in laboratories worldwide. Adult pluripotent stem cells are capable of regenerating tissues of all three primitive germ layers and express pluripotency markers, such as Oct4 or telomerase, which are associated with the primitive stem cell properties of embryonic stem cells. As our collective understanding of the biology of these unique cells has improved, so has our ability to isolate, expand and subsequently evaluate them as therapeutics in preclinical models of acute injury and disease. Pluripotent adult stem cells, as opposed to tissue-restricted adult stem cells, such as mesenchymal stromal cells; have extensive replicative capacity enabling large-scale clinical expansion. This is essential to achieving consistent clinical response data and enabling the cost-effective production necessary for commercial adoption. In addition, investigators have reported effective use of allogeneic adult pluripotent stem cells in acute ischemic injury models in the heart and brain, supporting the 'off the shelf' product concept for this cellular therapy. In this article, the authors review preclinical animal data demonstrating the benefit of pluripotent adult progenitor cells in the treatment of ischemic injuries of the heart, vascular system and CNS.

Trichosanthin down-regulated p210Bcr-Abl and enhanced imatinib-induced growth arrest in chronic myelogenous leukemia cell line K562

PURPOSE

Trichosanthin (TCS), an active component extracted from the root tubers of traditional Chinese medical herb Tian-Hua-Fen of the Cucurbitaceae family, has long been used for medical purpose in China; there is increasing interest in developing TCS as cancer therapeutic agents. The present study was to investigate the growth arrest of K562 cells and its molecular mechanisms, which the drugs induced by TCS and the possible functional interaction of TCS with imatinib (STI571) to K562 cells.

METHODS

Trypan blue exclusive staining was used to access the cell growth inhibition; western blot was used to evaluate the p210(Bcr-Abl), phosphorylated tyrosine kinase (PTK), and some signaling molecules involving in cell proliferation and apoptosis in K562 cells.

RESULTS

TCS and imatinib inhibited K562 cells at a time- and dose-dependent manners, respectively; TCS down-regulated p210(Bcr-Abl) at a time- and dose-dependent manners; TCS synergistically enhanced imatinib-induced K562 cell growth arrest and down-regulation of p210(Bcr-Abl), PTK activities, procaspase-3, Hsp90,NF-kappaB and PKC.

CONCLUSION

The results suggest that TCS not only by itself involves but also synergizes activities of imatinib to induce K562 cell growth arrest, down-regulation of p210(Bcr-Abl) and its downstream signals and to stimulate the effect of the tyrosine kinase inhibition.

Treatment of chronic myeloid leukemia in the imatinib era

BACKGROUND

There is paucity of data from developing countries on the efficacy and safety of imatinib mesylate in chronic myeloid leukemia (CML). The primary objective of this study was to document complete and partial cytogenetic responses to imatinib in all phases of CML. Secondary objectives included evaluations of complete hematologic response, safety, time to progression, and survival.

METHODS

Two hundred seventy-five patients in all phases of CML who received treatment with imatinib from January 2001 to December 2005 were included in the study. All patients had on bone marrow or BCR-ABL positive in peripheral blood by polymerase chain reaction.

RESULTS

After a median follow-up of 18 months, major cytogenetic responses (Ph <35%) in chronic phase (CP), accelerated phase (AP), and blastic phase (BP) were documented in 61%, 57%, and 28% of patients, respectively. A complete cytogenetic response was observed in 39.4%, 35.7%, and 14.3% of patients in CP, AP, and BP, respectively; and a complete hematologic response was observed in 90%, 86%, and 30%, respectively. The median time to progression at 18 months was 91% in CP and 68% in AP. The overall survivals in CP, AP, and BP at 18 months was 92%, 74%, and 38%, respectively.

CONCLUSIONS

Impressive hematologic, cytogenetic, and molecular responses to imatinib were observed, similar to the responses reported in patients from Western countries. Patients had good compliance, toxicity was limited, and overall quality of life was improved markedly. The results indicated that the biology of CML is not different in patients from developing countries.

Curcumin synergistically augments bcr/abl phosphorothioate antisense oligonucleotides to inhibit growth of chronic myelogenous leukemia cells

AIM

To investigate the growth inhibition effect of the combination of bcr/abl phosphorothioate antisense oligonucleotides (PS-ASODN) and curcumin (cur), and the possible mechanisms of cur on the chronic myelogenous leukemia cell line K562.

METHODS

The K562 cell line was used as a P210( bcr/abl )-positive cell model in vitro and was exposed to different concentrations of PS-ASODN (0-20 micromol/L), cur (0-20 micromol/L), or a combination of both. Growth inhibition and apoptosis of K562 cells were assessed by MTT assay and AO/EB fluorescent staining, respectively. The expression levels of P210( bcr/abl ), NF-kappaB and heat shock protein 90 (Hsp90) were assessed by Western blot.

RESULTS

Exposure to cur (5-20 micromol/L) and PSASODN (5-20 micromol/L) resulted in a synergistic inhibitory effect on cell growth. Growth inhibition was associated with the inhibition of the proliferation and induction of apoptosis. Western blot analysis showed that the drugs synergistically downregulated the level of P210( bcr/abl ) and NF-kappaB. Cur downregulated Hsp90, whereas no synergism was observed when cur was combined with PS-ASODN.

CONCLUSION

PS-ASODN and cur exhibited a synergistic inhibitory effect on the cell growth of K562. The synergistic growth inhibition was mediated through different mechanisms that involved the inhibition of P210( bcr/abl ).

Chronic Myelogenous Leukemia: From Molecular Biology to Clinical Aspects and Novel Targeted Therapies

The critical causative event in chronic myelogenous leukemia (CML) is the fusion of the head of the bcr gene with the body of the abl gene, named bcr/abl gene. This chimeric BCR/ABL molecule transforms primary myeloid cells to leukemic cells and induces a CML-like disease in mice. The mouse CML model expressing the BCR/ABL molecule has provided important new insights into the molecular pathophysiology of CML and has directly answered many questions regarding this disease. Furthermore, numerous clinical studies have demonstrated a correlation between leukemic clinical features and the position of the breakpoint in the BCR gene of the chimeric BCR/ABL gene. Understanding of the molecular pathogenesis of CML has led to the development of several novel therapies. The BCR/ABL molecule is unique oncogeneiety, having ABL tyrosine kinase activity, making it an ideal target for drug development. Subsequent clinical studies now realize the hypothesis that selective inhibition of the abl tyrosine kinase activity using imatinib mesylate might be useful for the treatment of CML. This article reviews the history of BCR/ABL molecular biology, including the CML model mouse, clinical molecular studies and the recent findings of imatinib mesylate and more potent tyrosine kinase inhibitors developed for the treatment of CML.

Oncogenes as novel targets for cancer therapy (part III): transcription factors

This is the third paper in a four-part serial review on potential therapeutic targeting of oncogenes. The previous parts described the involvement of oncogenes in different aspects of cancer growth and development, and considered the new technologies responsible for the advancement of oncogene identification, target validation, and drug design. Because of such advances, new specific and more efficient therapeutic agents can be developed for cancer. This part of the review continues the exploration of various oncogenes that we have grouped within seven categories: growth factors, tyrosine kinases, intermediate signaling molecules, transcription factors, cell cycle regulators, DNA damage repair genes, and genes involved in apoptosis. Part one discussed growth factors and tyrosine kinases and part two discussed intermediate signaling molecules. This portion of the review covers transcription factors and the various strategies being used to inhibit their expression or decrease their activities.

SKI pathways inducing progression of human melanoma

The proteins SKI and SnoN are implicated in processes as diverse as differentiation, transformation and tumor progression. Until recently, SKI was solely viewed as a nuclear protein with a principal function of inhibiting TGF-beta signaling through its association with the Smad proteins. However, new studies suggest that SKI plays additional roles not only inside but also outside the nucleus. In normal melanocytes and primary non-invasive melanomas, SKI localizes predominantly in the nucleus, whereas in primary invasive melanomas SKI displays both nuclear and cytoplasmic localization. Intriguingly, metastatic melanoma tumors display nuclear and cytoplasmic or predominantly cytoplasmic SKI distribution. Cytoplasmic SKI is functional, as it associates with Smad3 and prevents its nuclear localization mediated by TGF-beta. SKI can also function as a transcriptional activator, targeting the beta -catenin pathway and activating MITF and NrCAM, two proteins involved in survival, migration and invasion. Intriguingly, SKI appears to live a dual life, one as a tumor suppressor and another as a transforming protein. Loss of one copy of mouse ski increases susceptibility to tumorigenesis in mice, whereas its overexpression is associated with cancer progression of human melanoma, esophageal, breast and colon. The molecular reasons for such dramatic change in SKI function appear to result from new acquired activities. In this review, we discuss the mechanisms by which SKI regulates crucial pathways involved in the progression of human malignant melanoma.

Peripheral blood progenitor cell collection in chronic myeloid leukemia patients with complete cytogenetic response after treatment with imatinib mesylate

BACKGROUND

Imatinib mesylate (IM) was introduced in chronic myeloid leukemia (CML) treatment in the late 1990s and substantially changed the therapeutic approach to the disease, by inducing complete cytogenetic response (CCR) in approximately 60 percent of cases. Nevertheless, some concerns exist about the duration of response to treatment and the onset of resistance to IM.

STUDY DESIGN AND METHODS

Twenty-five chronic-phase CML patients in stable CCR (>6 months) treated for at least 1 year with IM at the standard dose (400 mg/day) were mobilized with recombinant human granulocyte-colony-stimulating factor (Filgrastim) at 10 microg per kg for 4 to 6 days, with the aim of collecting at least 2 x 10(6) CD34+ cells per kg. Standard cytogenetic analysis and first-round and/or nested polymerase chain reaction were performed in basal and postmobilization samples to examine the presence of bcr-abl transcripts.

RESULTS

CD34+ cells collection was successful in 16 patients, yielding a median of 3.01 x 10(6) +/- 1.09 x 10(6) CD34+ cells per kg at the first attempt, and in 4 of the 9 remaining patients who were remobilized after a temporary withdrawal of IM, yielding a median of 2.65 x 10(6) +/- 0.7 x 10(6) CD34+ cells per kg, with an overall 80 percent success rate. No correlation between mobilization and duration of the disease, length of IM treatment, or previous interferon-alpha and/or hydroxyurea treatment was found.

CONCLUSIONS

Autologous CD34+ cells may be mobilized and collected in most CML patients who achieve CCR after IM treatment, with a view to possible use in the event that resistance to IM occurs in patients not eligible for allogeneic peripheral blood progenitor cell transplantation or those lacking an HLA-matched donor.

The in vitro effects of CRE-decoy oligonucleotides in combination with conventional chemotherapy in colorectal cancer cell lines

The cAMP response element consensus sequence directs the transcription of a wide range of genes. A 24-mer single-stranded cAMP response element decoy oligonucleotide (CDO) has been shown to compete with these sequences for binding transcription factors and therefore interferes with cAMP-induced gene transcription. We have examined the effect of this CDO alone and in combination with a range of common chemotherapeutic agents in colorectal cancer cell lines. CDO had a potent anti-proliferative effect in colorectal cell lines, yet, a similar enhancement of cell death was not observed. Simple drug-drug interaction studies showed that combining CDO with chemotherapy resulted in an enhancement of the antiproliferative effects. Furthermore, this cytostatic effect was protracted and associated with an increase in senescence-associated beta-galactosidase activity at pH 6. There is a possible role for p21(waf1) in mediating this effect, as the enhancement of cell growth inhibition was not observed in cells lacking the ability to correctly upregulate this protein. Additionally, significant decreases in cyclin-dependent kinase (CDK) 1 and CDK 4 function were seen in the responsive cells. These data provide a possible model of drug interaction in colorectal cell lines, which involves the complex interplay of the molecules regulating the cell cycle. Clinically, the cytostatic ability of CDO could improve and enhance the antiproliferative effects of conventional cytotoxic agents.

Chronic myeloid leukemia—still a few questions

The study of chronic myeloid leukemia has yielded many insights, especially after the discovery of the Ph chromosome, into the pathogenesis of leukemia and other forms of malignant disease. Most recently, knowledge of the central function of the BCR-ABL fusion gene led to the development of a small molecule, imatinib, that has proved remarkably effective at reducing the number of leukemia cells in individual CML patients and promises to prolong life substantially in comparison with earlier treatments. However, many questions relating to this exciting new agent remain unanswered, for example, how exactly it works, how patients develop resistance and what can be done to prevent or delay its onset, and whether any patient can really be "cured" by its use.

ICSBP/IRF-8 inhibits mitogenic activity of p210 Bcr/Abl in differentiating myeloid progenitor cells

Interferon consensus sequence binding protein/interferon regulatory factor 8 (ICSBP/IRF-8) is a transcription factor that controls myeloid cell development. ICSBP-/- mice develop a chronic myelogenous leukemia (CML)-like syndrome. Several observations on patients and mouse models have implicated ICSBP in the pathogenesis of CML. In this paper, we investigated whether ICSBP modulates the growth-promoting activity of Bcr/Abl, the causal oncoprotein for CML. When transformed with p210 Bcr/Abl, ICSBP-/- myeloid progenitor cells lost growth factor dependence and grew in the absence of granulocyte-macrophage colony-stimulating factor. When ICSBP was ectopically expressed, Bcr/Abl-transformed cells underwent complete growth arrest and differentiated into mature, functional macrophages without inhibiting the kinase activity of Bcr/Abl. Providing a mechanistic basis for the growth arrest, ICSBP markedly repressed c-Myc messenger RNA (mRNA)-expression, a downstream target of Bcr/Abl. A further analysis with the ICSBP/estrogen receptor chimera showed that ICSBP repression of c-Myc is indirect and is mediated by another gene(s). We identified Blimp-1 and METS/PE1, potent c-Myc repressors, as direct targets of ICSBP activated in these cells. Consistent with this, ectopic Blimp-1 repressed c-Myc expression and inhibited cell growth. These results indicate that ICSBP inhibits growth of Bcr/Abl-transformed myeloid progenitor cells by activating several genes that interfere with the c-Myc pathway.

Identification of novel inhibitors of BCR-ABL tyrosine kinase via virtual screening

Inhibition of BCR-ABL tyrosine kinase activity has shown to be essential for the treatment of chronic myelogenous leukemia (CML). However, drug resistance has quickly arisen in recent clinical trials for STI571 (Gleevec), which is the first approved drug of CML by inhibiting ABL tyrosine kinase. It is desirable to develop new types of ABL tyrosine kinase inhibitors that may overcome this drug resistance problem. Here we present the discovery of novel inhibitors targeted at the catalytic domain of ABL tyrosine kinase by using three-dimensional database searching techniques. From a database containing 200,000 commercially available compounds, the top 1000 compounds with the best DOCK energy score were selected and subjected to structural diversity and drug likeness analysis, 15 compounds were submitted for biological assay. Eight out of the 15 showed inhibitory activity against K562 cells with IC(50) value ranging from 10 to 200 microM. Two promising compounds showed inhibition in further ABL tyrosine phosphorylation assay. It is anticipated that those two compounds can serve as lead compounds for further drug design and optimization.

Multiplex RT-PCR for the detection of common BCR-ABL fusion transcripts in paraffin-embedded tissues from patients with chronic myeloid leukemia and acute lymphoblastic leukemia

Diagnosis of chronic myeloid leukemia and acute lymphoblastic leukemia requires the investigation of the Philadelphia chromosome translocation t(9;22) or the molecular detection of BCR-ABL fusion transcripts. Determination of the type of fusion transcript is crucial for quantitative molecular monitoring the course of the disease during treatment. Histopathologists, who usually use formalin-fixed tissues, may be confronted with the need to investigate the BCR-ABL rearrangement when evaluating tumor forming infiltrates and bone marrow trephines from patients presenting with chronic myeloproliferative disorders. Therefore, we have established a one-tube multiplex RT-PCR for the detection of common BCR-ABL fusion transcripts (b2a2, b3a2, e1a2) in routinely processed tissues and bone marrow trephines with respect to the inevitable fragmentation of ribonucleic acids in these specimens. RT-PCR products allow distinct and unequivocal differentiation of the underlying fusion in either the Major- or minor-breakpoint cluster region. Detection of BCR-ABL fusion transcripts by multiplex RT-PCR in routinely processed and fixed tissues is a time- and cost-sparing tool for definite diagnosis of typical chronic myeloid leukemia and Philadelphia chromosome positive acute lymphoblastic leukemia.

Ex vivo purging with NK-92 prior to autografting for chronic myelogenous leukemia

Although controversial, purging of the autograft may be necessary to optimize transplant outcome, especially if better treatments become available to eliminate or control residual disease that may be left after the conditioning regimen. The intent of this study was to show that immunological purging with the cytotoxic cell line NK-92 effectively reduces the number of clonogenic cells and that the method can be performed in compliance with GMP. Owing to the easy quantification of bcr-abl transcripts, chronic myelogenous leukemia (CML) was used as a model disease for proof of principle. A detection level of 10(-7) bcr-abl+ cells and purging efficiency of four logs were achievable for the bcr-abl+ cell line, K562. Leukapheresis products collected from CML patients after stem cell mobilization were then tested. For all patients tested, residual CML cells were highly sensitive to purging by NK-92 with a purging efficacy of several logs. No adverse effect on hematopoietic progenitor cell function was noted. These results demonstrate the efficacy of NK-92 as a purging agent to decrease or eliminate malignant contamination of autologous stem cell grafts and establish proof of principle for ex vivo purging of CML autografts using cytotoxic effector cells.

Quantitative intra-individual monitoring of BCR-ABL transcript levels in archival bone marrow trephines of patients with chronic myeloid leukemia

We established a quantitative real-time RT-PCR assay for the detection of chimeric BCR-ABL transcripts in archival formalin-fixed bone marrow trephines, both acrylate-embedded and paraffin-embedded. This new methodology enables determination of transcript levels in direct comparison to histopathological findings and therapeutic interventions during the time course of the disease in a retrospective and a prospective manner. We found an excellent correlation between the quantitative molecular data and the morphological evaluation as well as the clinical outcome for a cohort of chronic myeloid leukemia patients (n = 10). To the best of our knowledge, this is the first study demonstrating the feasibility of large-scale quantitative expression analysis in archival bone marrow trephines for monitoring molecular markers over several years or even decades.

Mechanisms of resistance to imatinib mesylate in Bcr-Abl-positive leukemias

The constitutive activity of the Bcr-Abl tyrosine kinase plays a critical role in the molecular pathogenesis of not only the chronic but also the accelerated and blastic phases of chronic myelogenous leukemia. Therefore, Bcr-Abl tyrosine kinase is a rational therapeutic target in all phases of chronic myelogenous leukemia. Although imatinib mesylate (STI571, Gleevec, Novartis, Basal, Switzerland) produces high rates of complete clinical and cytogenetic responses in the chronic phase, resistance is universal and clinical relapse develops rapidly in the advanced phases of chronic myelogenous leukemia. This resistance has been shown to be caused by specific ATP binding site mutations or amplification of Bcr-Abl gene, resulting in a Bcr-Abl tyrosine kinase that is resistant to further inhibition by imatinib. Alternative (Bcr-Abl-independent) mechanisms driving the growth and survival of the malignant clone may also be responsible for imatinib resistance. Novel tyrosine kinase inhibitors that also target Bcr-Abl tyrosine kinase, or agents that downregulate Bcr-Abl levels regardless of its wild-type or mutant status, may need to be developed clinically for the future therapy of imatinib-resistant chronic myelogenous leukemia.

Bcr-Abl variants: biological and clinical aspects

Bcr-Abl is an oncogene that arises from fusion of the Bcr gene with the c-Abl proto-oncogene. Three different Bcr-Abl variants can be formed, depending on the amount of Bcr gene included: p185, p210, and p230. The three variants are associated with distinct types of human leukemias. Examination of the signaling pathways differentially regulated by the Bcr-Abl proteins will help us gain better insight into Bcr-Abl mediated leukemogenesis.

Insights from pre-clinical studies for new combination treatment regimens with the Bcr-Abl kinase inhibitor imatinib mesylate (Gleevec/Glivec) in chronic myelogenous leukemia: a translational perspective

Clinical phase I/II studies with the Abl kinase inhibitor imatinib mesylate (Gleevec/Glivec, formerly STI571) for the treatment for chronic myelogenous leukemia (CML) demonstrated the safety and the remarkable efficacy of this molecularly targeted agent. However, a significant proportion of patients treated in the chronic phase of the disease after having failed interferon alpha (IFN) remain predominantly Philadelphia chromosome positive (Ph(+)), suggesting a risk of later relapses. Furthermore, results in blast crisis patients revealed a high frequency of relapses or resistance to imatinib. To circumvent resistance, improve response rates, or prolong survival, pre-clinical evaluations of combinations of imatinib with other agents have been pursued. Some of these have already been translated into clinical studies. Here, we first summarize evidence from pre-clinical studies on new combination regimens with imatinib in the treatment of CML. Second, we analyze preliminary clinical data of ongoing combination studies. Finally, we provide a summary of approaches that use novel antileukemic agents with molecularly characterized modes of action.