Therapy For Chronic Myelogenous Leukemia Research Articles

In vitro effect of adenovirus‐mediated human Gamma Interferon gene transfer into human mesenchymal stem cells for chronic myelogenous leukemia

For developing gene therapy for chronic myelogenous leukemia (CML), we evaluated the feasibility of using autologous bone marrow stromal cells (BMSCs) of one CML patient as a target cell population and studied the efficiency of recombinant adenovirus-mediated human Gamma Interferon (hIFN-gamma) gene transfer into BMSCs. BMSCs can be readily obtained, expanded, and successfully transduced with adenoviral vectors in vitro. We studied the in vitro expression of hIFN-gamma in human BMSCs following transduction with Ad/hIFN-gamma. On transduction of BMSCs at a MOI of 50, the expression and secretion of hIFN-gamma were achieved as high as 5492 +/- 660 approximately 50647 +/- 4049 ng/10(6) cells per 24 h over the course of 3 weeks. We further studied the effects of hIFN-gamma produced by transduced BMSCs on the proliferation of the human leukemia cell line K562 cells in vitro, proliferation of K562 cells was markedly inhibited in the experimental groups as compared with the other two control groups after 5 days of coculture. We also found that the percentage of K562 cells in the G(1) phase of cell cycle can be increased by treatment of hIFN-gamma produced by Ad/hIFN-gamma transduced BMSCs, but the percentage of K562 cells in the S phase of cell cycle can be decreased in the same time. Apoptosis rate of K562 cells in the experimental groups was 30.8 +/- 8.5%, as compared with the other two control groups (5.6 +/- 1.3% and 5.5 +/- 0.8%, respectively) (p < 0.01). Our results indicate that hIFN-gamma gene engineered BMSCs of CML donors could be successfully established and that local production of hIFN-gamma is sufficiently to inhibit the proliferation of K562 cells and induce apoptosis of K562 cells in vitro, suggesting an important potential use in the clinical gene therapy of CML.

Inhibition of Abl Kinases by Intramolecular and Intermolecular Interactions: A Lesson from Structure Studies and CML Therapy

BCR-ABL is a product of Philadelphia chromosome and is present in 95% of all cases of chronic myelogenous leukemia (CML) and 5-10% of acute lymphoblastic leukemia (ALL). The proto-oncogene, c-Abl, is essential for mouse development and postnatal survival. CML is believed to be caused by the abnormality of a single gene (BCR-ABL) and requires BCR-ABL expression for maintenance of the disease. Imatinib (Gleevec, STI571, or CP57148B), a synthetic inhibitor for Abl kinases, PDGF receptor and c-Kit, has been proven effective in the treatment of CML, especially in chronic phase patients. Yet imatinib is less efficacious in the treatment of blast crisis CML patients and some patients develop drug resistance. This has led to the search for additional inhibitors for combination therapy. The elucidation of the co-crystal structures of Abl with inhibitors and the identification of mutations in BCR-ABL that render imatinib resistance have shed light on the molecular mechanisms for Abl activation and inhibition. This knowledge will facilitate the design of alternative inhibitors for BCR-ABL. This review updates our understanding of the molecular mechanisms of Abl inhibition by intramolecular interactions between different domains, and by intermolecular interactions with proteins and small molecules. Structure-based drug design will expedite the development of new inhibitors that are effective on imatinib-resistant BCR-ABL and that can distinguish endogenous Abl from BCR-ABL.

Stem Cell Transplantation in Patients With Chronic Myelogenous Leukemia: When Should It Be Used?

Hematopoietic stem cell transplantation has been a cornerstone of therapy for chronic myelogenous leukemia (CML) for more than 15 years and is still a standard treatment option for patients with CML. The advent of imatinib mesylate, an inhibitor of the molecular defect driving CML, the BCR-ABL tyrosine kinase, has rewritten treatment algorithms for this disease and has shifted focus away from allografting. Despite advances in stem cell transplantation, such as broader availability with the use of modified conditioning regimens, use of allografting has diminished. Also, the nearly universal patient exposure to imatinib or other kinase inhibitors before transplantation may affect the biology of the disease that is currently being treated with an allograft and ultimately may affect outcomes. Exceedingly high rates of meaningful and stable response with longer follow-up continue to drive enthusiasm for imatinib use, and understanding of resistance mechanisms has driven rapid investigation of second-generation tyrosine kinase inhibitors to address imatinib failure and suboptimal response. In most patients, imatinib reduces CML to a minimal residual disease state in which options to further deepen remission, such as immunotherapy, are sought; monitoring techniques and interpretation of response advance in parallel to meet demands; and uncertainty remains as a new natural history of CML is defined in an era of kinase inhibitor therapy. This review summarizes the state of transplant and nontransplant therapy for CML and discusses the decision making for patients with an aim to optimize the use of our best therapies for CML in an era of uncertainty.

Secondary Leukemia after Imatinib Mesylate (IM) Therapy for Chronic Myelogenous Leukemia (CML).

Disease progression in CML is often marked by the acquisition of cytogenetic abnormalities beyond the Philadelphia chromosome (Ph), referred to as clonal evolution (CE). In contrast, some patients (pts) develop chromosomal abnormalities in Ph-negative cells while on various therapies for CML, including IM. These abnormalities are frequently transient and their clinical consequence is unclear. Although some reports have suggested these abnormalities might be associated with secondary myelodysplastic syndrome (MDS), the diagnosis has not been established using standard criteria, usually only with megaloblastoid changes and, rarely with increased blasts. We report 2 cases of pts treated with imatinib for CML who subsequently developed chromosomal abnormalities in Ph negative cells, one of whom later developed MDS (RAEB II) and the other acute myelogenous leukemia (AML), a clinical consequence as yet unreported in the literature.Patient #1: A 51-year-old woman presented to MDACC in January 2001 having been diagnosed with CML in October 1999. Her only treatment in the preceding 14 months had been hydroxyurea. She was begun on treatment with imatinib at a dose of 400 mg daily. With no evidence of a major cytogenetic response after six months, the dose was increased to 600mg daily. She developed pancytopenia, requiring the use of filgrastim (G-CSF), erythropoietin and frequent red cell and platelet transfusions. Bone marrow biopsy showed significant dysplasia with 4% blasts and no evidence of CML. Cytogenetic analysis showed 4/20 (20%) of Ph-negative cells with monosomy 7, and no cells with Ph. IM was held for 6 weeks with no improvement in pancytopenia. Repeat bone marrow biopsy showed 14% blasts and cytogenetic analysis continued to show the presence of 20% Ph-negative cells with monsomy 7. Fluorescence in situ hybridization (FISH) performed on the blasts showed only the presence of monosomy 7 with no Ph thus confirming the diagnosis of a secondary MDS (RAEB II).Patient 2: A 64-year-old man presented in January 2001 with CML. He was initially treated with hydroxyurea followed by interferon and cytarabine. Treatment related toxicities dictated a change to IM 400 mg daily. With no major cytogenetic response after 12 months, the dose was increased to 600 mg daily with filgrastim and erythropoietin to support suppressed cell counts. Twenty months later, a repeat bone marrow biopsy showed 12% blasts, suggesting a transformation to accelerated phase. Cytogenetics showed a dual population of cells, 2/10 (10%) Ph-positive with -Y and 3/20 (15%) with monosomy 7 and no Ph. Sixteen days later, after initiation of therapy with the experimental compound, AMN-107, the bone marrow showed 38% blasts. Repeat bone marrow biopsy 2 weeks later showed 62% blasts which by FISH showed monosomy 7 and no Ph confirming a secondary AML. To our knowledge these are the first cases of secondary high-risk MDS (RAEB II) and AML after imatinib mesylate therapy occurring in pts with chromosomal abnormalities in Ph-hegative metaphases. Interestingly, both patients had monsomy 7. This is a rare phenomenon as these represent 2 of 1186 pts (0.1%; 95CI 0.00, 0.01) treated with IM at our institution over more than 5 years. This underscores the need to monitor periodically with cytogenetic analysis pts. with CML treated with imatinib.

Comparative Analysis of Ablative and Reduced Intensity Conditioning Hematopoietic Stem Cell Transplantation in Treatment of Adult Patients with Chronic Myeloid Leukemia.

Allogeneic HSCT remains the only curative therapy for chronic myelogenous leukemia (CML) patients. We compared results of myeloablative (MAB) and reduced intensity conditioning (RIC) HSCT from sibling donor in 62 pts with CML, treated between 2000 and 2005. In MAB group, 44 pts (median age 39.5, range 17–54 yrs) were conditioned with BuCy2 regimen. Thirty four pts were in chronic, 7 in acceleration and 3 in 2nd chronic phase. 26 pts received PBSC and 18 were grafted with bone marrow HSC. Transplanted material contained 3.8 (1.24–14.6) x 106/kg CD34+ cells. Prophylaxis of graft versus host disease (GVHD) consisted of cyclosporin (CsA) and methotrexate. Eighteen pts (median age 48, range 37–56 yrs) were treated with fludarabine-based RIC regimen. This group comprised 13 pts in chronic and 5 with accelerated phase. Patients were grafted with PBSC only, containing 4.75 (2.25–10) x 106/kg CD34+. CsA alone was given as GVHD prophylaxis. RIC group differ from MAB group by 2 factors: higher age (p<0.001) and higher EBMT pre-transplant (Gratwohl) risk score (p=0.028).Results: Hematopoietic recovery occurred in all pts in MAB group, and in 94% in RIC group. Probability of overall survival for all pts was OS=0.57±0.09. 31 pts developed acute GVHD ≥2 grade (21 in MAB and 10 in RIC) and 25 pts extensive chronic GVHD (18 in MAB and 7 in RIC). Mean survival, estimated 5-yrs OS, probabilities of GVHD incidence, relapse and treatment related mortality (TRM), estimated by Kaplan-Meier method, with respect to transplantation method, are shown in Table.TABLE:COMPARISON OF RESULTS IN MAB-HSCT AND RIC-HSCTProbabilityMAB-HSCT (n=44)RIC-HSCT (n=18)PMean survival (years)4.1 (95%CI=3.5–4.6)2.1 (95%CI=1.1–3.0)Overall survival0.78±0.070.24±0.130.0010Relapse incidence0.21±0.080.30±0.150.4069Treatment related mortality0.14±0.050.61±0.180.0108Acute GVHD ≥ 20.51±0.080.64±0.120.9492Chronic extensive GVHD0.59±0.050.60±0.150.8344Factors predicting negative outcome by Cox univariate analysis for all pts, were: AGVHD≥2 grade (p=0.0001, HR=2.78 95%CI=1.49–5.26), extensive CGVHD (p=0.0253, HR=3.83, 95%CI=1.01–14.6), female donor (p=0.0551, HR=1.54, 95%CI=0.99–2.40), pre-transplant risk score >2 (p=0.0053, HR=1.89, 95%CI=1.22–2.94) and RIC (p=0.0027, HR=1.96, 95%CI=1.26–3.03). Factors predicting negative outcome by multivariate analysis were: AGVHD≥2 (p=0.0001, HR=3.03, 95%CI=1.56–5.39), extensive CGVHD (p=0.0370, HR=2.75, 95%CI=1.17–6.49), pre-transplant risk score >2 (p=0.0507, HR=1.59, 95%CI=0.99–2.53) and RIC (p=0.0342, HR=1.64, 95%CI=1.17–6.49). Age >45 yrs did not predict for OS. In matched-pair analysis, identified by pre-transplant risk score and age, RIC group had lower OS (0.24±0.13 vs 0.88±0.08 p=0.0010), higher TRM (0.61±0.18 vs 0.06±0.05, p=0.0064), with no difference in AGVHD, CGVHD and relapse incidence, when compared to MAB group. In summary, this experience with sibling donor allogeneic HSCT in CML, demonstrates a similar incidence of AGVHD≥2 and extensive CGVHD in RIC and MAB groups, and more importantly, results of RIC-HSCT in adult CML are not satisfactory, mainly because of high treatment related mortality.

Triphasic Exponential Decline of BCR-ABL Transcripts during Imatinib Therapy for Chronic Myelogenous Leukemia.

In Japan Adult Leukemia Study Group (JALSG) clinical trial, imatinib was used as initial therapy for 171 patients with chronic myelogenous leukemia. We measured levels of BCR-ABL transcripts in the blood of all patients in this trial before and 1, 2, 3, 6 and 12 months after the treatment. Levels of BCR-ABL transcripts were measured by a quantitative real-time polymerase-chain-reaction assay. Results were expressed copy number of BCR-ABL per 1 microgram of RNA. Median number of BCR-ABL transcript was 106,478 at diagnosis and 61328, 24213, 4981, 331 and 98 at 0, 1, 2, 3, 6, 12 months after the treatment, respectively. Three log reductions were obtained 0%, 35.5% and 50.9% of patients at 3, 6 and 12 months of the treatment. Half reduction time between 0 and 1 month (0M–1M) is 1.3 M. In the next month (1M–2M), it is 0.75M and those between 2–3 and 3–4.5 months are 0.44 and 0.51. Thereafter, reduction speed is down because half reduction time is 1.5 between 4.5 and 6 months. After 6 months half time is 4.1months. This reduction curve shows the. Exponential decline value per day are 1.8%, 3.1% and 5.2% during first, second and third month, respectively. Thereafter exponential decline value is decreasing as 4.4% (3M–4.5M), 1.5% (4.5M–6M) and 0.6% (6–12M). In the previous study reported that, successful therapy leads to a biphasic exponential decline of leukemic cells (Nature 435:1267–1270, 2005). The first slope is determined by calculating the exponential decline between 0 and 3 months; mean value of 0.05 per day was observed. While the second slope showed 0.008 per day. Our observation suggests that imatinib leads to a triphasic exponential decline of leukemic cells; between 0 and 2 months, much slower declining curve in comparison with between 2–6 months.

Hematologic Remission of Chronic Myelogenous Leukemia after Treatment with Imatinib Includes Normalization of the Red Cell Distribution Width.

After treatment with imatinib, the majority of patients with chronic myelogenous leukemia (CML) achieve hematologic remission. This includes normalization of blood counts (red cells, white cells, and platelets) normalization of the white cell differential, and disappearance of abnormal immature cells from the peripheral blood. However, abnormal erythropoiesis may be more subtle than abnormal red cell counts. We reviewed two other indices of erythropoiesis, the mean cell volume (MCV) and the red cell distribution width (RDW). We studied 15 patients with a diagnosis of CML confirmed by BCR-ABL, in whom the first-line therapy was imatinib. Treatment dosage varied from 400 – 800 mg/day. Pre-treatment, all patients had an elevated white cell count, 14 of 15 had a low hemoglobin, and 11 of 15 had an abnormal high platelet count. None had an abnormal MCV (mean, 91.3, range 82 – 97), and 13 of 15 had an abnormal RDW (mean 16.2, range 14.1 – 19.2). After treatment was started, all 15 achieved a normal white cell count, hemoglobin, and platelet count within 3 months. All continued to have a normal MCV, with no apparent change (mean 92.1, range 82 – 98). However, after treatment 14 of 15 developed a normal RDW (mean 13.7, range 12.0 – 15.2). The RDW progressively declined during the first 3 months after treatment and reached an asymptote at that time. We conclude that hematopoiesis normalizes qualitatively as well as quantitatively after successful imatinib therapy of CML. Future study will determine whether an isolated elevated RDW will predict relapse or briefer duration of remission.

Arsenic Trioxide Enhances STI571-Induced Apoptosis of K562 Cells through Downregulating Bcl-XL and Bcr-Abl.

We aimed to evaluate the effects of arsenic trioxide (ATO, Trisenox) on STI571 (Gleevec, imatinib mesylate)-induced apoptosis of a chronic myelogenous leukemia (CML) cell line, K562 cells. Cell prolifration and colony-forming assays were performed to determine the cytotoxicity of ATO alone and in combination with STI571. Apoptosis was analyzed by morphological changes, apoptosis rate and cell cycles. An Elisa assay was used to detect the levels of cytosolic cytochrome c (cyt c) and caspase-3 in K562 cells exposed to ATO and STI571 at graded concentrations. Semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) was used to assay the transcriptional levels of Bcl-XL and Bcr-Abl genes in K562 cells. Results showed that both the colony-forming assay and cell proliferation assay demonstrated additive to synergistic effects of ATO on STI571-induced apoptosis in K562 cells, a Bcr-Abl positive cell line. Caspase-3 was activated during apoptosis and there was an increase in cytosolic accumulation of cytochrome c. Treatment of K562 cells with STI571 alone led to down-regulation of transcriptional levels of Bcl-XL at 12 hours and Bcr-Abl at 96 hours after drug administration. Treatment with ATO alone only led to reduce the mRNA levels of Bcl-XL, but not Bcr-Abl. Combined treatment with ATO and STI571 down regulated the transcripts of Bcl-XL at 12 hours and Bcr-Abl 72 hours after drug administration. We conclude that ATO enhanced cytotoxic and proapoptotic actions of STI571 could be mediated by the down-regulation of Bcr-Abl and Bcl-XL genes in K562 cells. Therefore ATO in combination with STI571 could be a promising therapy for CML.

Anti-Leukemia Immune Responses in CML Patients Treated with Imatinib Mesylate.

Imatinib mesylate, a selective inhibitor of the bcr/abl tyrosine kinase, has revolutionized the treatment of patients with chronic myelogenous leukemia (CML). Most CML patients in chronic phase achieve hematologic remission with imatinib, while some achieve cytogenetic remission. As imatinib is an oral agent with few side effects, it has rapidly become the first-line therapy for most CML patients. However, this therapy does not represent a cure, as patients who discontinue the drug invariably relapse. Furthermore, imatinib resistance is beginning to emerge in some patients. Hence, the need to find alternate, potentially curative, therapies for CML remains. To date, the only curative treatment for CML is allogeneic bone marrow or stem cell transplantation (ABMT). A major mechanism of the curative potential of ABMT is immunological, as evidenced by the poor clinical outcome with T cell-depleted ABMT, and the efficacy of donor lymphocyte infusions (DLI) upon relapse. We hypothesized that an effective anti-leukemia immune response may emerge in patients entering remission on imatinib which may contribute to its clinical effectiveness. If so, strategies to further enhance this anti-leukemia immune response may lead to a potential cure. To determine if CML patients in remission on imatinib develop anti-leukemia immune responses, blood and bone marrow samples from patients before and after treatment were collected and analyzed. Pre-treatment samples were utilized as sources of autologous leukemic cells to detect anti-leukemia immune responses in post-treatment samples in IFN-g ELISPOT assays. Pre-treatment samples alone, post-treatment samples alone, and when available, serial post-treatment samples mixed together served as controls. In 9 of 14 patients investigated, IFN-g release was detected in pre- and post-treatment samples together with a median response of 22 spots above background (range 10 – 56 dots, p<0.01), whereas serial post-treatment samples together in 8 patients yielded results similar to background (median 5, range 5 – 20). In 6 of these patients in hematologic (or cytogenetic) remission, sufficient cells were available to allow additional analyses via intracellular staining for IFN-g, TNF-a, and IL-2 in autologous leukemia stimulated T cells (CD4 and CD8) and NK cells. In 4 of 6 patients, leukemia-reactive T cells were detected, most prominently in CD4+ T cells expressing TNF-a (1.4 – 37%), followed by IL-2 (0.3 – 12%) and IFN-g (0.1 – 4.6%). NK cells did not show significant expression of these cytokines upon stimulation with autologous leukemia cells. In pre-treatment and post-treatment samples alone, IL-2, TNF-a, and IFN-g expression was not detectable (0 – 0.5%). These results suggest that a significant portion of CML patients in remission with imatinib develop an anti-leukemia immune response, most notably in CD4+ T cells. Mechanisms by which imatinib treatment leads to anti-leukemia immune responses, and the molecular targets to which these cells are directed, will be further investigated. This knowledge will be useful in the development of immunotherapy strategies against CML as well as other leukemias, and raises the hope that immunotherapy may be combined with imatinib to eradicate residual leukemia cells for a durable cure of the disease.intracellular cytokine stainingCD4+ T CellsCD8+ T CellsIL-2IFN- γTNF- αIL-2IFN- γTNF- αpt 10.300.80.10.10.5pt 10.30.11.40.10.10.4pt 22.60.810.32.22.16.1pt 3212372.30.71.7pt 4124.6196.31.85.8

Resistance to Imatinib: Mechanisms and Management

Imatinib, a specific small molecule inhibitor of the Abl kinase, has become the standard drug therapy for chronic myelogenous leukemia in all phases. More than 80% of newly diagnosed patients with chronic phase attain a complete cytogenetic response (CCR). Although remissions in patients with early disease are generally durable, acquired resistance after an initial response is common in advanced disease. Reactivation of Bcr-Abl signaling is almost invariably present at the time of relapse, consistent with re-establishment of the initial pathogenetic mechanism. Mutations in the kinase domain (KD) of Bcr-Abl that impair drug binding and increased expression of Bcr-Abl have been identified as major mechanism of acquired drug resistance. The fact that Bcr-Abl remains central to disease pathogenesis at the time of relapse implies that it also remains the optimal drug target. Alternative Abl kinase inhibitors with increased potency and activity against most Bcr-Abl KD mutants are currently undergoing phase I/II clinical testing, with encouraging early results. Despite the high rates of CCR, persistence of residual leukemia as assessed by reverse transcription polymerase chain reaction is the rule even in patients with chronic phase, suggesting that even these patients may remain at risk of relapse. Understanding the mechanisms underlying disease persistence will be crucial for developing strategies to eradicate residual leukemia.

Sustained Complete Molecular Remissions After Treatment With Imatinib-Mesylate in Patients With Failure After Allogeneic Stem Cell Transplantation for Chronic Myelogenous Leukemia: Results of a Prospective Phase II Open-Label Multicenter Study

In the era of molecular therapy of chronic myelogenous leukemia (CML) applying BCR-ABL tyrosine kinase inhibitors, the usefulness of molecular end points, in particular, quantitative polymerase chain reaction (PCR) for BCR-ABL in monitoring responses has been broadly accepted. Therefore, we have designed a prospective phase II trial in CML, which, for the first time, evaluated the feasibility and safety of molecular end points as surrogate markers to guide through a stratified treatment algorithm within a multicenter trial. As a clinical model, we adopted minimal residual disease (MRD) found in relapse after allogeneic stem cell transplantation (SCT) in CML. Forty-four patients were enrolled and received the BCR-ABL tyrosine kinase inhibitor imatinib (IM) at a starting dose of 400 mg/d. The quality of molecular responses achieved then decided on discontinuation of IM or dose escalation up to 800 mg/d, and finally, on application of donor lymphocyte infusions. Results Seventy percent of patients achieved a complete molecular response (CMR), defined as nested PCR-negativity for BCR-ABL in three consecutive samples. Interestingly, in four out of 10 patients who discontinued IM, CMR was durable even after cessation of IM with a median follow-up of 494 days. This suggests the possibility of long-term tumor control in a subset of patients. The treatment strategy showed that IM treatment was well-tolerated and highly efficacious in MRD after allogeneic SCT. Moreover, this study demonstrated that evaluation of a molecular end point within a multicenter trial can be a safe and effective tool for clinical decision making.

Chronic Myelogenous Leukemia

Chronic myelogenous leukemia (CML) represents about 14% of all leukemias and occurs with a frequency of about 1 in 100,000. It is rare in children. Symptoms include fatigue, weight loss, sweating, and abdominal discomfort from an enlarged spleen. The white blood cell count can range from 100-600 ul. CML has three phases: the chronic phase, accelerated phase, and blast phase. Most patients are diagnosed during the chronic phase. Ionizing radiation has been implicated in some cases of CML, but in most individuals no cause is known. The Philadelphia chromosome, an acquired genetic mutation represented by a translocation of chromosome 22 and chromosome 9, drives the leukemic changes in CML. Imatinib mesylate, a tyrosine kinase inhibitor, was approved in 2002 for the treatment of all phases of CML. Because of its effectiveness, imatinib has become the treatment of choice for most patients with CML. Stem cell transplantation also is an option for eligible patients. It is the only curative treatment for CML. Two drugs under study for patients who cannot tolerate or who become resistant to imatinib are BMS-354825 and AMN107. Oncology nurses who are knowledgeable about new therapies for CML can be effective resources for their patients.

Loss of P-glycoprotein expression in hematopoietic stem cells does not improve responses to imatinib in a murine model of chronic myelogenous leukemia

Selective inhibition of the BCR/ABL tyrosine kinase by imatinib has become a first-line therapy for chronic myelogenous leukemia (CML). However, BCR/ABL-positive progenitors often persist despite treatment, and relapse associated with resistance to imatinib has been described in many patients with advanced disease. Drug efflux by P-glycoprotein (P-gp), as well as point mutations in BCR/ABL oncoprotein, has been implicated in the mechanism of resistance to imatinib. In this study, we established a murine transplantation model of CML-like myeloproliferative disease using Mdr1a/1b-null mice and analyzed the effects of loss of P-gp on resistance to imatinib. We found that mice transplanted with Mdr1a/1b-null bone marrow (BM) that had been transduced with a BCR/ABL retroviral vector displayed similar responses to imatinib, compared with those transplanted with BCR/ABL-transduced wild-type BM. In the absence of P-gp, the incidence and latency of disease in secondary recipients was not changed in imatinib-treated mice, relative to wild-type controls. Furthermore, K562 cells engineered to overexpress P-gp remained sensitive to imatinib-induced growth inhibition and cell death. Together, our findings suggest that P-gp expression in hematopoietic stem cells does not significantly contribute to imatinib resistance in CML.

Molecular Responses in Patients with Chronic Myelogenous Leukemia in Chronic Phase Treated with Imatinib Mesylate

To determine the clinical significance of molecular response and relapse among patients with chronic myelogenous leukemia (CML) treated with imatinib. We analyzed the results of quantitative PCR in 280 patients with CML in chronic phase who achieved complete cytogenetic remission with imatinib (117 after IFN-alpha failure and 163 previously untreated). Median follow-up was 31 months (range, 3-52 months). Median BCR-ABL/ABL ratio before the start of therapy was 39.44 (range, 0.252-170.53). A major molecular response (BCR-ABL/ABL ratio <0.05%) was achieved in 174 (62%), and transcripts became undetectable (complete molecular response) in 95 (34%). By multivariate analysis, only treatment with high-dose imatinib (P = 0.02) was associated with achievement of a major molecular response. Nine of 166 (5%) patients who achieved a major molecular response lost their cytogenetic remission, compared with 25 of 68 (37%) among those who did not achieve this response (P < 0.0001). Patients achieving a major molecular response 12 months after the start of therapy had significantly better complete cytogenetic remission duration than others. A >1-log reduction in transcript levels after 3 months of therapy predicted for an improved probability of achieving a major molecular response at 24 months. Increasing levels of BCR-ABL transcripts predicted for a loss of cytogenetic remission only among patients who did not achieve a major molecular response. Achieving a major molecular response, particularly within the first year of therapy, is predictive of a durable cytogenetic remission and may be the future goal of therapy in CML.

A variant t(8;10;21) in a patient with pathological features mimicking atypical chronic myeloid leukemia

We report the case of an 11-year-old girl who was initially diagnosed with a chronic myeloproliferative disorder, possibly chronic myelogenous leukemia (CML), based on laboratory and blood and marrow morphological findings. The patient's high leukocyte count did not respond to hydroxyurea, a standard initial therapy for CML. Chromosomal analysis revealed that the patient did not have t(9;22), but a complex t(8;10;21)(q22;q24;q22), a variant of t(8;21). The treatment regime was switched to an acute myeloid leukemia (AML) protocol; the patient responded well and is now in remission. This case demonstrates again that routine clinical cytogenetic analysis plays an important role in the clinical diagnosis, guidance of treatment, and prognostication in hematological disorders.

Absence of Gene Mutation in TRAIL Receptor 1 (TRAIL-R1) and TRAIL Receptor 2 (TRAIL-R2) in Chronic Myelogenous Leukemia and Myelodysplastic Syndrome, and Analysis of mRNA Expressions of TRAIL and TRAIL-Related Genes in Chronic Myelogenous Leukemia

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an interferon (IFN)-induced molecule with apoptotic activity. We examined gene mutations in the death domains of TRAIL receptor 1 (TRAIL-R1) and TRAIL receptor 2 (TRAIL-R2), and in the TRAIL gene promoter in 46 chronic myelogenous leukemia (CML) patients. In 23 of the 46 patients, all the coding regions of TRAIL-R2 were also examined. However, no mutation or loss of heterozygosity was found. Furthermore, no mutation in the death domains of TRAIL-R1 and TRAIL-R2 genes, which causes amino acid change, was found in 18 myelodysplastic syndrome (MDS) patients. Ribonuclease protection assay (RPA) and real-time quantitative polymerase chain reaction using polymorphonuclear neutrophils of five new CML patients showed that the TRAIL mRNA expression was very low before in vitro IFN-α stimulation and markedly upregulated after IFN-α stimulation. FAS mRNA was also upregulated with IFN-α stimulation but the fold induction was far lower than that of TRAIL mRNA. In addition, RPA revealed that the ratio of (TRAIL-R1 plus TRAIL-R2) to TRAIL-R3 was also increased after IFN-α stimulation. Taken together, gene mutations of TRAIL-R1, TRAIL-R2 are infrequent in patients with CML and MDS. Andso is the TRAIL promoter for CML. These mutations seem unrelated to tumorigenesis, disease progression, and response to IFN-α therapy in CML. A markedly high induction of TRAIL mRNA by IFN-α may have some relevance to IFN-α action in CML patients.

Immune therapy of chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a prototype for immune therapy of cancer in humans. CML cells express one or more cancer-specific antigens: peptide sequences spanning the BCR-ABL-related gene product. Substantial data in humans receiving blood cell and bone marrow transplants indicate a strong immune- mediated anti-leukemia effect. Because this effect occurs in an allogeneic setting it is uncertain whether this anti-leukemia effect will operate in other clinical settings. Additional data supporting a role for immune therapy of CML come from clinical trials of interferon and donor lymphocyte infusions. Here, we critically review data in two major areas of vaccine development: (1) peptides like BCR-ABL, Pr-3, and WT-1; and (2) autologous vaccines like dendritic cells and heat shock protein- peptide complexes. We also consider other related approaches. The data we review indicate encouraging results from preliminary uncontrolled clinical trials with some of these approaches. However, a definitive conclusion awaits results of randomized studies.

Imatinib mesylate (Gleevec, STI-571) suppresses cytokine production by normal T-cells activated through T-cell receptor (TCR) signaling

RATIONALE: Imatinib mesylate (IM) is a tyrosine kinase inhibitor that inhibits the BCR-ABL oncogene and is an effective therapy for BCR-ABL (+) leukemias. IM is the first successful targeted therapy for chronic myelogenous leukemia (CML). Recent reports demonstrated that IM inhibited proliferation of normal T cells, but its effect on cytokine synthesis by T cells is not known.

Interferon a and T-cell responses in chronic myeloid leukemia

Chronic myelogenous leukemia (CML) was the first human malignancy where a consistent chromosomal abnormality, the BCR-ABL translocation, was identified as the causative genetic aberration. There is a mounting body of evidence suggesting that CML cells are particularly good targets for immunological surveillance mechanisms, the most intriguing being the curative effect of allogeneic donor lymphocyte infusion given in relapsed disease after allogeneic bone marrow transplantation. Likewise, interferon α (IFN α), which has long been considered as the standard conservative therapy in CML, may exert its life-prolonging effect by activating immunological effector functions. This review will focus on the recent advances in the understanding of the contribution of IFN α in eliciting T-cell responses against self-antigens in CML.

Psoriasis vulgaris exacerbated by imatinib therapy in chronic myelogenous leukemia

Psoriasis vulgaris exacerbated by imatinib therapy in chronic myelogenous leukemia