Autologous transplantation for Philadelphia chromosome-positive acute lymphoblastic leukemia achieves outcomes similar to allogeneic transplantation: results of CALGB Study 10001 (Alliance)

Matched and mismatched unrelated donor compared to autologous stem cell transplantation for acute myeloid leukemia in first complete remission: a retrospective, propensity score-weighted analysis from the ALWP of the EBMT

BACKGROUND

Optimal post-remission strategy for patients with acute myeloid leukemia (AML) is matter of intense debate. Recent reports have shown stronger anti-leukemic activity but similar survival for allogeneic stem cell transplantation (allo-HSCT) from matched sibling donor compared to autologous transplantation (auto-HSCT); however, there is scarcity of literature confronting auto-HSCT with allo-HSCT from unrelated donor (UD-HSCT), especially mismatched UD-HSCT.

METHODS

We retrospectively compared outcome of allogeneic transplantation from matched (10/10 UD-HSCT) or mismatched at a single HLA-locus unrelated donor (9/10 UD-HSCT) to autologous transplantation in patients with AML in first complete remission (CR1). A total of 2879 patients were included; 1202 patients received auto-HSCT, 1302 10/10 UD-HSCT, and 375 9/10 UD-HSCT. A propensity score-weighted analysis was conducted to control for disease risk imbalances between the groups.

RESULTS

Matched 10/10 UD-HSCT was associated with the best leukemia-free survival (10/10 UD-HSCT vs auto-HSCT: HR 0.7, p = 0.0016). Leukemia-free survival was not statistically different between auto-HSCT and 9/10 UD-HSCT (9/10 UD-HSCT vs auto-HSCT: HR 0.8, p = 0.2). Overall survival was similar across the groups (10/10 UD-HSCT vs auto-HSCT: HR 0.98, p = 0.84; 9/10 UD-HSCT vs auto-HSCT: HR 1.1, p = 0.49). Notably, in intermediate-risk patients, OS was significantly worse for 9/10 UD-HSCT (9/10 UD-HSCT vs auto-HSCT: HR 1.6, p = 0.049), while it did not differ between auto-HSCT and 10/10 UD-HSCT (HR 0.95, p = 0.88). In favorable risk patients, auto-HSCT resulted in 3-year LFS and OS rates of 59 and 78 %, respectively.

CONCLUSIONS

Our findings suggest that in AML patients in CR1 lacking an HLA-matched sibling donor, 10/10 UD-HSCT significantly improves LFS, but this advantage does not translate in better OS compared to auto-HSCT. In intermediate-risk patients lacking a fully HLA-matched donor, auto-HSCT should be considered as a valid option, as better survival appears to be provided by auto-HSCT compared to mismatched UD-HSCT. Finally, auto-HSCT provided an encouraging outcome in patients with favorable risk AML.

A sequential approach with imatinib, chemotherapy and transplant for adult Ph+ acute lymphoblastic leukemia: final results of the GIMEMA LAL 0904 study

In the GIMEMA LAL 0904 protocol, adult Philadelphia positive acute lymphoblastic leukemia patients were treated with chemotherapy for induction and consolidation, followed by maintenance with imatinib. The protocol was subsequently amended and imatinib was incorporated in the induction and post-remission phase together with chemotherapy. Due to the toxicity of this combined approach, the protocol was further amended to a sequential scheme based on imatinib plus steroids as induction, followed by consolidation with chemotherapy plus imatinib and, when applicable, by a hematopoietic stem cell transplant. Fifty-one patients (median age 45.9 years) were enrolled in the final sequential protocol. At the end of induction (day +50), 96% of evaluable patients (n=49) achieved a complete hematologic remission; after consolidation, all were in complete hematologic remission. No deaths in induction were recorded. Overall survival and disease-free survival at 60 months are 48.8% and 45.8%, respectively. At day +50 (end of imatinib induction), a more than 1.3 log-reduction of BCR-ABL1 levels was associated with a significantly longer disease-free survival (55.6%, 95%CI: 39.0-79.3 vs. 20%, 95%CI: 5.8-69.1; P=0.03), overall survival (59.1%, 95%CI: 42.3-82.6 vs. 20%, 95%CI: 5.8-69.1; P=0.02) and lower incidence of relapse (20.5%, 95%CI: 7.2-38.6 vs. 60.0%, 95%CI: 21.6-84.3; P=0.01). Mean BCR-ABL1 levels remained significantly higher in patients who subsequently relapsed. Finally, BCR-ABL1^p190 patients showed a significantly faster molecular response than BCR-ABL1^p210 patients (P=0.023). Though the study was not powered to evaluate the role of allogeneic stem cell transplant, allografting positively impacted on both overall and disease-free survival. In conclusion, a sequential approach with imatinib alone in induction, consolidated by chemotherapy plus imatinib followed by a stem cell transplant is a feasible, well-tolerated and effective strategy for adult Philadelphia positive acute lymphoblastic leukemia, leading to the best long-term survival rates so far reported. (clinicaltrials.gov identifier: 00458848).

Refining the Role of Hematopoietic Cell Transplantation for Acute Lymphoblastic Leukemia as Novel Therapies Emerge

Acute lymphoblastic leukemia (ALL) is a rare adult neoplasm. The disorder consists of precursor B or T phenotypes. In the pediatric population, ALL was a success story in that 80% of children with ALL enjoy long-term survival. In adults, similar complete remission rates are achieved with current induction regimens; however, less than 50% of patients are alive at 5 years, with most deaths due to relapsed disease. Accordingly, optimizing post remission consolidation therapy might improve in outcomes. Such strategies may include chemotherapy and autologous or allogeneic transplant. Moreover, the ability to modify such therapy based on better disease risk stratification while taking into account patient characteristics such as performance status and presence of comorbidities is necessary to tailor treatment accordingly. Here, we review available medical literature on the use of hematopoietic cell transplantation as a consolidation modality in the treatment of adult ALL.

Use of tyrosine kinase inhibitors to prevent relapse after allogeneic hematopoietic stem cell transplantation for patients with Philadelphia chromosome-positive acute lymphoblastic leukemia: A position statement of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a standard of care for patients with Philadelphia chromosome (Ph)-positive acute lymphoblastic leukemia (ALL). The introduction of tyrosine kinase inhibitors (TKIs) to first-line therapy has improved overall outcomes; however, a significant proportion of patients still relapse after alloHSCT. Posttransplant TKI maintenance was demonstrated to reduce the risk of relapse in a large retrospective study and, therefore, should be considered a valuable option. This consensus paper, written on behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, presents an overview of clinical studies on the use of TKIs after alloHSCT and proposes practical recommendations regarding the choice of TKI, treatment timing, and dosage. It is hoped that these recommendations will become the state of art in this field and, more importantly, lead to a reduction of Ph-positive ALL relapse after alloHSCT. Cancer 2016;122:2941-2951. © 2016 American Cancer Society.

Clinical impact of ABL1 kinase domain mutations and IKZF1 deletion in adults under age 60 with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL): molecular analysis of CALGB (Alliance) 10001 and 9665

Recent studies have identified oncogenic lesions in Philadelphia chromosome-positive (Ph+)  acute lymphoblastic leukemia (ALL) and ABL1 kinase mutations that confer resistance to tyrosine kinase inhibitors. We sought to determine the prevalence and clinical impact of these lesions in patients on CALGB 10001, a previously reported Phase II study of imatinib, chemotherapy, and hematopoietic cell transplant in adult Ph + ALL. Of the 58 enrolled, 22 relapsed. By direct sequencing, an ABL1 kinase mutation known to induce imatinib resistance was present at relapse in 13 of 20. Using quantitative PCR assays, the mutations were detectable at diagnosis or early during treatment in most (62%) relapsed patients. Aberrations in IKZF1, CDKN2A/B, and PAX5 were assessed in 28 samples using SNP arrays and genomic DNA sequencing. Of these, 22 (79%) had IKZF1 deletion. The combination of IKZF1 deletion and p210 BCR-ABL1 (p < 0.0001), high white blood cell count (p = 0.021), and minimal residual disease (p = 0.013) were associated with worse disease-free survival.

Treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia in adults: a broader range of options, improved outcomes, and more therapeutic dilemmas

The article addresses selected key areas of flux in the management of Philadelphia chromosome-positive acute lymphoblastic leukemia. There is no doubt that tyrosine kinase inhibitors (TKIs) have made a major contribution to higher rates of complete remission and that more patients are now surviving long term. Many patients tolerate TKIs well, and remission can be achieved with minimal toxicity. Because remissions can include a proportion of patients who become BCR-ABL1 transcript negative, the question of whether allogeneic hematopoietic stem cell transplantation can be avoided requires discussion. Despite the major progress that has been made and the relative profusion of therapeutic choice compared with 10 years ago, evidence is still lacking for many of the major possible interventions, and how to combine them is unclear. Because of the rarity of the condition and the enticing possibility of increasing traction to therapy, clinical trials and international cooperation remain paramount.

Clinical updates in adult acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a clonal disease characterized by B or T lineage. Here we cover the clinical manifestations, pathophysiology and therapy for ALL. Additionally, we will discuss the evidence for minimal residual disease assessment, novel molecular targets and newly developed targeted therapies. The separation of ALL into Philadelphia chromosome positive and recently into Philadelphia-like disease represents the most exciting developments in this disease. Finally, the advent of new immunotherapeutic approaches led us to predict that in few years, ALL therapy might be based heavily on non-chemotherapeutic approaches.

Management of adult Ph-positive acute lymphoblastic leukemia

Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL) has been regarded for decades as the ALL subgroup with the worse outcome. It represents the most frequent genetic subtype of adult ALL, and increases progressively with age. The introduction of tyrosine kinase inhibitors (TKIs) has enabled to obtain complete hematologic remissions (CHRs) in virtually all patients, including the elderly, to improve disease-free survival and overall survival, as well as to increase the percentage of patients who can undergo an allogeneic stem cell transplant (allo-SCT).

The current management of adult Ph+ ALL patients relies on the use of a TKI with or without chemotherapy followed by an allo-SCT, which still remains the only curative option. Minimal residual disease screening is permitting not only a better stratification of patients, but has also allowed to reconsider the role of autologous stem cell transplant for a set of patients who do not have a donor or are not eligible for an allo-SCT. At present, clinical challenges are represented by the emergence of resistant mutations, particularly the gatekeeper T315I, for which alternative approaches, comprising novel TKIs or therapies based on the combination of TKI with immunotherapeutic strategies, are being considered in order to overcome resistance.

Autologous stem cell transplantation for adult acute leukemia in 2015: time to rethink? Present status and future prospects

The use of autologous stem cell transplantation (ASCT) as consolidation therapy for adult patients with acute leukemia has declined over time. However, multiple randomized studies in the past have reported lower relapse rates after autologous transplantation compared with chemotherapy and lower non-relapse mortality rates compared with allogeneic transplantation. In addition, quality of life of long-term survivors is better after autologous transplantation than after allogeneic transplantation. Further, recent developments may improve outcomes of autograft recipients. These include the use of IV busulfan and the busulfan+melphalan combination, better detection of minimal residual disease (MRD) with molecular biology techniques, the introduction of targeted therapies and post-transplant maintenance therapy. Therefore, ASCT may nowadays be reconsidered for consolidation in the following patients if and when they reach a MRD-negative status: good- and at least intermediate-1 risk acute myelocytic leukemia in first CR, acute promyelocytic leukemia in second CR, Ph-positive acute lymphocytic leukemia. Conversely, patients with MRD-positive status or high-risk leukemia should not be considered for consolidation with ASCT.

Nilotinib combined with multiagent chemotherapy for newly diagnosed Philadelphia-positive acute lymphoblastic leukemia

We investigated the effects of nilotinib plus multiagent chemotherapy, followed by consolidation/maintenance or allogeneic hematopoietic cell transplantation (allo-HCT) for adult patients with newly diagnosed Philadelphia-positive (Ph-pos) acute lymphoblastic leukemia (ALL). Study subjects received induction treatment that comprised concurrent vincristine, daunorubicin, prednisolone, and nilotinib. After achieving complete hematologic remission (HCR), subjects received either 5 courses of consolidation, followed by 2-year maintenance with nilotinib, or allo-HCT. Minimal residual disease (MRD) was assessed at HCR, and every 3 months thereafter. The molecular responses (MRs) were defined as MR3 for BCR-ABL1/G6PDH ratios ≤10(-3) and MR5 for ratios <10(-5). Ninety evaluable subjects, ages 17 to 71 years, were enrolled in 17 centers. The HCR rate was 91%; 57 subjects received allo-HCT. The cumulative MR5 rate was 94%; the 2-year hematologic relapse-free survival (HRFS) rate was 72% for 82 subjects that achieved HCR, and the 2-year overall survival rate was 72%. Subjects that failed to achieve MR3 or MR5 were 9.1 times (P = .004) or 6.3 times (P = .001) more prone to hematologic relapse, respectively, than those that achieved MR3 or MR5. MRD statuses just before allo-HCT and at 3 months after allo-HCT were predictive of 2-year HRFS. Adverse events occurred mainly during induction, and most were reversible with dose reduction or transient interruption of nilotinib. The combination of nilotinib with high-dose cytotoxic drugs was feasible, and it effectively achieved high cumulative complete molecular remission and HRFS rates. The MRD status at early postremission time was predictive of the HRFS. This trial was registered at www.clinicaltrials.gov as #NCT00844298.

Indications for allo- and auto-SCT for haematological diseases, solid tumours and immune disorders: current practice in Europe, 2015

This is the sixth special report that the European Society for Blood and Marrow Transplantation regularly publishes on the current practice and indications for haematopoietic SCT for haematological diseases, solid tumours and immune disorders in Europe. Major changes have occurred in the field of haematopoietic SCT over the last years. Cord blood units as well as haploidentical donors have been increasingly used as stem cell sources for allo-SCT, thus, augmenting the possibility of finding a suitable donor for a patient. Continuous refinement of conditioning strategies has also expanded not only the number of potential indications but also has permitted consideration of older patients or those with co-morbidity for a transplant. There is accumulating evidence of the role of haematopoietic SCT in non-haematological disorders such as autoimmune diseases. On the other hand, the advent of new drugs and very effective targeted therapy has challenged the role of SCT in some instances or at least, modified its position in the treatment armamentarium of a given patient. An updated report with revised tables and operating definitions is presented.

[Comparison of outcomes of adult acute lymphoblastic leukemia patients underwent autologous and allogeneic hematopoietic stem cell transplantation]

OBJECTIVE

To compare the outcomes of adult patients with acute lymphoblastic leukemia (ALL) who underwent autologous hematopoietic stem cell transplantation (auto-HSCT) and allogeneic hematopoietic stem cell transplantation (allo-HSCT).

METHODS

From Jan 2007 to Dec 2010, 106 adult ALL patients were retrospectively divided into two groups, 50 in auto-HSCT group and 56 in allo-HSCT group. Auto-HSCT group included 21 patients with high-risk, 46 patients in CR1 and 4 cases in CR2. All the 50 patients had negative minimal residual disease (MRD) prior to HSCT. Allo-HSCT group included 44 patients with high risk, 51 patients in CR1 and 5 cases in CR2, 15 patients with positive MRD before allo-HSCT. response, regulatory T cells (Treg), cytokines levels and treatment-related adverse effects were observed.

RESULTS

Of the total 106 patients, 29 patients relapsed at a medium follow-up of 22.9(0.8-63.3) months. The 3-year cumulative relapse rate (RR) was (29.9±8.0) % in auto-HSCT group and (32.7±6.8) % in allo-HSCT group. There were no significant differences in RR and overall survival (OS) between auto-HSCT and allo-HSCT groups, even of stratified risk groups. In standard risk group, 3-year OS was (77.1±13.2) % in auto-HSCT group and (90.9±8.7) % in allo-HSCT group (P=0.739). In high-risk group, 3-year OS was (68.7±10.8) % after auto-HSCT and (45.2±8.5) % after allo-HSCT (P=0.094).

CONCLUSION

Due to acceptable RR and OS, adult ALL patients with no MRD before HSCT showed favorable survival. Auto-HSCT may be a considerable choice for adult ALL patients with negative MRD when lacking of donors for allo-HSCT.

How I treat mixed-phenotype acute leukemia

Mixed-phenotype acute leukemia (MPAL) encompasses a heterogeneous group of rare leukemias in which assigning a single lineage of origin is not possible. A variety of different terms and classification systems have been used historically to describe this entity. MPAL is currently defined by a limited set of lineage-specific markers proposed in the 2008 World Health Organization monograph on classification of tumors of hematopoietic and lymphoid tissues. In adult patients, MPAL is characterized by relative therapeutic resistance that may be attributed in part to the high proportion of patients with adverse cytogenetic abnormalities. No prospective, controlled trials exist to guide therapy. The limited available data suggest that an "acute lymphoblastic leukemia-like" regimen followed by allogeneic stem-cell transplant may be advisable; addition of a tyrosine kinase inhibitor in patients with t(9;22) translocation is recommended. The role of immunophenotypic and genetic markers in guiding chemotherapy choice and postremission strategy, as well as the utility of targeted therapies in non-Ph-positive MPALs is unknown.

Prognostic impact of minimal residual disease in adult acute lymphoblastic leukemia

SUMMARY 

While adult acute lymphoblastic leukemia (ALL) is curable in 40–50% of the patients, the individual prognosis is rather unpredictable due to associated biological and clinical risk factors. In both B- and T-precursor ALL, minimal residual disease (MRD) represents the most sensitive prognostic marker, useful to support critical treatment decisions, ranging from allogeneic stem cell transplantation in patients with inadequate MRD response to chemotherapy only in MRD responsive ones. This optimized risk-adapted strategy allows to spare transplant-associated morbidity and mortality in patients curable by chemotherapy. Further progress is expected from the integration of the MRD-based strategy with improved pediatric-type regimens and novel targeting agents for discrete ALL subsets. These changes are increasing the cure rate to above 50%.

Pre-transplant achievement of negativity in minimal residual disease and French-American-British L1 morphology predict superior outcome after allogeneic transplant for Philadelphia chromosome positive acute lymphoblastic leukemia: an analysis of Southeast Asian patients

To better understand predictive factors and improve the clinical outcome of allogeneic transplant for patients with Philadelphia positive acute lymphoblastic leukemia, we analyzed 67 Southeast Asian patients transplanted in our institutions. Multivariate analysis showed that disease status before transplant, year of transplant and, interestingly, French-American-British (FAB) subtype had a significant impact on overall survival (OS) and non-relapse mortality. Patients who were minimal residual disease (MRD) negative at transplant had a 3-year OS of 73% compared to those who were MRD positive (45%) and refractory (0%). The 3-year cumulative incidence of relapse was 18% and 36% for the MRD negative and positive groups, respectively. FAB L1 subtype had a significantly superior 3-year OS of 63% vs. 29% for L2 subtype. Pre-transplant use of a tyrosine kinase inhibitor significantly improved outcomes in univariate but not multivariate analysis, as it served to induce more patients into MRD negativity, which was the factor that directly improved transplant outcome.

Autologous Hematopoietic Stem Cell Transplantation for High-risk Acute Lymphoblastic Leukemia: non-Randomized Study with a maximum Follow-up of more than 22 Years

OBJECTIVE

To evaluate the efficacy and toxicity of autologous hematopoietic stem cell transplantation (AHSCT) for high-risk acute lymphoblastic leukemia (ALL).

MATERIAL AND METHODS

Overall, 128 high-risk ALL patients at a median age of 26 years (range 18-56 years) at diagnosis received AHSCT between 1991-2008. Induction treatment was anthracycline-based in all patients. Conditioning regimen consisted of CAV (cyclophosphamide, cytarabine, etoposide) in 125 patients whereas 3 subjects received cyclophosphamide and TBI (total body irradiation). Bone marrow was stored for 72 hours in 4°C and re-infused 24 hours after conditioning completion. Bone marrow was a source of stem cells in 119 patients, peripheral blood in 2 and 7 subjects received both bone marrow and peripheral blood.

RESULTS

With a median follow-up after AHSCT of 1.6 years (range 0.1-22.3 years), the probability of leukemia-free survival (LFS) for the whole group at 10 years was 27% and 23% at 20 years. Transplant-related mortality at 100 days after AHSCT was 3.2%. There was a strong tendency for better LFS for MRD-negative patients if compared with patients who had positive or unknown MRD status at AHSCT (32% vs 23% and 25%, respectively; p=0.06). There was no difference in LFS between B- and T-lineage ALL as well as between patients transplanted in first complete remission (CR1) and CR2. LFS at 10 years for patients with Philadelphia-positive (Ph+) ALL at transplant was 20% and this was comparable with subjects with negative and missing Ph status (26% and 28%; p=0.97).

CONCLUSIONS

The results of AHSCT for high-risk ALL remains unsatisfactory with low probability of long-term LFS.

Philadelphia chromosome-positive mixed phenotype acute leukemia in the imatinib era

Although the introduction of imatinib dramatically improved the outcomes for patients with Philadelphia chromosome-positive B-cell precursor acute lymphoblastic leukemia (Ph + BCP-ALL), the survival benefit of imatinib has not been assessed in the context of Ph + mixed phenotype acute leukemia (Ph + MPAL). To clarify this important issue, we studied 42 Ph+ acute leukemia (Ph + AL) patients who received intensive chemotherapy and concurrent administration of imatinib. Of the 42 Ph + AL patients, 13 (31%) patients were categorized as Ph + MPAL (positive for both myeloid and B-cell lineage), 27 (64%) were categorized as Ph + BCP-ALL, and two (5%) were categorized as Ph + acute myeloid leukemia. The complete remission rates after the initial induction therapy were not significantly different when comparing Ph + MPAL and Ph + BCP-ALL patients (100% vs. 85%, respectively, P = 0.14). Likewise, there were no significant differences in the 5-yr overall survival (OS) or disease-free survival (DFS) rates when comparing the MPAL and BCP-ALL groups (OS: 55% vs. 53%, respectively, P = 0.87, DFS: 46% vs. 42%, respectively, P = 0.94). These findings suggest that concurrent imatinib administration with chemotherapy improved the outcomes of Ph + MPAL patients to the level seen in Ph+BCP-ALL patients and should, therefore, be considered as the standard therapy for these patients.

Current and future management of Ph/BCR-ABL positive ALL

Following the introduction of targeted therapy with tyrosine kinase inhibitors (TKI) at the beginning of the past decade, the outcome of patients with Philadelphia-chromosome positive acute lymphoblastic leukemia (Ph+ ALL) has dramatically improved. Presently, the use of refined programs with first/second generation TKI's and chemotherapy together with allogeneic stem cell transplantation allow up to 50% of all patients to be cured. Further progress is expected with the new TKI ponatinib, overcoming resistance caused by T315I point mutation, other targeted therapies, autologous transplantation in molecularly negative patients, therapeutic monoclonal antibodies like inotuzumab ozogamicin and blinatumomab, and chimeric antigen receptor-modified T cells. Ph+ ALL could become curable in the near future even without allogeneic stem cell transplantation, minimizing the risk of therapy-related death and improving greatly the quality of patients' life.

Treatment of Philadelphia-positive acute lymphoid leukemia

SUMMARY Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL) represents approximately 15–30% of ALL in adults and is characterized by the expression of the fusion protein BCR–ABL with oncogenic activity. Remission and survival rates were lower whereas relapse risk was increased in Ph+ compared with Philadelphia-negative ALL, until remarkable improvements in the management of Ph+ ALL were achieved through the introduction of tyrosine kinase inhibitors that reduce the activity of the BCR–ABL protein. However, in patients achieving complete remission, allogeneic hematopoietic stem cell transplantation is in most cases a mandatory therapeutic step because rate of relapses are still high. This review will illustrate the current therapeutic options for the management of Ph+ ALL and indicate how better curative options may stem from appropriate implementation of tyrosine kinase inhibitors and novel antitumoral agents.

Selectins and their ligands are required for homing and engraftment of BCR-ABL1+ leukemic stem cells in the bone marrow niche

We investigated adhesion pathways that contribute to engraftment of breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1 (BCR-ABL1)-induced chronic myelogenous leukemia (CML)-like myeloproliferative neoplasia in a mouse retroviral transduction/transplantation model. Compared with normal stem/progenitor cells, BCR-ABL1(+) progenitors had similar expression of very late antigen-4 (VLA4), VLA5, leukocyte functional antigen-1, and CXCR4 but lower expression of P-selectin glycoprotein ligand-1 (PSGL-1) and of L-selectin. Whereas vascular cell adhesion molecule-1 and P-selectin were not required, deficiency of E-selectin in the recipient bone marrow endothelium significantly reduced engraftment by BCR-ABL1-expressing stem cells following intravenous injection, with leukemogenesis restored by direct intrafemoral injection. BCR-ABL1-expressing cells deficient for PSGL-1 or the selectin ligand-synthesizing enzymes core-2 β1,6-N-acetylglucosaminyltransferase or fucosyltransferases IV/VII were impaired for engraftment, and destruction of selectin ligands on leukemic progenitors by neuraminidase reduced engraftment. BCR-ABL1-expressing L-selectin-deficient progenitors were also defective in homing and engraftment, with leukemogenesis rescued by coexpression of chimeric E/L-selectin. Antibody to L-selectin decreased the engraftment of BCR-ABL1-transduced stem cells. These results establish that BCR-ABL1(+) leukemic stem cells rely to a greater extent on selectins and their ligands for homing and engraftment than do normal stem cells. Selectin blockade is a novel strategy to exploit differences between normal and leukemic stem cells that may be beneficial in autologous transplantation for CML and perhaps other leukemias.

Back to the future! The evolving role of maintenance therapy after hematopoietic stem cell transplantation

Relapse is a devastating event for patients with hematologic cancers treated with hematopoietic stem cell transplantation. In most situations, relapse treatment options are limited. Maintenance therapy offers the possibility of delaying or avoiding disease recurrence, but its role remains unclear in most conditions that we treat with transplantation. Here, Dr. Hourigan presents an overview of minimal residual disease (MRD) measurement in hematologic malignancies and the applicability of MRD-based post-transplantation interventions. Dr. McCarthy reviews current knowledge of maintenance therapy in the autologous transplantation context, with emphasis on immunologic interventions and immune modulation strategies designed to prevent relapse. Dr. de Lima discusses current lines of investigation in disease recurrence prevention after allogeneic transplantation, focusing on acute myeloid leukemia and myelodysplastic syndrome.