Current role of stem cell transplantation in chronic myeloid leukaemia

Outcomes after allogeneic haematopoietic stem cell transplantation in young adults in Germany

Young adults (YA) represent a minority among recipients of allogeneic haematopoietic stem cell transplantation (HSCT). In order to describe the outcome of YA following HSCT in Germany, 9299 patients who were registered with the German Registry for Stem Cell Transplantation were included in this retrospective analysis of the years 1998-2019. The impact of the variables, such as patient age and sex, sex differences, stem cell source, donor type, conditioning, year of HSCT, the diagnosis, and the achieved remission status were tested in univariable and multivariable analysis for overall, event-free and relapse-free survival as well as for the cumulative incidences of non-relapse and therapy-related mortality. Altogether, the outcome of YA after HSCT improved over time and was determined by the underlying disease, the age at disease onset, stem cell source, and donor type. Patients were most likely to die from relapse, and survival of HSCT recipients after 10 years was reduced by more than half in comparison to the general population of YA. Deeper understanding of modifiable risk factors may be gained by studies comparing the outcome of YA post-HSCT with that of children, adolescents and elderly patients. A deliberate and strong patient selection may further improve mortality rates.

Endogenous Opioids and Their Role in Stem Cell Biology and Tissue Rescue

Opioids are considered the oldest drugs known by humans and have been used for sedation and pain relief for several centuries. Nowadays, endogenous opioid peptides are divided into four families: enkephalins, dynorphins, endorphins, and nociceptin/orphanin FQ. They exert their action through the opioid receptors (ORs), transmembrane proteins belonging to the super-family of G-protein-coupled receptors, and are expressed throughout the body; the receptors are the δ opioid receptor (DOR), μ opioid receptor (MOR), κ opioid receptor (KOR), and nociceptin/orphanin FQ receptor (NOP). Endogenous opioids are mainly studied in the central nervous system (CNS), but their role has been investigated in other organs, both in physiological and in pathological conditions. Here, we revise their role in stem cell (SC) biology, since these cells are a subject of great scientific interest due to their peculiar features and their involvement in cell-based therapies in regenerative medicine. In particular, we focus on endogenous opioids’ ability to modulate SC proliferation, stress response (to oxidative stress, starvation, or damage following ischemia–reperfusion), and differentiation towards different lineages, such as neurogenesis, vasculogenesis, and cardiogenesis.

Repeat Endoscopy Affects Patient Management in Gastrointestinal Graft-Versus-Host Disease

Graft versus host disease (GVHD) of the gut is associated with significant morbidity and mortality after allogeneic hematopoietic cell transplant (allo-HCT). No guidelines exist regarding repeat endoscopy after failure of first-line treatment with steroids. We aimed to study if repeat endoscopic biopsy can be helpful in these patients to guide treatment decisions. We retrospectively reviewed medical records of all patients who underwent repeat endoscopy for clinical suspicion of gastrointestinal (GI) GVHD after allo-HCT. Of the 318 patients, 24 underwent endoscopy twice after allo-HCT. At first endoscopy, 20 patients (80%) showed abnormal findings: 16 with GVHD alone, 1 with GVHD plus cytomegalovirus (CMV), and 3 with GVHD plus infectious colitis. On repeat endoscopy in these 20 patients with GVHD, 6 showed improvement leading to de-escalation of therapy, 8 showed worsening of GVHD including detection of CMV in 2 patients, and 2 had no histological changes. One patient with simultaneous GVHD and CMV diagnosed on first biopsy, displayed significant improvement leading to de-escalation of therapy. Three patients with GVHD along with infectious colitis on biopsy subsequently showed improvement on repeat biopsy leading to de-escalation of therapy. Among 4 patients with normal findings on first endoscopy, 3 had GVHD and 1 had epstein-barrvirus-associated post-transplant lymphoproliferative disorder (EBV-PTLD) on repeat procedures. This study supports the usefulness of repeat endoscopy in persistently symptomatic patients when there is no improvement after the initial treatment based on the results of the first endoscopy. Repeat endoscopy may guide therapy without significant complications.

Allogeneic Stem Cell Transplantation for Blast Crisis Chronic Myeloid Leukemia in the Era of Tyrosine Kinase Inhibitors: A Retrospective Study by the EBMT Chronic Malignancies Working Party

The prognosis of patients with blast crisis (BC) chronic myeloid leukemia (CML) is still dismal. Allogeneic stem cell transplantation represents the only curative treatment option, but data on transplant outcomes are scarce. We therefore conducted a retrospective, registry-based study of adult patients allografted for BC CML, focusing on patients with active disease at transplant and pretransplant prognostic factors. One hundred seventy patients allografted for BC CML after tyrosine kinase inhibitor pretreatment between 2004 and 2016 were analyzed. Before transplant, 95 patients were in remission, whereas 75 patients had active BC. In multivariable analysis of the entire cohort, active BC at transplant was the strongest factor associated with decreased overall survival (hazrd ratio, 1.87; P = .010) and shorter leukemia-free survival (LFS; hazard ratio, 1.69; P = .017). For patients with BC in remission at transplant, advanced age (≥45 years), lower performance status (≤80%), longer interval from diagnosis BC to transplant (>12 months), myeloablative conditioning, and unrelated donor (UD) transplant were risk factors for inferior survival. In patients with active BC, only UD transplant was significantly associated with prolonged LFS and trended toward improved overall survival. In summary, survival of patients allografted for BC CML was strongly dependent on pretransplant remission status. In patients with remission of BC, conventional prognostic factors remained the major determinants of outcome, whereas in those with active BC at transplant, UD transplant was associated with prolonged LFS in our study.

CML Hematopoietic Stem Cells Expressing IL1RAP Can Be Targeted by Chimeric Antigen Receptor-Engineered T Cells

Chronic myeloid leukemia (CML) is a chronic disease resulting in myeloid cell expansion through expression of the BCR-ABL1 fusion transcript. Tyrosine kinase inhibitors (TKI) have significantly increased survival of patients with CML, and deep responders may consider stopping the treatment. However, more than 50% of patients relapse and restart TKI, subsequently suffering unknown toxicity. Because CML is a model immune system-sensitive disease, we hypothesize that chimeric antigen receptor (CAR) T cells targeting IL1 receptor-associated protein (IL1RAP) in quiescent CML stem cells may offer an opportunity for a permanent cure. In this study, we produced and molecularly characterized a specific monoclonal anti-IL1RAP antibody from which fragment antigen-binding nucleotide coding sequences were cloned as a single chain into a lentiviral backbone and secured with the suicide gene iCASP9/rimiducid system. Our CAR T-cell therapy exhibited cytotoxicity against both leukemic stem cells and, to a lesser extent, monocytes expressing IL1RAP, with no apparent effect on the hematopoietic system, including CD34⁺ stem cells. This suggests IL1RAP as a tumor-associated antigen for immunotherapy cell targeting. IL1RAP CAR T cells were activated in the presence of IL1RAP⁺ cell lines or primary CML cells, resulting in secretion of proinflammatory cytokines and specifically killing in vitro and in a xenograft murine model. Overall, we demonstrate the proof of concept of a CAR T-cell immunotherapy approach in the context of CML that is applicable for young patients and primary TKI-resistant, intolerant, or allograft candidate patients. SIGNIFICANCE: These findings present the first characterization and proof of concept of a chimeric antigen receptor directed against IL1RAP expressed by leukemic stem cells in the context of CML.

Management of CML-blast crisis

Tyrosine kinase inhibitors (TKI) have moderately improved survival in BC, but a median survival of less than 1 year is still unsatisfactory. This article reviews the various tests required for diagnosis of BC, features at diagnosis, treatment modalities (intensive chemotherapy, TKI, allo-SCT and a selection of investigational agents), options of prevention and predictors of progression. The best prognosis is observed in patients that achieve a 2nd CP. Allo-SCT probably further improves prognosis of patients in 2nd CP. The choice of TKI should be directed by the mutation profile of the patient. BC can be prevented. A careful analysis of risk factors for progression may help. Current treatment options are combined in a concluding strategy for the management of BC.

Allogeneic transplantation for CML in the TKI era: striking the right balance

The management of chronic myeloid leukaemia (CML) has changed extensively over the past 15 years. Prior to the development of targeted therapies and in the absence of allogeneic haematopoetic stem-cell transplantation (HSCT), the median survival was 5-7 years. HSCT was quickly established as the standard of care for eligible patients through the 1980s and 1990s, when considerable advances were made in the optimization of conditioning regimens and supportive care. Exploiting a deeper understanding of the molecular basis of CML, the development of tyrosine kinase inhibitors (TKIs) in the late 1990s revolutionized the management of the disease. TKIs offer the prospect of long-term disease control with a simple oral therapy, and are the first-line treatment in the 21(st) century. The majority of patients treated with TKIs achieve excellent responses with sustained treatment, and some even continue to have undetectable or exceptionally low level disease upon TKI withdrawal; however, for an almost equal number of patients, an adequate response cannot be achieved with any of the currently available TKIs. For those patients who fail to respond adequately to TKIs, HSCT offers the best prospect of long-term survival.

Donor Lymphocyte Infusions for Chronic Myeloid Leukemia Relapsing after Allogeneic Stem Cell Transplantation: May We Predict Graft-versus-Leukemia Without Graft-versus-Host Disease?

Donor lymphocyte infusions (DLI) are an effective treatment for relapsed chronic myeloid leukemia (CML) after allogeneic stem cell transplantation (alloSCT). Leukemia resistance and secondary graft-versus-host disease (GVHD) are major obstacles to success with DLI. The aim of this study was to identify pre-DLI factors associated with prolonged survival in remission without secondary GVHD. We retrospectively analyzed 500 patients treated with DLI for CML relapse (16% molecular, 30% cytogenetic, and 54% hematological) after alloSCT. The overall probabilities of failure- and secondary GVHD-free survival (FGFS) were 29% and 27% at 5 and 10 years after DLI, respectively. The type of relapse was the major factor influencing FGFS (40% for molecular and/or cytogenetic relapse and 20% for hematological relapse at 5 years, P < .001). Chronic GVHD before DLI and an interval <1 year between alloSCT and first DLI were independently associated with inferior FGFS in patients with molecular and/or cytogenetic relapse. Consequently, FGFS was 13%, 35%, to 56% at 5 years in patients with 2, 1, and 0 adverse features, respectively. In patients with hematological relapse, independent adverse prognostic factors for FGFS were initial dose of CD3(+) cells ≥ 50 × 10(6)/kg, donor-recipient sex mismatch, and chronic GVHD before DLI. FGFS was 0%, 17%, 33%, to 37% in patients with 3, 2, 1, and 0 adverse features, respectively. The probability of survival in remission without secondary GVHD was highest (>50% at 5 years) when DLI were given beyond 1 year from alloSCT for molecular and/or cytogenetic CML relapse that was not preceded by chronic GVHD.

Chronic myeloid leukemia-transplantation in the tyrosine kinase era

Allogeneic hematopoietic stem cell transplantation (HSCT) revolutionized the outlook for many patients with chronic myeloid leukemia (CML) in the 1980s. The introduction of the tyrosine kinase inhibitors (TKIs) nearly 15 years ago displaced HSCT as the first-line treatment for most CML patients. However, in the twenty-first century HSCT remains a viable treatment option for many patients with CML. This review focuses on the role of HSCT for CML in the TKI era, paying particular attention to patient selection and transplant outcome.

A comparison of long-term outcomes of donor lymphocyte infusions and tyrosine kinase inhibitors in patients with relapsed CML after allogeneic hematopoietic cell transplantation

BACKGROUND

Donor lymphocyte infusion (DLI) and tyrosine kinase inhibitors (TKIs) are the 2 standard treatment options in chronic myeloid leukemia (CML) that relapses after hematopoietic cell transplantation (HCT), but reports comparing long-term outcomes of these modalities are rare.

PATIENTS AND METHODS

A total of 46 patients were treated with either DLI (n = 28) or TKIs (n = 18) during a first relapse of CML after HCT between 1993 and 2012. The stage of relapse was the chronic phase in 37 patients and the advanced phase in 9 patients. All patients had myeloablative conditioning without T-cell depletion during HCT. The median interval between HCT and treatment for relapse was 34 (range, 2-197) months.

RESULTS

At a median follow-up of 146 and 70 months, respectively, 32% of the DLI group and 33% of the TKI group had died. Six (21%) patients initially treated with DLI received TKIs during a second relapse. In multivariable analyses, DLI was associated with inferior overall survival (OS) (hazard ratio [HR], 37.4; 95% confidence interval [CI], 2.2-625.4; P = .01), shorter failure-free survival (FFS) (HR, 21.15; 95% CI, 1.8-251; P = .02), higher cumulative incidence of failure (CIF) (HR, 19.5; 95% CI, 1.6-236.5; P = .02), and increased incidence of treatment-induced graft vs. host disease (GVHD) (68% vs. 6%; P = .001).

CONCLUSION

TKIs appear better than DLI in chronic-phase relapses after myeloablative non-T-cell-depleted HCT. Outcomes were poor in advanced-phase relapses irrespective of treatment modality.

Outcome of allogeneic SCT in patients with chronic myeloid leukemia in the era of tyrosine kinase inhibitor therapy

The introduction of tyrosine kinase inhibitors (TKIs) for chronic myeloid leukemia (CML) led to a dramatic change in the role of allogeneic stem cell transplantation (SCT) with a rapid decline in the number of patients receiving SCT in first chronic phase (CP1). We evaluated 68 consecutive patients in all phases of CML (male/female = 39:29, 27 in CP1), who received SCT from related/unrelated donors (related/unrelated = 23:45) under myeloablative or reduced intensity conditioning (MAC/RIC = 45:23). Forty-eight patients (71 %) received TKIs pre-SCT, 20 patients post-SCT (29 %). Overall survival (OS) of CP1 patients achieved a plateau of 85 % at 10 months. Relapse-free survival (RFS) of CP1 patients was 85 % at 1 and 2 years, and 81 % at 5 years. Multivariate analysis showed adverse OS and RFS for patients transplanted >CP1 (hazard ratio (HR) = 6.61 and 4.62) and those who had grade III-IV aGvHD (HR = 2.45 and 1.82). Patients with advanced CML had estimated OS of 65 and 47 %; and RFS of 41 and 32 % at 1 and 2 years respectively. Therefore, for patients with advanced CML phases, allogeneic SCT provides an acceptable chance of cure. Transplant research should focus on improving conditioning regimens and post-SCT management for this subgroup of CML patients.

Introduction to stem cells and regenerative medicine

Stem cells are a population of undifferentiated cells characterized by the ability to extensively proliferate (self-renewal), usually arise from a single cell (clonal), and differentiate into different types of cells and tissue (potent). There are several sources of stem cells with varying potencies. Pluripotent cells are embryonic stem cells derived from the inner cell mass of the embryo and induced pluripotent cells are formed following reprogramming of somatic cells. Pluripotent cells can differentiate into tissue from all 3 germ layers (endoderm, mesoderm, and ectoderm). Multipotent stem cells may differentiate into tissue derived from a single germ layer such as mesenchymal stem cells which form adipose tissue, bone, and cartilage. Tissue-resident stem cells are oligopotent since they can form terminally differentiated cells of a specific tissue. Stem cells can be used in cellular therapy to replace damaged cells or to regenerate organs. In addition, stem cells have expanded our understanding of development as well as the pathogenesis of disease. Disease-specific cell lines can also be propagated and used in drug development. Despite the significant advances in stem cell biology, issues such as ethical controversies with embryonic stem cells, tumor formation, and rejection limit their utility. However, many of these limitations are being bypassed and this could lead to major advances in the management of disease. This review is an introduction to the world of stem cells and discusses their definition, origin, and classification, as well as applications of these cells in regenerative medicine.

Trends in the treatment changes and medication persistence of chronic myeloid leukemia in Taiwan from 1997 to 2007: a longitudinal population database analysis

BACKGROUND

Few studies have examined the longitudinal changes in the patterns, selection, and utilization of treatments for chronic myeloid leukemia (CML) in routine clinical practice since the introduction of imatinib. Therefore, we investigated the trends in CML therapy, including changes, patterns, and persistence to imatinib therapy among patients with newly diagnosed CML.

METHODS

We conducted a cross-sectional and longitudinal analysis of 11 years of claims data for patients with newly diagnosed CML included in the Taiwan National Health Insurance program. Pharmacy and diagnosis claims for newly diagnosed CML recorded between 1997 and 2007 year were extracted from the database. Annual overall use, new use of CML therapy, and persistence to imatinib therapy were estimated. The Anatomical Therapeutic Chemical codes for CML therapy [i.e., imatinib and conventional therapy: busulfan, hydroxyurea, interferon-α (IFNα), and cytarabine], and the process code for hematopoietic stem cell transplantation were used to categorize treatment patterns. Associations with patients characteristics were analyzed by multivariate logistic regression.

RESULTS

Overall, the proportion of patients with newly diagnosed CML to all patients with CML increased by approximately 4-fold between 1998 and 2007. There were steady increases in the proportions of all treated patients and those starting therapy from 2003 to 2007. Fewer comorbid conditions and lower severity of CML were associated with treatment initiation. Medication persistence varied according to treatment duration, as 38.7% patients continued imatinib for ≥ 18 months without interruption but only 7.7% continued imatinib for ≥ 5 years. Factors associated with persistence to imatinib therapy were removal of the need for prior authorization for imatinib, and prior use of hydroxyurea and IFNα, whereas having undergone hematopoietic stem cell transplantation led to reduced likelihood of persistence to imatinib therapy.

CONCLUSION

Treatment decisions for patients with CML changed over time in routine clinical practice. Our findings suggest that clinicians are increasingly adopting the recommendations of international treatment guidelines for CML. However, persistence to imatinib therapy is still substantially below the recommended level based on current evidence for its efficacy. Our study also highlights the need to improve treatment persistence and effectiveness of imatinib over the long term.

Allogeneic stem cell transplantation for patients with chronic myeloid leukemia: risk stratified approach with a long-term follow-up

The use of allogeneic stem cell transplantation (SCT) for chronic myeloid leukemia (CML) was almost abandoned in recent years for very effective targeted therapy with tyrosine kinase inhibitors (TKIs). However, approximately one third of patients still need another treatment including SCT. 38 consecutive CML patients were treated (most in preimatinib era) with allogeneic SCT, using partial T cell depletion (TCD) and preemptive donor lymphocyte infusion (DLI), without post-transplant graft-versus-host disease (GvHD) prophylaxis. Conditioning included busulfan, cyclophosphamide, antithymocytic globulin, and fludarabine followed by donor stem cell transfusion. With a median follow up of 90.5 months (1-134), 32 patients are alive. 97% engrafted. 5-year leukemia free survival (LFS) and overall survival (OS) were 78.95% and 84.2%, respectively. All patients are in major molecular remission and 78% in complete molecular remission. Transplant-related mortality (TRM) was 13%. Twenty-four patients received DLI for residual disease. Acute GvHD, mostly Grades I-II, occurred in 18% of patients post-transplant and in 24% of patients receiving DLI. In conclusion, the risk-adapted approach using only partial TCD and preemptive escalated dose of DLI precluded the need for immunosuppressive medications and reduced the risk of significant GvHD without compromising engraftment and long-term disease control. Am. J. Hematol. 2012. © 2012 Wiley Periodicals, Inc.

Management of chronic myeloid leukemia in childhood

Childhood chronic myelogenous leukemia (CML) is a rare malignancy, and experience with optimal treatment is very limited. Traditionally, allogeneic hematopoietic stem cell transplantation was considered the only curative treatment. Imatinib, a small-molecule inhibitor of the BCR-ABL tyrosine kinase (TKI), has been proven highly successful in adults with CML, resulting in prolonged molecular response with limited drug toxicity. This drug is now included as front-line therapy for CML in pediatrics as well, though valid concerns about serious late sequelae remain unresolved. Specific pediatric treatment guidelines have not yet been formulated, and most algorithms are derived from experience in adult CML. This overview attempts to summarize pediatric studies on issues such as dose, duration, adverse effects, and steering criteria for TKI treatment, adapting guidelines developed in adult medicine to pediatrics. Most importantly, pediatric patients with CML receiving TKI treatment should be enrolled into formal trials.

How I treat CML blast crisis

Blast crisis (BC) remains the major challenge in the management of chronic myeloid leukemia (CML). It is now generally accepted that BC is the consequence of continued BCR-ABL activity leading to genetic instability, DNA damage, and impaired DNA repair. Most patients with BC carry multiple mutations, and up to 80% show additional chromosomal aberrations in a nonrandom pattern. Treatment with tyrosine kinase inhibitors has improved survival in BC modestly, but most long-term survivors are those who have been transplanted. Patients in BC should be treated with a tyrosine kinase inhibitor according to mutation profile, with or without chemotherapy, with the goal of achieving a second chronic phase and proceeding to allogeneic stem cell transplantation as quickly as possible. Although long-term remissions are rare, allogeneic stem cell transplantation provides the best chance of a cure in BC. Investigational agents are not likely to provide an alternative in the near future. In view of these limited options, prevention of BC by a rigorous and early elimination of BCR-ABL is recommended. Early response indicators should be used to select patients for alternative therapies and early transplantation. Every attempt should be made to reduce or eliminate BCR-ABL consistent with good patient care as far as possible.

Chronic myelogenous leukemia: role of stem cell transplant in the imatinib era

In the pre-tyrosine kinase (TKI) era, allogeneic stem cell transplant (allo-SCT) was the front-line treatment of choice for young patients with chronic myelogenous leukemia (CML). Today, imatinib is well established as front-line therapy for CML, with excellent long-term outcomes. This has changed the role of allo-SCT and the number of patients undergoing allo-SCT has declined dramatically. Allo-SCT is currently recommended for patients in accelerated/blast phase disease, those who have failed a second-generation TKI and those with TKI-resistant mutations such as T315I. The role of allo-SCT in the management of CML will require continual reappraisal as medical therapies continue to evolve.

Natural killer cell mediated missing-self recognition can protect mice from primary chronic myeloid leukemia in vivo

Background

Natural Killer (NK) cells are thought to protect from residual leukemic cells in patients receiving stem cell transplantation. However, multiple retrospective analyses of patient data have yielded conflicting conclusions regarding a putative role of NK cells and the essential NK cell recognition events mediating a protective effect against leukemia. Further, a NK cell mediated protective effect against primary leukemia in vivo has not been shown directly.

Methodology/Principal Findings

Here we addressed whether NK cells have the potential to control chronic myeloid leukemia (CML) arising based on the transplantation of BCR-ABL1 oncogene expressing primary bone marrow precursor cells into lethally irradiated recipient mice. These analyses identified missing-self recognition as the only NK cell-mediated recognition strategy, which is able to significantly protect from the development of CML disease in vivo.

Conclusion

Our data provide a proof of principle that NK cells can control primary leukemic cells in vivo. Since the presence of NK cells reduced the abundance of leukemia propagating cancer stem cells, the data raise the possibility that NK cell recognition has the potential to cure CML, which may be difficult using small molecule BCR-ABL1 inhibitors. Finally, our findings validate approaches to treat leukemia using antibody-based blockade of self-specific inhibitory MHC class I receptors.

Distinct graft-versus-leukemic stem cell effects of early or delayed donor leukocyte infusions in a mouse chronic myeloid leukemia model

Among hematologic neoplasms, chronic myeloid leukemia (CML) is exquisitely sensitive to graft-versus-leukemia (GVL) because patients relapsing after allogeneic hematopoietic stem-cell transplantation (alloHSCT) can be cured by donor leukocyte infusion (DLI); however, the cellular mechanisms and strategies to separate GVL from GVHD are unclear. We used a BCR-ABL1 transduction/transplantation mouse model to study the mechanisms of DLI in MHC-matched, minor histocompatibility antigen-mismatched allogeneic chimeras with CML-like leukemia, in which DLI can be administered at the time of transplantation (early) or after recovery of hematopoiesis (delayed). After early DLI, CML-like leukemia cannot be transferred into immunocompetent secondary recipients as soon as 4 days after primary transplantation, demonstrating that cotransplantation of T lymphocytes blocks the engraftment of BCR-ABL1-transduced stem cells. In contrast, in allogeneic chimeras with established CML-like leukemia, combined treatment with delayed DLI and the kinase inhibitor imatinib eradicates leukemia with minimal GVHD. The GVL effect is directed against minor histocompatibility antigens shared by normal and leukemic stem cells, and is mediated predominantly by CD8+ T cells, with minor contributions from CD5- splenocytes, including natural killer cells. These results define a physiologic model of adoptive immunotherapy of CML that will be useful for investigating the cellular and molecular mechanisms of GVL.

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.

Endoscopic diagnosis of acute intestinal GVHD following allogeneic hematopoietic SCT: a retrospective analysis in 175 patients

Diagnosis of acute intestinal GVHD (aGVHD) following allogeneic hematopoietic cell transplantation is based on clinical symptoms and histological lesions. This retrospective analysis aimed to validate the 'Freiburg Criteria' for the endoscopic grading of intestinal aGVHD. Grade 1: no clear-cut criteria; grade 2: spotted erythema; grade 3: aphthous lesions; and grade 4: confluent defects, ulcers, denudation of the mucosa. Having excluded patients with infectious diarrhea, we evaluated 175 consecutive patients between January 2001 and June 2009. Setting a cutoff between grade 1 (no change in therapy) and grade 2 (intensification of immunosuppression), macroscopy had a sensitivity of 89.2% (95% confidence interval (CI): 80.4-94.9%), a specificity of 79.4% (95% CI: 69.6-87.1%), a positive-predictive value of 79.6% (95% CI: 70.0-87.2%) and a negative-predictive value of 89.0% (95% CI: 80.2-94.9%). In all, 20% of patients with aGVHD in the lower gastrointestinal tract (GIT) had lesions only in the terminal ileum. In all patients with aGVHD ≥2 of the upper GIT, typical lesions were also found in the lower GIT. Ileo-colonoscopy showed the highest diagnostic yield for aGVHD. In conclusion, the 'Freiburg Criteria' for macroscopic diagnosis of intestinal aGVHD provide high accuracy for identifying aGVHD ≥2.

Improved outcome following allogeneic stem cell transplantation in chronic myeloid leukemia is associated with higher expression of BMI-1 and immune responses to BMI-1 protein

BMI-1 and EZH2 are polycomb group (PcG) proteins which maintain self-renewal of stem cells, and are overexpressed in leukemia. To investigate the potential of PcG proteins as leukemia-associated antigens, and targets for graft-versus-leukemia (GVL) effects, we studied cells from 86 chronic myeloid leukemia (CML) patients and 25 HLA-A*0201⁺ sibling donors collected prior to allogeneic stem cell transplantation (SCT). Although BMI-1 overexpression in CD34⁺ cells of CML patients treated with pharmacotherapy is associated with poor prognosis, we found, conversely, that in CML patients treated with SCT, a higher expression of BMI-1, and correspondingly lower expression of its target for repression, CDKN2A, is associated with improved leukemia-free survival. Cytotoxic T lymphocyte (CTL) responses to BMI-1 peptide were detected in 5 of 25 (20%) donors, and 8 of 19 (42%) HLA-A*0201⁺ CML patients. BMI-1 generated more total and high avidity immune responses, and was more immunogenic than EZH2. PcG-specific CTLs had memory phenotype, were readily expanded in short-term cultures, and were detected post-SCT in recipients of PcG-specific CTL-positive donors. A higher BMI-1 expression in CML CD34⁺ progenitors was associated with native BMI-1 immune responses. These immune responses to PcG proteins may target leukemia stem cells and have relevance for disease control by GVL.

Imatinib mesylate versus allogeneic hematopoietic stem cell transplantation for patients with chronic myelogenous leukemia in the accelerated phase

The relative merits of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and imatinib for chronic myelogenous leukemia in the accelerated phase (AP-CML) have not previously been evaluated. This cohort study was designed to compare the outcomes of imatinib (n = 87) versus allo-HSCT (n = 45) for AP-CML. A multivariate analysis of the total population revealed that a CML duration ≥ 12 months, hemoglobin < 100 g/L, and peripheral blood blasts ≥ 5% were independent adverse prognostic factors for both overall survival (OS) and progression-free survival (PFS). Both treatments resulted in similar survival in low-risk (no factor) patients, with 6-year event-free survival (EFS), OS, and PFS rates of more than 80.0%. Intermediate-risk (any factor) patients showed no difference in EFS and OS, but 6-year PFS rates were 55.7% versus 92.9% (P = .047) with imatinib versus allo-HSCT, respectively. Among high-risk (at least 2 factors) patients, imatinib was by far inferior to allo-HSCT, with 5-year EFS, OS, and PFS rates of 9.3% versus 66.7% (P = .034), 17.7% versus 100% (P = .008), and 18.8% versus 100% (P = .006), respectively. We conclude that allo-HSCT confers significant survival advantages for high- and intermediate-risk patients with AP-CML compared with imatinib treatment; however, the outcomes of the 2 therapies are equally good in low-risk patients. All trials were registered with the Chinese Clinical Trial Registry (www.chictr.org) as CHiCTR-TNC-10000955.

Human stem cell research and regenerative medicine--present and future

INTRODUCTION

Stem cells are cells with the ability to grow and differentiate into more than 200 cell types.

SOURCES OF DATA

We review here the characteristics and potential of human embryonic stem cells (hESCs), induced pluripotent stem cells (iPSCs) and adult stem cells (ASCs).

AREAS OF AGREEMENT

The differentiation ability of all stem cell types could be stimulated to obtain specialized cells that represent renewable sources of functional cells useful for cell-based therapy.

AREAS OF CONTROVERSY

The proof of functional differentiated cells needs to be investigated in more detail using both in vitro and in vivo assays including animal disease models and clinical studies.

GROWING POINTS

Much progress has been made in the ASCs-based therapies. Meanwhile hESCs and iPSCs have dramatically emerged as novel approaches to understand pathogenesis of different diseases.

AREAS TIMELY FOR DEVELOPING RESEARCH

A number of new strategies become very important in regenerative medicine. However, we discuss the limitations of stem cells and latest development in the reprogramming research.

Chronic myeloid leukemia: cytogenetic methods and applications for diagnosis and treatment

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disease caused by recombination between the BCR gene on chromosome 22 and the ABL1 gene on chromosome 9. This rearrangement generates the BCR-ABL1 fusion gene that characterizes leukemic cells in all CML cases. In about 90% of cases, the BCR-ABL1 rearrangement is manifest cytogenetically by the Philadelphia (Ph) chromosome, a derivative of the reciprocal translocation t(9;22)(q34;q11.2). For the remaining cases, recombination may be more complex, involving BCR, ABL1, and genomic sites on one or more other chromosomal regions, or it may occur cryptically within an apparently normal karyotype. Detection of the Ph and associated t(9;22) translocation is a recognized clinical hallmark for CML diagnosis. The disease has a natural multistep pathogenesis, and during chronic phase CML, the t(9;22) or complex variant is usually the sole abnormality. In 60-80% of cases, additional cytogenetic changes appear and often forecast progression to an accelerated disease phase or a terminal blast crisis. Because new frontline therapies such as imatinib specifically target the abnormal protein product of the BCR-ABL1 fusion gene to eliminate BCR-ABL1 positive cells, there is a new reliance on the cytogenetic evaluation of bone marrow cells at diagnosis, then at regular posttreatment intervals. Combined with other parameters, presence or absence of Ph-positive cells in the bone marrow is a powerful early indicator for clinical risk stratification. Cytogenetic changes detected at any stage during treatment, including in the BCR-ABL1-negative cells, may also provide useful prognostic information. Laboratory methods detailed here extend from initial collection of peripheral blood or bone marrow samples through cell culture with or without synchronization, metaphase or interphase harvest, hypotonic treatment and fixation, slide preparation for G-banding or fluorescent in situ hybridization (FISH), and final interpretation.

Challenges for allogeneic hematopoietic stem cell transplantation in chronic myeloid leukemia in the era of tyrosine kinase inhibitors

Following the introduction of the tyrosine kinase inhibitor (TKI) imatinib in the treatment of chronic myeloid leukemia (CML) patients, the allogeneic hematopoietic stem cell transplantation (HSCT) scene in CML has changed dramatically. The number of patients receiving HSCT in first chronic phase (CP) has declined rapidly, as allogeneic HSCT in CP is now performed in these patients only in case of failure or intolerance of TKIs. Second, those CML patients who undergo allogeneic HSCT represent a selection of high-risk patients due to more advanced disease with high rates of accelerated or blast phase (being associated with an increased relapse risk), advanced age and relevant co-morbidities. Efforts at meeting these special challenges are being developed: treatment with TKIs aims to improve the pre-transplant remission status before HSCT. Dose-reduced conditioning protocols were introduced to decrease transplant-related mortality in patients with co-morbidities or older age. In the post-transplant period, TKIs may be administered for prophylaxis and for treatment of post-transplant relapse. Still, the outcome of patients in advanced CML phases remains guarded, and requires an improvement in current transplant strategies.

Seeking the causes and solutions to imatinib-resistance in chronic myeloid leukemia

Although only 5000 new cases of chronic myeloid leukemia (CML) were seen in the United States in 2009, this neoplasm continues to make scientific headlines year-after-year. Advances in understanding the molecular pathogenesis coupled with exciting developments in both drug design and development, targeting the initiating tyrosine kinase, have kept CML in the scientific limelight for more than a decade. Indeed, imatinib, a small-molecule inhibitor of the leukemia-initiating Bcr-Abl tyrosine kinase, has quickly become the therapeutic standard for newly diagnosed chronic phase-CML (CP-CML) patients. Yet, nearly one-third of patients will still have an inferior response to imatinib, either failing to respond to primary therapy or demonstrating progression after an initial response. Significant efforts geared toward understanding the molecular mechanisms of imatinib resistance have yielded valuable insights into the cellular biology of drug trafficking, enzyme structure and function, and the rational design of novel small molecule enzyme inhibitors. Indeed, new classes of kinase inhibitors have recently been investigated in imatinib-resistant CML. Understanding the pathogenesis of tyrosine kinase inhibitor resistance and the molecular rationale for the development of second and now third generation therapies for patients with CML will be keys to further disease control over the next 10 years.

Umbilical cord blood transplantation from unrelated donors in adult patients with chronic myeloid leukaemia

Allogeneic haematopoietic stem cell transplantation (HSCT) remains an important treatment option for patients with chronic myeloid leukaemia (CML) failing tyrosine-kinase inhibitors or progressing to an advanced phase. In this setting, umbilical cord blood (UCB) could be used as an alternative stem cell source for patients in whom allogeneic HSCT is indicated and lack a human leucocyte antigen (HLA)-matched adult donor. However, very little information exists on the outcome after UCB transplantation (UCBT) of these patients. Early registry-based studies of patients undergoing UCBT suggested a particularly poor outcome for patients with CML. However, more recent reports with special focus on patients with CML have confirmed feasibility and efficacy of the procedure and identified variables influencing short- and long-term outcomes. Currently, UCBT should be considered as a potential curative alternative for CML patients requiring allogeneic HSCT but lacking an appropriate adult donor.

The bone marrow microenvironment as a sanctuary for minimal residual disease in CML

Bcr-abl kinase inhibitors have provided proof of principal that targeted therapy holds great promise for the treatment of cancer. However, despite the success of these agents in treating chronic myelogenous leukemia (CML), the majority of patients continue to present with minimal residual disease contained within the bone marrow microenvironment. These clinical observations suggest that the bone marrow microenvironment may provide survival signals that contribute to the failure to eliminate minimal residual disease. The bone marrow microenvironment is comprised of multiple sub-domains which vary in cellular composition and gradients of soluble factors and matrix composition. Experimental evidence indicate that exposure of tumor cells to either bone marrow derived soluble factors or the extracellular matrix can confer a multi-drug resistance phenotype. Together, these data indicate that targeting such pathways may be a viable approach for increasing the efficacy of chemotherapy. Moreover, we propose that personalized medicine must go beyond understanding predictive models inherent to tumors but rather build predictive models that consider diversity in response due to interactions with the tumor microenvironment. Although review will focus on CML, understanding the contribution of the bone marrow microenvironment could contribute to rationale combination therapy in other types of leukemia, multiple myeloma and solid tumors which metastasize to the bone.