The maintenance mechanism of hematopoietic stem cell dormancy: role for a subset of macrophages

Hematopoiesis is regulated by crosstalk between long-term repopulating hematopoietic stem cells (LT-HSCs) and supporting niche cells in the bone marrow (BM). Here, we describe the role of KAI1, which is mainly expressed on LT-HSCs and rarely on other hematopoietic stem-progenitor cells (HSPCs), in nichemediated LT-HSC maintenance. KAI1 activates TGF-β1/Smad3 signal in LT-HSCs, leading to the induction of CDK inhibitors and inhibition of the cell cycle. The KAI1-binding partner DARC is expressed on macrophages and stabilizes KAI1 on LT-HSCs, promoting their quiescence. Conversely, when DARC+ BM macrophages were absent, the level of surface KAI1 on LT-HSCs decreases, leading to cell-cycle entry, proliferation, and differentiation. Thus, KAI1 acts as a functional surface marker of LTHSCs that regulates dormancy through interaction with DARCexpressing macrophages in the BM stem cell niche. Recently, we showed very special and rare macrophages expressing α-SMA+ COX2+ & DARC+ induce not only dormancy of LTHSC through interaction of KAI1-DARC but also protect HSCs by down-regulating ROS through COX2 signaling. In the near future, the strategy to combine KAI1-positive LT-HSCs and α-SMA/Cox2/DARC triple-positive macrophages will improve the efficacy of stem cell transplantation after the ablative chemo-therapy for hematological disorders including leukemia. [BMB Reports 2023; 56(9): 482-487].

Haploidentical haematopoietic stem cell transplantation for TP53-mutated acute myeloid leukaemia

Acute myeloid leukaemia (AML) patients with tumour protein p53 (TP53) mutations are often resistant to chemotherapy and have worse clinical outcomes than patients without TP53 mutations. In this study, we compared clinical outcomes of patients with AML with and without TP53 mutations who underwent haploidentical haematopoietic stem cell transplantation (haplo-HSCT). For the TP53-mutation group and TP53 wild-type group, the 2-year cumulative incidence of relapse (CIR) was (39.0% vs. 21.2% respectively, p = 0.088), the 2-year non-relapse mortality (NRM) rate was (3.2% vs. 8.4% respectively, p = 0.370), the 2-year leukaemia-free survival (LFS) was (57.7% vs. 71.3% respectively, p = 0.205), the 2-year overall survival (OS) rate was (69.9% vs. 81.3% respectively, p = 0.317), the 100-day cumulative incidence of Grade II-IV acute graft-versus-host disease (GvHD) was (6.5% vs. 20.7% respectively, p = 0.074), the 2-year cumulative incidence of chronic GvHD was (52.3% vs. 53.1% respectively, p = 0.493) and the 2-year GvHD-free/relapse-free survival (GRFS) was (57.7% vs. 69.6% respectively, p = 0.347). Our data showed that there were no significant differences in 2-year clinical outcomes between the two groups. Multivariable analysis showed TP53 mutations had no significant impact on CIR, NRM, OS, GvHD, LFS or GRFS. Our findings suggest that patients with AML with TP53 mutations may at least partially benefit from haplo-HSCT. Haplo-HSCT might be the recommended treatment for such patients.

Cytomegalovirus infection is associated with rapid NK differentiation and reduced incidence of relapse in HLA matched sibling donor transplant patients

The effect of cytomegalovirus (CMV) infection on leukemia relapse and the potential mechanism remains controversial. In this retrospective study, we evaluated the association among CMV infection, NK reconstitution and clinical outcomes in consecutive patients with hematologic malignancy who underwent HLA matched sibling donor transplantation (MST). In total, 228 patients were enrolled in the study between January 2010 and December 2011. The cumulative incidence of CMV infection on day 100 post-HSCT was 13.6 ± 4.9%. The probabilities of OS and DFS were 45.4% vs. 71.7% (P = 0.004) and 43.9% vs. 64.2% (P = 0.050) in the patients with CMV infection and without CMV infection, respectively. The cumulative incidence of treatment-related mortality (TRM) and relapse at 5 years was 48.6 ± 9.6% vs. 11.5 ± 2.9% (P < 0.001) and 6.2 ± 4.3% vs. 29.2 ± 3.9% (P = 0.024) in the patients with CMV infection and without CMV infection, respectively. In the multivariate analysis, CMV infection was associated with higher TRM, lower OS, and lower DFS. In addition, we found that CMV infection may promote the recovery of the absolute number of NK cells and promote the differentiation of NK cells post-MST. In conclusion, CMV infection may promote the recovery and differentiation of NK cells and was correlated with a lower relapse rate post-MST.

Second unmanipulated allogeneic transplantation could be used as a salvage option for patients with relapsed acute leukemia post-chemotherapy plus modified donor lymphocyte infusion

Relapse is the main problem after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The outcome of a second allo-HSCT (HSCT2) for relapse post-HSCT has shown promising results in some previous studies. However, little is known about the efficacy of HSCT2 in patients with relapsed/refractory acute leukemia (AL) post-chemotherapy plus modified donor lymphocyte infusion (post-Chemo + m-DLI) after the first allo-HSCT (HSCT1). Therefore, we retrospectively analyzed the efficacy of HSCT2 in 28 patients with relapsed/refractory AL post-Chemo + m-DLI in our center. With a median follow-up of 918 (457-1732) days, 26 patients (92.9%) achieved complete remission, and 2 patients exhibited persistent disease. The probabilities of overall survival (OS) and disease-free survival (DFS) 1 year after HSCT2 were 25.0% and 21.4%, respectively. The cumulative incidences of nonrelapse mortality on day 100 and at 1 year post-HSCT2 were 7.1% ± 4.9% and 25.0% ± 8.4%. The cumulative incidences of relapse were 50.0% ± 9.8% and 53.5% ± 9.9% at 1 and 2 years post-HSCT2, respectively. Risk stratification prior to HSCT1 and percentage of blasts before HSCT2 were independent risk factors for OS post-HSCT2, and relapse within 6 months post-HSCT1 was an independent risk factor for DFS and relapse post-HSCT2. Our findings suggest that HSCT2 could be a salvage option for patients with relapsed AL post-Chemo + m-DLI.

Hepatitis B Seropositive Status in Recipients or Donors Is Not Related to Worse Outcomes after Haploidentical Hematopoietic Stem Cell Transplantation

Hepatitis B virus (HBV) has a high rate of chronic infection in Asian populations, and only limited studies have been performed to analyze the impact of HBV-seropositive haploidentical hematopoietic stem cell transplantation (haplo-HSCT) recipients and donors. The present study aimed to evaluate the effect on clinical outcomes in those patients. We conducted a retrospective study enrolling 237 consecutive patients undergoing first haplo-HSCT. The patients were classified into 3 groups: recipient HBV-positive group (R+D-; n = 62), donor HBV-positive group (D+; n = 83), and HBV-negative group (R-D-; n = 92). Corresponding prophylactic antiviral treatment was given in the R+D- and D+ groups. The results were compared among the 3 groups using the Kruskal-Wallis test for continuous variables, Pearson's chi-square test for categorical variables, the competing-risk method to evaluate cumulative incidence, Kaplan-Meier curves to estimate overall survival (OS) and disease-free survival (DFS), and a Cox proportional hazard model to analyze multivariable influences. The 3-year cumulative HBV reactivation rate was 4.2%. The median time to HBV reactivation was 845 days (range, 545 to 1439 days) after haplo-HSCT. The R+D- group tended to have a higher cumulative incidence of HBV reactivation compared with the D+ group (11.8% versus 3.1%; P = .080). Significant differences in the causes of hepatic damage were observed among the 3 groups (P = .017), and all patients with acute hepatitis B after haplo-HSCT were from the R+D- group. Multivariate analysis showed that pretransplantation HBV status was associated with cytomegalovirus reactivation (R+D- versus R-D-: hazard ratio, 1.514; 95% confidence interval, 1.060 to 2.163; P = .023). The 3-year OS and DFS, 3-year cumulative incidence of nonrelapse mortality (NRM), rates of relapse and graft-versus-host disease (GVHD), and causes of death were comparable among the 3 groups. Pretransplantation HBV serostatus had no significant effect on OS, DFS, NRM, relapse, or GVHD in the multivariate analysis. Based on our data, seropositivity for hepatitis B surface antigen (HbsAg) or core antibody (HBcAb) in donors or recipients before transplantation did not negatively affect the overall outcome after haplo-HSCT under the premise of proper antiviral prophylaxis along with regular post-transplantation surveillance, and HBV seropositivity should not be considered a contraindication to haplo-HSCT.

Donor and host coexpressing KIR ligands promote NK education after allogeneic hematopoietic stem cell transplantation

The rate and extent of natural killer (NK)-cell education after hematopoietic cell transplantation correlates with leukemia control. To study the effect of donor and host HLA on NK-cell reconstitution, single killer-cell immunoglobulin-like receptor (KIR)+ NK cells (exhibiting KIR2DL1, KIR2DL2/KIR2DL3, or KIR3DL1 as their sole receptor) were grouped into 4 groups based on the interaction between donor/host HLA and donor inhibitory KIR in 2 cohorts (n = 114 and n = 276, respectively). On days 90 to 180 after transplantation, the absolute number and responsiveness against K562 cells (CD107a or interferon-γ expression) of single-KIR+ NK cells were higher in pairs where donor and host HLA both expressed ligands for donor inhibitory KIRs than in pairs where 1 or both of the donor and recipient HLA lacked at least 1 KIR ligand. NK-cell responsiveness was tuned commensurate with the number of inhibitory receptors from the donor. When both donor and host expressed the 3 major KIR ligands (HLA-C1, HLA-C2, and HLA-Bw4), NK cells expressing 3 inhibitory receptors (KIR2DL1/2DL3/3DL1) reached the maximum responsiveness against K562 cells compared with those NK cells expressing only 1 or 2 inhibitory receptors. When donor and host HLA both expressed all ligands for donor inhibitory KIRs, patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) showed the lowest recurrence rate after haploidentical hematopoietic stem cell transplantation (haplo-HSCT). In conclusion, this study demonstrates that when both donors and hosts present all the KIR ligands for donor KIRs, reconstituted NK cells achieve better functional education and contribute to least relapse among patients. This observation study was registered at www.clinicaltrials.gov as #NCT02978274.

Different Effects of Pre-transplantation Measurable Residual Disease on Outcomes According to Transplant Modality in Patients With Philadelphia Chromosome Positive ALL

Background: This study compared the effects of pre-transplantation measurable residual disease (pre-MRD) on outcomes in Philadelphia chromosome (Ph)-positive ALL patients who underwent human leukocyte antigen-matched sibling donor transplantation (MSDT) or who received unmanipulated haploidentical SCT (haplo-SCT). Methods: A retrospective study (n = 202) was performed. MRD was detected by RT-PCR and multiparameter flow cytometry. Results: In the total patient group, patients with positive pre-MRD had a higher 4-year cumulative incidence of relapse (CIR) than that in patients with negative pre-MRD (26.1% vs. 12.1%, P = 0.009); however, the cumulative incidence of non-relapse mortality (NRM) (7.4% vs. 15.9%, P = 0.148), probability of leukemia-free survival (LFS) (66.3% vs. 71.4%, P = 0.480), and overall survival (OS) (68.8% vs. 76.5%, P = 0.322) were comparable. In the MSDT group, patients with positive pre-MRD had increased 4-year CIR (56.4% vs. 13.8%, P < 0.001) and decreased 4-year LFS (35.9% vs. 71.0%, P = 0.024) and OS (35.9% vs. 77.6%, P = 0.011) compared with those with negative pre-MRD. In haplo-SCT settings, the 4-year CIR (14.8% vs. 10.7%, P = 0.297), NRM (7.3% vs. 16.3%, P = 0.187) and the 4-year probability of OS (77.7% vs. 72.3%, P = 0.804) and LFS (80.5% vs. 75.7%, P = 0.660) were comparable between pre-MRD positive and negative groups. In subgroup patients with positive pre-MRD, haplo-SCT had a lower 4-year CIR (14.8% vs. 56.4%, P = 0.021) and a higher 4-year LFS (77.7% vs. 35.9%, P = 0.036) and OS (80.5% vs. 35.9%, P = 0.027) than those of MSDT. Multivariate analysis showed that haplo-SCT was associated with lower CIR (HR, 0.288; P = 0.031), superior LFS (HR, 0.283; P = 0.019) and OS (HR, 0.252; P = 0.013) in cases with a positive pre-MRD subgroup. Conclusions: Our results indicate that the effects of positive pre-MRD on the outcomes of patients with Ph-positive ALL are different according to transplant modality. For Ph-positive cases with positive pre-MRD, haplo-SCT might have strong graft-vs.-leukemia (GVL) effects.

Pediatric acute myeloid leukemia: updates on biology, risk stratification, and therapy

PURPOSE OF REVIEW

Despite advances in therapy over the past decades, overall survival for children with acute myeloid leukemia (AML) has not exceeded 70%. In this review, we highlight recent insights into risk stratification for patients with pediatric AML and discuss data driving current and developing therapeutic approaches.

RECENT FINDINGS

Advances in cytogenetics and molecular profiling, as well as improvements in detection of minimal residual disease after induction therapy, have informed risk stratification, which now relies heavily on these elements. The treatment of childhood AML continues to be based primarily on intensive, conventional chemotherapy. However, recent trials focus on limiting treatment-related toxicity through the identification of low-risk subsets who can safely receive fewer cycles of chemotherapy, allocation of hematopoietic stem-cell transplant to only high-risk patients and optimization of infectious and cardioprotective supportive care.

SUMMARY

Further incorporation of genomic and molecular data in pediatric AML will allow for additional refinements in risk stratification to enable the tailoring of treatment intensity. These data will also dictate the incorporation of molecularly targeted therapeutics into frontline treatment in the hope of improving survival while decreasing treatment-related toxicity.

Incidence, Risk Factors, and Outcome of Immune-Mediated Neuropathies (IMNs) following Haploidentical Hematopoietic Stem Cell Transplantation

Immune-mediated neuropathies (IMNs) following hematopoietic stem cell transplantation have been described recently, which, excluding Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy, may present with atypical patterns. This retrospective, nested, case-control study reviewed data from 3858 patients who received haploidentical hematopoietic stem cell transplantation (haplo-HSCT) during the past 10 years at a single center, and 40 patients (1.04%) with IMN following haplo-HSCT were identified. Chronic graft-versus-host disease (cGVHD) (P = .043) and cytomegalovirus (CMV) viremia (P = .035) were recognized as independent risk factors for the development of IMN after haplo-HSCT. There were no significant differences in overall survival (P = .619), disease-free survival (P = .609), nonrelapse mortality (P = .87), or the incidence of relapse (P = .583) between patients with and without IMN after haplo-HSCT. However, patients with post-transplant IMN were at higher risk of developing cGVHD (P = .012) than patients who did not develop IMN. Twenty-four of the 40 patients with IMN (60%) attained neurologic improvement after treatments including vitamins B₁ and B₁₂ and/or immunomodulatory agents. However, 19 (47.5%) patients still had persistent motor/sensory deficits despite receiving timely treatment. More studies are needed to help develop standardized diagnostic and therapeutic strategies for patients with post-transplant IMN.

[Impact of mycophenolate mofetil prophylaxis duration on acute graft-versus-host disease after haploidentical stem cell transplantation]

Objective: To investigate the impact of mycophenolate mofetil (MMF) prophylaxis duration on acute graft-versus-host disease (aGVHD) after haploidentical stem cell transplantation (haplo-HSCT) using 'Beijing Protocol'. Methods: Adult patients (≥14 years) received haplo-HSCT in Peking University Institute of Hematology from Sep, 2016 to Mar, 2017 were retrospectively reviewed if they fulfilled the criterias: ①diagnosed with hematological maligancies; ②standard-risk status at haplo-HSCT. A total of 237 patients [including 102 patients with long MMF duration (defined as started on day -9 with 100 mg/d, adjusted to 500 mg/d from day +30 and discontinued on day +45 to +60 or occurrence of CMV/EBV reactivation or late-onset hemorrhagic cytitis), and 135 patients with short MMF duration (defined as started on day -9 with 500 mg/d and discontinued on the day achieved neutrophil engraftment)] were reviewed. The incidence of aGVHD, virus infection and overall survival (OS) were compared between the two groups. Results: The median durations of MMF prophylaxis of long and short duration groups were 27(7-71) and 15(9-24) days, respectively after haplo-HSCT. There were no differences of baseline characteristics (including sex, patient age, disease, mismatched HLA loci, donor-recipient relation, donor-recipient sex and donor age) between the two groups. The incidences of the grade Ⅱ-Ⅳ and Ⅲ/Ⅳ aGVHD in long and short duration groups were 31.1% versus 17.6% (P=0.018) and 7.4% verus 7.8% (P=0.900), respectively. The duration of MMF prophylaxis was not found to be associated with gradeⅡ-Ⅳ aGVHD by the multivariate analysis. There were no significant differences in terms of CMV viremia, EBV viremia, hemorrhagic cytitis and OS between the two groups. Conclusion: Prophylaxis with short duration MMF in the setting of 'Beijing protocol' haplo-SCT was not associated with increased acute GVHD with no impact on OS, which indicated that short duration MMF might be a feasible GVHD prophylaxis regimen.

T-cell replete haploidentical stem cell transplantation attenuates the prognostic impact of FLT3-ITD in acute myeloid leukemia: A report from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Acute myeloid leukemia (AML) patients harboring the FLT3-ITD mutation are considered a high risk patient subset preferentially allocated for allogeneic stem cell transplantation in first remission. Whether FLT3-ITD retains a prognostic role in haploidentical stem cell transplantation (haplo-SCT) is unknown. To analyze the prognostic impact of FLT3-ITD in haplo-SCT, we performed a retrospective analysis of the multicenter registry of the acute leukemia working party of the European Society for Blood and Marrow Transplantation. We included all adult AML patients with known FLT3 status who underwent a first T-cell replete related haplo-HCT in first complete remission from 2005 to 2016. We evaluated 293 patients of whom 202 were FLT3^wt and 91 were FLT3-ITD mutated. FLT3-ITD patients were more likely to be NPM1 mutated as well as be in the intermediate risk cytogenetic risk category. In multivariate analysis, patients with FLT3-ITD had comparable rates of relapse incidence [Hazard ratio (HR) = 1.34, confidence interval (CI) 95%, 0.67-2.7; P = .9] and leukemia-free survival (HR = 0.99, CI 95%, 0.62-1.57; P = .9) to those of FLT3^wt patients. Overall survival, the incidence of nonrelapse mortality, and graft versus host disease-free/relapse-free survival were not significantly impacted by FLT3-ITD status. Furthermore, relapse and overall survival were comparable between FLT3-ITD patients transplanted from various donor pools, namely matched siblings, unrelated donors, haplo-SCT). Finally, subset analysis of patients with intermediate risk cytogenetics confirmed the absence of a prognostic impact of FLT3-ITD also for this patient segment. In AML patients undergoing T-cell replete haplo-SCT, the FLT3-ITD mutation possibly does not retain its prognostic significance.

Infusion of basic fibroblast growth factor ameliorates acute graft versus host disease in mice after haploidentical hematopoietic stem cell transplantation

The aim of this study was to investigate the effect of basic fibroblast growth factor (bFGF) on acute graft versus host disease (aGVHD) in mice after haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Haplo-HSCT mice model was established followed by dividing into three groups with 12 mice in each group, group 1 with infusion of 100g/kg bFGF, group 2 with infusion of 20 g/kg bFGF and control group without infusion. Clinical manifestation and survival time of mice after haplo-HSCT were monitored. On day 14 post transplantation, mice were sacrificed for pathology analysis of liver and the changes of mesenchymal stem cells (MSC). Compared to haplo-HSCT group, clinical manifestations of aGVHD in bFGF infusion group were significantly ameliorated. Furthermore, bFGF infusion also significantly prolonged the survival time of mice after transplantation (P<0.05) as demonstrated by Kaplan-Meier survival analysis with more infusion of bFGF, the longer survival of mice. Pathology analysis showed the severity of aGVHD in bFGF infusion group (1 and 2) was less severe than haplo-HSCT group with higher proliferation of bone marrow MSC in group 1. In conclusion, these studies demonstrated that infusion of bFGF ameliorated aGVHD in mice after haplo-HSCT.