Allogeneic stem cell transplant in adult patients with acute myelogenous leukemia: a systematic analysis of international guidelines and recommendations

In patients with acute myelogenous leukemia, published guidelines and treatment recommendations are usually the basis for starting the work-up process for allogeneic transplant. However, only consistent recommendations would allow a standardized clinical practice. We conducted a comprehensive systematic literature search to identify and evaluate the best available evidence from controlled clinical trials. In addition, recommendations given by leading organizations in the USA and Europe were analyzed. The following aspects were selected for systematic comparison: factors for risk assessment and categorization, role of type of donor, significance of allogeneic transplant in first or second complete remission and in relapse/progressive disease; and role of reduced intensity conditioning regimens. In conclusion, the recommendations for the use of allogeneic transplant given by the literature and by published guidelines are inconsistent and will need clarification.

NDRG1/2 expression is inhibited in primary acute myeloid leukemia

Expression of N-myc downregulated gene 1 (NDRG1) is associated with growth arrest and differentiation of tumor cells. In hematopoietic cells, NDRG1 was identified in a screen for differentiation-related genes in human myelomonocytic leukemic U937 cells. In the present study, we found significantly higher NDRG1 mRNA levels in granulocytes of healthy donors than in primary acute myeloid leukemia (AML) cells. Another NDRG family member, NDRG2, was significantly higher expressed in normal macrophages compared to primary AML cells. Moreover, NDRG1 mRNA levels increased in two acute promyelocytic leukemia (APL) patients as well as in NB4 and HT93 APL cells upon all-trans retinoic acid (ATRA) therapy. In line with these observations, silencing of NDRG1 diminished neutrophil differentiation of leukemic cell lines. In conclusion, we found an association of low NDRG1 levels with an immature cell phenotype and provide evidence that NDRG1 is functionally involved in neutrophil maturation.

Family characteristics as risk factors for childhood acute lymphoblastic leukemia: a population-based case-control study

To date, few risk factors for childhood acute lymphoblastic leukemia (ALL) have been confirmed and the scientific literature is full of controversial "evidence." We examined if family characteristics, particularly maternal and paternal age and number of older siblings, were risk factors for childhood acute lymphoblastic leukemia (ALL).

Chronic myelogenous leukemia maintains specific CD8(+) T cells through IL-7 signaling

Chronic myelogenous leukemia (CML) is a malignant myeloproliferative disease of hematopoietic stem cells. The disease progresses after several years from an initial chronic phase to a blast phase. Leukemia-specific T cells are regularly detected in CML patients and may be involved in the immunological control of the disease. Here, we analyzed the role of leukemia-specific CD8(+) T cells in CML disease control and the mechanism that maintains CD8(+) T-cell immunosurveillance in a retroviral-induced murine CML model. To study antigen-specific immune responses, the glycoprotein of the lymphocytic choriomeningitis virus was used as model leukemia antigen. Leukemia-specific CTL activity was detectable in vivo in CML mice and depletion of CD8(+) T cells rapidly led to disease progression. CML-specific CTL were characterized by the expression of the IL-7 receptor -chain. In addition, leukemia cells produced IL-7 that was crucial for the maintenance of leukemia-specific CTL and for disease control. Therefore, CML cells maintain the specific CD8(+) T-cell-mediated immune control by IL-7 secretion. This results in prolonged control of disease and probably contributes to the characteristic chronic phase of the disease.

Sperm analysis of patients after successful treatment of childhood acute lymphoblastic leukemia with chemotherapy

Survivors of childhood acute lymphoblastic leukemia (ALL) treated with radiotherapy are at risk for impaired fertility. Whether chemotherapy alone is also long-term gonadotoxic is unclear. We assessed gonadal function in 11 male ALL-survivors treated with the same chemotherapy regimen and compared sperm analysis to healthy men. While sex hormone levels were normal in all subjects, 5/11 survivors showed pathological sperm concentration and 4/11 a decreased total sperm count compared to WHO criteria. Compared to healthy controls, all quantitative parameters in semen analysis of survivors were decreased. This suggests that treatment with chemotherapeutic agents alone, even in moderate doses, might have a gonadotoxic effect.

Deregulated expression of Kruppel-like factors in acute myeloid leukemia

The known participation of Kruppel-like transcription factors (KLF) in cellular differentiation prompted us to investigate their expression in acute myeloid leukemia (AML) blast cells that are typically blocked in their differentiation. We determined the expression patterns of KLFs with a putative role in myeloid differentiation in a large cohort of primary AML patient samples, CD34+ progenitor cells and granulocytes from healthy donors. We found that KLF2, KLF3, KLF5 and KLF6 are significantly lower expressed in AML blast and CD34+ progenitor cells as compared to normal granulocytes. Moreover, we found markedly increased KLF levels in acute promyelocytic leukemia patients who received oral ATRA. Accordingly, we observed a strong induction of KLF5/6 upon ATRA-treatment in NB4 and HT93 APL but not in ATRA-resistant NB4-R cells. Lastly, knocking down KLF5 or KLF6 in NB4 cells significantly attenuated neutrophil differentiation. In conclusion, we found a significant repression of KLF transcription factors in primary AML samples as compared to mature neutrophils and further show that KLF5 and KLF6 are functionally involved in neutrophil differentiation of APL cells.

CD27 signaling on chronic myelogenous leukemia stem cells activates Wnt target genes and promotes disease progression

Chronic myelogenous leukemia (CML) results from a chromosomal translocation in hematopoietic stem or early progenitor cells that gives rise to the oncogenic BCR/ABL fusion protein. Clinically, CML has a chronic phase that eventually evolves into an accelerated stage and blast crisis. A CML-specific immune response is thought to contribute to the control of disease. Whether the immune system can also promote disease progression is not known. In the present study, we investigated the possibility that the TNF receptor family member CD27 is present on leukemia stem cells (LSCs) and mediates effects of the immune system on CML. In a mouse model of CML, BCR/ABL+ LSCs and leukemia progenitor cells were found to express CD27. Binding of CD27 by its ligand, CD70, increased expression of Wnt target genes in LSCs by enhancing nuclear localization of active β-catenin and TRAF2- and NCK-interacting kinase (TNIK). This resulted in increased proliferation and differentiation of LSCs. Blocking CD27 signaling in LSCs delayed disease progression and prolonged survival. Furthermore, CD27 was expressed on CML stem/progenitor cells in the bone marrow of CML patients, and CD27 signaling promoted growth of BCR/ABL+ human leukemia cells by activating the Wnt pathway. Since expression of CD70 is limited to activated lymphocytes and dendritic cells, our results reveal a mechanism by which adaptive immunity contributes to leukemia progression. In addition, targeting CD27 on LSCs may represent an attractive therapeutic approach to blocking the Wnt/β-catenin pathway in CML.

Favorable effect of priming with granulocyte colony-stimulating factor in remission induction of acute myeloid leukemia restricted to dose-escalation of cytarabine

The clinical value of chemotherapy sensitization of acute myeloid leukemia (AML) with G-CSF priming has remained controversial. Cytarabine is a key constituent of remission induction chemotherapy. The effect of G-CSF priming has not been investigated in relationship with variable dose levels of cytarabine. We randomized 917 AML patients to receive G-CSF (456 patients) or no G-CSF (461 patients) at the days of chemotherapy. In the initial part of the study, 406 patients were also randomized between 2 cytarabine regimens comparing conventional-dose (199 patients) versus escalated-dose (207 patients) cytarabine in cycles 1 and 2. We found that patients after induction chemotherapy plus G-CSF had similar overall survival (43% vs 40%, P = .88), event-free survival (37% vs 31%, P = .29), and relapse rates (34% vs 36%, P = .77) at 5 years as those not receiving G-CSF. However, patients treated with the escalated-dose cytarabine regimen benefited from G-CSF priming, with improved event-free survival (P = .01) and overall survival (P = .003), compared with patients without G-CSF undergoing escalated-dose cytarabine treatment. A significant survival advantage of sensitizing AML for chemotherapy with G-CSF was not apparent in the entire study group, but it was seen in patients treated with escalated-dose cytarabine during remission induction. The HOVON-42 study is registered under The Netherlands Trial Registry (www.trialregister.nl) as #NTR230.

Cytarabine dose for acute myeloid leukemia

Cytarabine (ara-C) is an important drug in the treatment of acute myeloid leukemia (AML). High-dose cytarabine (2000 to 3000 mg per square meter of body-surface area) is toxic but results in higher rates of relapse-free survival than does the conventional dose of 100 to 400 mg per square meter. Intermediate dose levels have not been thoroughly evaluated.

Activation of the unfolded protein response in human acute myeloid leukemia

There is accumulating evidence for the involvement of the unfolded protein response (UPR) in the pathogenesis of many tumor types in humans. This is particularly the case in rapidly growing solid tumors in which the demand for oxygen and nutrients can exceed the supply until new tumor-initiated blood vessels are formed. In contrast, the role of the UPR during leukemogenesis remains largely unknown. Acute myeloid leukemia (AML) is a genetically heterogeneous clonal disorder characterized by the accumulation of somatic mutations in hematopoietic progenitor cells that alter the physiological regulation of self-renewal, survival, proliferation, or differentiation. The CCAAT/enhancer-binding protein alpha (CEBPA) gene is a key myeloid transcription factor and a frequent target for disruption in AML. In particular, translation of CEBPA mRNA can be specifically blocked by binding of the chaperone calreticulin (CALR), a well-established effector of the UPR, to a stem loop structure within the 5' region of the CEBPA mRNA. The relevance of this mechanism was first elucidated in certain AML subtypes carrying the gene rearrangements t(3;21) or inv(16). In our recent work, we could demonstrate the induction of key effectors of the UPR in leukemic cells of AML patients comprising all subtypes (according to the French-American-British (FAB) classification for human AML). The formation of the spliced variant of the X-box binding protein (XBP1s) was detectable in 17.4% (17 of 105) of AML patients. Consistent with an activated UPR, this group had significantly increased expression of the UPR target genes CALR, the 78 kDa glucose-regulated protein (GRP78), and the CCAAT/enhancer-binding protein homologous protein (CHOP). Consistently, in vitro studies confirmed that calreticulin expression was upregulated via activation of the ATF6 pathway in myeloid leukemic cells. As a consequence, CEBPA protein expression was inhibited in vitro as well as in leukemic cells from patients with activated UPR. We therefore propose a model of the UPR being involved in leukemogenesis through induction of calreticulin along the ATF6 pathway, thereby ultimately suppressing CEBPA translation and contributing to the block in myeloid differentiation and cell-cycle deregulation which represent key features of the leukemic phenotype. From a more clinical point of view, the presence of activated UPR in AML patient samples was found to be associated with a favorable disease course.

High activity of sorafenib in FLT3-ITD-positive acute myeloid leukemia synergizes with allo-immune effects to induce sustained responses

Preliminary evidence suggests that the multikinase inhibitor sorafenib has clinical activity in FLT3-ITD-positive (FLT3-ITD) acute myeloid leukemia (AML). However, the quality and sustainability of achievable remissions and clinical variables that influence the outcome of sorafenib monotherapy are largely undefined. To address these questions, we evaluated sorafenib monotherapy in 65 FLT3-ITD AML patients treated at 23 centers. All but two patients had relapsed or were chemotherapy-refractory after a median of three prior chemotherapy cycles. Twenty-nine patients (45%) had undergone prior allogeneic stem cell transplantation (allo-SCT). The documented best responses were: hematological remission in 24 patients (37%), bone marrow remission in 5 patients (8%), complete remission (with and without normalization of peripheral blood counts) in 15 patients (23%) and molecular remission with undetectable FLT3-ITD mRNA in 10 patients (15%), respectively. Seventeen of the patients without prior allo-SCT (47%) developed sorafenib resistance after a median treatment duration of 136 days (range, 56-270 days). In contrast, allo-SCT patients developed sorafenib resistance less frequently (38%) and significantly later (197 days, range 38-225 days; P=0.03). Sustained remissions were seen exclusively in the allo-SCT cohort. Thus, sorafenib monotherapy has significant activity in FLT3-ITD AML and may synergize with allogeneic immune effects to induce durable remissions.Leukemia advance online publication, 8 May 2012; doi:10.1038/leu.2012.105.

Autologous peripheral blood stem cell transplantation for acute myeloid leukemia

We report the results of a prospective, randomized phase 3 trial evaluating autologous peripheral blood stem cell transplantation (ASCT) versus intensive consolidation chemotherapy in newly diagnosed AML patients in complete remission (CR1). Patients with AML (16-60 years) in CR1 after 2 cycles of intensive chemotherapy and not eligible for allogeneic SCT were randomized between intensive chemotherapy with etoposide and mitoxantrone or ASCT ater high-dose cyclophosphamide and busulfan. Of patients randomized (chemotherapy, n = 259; ASCT, n = 258), more than 90% received their assigned treatment. The 2 groups were comparable with regard to prognostic factors. The ASCT group showed a markedly reduced relapse rate (58% vs 70%, P = .02) and better relapse-free survival at 5 years (38% vs 29%, P = .065, hazard ratio = 0.82; 95% confidence interval, 0.66-1.1) with nonrelapse mortality of 4% versus 1% in the chemotherapy arm (P = .02). Overall survival was similar (44% vs 41% at 5 years, P = .86) because of more opportunities for salvage with second-line chemotherapy and stem cell transplantation in patients relapsing on the chemotherapy arm. This large study shows a relapse advantage for ASCT as postremission therapy but similar survival because more relapsing patients on the chemotherapy arm were salvaged with a late transplantation for relapse. This trial is registered at www.trialregister.nl as #NTR230 and #NTR291.

Disruption of SIRPα signaling in macrophages eliminates human acute myeloid leukemia stem cells in xenografts

Although tumor surveillance by T and B lymphocytes is well studied, the role of innate immune cells, in particular macrophages, is less clear. Moreover, the existence of subclonal genetic and functional diversity in some human cancers such as leukemia underscores the importance of defining tumor surveillance mechanisms that effectively target the disease-sustaining cancer stem cells in addition to bulk cells. In this study, we report that leukemia stem cell function in xenotransplant models of acute myeloid leukemia (AML) depends on SIRPα-mediated inhibition of macrophages through engagement with its ligand CD47. We generated mice expressing SIRPα variants with differential ability to bind human CD47 and demonstrated that macrophage-mediated phagocytosis and clearance of AML stem cells depend on absent SIRPα signaling. We obtained independent confirmation of the genetic restriction observed in our mouse models by using SIRPα-Fc fusion protein to disrupt SIRPα-CD47 engagement. Treatment with SIRPα-Fc enhanced phagocytosis of AML cells by both mouse and human macrophages and impaired leukemic engraftment in mice. Importantly, SIRPα-Fc treatment did not significantly enhance phagocytosis of normal hematopoietic targets. These findings support the development of therapeutics that antagonize SIRPα signaling to enhance macrophage-mediated elimination of AML.

Patterns of molecular response to and relapse after combination of sorafenib, idarubicin, and cytarabine in patients with FLT3 mutant acute myeloid leukemia

BACKGROUND: FMS-like tyrosine kinase 3 (FLT3) is a class III receptor tyrosine kinase involved in hematopoietic progenitor cell development. Mutations of FLT3 have been reported in about a third of patients with acute myeloid leukemia (AML), and inhibitors of FLT3 are of clinical interest. Sorafenib is an orally active multikinase inhibitor with potent activity against FLT3 and the Raf/ERK/MEK kinase pathway. METHODS: We studied the patterns of molecular response and relapse in 18 patients with mutated FLT3 treated with the combination of sorafenib, idarubicin, and cytarabine. RESULTS: The median follow-up was 9 months. Sixteen patients achieved complete remission (CR), and the other 2 patients achieved CR but lacked platelet recovery for an overall response rate of 100%. Ten patients had their FLT3-mutated clone eradicated, with 6 patients who showed some residual FLT3-mutated cells, and 2 patients who showed persistent FLT3-mutated cells. The elimination of FLT3-mutated population at the time of morphologic CR, however, was not predictive of relapse. After a median follow-up of 9 months (range, 1-16 months), 10 (55%) patients had relapsed, with a median CR duration of 8.8 months (range, 1-9.5 months). By DNA sequencing, there was no evidence of an acquired FLT3 point mutation at the time of relapse in 7 patients tested, which suggested the presence of other mechanisms of sorafenib resistance. CONCLUSION: Sorafenib, combined with chemotherapy, is effective in attaining CR, but relapses still occur.

High-grade supraclavicular soft tissue sarcoma as secondary malignancy after successful treatment of acute myeloid leukemia: case report and literature review

It is well known that the treatment protocols for hematopoetic neoplasms carry a high risk of long-term oncogenicity. However, few reports have been published of sarcomas as secondary malignancies. An unusual case report of a soft tissue sarcoma appearing as a secondary cancer is presented, with a review of the published data. The present report involves a soft tissue sarcoma of the neck that occurred 18 years after curative treatment of acute myeloid leukemia by induction chemotherapy and bone marrow transplantation. Consecutive graft-versus-host disease affected the cervical skin. Soft tissue sarcomas appearing as secondary tumors are rare in oncology. The presented case describes the appearance of a sarcoma 18 years after curative treatment of acute myeloid leukemia. This is only the second case of this type reported in published studies.