First-line high-dose therapy and autologous blood stem cell transplantation in patients with primary central nervous system non-Hodgkin lymphomas-a single-centre experience in 61 patients.

Primary central nervous system non-Hodgkin lymphomas (PCNS-NHLs) are extranodal B-cell lymphomas with poor prognosis. The role of high-dose therapy (HDT) followed by autologous blood stem cell transplantation (ASCT) as first-line therapy is still not clear. We retrospectively collected long-term follow up data of 61 consecutive patients with PCNS-NHL at the University Hospital Düsseldorf from January 2004 to December 2016. Thirty-six patients were treated with conventional chemoimmunotherapy (cCIT) only (CT-group). Seventeen patients received an induction cCIT followed by HDT and ASCT. In the CT-group, the overall response rate (ORR) was 61% (CR 47%, PR 14%), and there were 8% treatment-related deaths (TRD). Progression-free survival (PFS) was 31.8 months, and overall survival (OS) was 57.3 months. In the HDT-group, the ORR was 88% (59% CR, 29% PR), and there were 6% TRD. Median PFS and OS were not reached at 5 years. The 5-year PFS and OS were 64.7%. After a median follow up of 71 months, 10 patients (59%) were still alive in CR/PR following HDT and ASCT, one patient was treated for progressive disease (PD), and 7 had died (41%, 6 PD, 1 TRD). All patients achieving CR prior to HDT achieved durable CR. In the CT-group, 8 patients (22%) were alive in CR/PR after a median follow-up of 100 months. Twenty-eight patients died (78%, 24 PD, 2 TRD, 2 deaths in remission). In the univariate analysis, the HDT-group patients had significantly better PFS (not reached vs 31.8 months, p = 0.004) and OS (not reached vs 57.3 months, p = 0.021). The multivariate analysis showed HDT was not predictive for survival. Treatment with HDT + ASCT is feasible and offers the chance for long-term survival with low treatment-related mortality in younger patients. In this analysis, ORR, PFS and OS were better with HDT than with conventional cCIT alone. This result was not confirmed in the multivariate analysis, and further studies need to be done to examine the role of HDT in PCNSL.

Therapy-related myeloid neoplasms following treatment for multiple myeloma-a single center analysis.

Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) can be late complications following mutagenic treatment. Limited data is available on the outcome of patients developing therapy-related MDS and AML after treatment for multiple myeloma (MM). We identified 250 patients with therapy-associated MDS or AML in the Duesseldorf MDS registry. Of those, 50 patients were previously diagnosed with multiple myeloma (mm-MDS/AML). We compared them to patients with de novo MDS (n = 4862) and to patients with MDS following other underlying diseases (tMDS) (n = 200). mm-MDS patients and tMDS patients showed similar karyotypes and degrees of cytopenia. However, mm-MDS patients had significantly higher blast counts and more often belonged to the high-risk group according to the International Prognostic Scoring System (IPSS) (both p < 0.05). Although the rate of progression to AML was similar in mm-MDS and tMDS, both transformed significantly more often than de novo MDS (p < 0.05). Median overall survival of patients with mm-MDS (13 months; range: 1-99) and tMDS (13 months; range 0-160) was also similar yet significantly shorter than patients with de novo MDS (32 months; range 0-345 months; p < 0.05). Furthermore, survival of mm-MDS patients was not affected by myeloma activity. Despite significantly more high-risk disease and higher blast cell counts, myeloma-associated MDS-patients show features akin to other tMDS. Survival is similar to other tMDS and irrespective of myeloma remission status or transformation to AML. Thus, patient outcome is not determined by competing clones but rather by MDS governing the stem cell niche.

Analysis of the impact of adherence to guidelines and expert advice in patients with myelodysplastic syndromes.

The European Leukemia Net (ELN) guidelines for treatment of myelodysplastic syndromes (MDS) connect heterogeneous MDS subgroups with a number of therapeutic options ranging from best supportive care to allogeneic stem cell transplantation (alloSCT). However, it is currently unknown whether adherence to guideline recommendations translates into improved survival. The sizeable database of the Duesseldorf MDS Registry allowed us to address this question. We first performed a retrospective analysis including 1698 patients (cohort 1) to whom we retrospectively applied the ELN guidelines. We compared patients treated according to the guidelines with patients who deviated from it, either because they received a certain treatment though it was not recommended or because they did not receive that treatment despite being eligible. We also performed a prospective study with 381 patients (cohort 2) who were seen in our department and received guideline-based expert advice. Again, we compared the impact of subsequent guideline-adherent versus non-adherent treatment. For the majority of treatment options (best supportive care, lenalidomide, hypomethylating agents, low-dose chemotherapy, and intensive chemotherapy), we found that adherence to the ELN guidelines did not improve survival in cohort 1. The same was true when patient management was prospectively enhanced through guideline-based treatment advice given by MDS experts (cohort 2). The only exceptions were alloSCT and iron chelation (ICT). Patients receiving ICT and alloSCT as recommended fared significantly better than those who were eligible but received other treatment. Our analysis underscores the limited survival impact of most MDS therapies and suggests to pursue alloSCT in all suitable candidates. Graphical abstract.

Allogeneic hematopoietic stem cell transplantation in solid organ transplant recipients: a retrospective, multicenter study of the EBMT.

We conducted a questionnaire survey of the 565 European Society for Blood and Marrow Transplantation centers to analyze the outcome of allogeneic hematopoietic stem cell transplantation (alloSCT) in recipients of solid organ transplantation (SOT). We investigated 28 patients with malignant (N = 22) or nonmalignant diseases (N = 6), who underwent 31 alloSCT procedures: 12 after kidney, 13 after liver and 3 after heart transplantation. The incidence of solid organ graft failure at 60 months after first alloSCT was 33% (95% confidence interval [CI], 16-51%) for all patients, 15% (95% CI, 2-40%) for liver recipients and 50% (95% CI, 19-75%) for kidney recipients (p = 0.06). The relapse rate after alloSCT (22%) was low following transplantation for malignant disorders, despite advanced stages of malignancy. Overall survival at 60 months after first alloSCT was 40% (95% CI, 19-60%) for all patients, 51% (95% CI, 16-86%) for liver recipients and 42% (95% CI, 14-70%) for kidney recipients (p = 0.39). In summary, we show that selected SOT recipients suffering from hematologic disorders may benefit from alloSCT and experience enhanced long-term survival without loss of organ function.

Outcome and prognostic factors in patients with mantle-cell lymphoma relapsing after autologous stem-cell transplantation: a retrospective study of the European Group for Blood and Marrow Transplantation (EBMT).

BACKGROUND: Autologous stem-cell transplantation (autoSCT) is considered a standard treatment of non-frail patients with mantle cell lymphoma (MCL), but little is known about outcome of MCL patients relapsing after autoSCT. We therefore sought to analyse the outcome after autoSCT failure and the efficacy of a rescue stem-cell transplantation (SCT) in this setting. PATIENTS AND METHODS: Patients with MCL were eligible if they had relapsed after autoSCT performed between 2000 and 2009. A total of 1054 patients could be identified in the EBMT registry. By contacting the transplant centres, a full dataset could be retrieved for 360 patients. RESULTS: Median overall survival (OS) after relapse of the whole study group was 19 months. A long (>12 months) interval between autoSCT and relapse [P < 0.001, hazard ratio (HR) 0.62], primary refractory disease (P < 0.02, HR 1.92), prior high-dose ARA-C treatment (P = 0.04, HR 1.43), and the year of relapse (P = 0.02, HR 0.92) significantly influenced OS from relapse in multivariate analysis. Eighty patients (22%) received a rescue allogeneic SCT (alloSCT). Relapse incidence, non-relapse mortality, and OS 2 years after alloSCT was 33% [confidence interval (95% CI 21% to 45%)], 30% (95% CI 19% to 42%), and 46% (95% CI 33% to 59%), respectively. Remission duration after autoSCT was the only variable significantly affecting the outcome of salvage alloSCT. In contrast, rescue autoSCT was not associated with long-term disease control. However, individual patients survived long term even without salvage transplantation. CONCLUSIONS: MCL recurrence within 1 year after autoSCT has an extremely dismal outcome, while the prognosis of patients with longer remission durations after autoSCT is significantly better. AlloSCT may offer the possibility of durable survival when performed for patients with a remission duration of more than 12 months after first autoSCT, but the favourable effect of a salvage alloSCT in this setting needs further validation.

The WHO 2016 diagnostic criteria for Acute Myeloid leukemia with myelodysplasia related changes (AML-MRC) produce a very heterogeneous entity: A retrospective analysis of the FAB subtype RAEB-T.

We studied 79 patients with AML-MRC or RAEB-T, who were later reclassified according to the WHO classification. Marrow slides were examined cytomorphologically with regard to dysplasia. Patients were followed up until March 2020. Thirty-one patients underwent allogeneic stem cell transplantation (median survival (ms) 16 months), 14 were treated with induction chemotherapy (ms 8.4 months), 18 received hypomethylating agents (ms 9.2 months), 16 received low dose chemotherapy or best supportive care (ms 2.4 months). Only 30.4 % fulfilled the morphologic WHO criteria. 46.8 % were classified as AML-MRC by an antecedent MDS, 54.4 % of the pts were classified by MDS-related chromosomal abnormalities. 5 % did not fulfill any of the criteria and were entered based on 20-29 % medullary blasts. There was no difference in ms between pts presenting with > 50 % dysplasia as compared to pts with dysplasia between 10 % and 50 % (ms 9.1 vs 9.9 months, p = n.s.) or for pts with antecedent MDS (ms 9.1 vs 8.9 months, p = n.s.). Myelodysplasia-related cytogenetic abnormalities were associated with a worse outcome (ms 8.1 vs 13.5 months, p = 0.026). AML-MRC in its current definition is a heterogenous entity. Dysplasia of ≥ 50 % in ≥ two lineages is not helpful for diagnostics and prognostication and therefore should be deleted in future classifications. We recommend utilizing the WHO guidelines for defining dysplasia (10 % or greater in ≥ 1 of the three myeloid cell lines) assisting in establishing the diagnosis of MDS.

Allogeneic hematopoietic stem cell transplantation for advanced mycosis fungoides and Sézary syndrome. An updated experience of the Lymphoma Working Party of the European Society for Blood and Marrow Transplantation.

BACKGROUND: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative treatment option in advanced-stage mycosis fungoides (MF) and Sézary syndrome (SS). This study presents an updated analysis of the initial experience of the Lymphoma Working Party of the European Society for Blood and Marrow Transplantation (EBMT) describing the outcomes after allo-HSCT for MF and SS, with special emphasis on the impact of the use of unrelated donors (URD). METHODS AND PATIENTS: Eligible for this study were patients with advanced-stage MF or SS who underwent a first allo-HSCT from matched HLA-identical related or URD between January/1997 and December/2011. Sixty patients have been previously reported. RESULTS: 113 patients were included [77 MF (68%)]; 61 (54%) were in complete or partial remission, 86 (76%) received reduced-intensity protocols and 44 (39%) an URD allo-HSCT. With a median follow up for surviving patients of 73 months, allo-HSCT resulted in an estimated overall survival (OS) of 38% at 5 years, and a progression-free survival (PFS) of 26% at 5 years. Multivariate analysis demonstrated that advanced-phase disease (complete remission/partial remission >3, primary refractory or relapse/progression in patients that had received 3 or more lines of systemic treatment prior to transplant or the number of treatment lines was not known), a short interval between diagnosis and transplant (<18 months) were independent adverse prognostic factors for PFS; advanced-phase disease and the use of URDs were independent adverse prognostic factors for OS. CONCLUSIONS: This extended series supports that allo-HSCT is able to effectively rescue over one third of the population of patients with advanced-stage MF/SS. High relapse rate is still the major cause of failure and needs to be improved with better strategies before and after transplant. The negative impact of URD is a matter of concern and needs to be further elucidated in future studies.

A 3-day short course of palifermin before HDT reduces toxicity and need for supportive care after autologous blood stem-cell transplantation in patients with multiple myeloma.

BACKGROUND: We retrospectively determined whether a 3-day short course of palifermin could reduce the toxicity of high-dose therapy (HDT) and autologous blood stem-cell transplantation (ASCT) in patients with multiple myeloma (MM). PATIENTS AND METHODS: Sixty-seven consecutive patients received 60 mug/kg palifermin for 3 days before HDT with melphalan 200 or 140 mg/m(2) for patients with renal failure (group A). Granulocyte colony-stimulating factor (G-CSF) was applied after ASCT. Data on haematopoietic reconstitution and toxicity were compared with two previously published patient groups from our institution who had received pegfilgrastim but not palifermin (group B, n = 21) and patients who had received neither palifermin nor G-CSF (group C, n = 21). RESULTS: In group A, patients with renal failure had a significantly higher risk for severe mucositis (64% versus 16%, P < 0.002). Patients with normal renal function who received palifermin experienced significantly less days of hospitalisation (P < 0.05) and less need for narcotic analgesia (P < 0.05), parenteral nutrition (P < 0.05) and erythrocyte transfusions (P < 0.05) in comparison with groups B and C. Time to haematopoietic reconstitution was not compromised by the use of palifermin. CONCLUSIONS: In conclusion, a short 3-day course of palifermin may be able to reduce the toxicity of HDT and ASCT in patients with MM. Patients with impaired renal function at the time of HDT need additional strategies to further reduce the incidence of severe mucositis.

Bendamustine in patients with relapsed or refractory multiple myeloma.

OBJECTIVE: In patients with multiple myeloma, bendamustine monotherapy is effective as 1st and 2nd line therapy. However, data for patients with advanced multiple myeloma is rare. METHODS: In this retrospective analysis we have identified 39 patients with relapsed or refractory multiple myeloma by means of case research, who have been treated at our institution with bendamustine as salvage therapy. After in median 2 lines of prior therapy (range: 1-5) patients received in median 3 (range: 1-10) cycles of bendamustine. Bendamustine dosage was 80-150 mg on day 1+2 of a monthly cycle. Bendamustine was administered as monotherapy in 39% of patients, whereas 61% received concomitant steroids. RESULTS: Toxicity was mild to moderate. Response rates were as follows: 3% vgPR, 33% PR, 18% MR, 26% SD and 20% PD. The median event-free and overall survival were 7 and 17 months, respectively. CONCLUSIONS: In conclusion, in patients with advanced multiple myeloma bendamustine is effective and associated with mild toxicity. Therefore, the role of bendamustine in patients with multiple myeloma should be investigated in further clinical trials.

Molecular signature of CD34(+) hematopoietic stem and progenitor cells of patients with CML in chronic phase.

In this study, we provide a molecular signature of highly enriched CD34+ cells from bone marrow of untreated patients with chronic myelogenous leukemia (CML) in chronic phase in comparison with normal CD34+ cells using microarrays covering 8746 genes. Expression data reflected several BCR-ABL-induced effects in primary CML progenitors, such as transcriptional activation of the classical mitogen-activated protein kinase pathway and the phosphoinositide-3 kinase/AKT pathway as well as downregulation of the proapoptotic gene IRF8. Moreover, novel transcriptional changes in comparison with normal CD34+ cells were identified. These include upregulation of genes involved in the transforming growth factorbeta pathway, fetal hemoglobin genes, leptin receptor, sorcin, tissue inhibitor of metalloproteinase 1, the neuroepithelial cell transforming gene 1 and downregulation of selenoprotein P. Additionally, genes associated with early hematopoietic stem cells (HSC) and leukemogenesis such as HoxA9 and MEIS1 were transcriptionally activated. Differential expression of differentiation-associated genes suggested an altered composition of the CD34+ cell population in CML. This was confirmed by subset analyses of chronic phase CML CD34+ cells showing an increase of the proportion of megakaryocyte-erythroid progenitors, whereas the proportion of HSC and granulocyte-macrophage progenitors was decreased in CML. In conclusion, our results give novel insights into the biology of CML and could provide the basis for identification of new therapeutic targets.

HLA-identical sibling allogeneic peripheral blood stem cell transplantation with reduced intensity conditioning compared to autologous peripheral blood stem cell transplantation for elderly patients with de novo acute myeloid leukemia.

We conducted a retrospective registry-based analysis to compare the outcome of 361 allogeneic human leukocyte antigen (HLA)-identical peripheral blood stem cell transplants (PBSCT) with reduced intensity conditioning (RIC) to that of 1369 autologous (auto) PBSCT in patients aged 50 years or older with de novo acute myeloid leukemia (AML), performed from 1997 until 2003 and reported to the European Group for Blood and Marrow Transplantation. Median age was 58 and 57 years in the RIC and auto groups, respectively. RIC patients had more advanced disease at the time of transplant. At a median follow-up of 24 months for RIC and 16 months for auto, multivariate analysis showed a lower risk for relapse (RR 0.77, P=0.013) without increased non-relapse mortality (NRM) in RIC patients (RR 1.26, P=0.28). Moreover, leukemia-free survival (RR 1.22, P=0.02) and overall survival (OS) (RR 1.32, P=0.005) were superior in the RIC group. In patients in 1st (CR), fewer relapses were counterbalanced by significantly increased NRM. Therefore, there was no survival advantage in this subgroup. In patients in 2nd or subsequent CR, LFS and OS were superior in the RIC group. RIC transplants show encouraging results in this older patient population with de novo AML.

[Successful use of allogeneic stem cell transplantation for treatment-refractory mycosis fungoides]. / Erfolgreicher Einsatz einer allogenen Stammzelltransplantation bei therapierefraktärer Mycosis fungoides.

Mycosis fungoides is the most common type of cutaneous T-cell lymphoma and characterized by a chronic progressive course spanning decades. The choice of treatment options should be tailored to the stage depending on the extent and aggressiveness of the disease and taking the individual situation of the patient into consideration. Long-term complete remissions can only be achieved in the early phase of the disease, while there is no therapy that results in a cure or long-term remission in advanced stages. In young patients with a treatment-refractory course of mycosis fungoides, allogeneic stem cell transplantation represents an important alternative option to manage the disease since complete clinical remission can be obtained even in advanced stages.

Induction of complete remission in a patient with acute myeloid leukemia refractory to high-dose chemotherapy through treatment with 5-azacytidine.

For patients with acute myeloid leukemia refractory to intensive chemotherapy prognosis is very poor and treatment options are limited. 5-Azacytidine, a demethylating drug, is effective in the treatment of myelodysplastic syndromes when administered at a low-dose, subcutaneously. We report a case of a patient with AML refractory to induction chemotherapy as well as to two high-dose salvage regimens. The patient achieved CR through monotherapy with low-dose azacytidine.

Long-term survival of sorafenib-treated FLT3-ITD-positive acute myeloid leukaemia patients relapsing after allogeneic stem cell transplantation.

BACKGROUND: Fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD)-positive acute myeloid leukaemia (AML) relapsing after allogeneic stem cell transplantation (allo-SCT) has a dismal prognosis with limited therapeutic options. FLT3-ITD kinase inhibition is a reasonable but palliative experimental treatment alternative in this situation. Information on long-term outcome is not available. METHODS: We performed a long-term follow-up analysis of a previously reported cohort of 29 FLT3-ITD-positive AML patients, which were treated in relapse after allo-SCT with sorafenib monotherapy. FINDINGS: With a median follow-up of 7.5 years, 6 of 29 patients (21%) are still alive. Excluding one patient who received a second allo-SCT, five patients (17%) achieved sustained complete remissions with sorafenib. Four of these patients are in treatment-free remission for a median of 4.4 years. INTERPRETATION: Sorafenib may enable cure of a proportion of very poor risk FLT3-ITD-positive AML relapsing after allo-SCT.

Transfer of minimally manipulated CMV-specific T cells from stem cell or third-party donors to treat CMV infection after allo-HSCT.

Cytomegalovirus (CMV) infection is a common, potentially life-threatening complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT). We assessed prospectively the safety and efficacy of stem cell-donor- or third-party-donor-derived CMV-specific T cells for the treatment of persistent CMV infections after allo-HSCT in a phase I/IIa trial. Allo-HSCT patients with drug-refractory CMV infection and lacking virus-specific T cells were treated with a single dose of ex vivo major histocompatibility complex-Streptamer-isolated CMV epitope-specific donor T cells. Forty-four allo-HSCT patients receiving a T-cell-replete (D+ repl; n=28) or T-cell-depleted (D+ depl; n=16) graft from a CMV-seropositive donor were screened for CMV-specific T-cell immunity. Eight D+ depl recipients received adoptive T-cell therapy from their stem cell donor. CMV epitope-specific T cells were well supported and became detectable in all treated patients. Complete and partial virological response rates were 62.5% and 25%, respectively. Owing to longsome third-party donor (TPD) identification, only 8 of the 57 CMV patients transplanted from CMV-seronegative donors (D-) received antigen-specific T cells from partially human leukocyte antigen (HLA)-matched TPDs. In all but one, TPD-derived CMV-specific T cells remained undetectable. In summary, adoptive transfer correlated with functional virus-specific T-cell reconstitution in D+ depl patients. Suboptimal HLA match may counteract expansion of TPD-derived virus-specific T cells in D- patients.

Surveillance of nosocomial infections in paediatric recipients of bone marrow or peripheral blood stem cell transplantation during neutropenia, compared with adult recipients.

The aim of this prospective study was to analyse the incidence of nosocomial infections (NIs) during neutropenia after haematopoietic stem cell transplantation (HSCT) in paediatric and adult patients. Diagnosis of NI followed the modified surveillance protocol of the German National Reference Centre for Surveillance of NIs. During the 24-month study period, 38 and 39 transplantations were performed in paediatric and adult patients, respectively. Eighty percent and 92% of the paediatric and adult patients, respectively, underwent allogenic HSCT. In total, 1156 neutropenic days were documented. The incidence of NI during neutropenia in all recorded cases was 38.9 NI per 1000 days, without significant difference between the groups. No difference was found in the incidence rates of pneumonia, while there was a trend towards a higher incidence of bloodstream infection in adult patients. Significantly more episodes of fever of unknown origin were found in paediatric than adult patients. Pathogens were isolated in 19 of 45 cases of NI. Of the clinically documented infections, Gram-positive organisms were isolated in 79%, Gram-negative organisms were isolated in 16% and fungi were isolated in 5%. Surveillance of NI is an effective instrument to control the quality of health care. It should focus on device-associated infections or specific high-risk targets such as nosocomial pneumonia.

G-CSF during large field radiotherapy reduces bone marrow recovery capacity.

OBJECTIVE: Side effects of chemo- and radiotherapy are granulo- and thrombocytopenia. However, the long-term effects of in vivo granulocyte-colony-stimulating factor (G-CSF) stimulation of the hematopoietic system during radiotherapy are not yet completely understood. In the present study, we sought to determine the bone marrow effect of G-CSF during radiotherapy. MATERIAL AND METHODS: In a prospective, randomized clinical trial 10 patients (6 m, 4 f, 30-64 yrs, mean 50.6 yrs) were assigned to large field radiotherapy (RT). 7 patients (pat.) with non-Hodgkin lymphoma, one patient with Hodgkin's disease and 2 patients with small-cell carcinoma of the lung were included. The patients were randomized to either radiotherapy alone (group A) or radiotherapy with simultaneous G-CSF (group B) treatment and assessed for acute and late toxicity. Blood samples were drawn and analyzed before and after G-CSF stimulation. The mobilization effectivity of G-CSF on CD34 superset+ progenitor cells was measured using flow cytometry and colony forming units (CFU) testing on admission and during the complete follow-up period (1, 3 and 18 months post RTx). RESULTS: Overall, 50 pat. were intended to be included to the protocol. However, the preliminary analysis revealed a significant decrease of thrombocytes and CD34 superset+ progenitor cells in the G-CSF treatment group. According to the study protocol further treatment was stopped. Peripheral leukocyte counts ranged between 2800 - 4375 /mul in 9/10 pat. In group B mean thrombocyte levels dropped below 30.000 mg/l and CD34 superset+ progenitor cells to 50% (interruption criteria, p<0.02, Student's t-test). Hemoglobin values did not vary. Differential blood smears showed differences in granulocyte counts and a higher proportion of neutrophils in group B. Lymphocyte counts of patients randomized to group A were significantly decreased when compared to group B. In group A, 3/5 pat. developed an overshooting reaction (4,7 x increase) after G-CSF-stimulation. In arm B circulating CD34 superset+ progenitor cells dropped. In arm A, 3/5 pat. had an initial overshoot reaction when compared to none in group B. CFU (> 40 cells) and cluster (4 -39 cells) showed considerable variations. CONCLUSION: Our results demonstrate that simultaneous treatment with G-CSF during radiotherapy reduces the mobilization of CD34+ progenitor cells and exhaust the bone marrow capacity while peripheral leukocyte counts remain at baseline levels.

Functional inhibition of mesenchymal stromal cells in acute myeloid leukemia.

Hematopoietic insufficiency is the hallmark of acute myeloid leukemia (AML) and predisposes patients to life-threatening complications such as bleeding and infections. Addressing the contribution of mesenchymal stromal cells (MSC) to AML-induced hematopoietic failure we show that MSC from AML patients (n=64) exhibit significant growth deficiency and impaired osteogenic differentiation capacity. This was molecularly reflected by a specific methylation signature affecting pathways involved in cell differentiation, proliferation and skeletal development. In addition, we found distinct alterations of hematopoiesis-regulating factors such as Kit-ligand and Jagged1 accompanied by a significantly diminished ability to support CD34+ hematopoietic stem and progenitor cells in long-term culture-initiating cells (LTC-ICs) assays. This deficient osteogenic differentiation and insufficient stromal support was reversible and correlated with disease status as indicated by Osteocalcin serum levels and LTC-IC frequencies returning to normal values at remission. In line with this, cultivation of healthy MSC in conditioned medium from four AML cell lines resulted in decreased proliferation and osteogenic differentiation. Taken together, AML-derived MSC are molecularly and functionally altered and contribute to hematopoietic insufficiency. Inverse correlation with disease status and adoption of an AML-like phenotype after exposure to leukemic conditions suggests an instructive role of leukemic cells on bone marrow microenvironment.