Risk Prediction for Clonal Cytopenia: Multicenter Real-World Evidence.

Clonal cytopenia of undetermined significance (CCUS) represents a distinct disease entity characterized by myeloid-related somatic mutations with a variant allele fraction of ≥2% in individuals with unexplained cytopenia(s) but without a myeloid neoplasm (MN). Notably, CCUS carries a risk of progressing to MN, particularly in cases featuring high-risk mutations. Understanding CCUS requires dedicated studies to elucidate its risk factors and natural history. Our analysis of 357 CCUS patients investigated the interplay between clonality, cytopenia, and prognosis. Multivariate analysis identified 3 key adverse prognostic factors: the presence of splicing mutation(s) (score = 2 points), platelet count <100×109/L (score = 2.5), and ≥2 mutations (score = 3). Variable scores were based on the coefficients from the Cox proportional hazards model. This led to the development of the Clonal Cytopenia Risk Score (CCRS), which stratified patients into low- (score <2.5 points), intermediate- (score 2.5-<5), and high-risk (score ≥5) groups. The CCRS effectively predicted 2-year cumulative incidence of MN for low- (6.4%), intermediate- (14.1%), and high- (37.2%) risk groups, respectively, by Gray's test (P <.0001). We further validated the CCRS by applying it to an independent CCUS cohort of 104 patients, demonstrating a c-index of 0.64 (P =.005) in stratifying the cumulative incidence of MN. Our study underscores the importance of integrating clinical and molecular data to assess the risk of CCUS progression, making the CCRS a valuable tool that is practical and easily calculable. These findings are clinically relevant, shaping the management strategies for CCUS and informing future clinical trial designs.

Racial and ethnic disparities in Acute Myeloid Leukemia: 15-year experience at a safety net hospital system.

Despite recent therapeutic advances, ethnic minorities in the U.S. continue to have disproportionately poor outcomes in many hematologic malignancies including AML. We identified 162 adult AML patients treated at a non-transplant safety net hospital from 2007 to 2022 and evaluated differences in disease characteristics, treatment and clinical outcomes based on race and ethnicity. Our cohort consisted of 82 (50.6%) Hispanic, 36 (22.2%) non-Hispanic black and 44 (27.2%) non-Hispanic white and Asian patients. Median age at diagnosis was 42.5, 49.0 and 52.5 years respectively (p=0.025). Hispanics had higher rates of intermediate and high-risk disease (p=0.699) and received high intensity induction and consolidation chemotherapy at lower rates (p=0.962), although differences did not reach statistical significance. Despite this, similar remission rates were achieved. Hispanics with high-risk disease had longer overall survival (OS) than the combined non-Hispanic cohort (mOS 14 m vs 7 m, p=0.030). Multivariate regression analysis showed that OS was negatively associated with age (HR 1.023, p=0.006), intermediate (HR 3.431, p=0.0003) and high-risk disease (HR 4.689, p<0.0001) and positively associated with Hispanic ethnicity (HR 0.614, p=0.026). This report suggests that contrary to other studies, Hispanics, particularly those with high-risk AML, may have improved OS compared to other ethnic groups. These results are unique to our safety net hospital setting where common barriers to medical care and healthcare disparities are largely mitigated.

Identifying patients at risk for hereditary myeloid malignancy syndromes incorporating a novel, self-administered questionnaire to an initial screening platform.

INTRODUCTION: Four to 10% of cases of myeloid malignancies are inherited. We report our experience on hereditary myeloid malignancy syndromes (HMMS) incorporating a novel questionnaire in the screening platform for patients with myeloid malignancies and aplastic anemia. METHODS: The questionnaire was sent via electronic patient portal prior to clinic visits. Patients screened positive based on responses to questionnaire items, presence of suspicion disease characteristics (young age, family history, monosomy 7 etc.) and/or presence of signs of HMMS. Those deemed at-risk based on questionnaire responses, clinical features and/or somatic mutation profile were offered germline testing. RESULTS: A total of 408 patients were screened, 141 (35%) were deemed at-risk. Fifty-four (38%) of at-risk patients were seen in the genetics clinic. Forty-one (76%) of the patients seen agreed to germline testing and 13 declined due to cost or personal decision. Twenty pathogenic (P)/likely-pathogenic (LP) germline mutations were identified in 16 (39%) of the tested patients. Five patients also had a variant of uncertain significance (VUS) and an additional 13 had at least 1 VUS without P/LP mutations (total 29 VUS's were found in 18 (44%) of tested patients). The median age of diagnosis for patients with P/LP mutations was 56 years versus 66 years in the entire cohort. CONCLUSION: Incorporating an electronic questionnaire is an effective screening method for HMMS. Many patients declined testing due to cost. These results highlight the importance of germline testing in patients with myeloid malignancies, further research in HMMS, and coverage by healthcare plans.

SARS-CoV-2 Vaccination IgG Antibody Responses in Patients with Hematologic Malignancies in a Myeloid Enriched Cohort: A Single Center Observation.

OBJECTIVE: Patients diagnosed with hematologic malignancies are at increased risk for severe SARS-CoV-2 infection. We evaluated the serological IgG response following two doses of the SARS-CoV-2 vaccine in patients with hematologic malignancies. METHODS: Patients treated at UT Southwestern Medical Center with a diagnosis of a myeloid or lymphoid neoplasm were included. SARS-CoV-2 vaccination response was defined as a positive quantifiable spike IgG antibody titer. RESULTS: Sixty patients were included in the study and 60% were diagnosed with a myeloid neoplasm. The majority (85%) of the patients with a myeloid malignancy and 50% of the patients with a lymphoid malignancy mounted a serological response after receiving two doses of the vaccine. CONCLUSION: Vaccination should be offered irrespective of ongoing treatment or active disease. Findings require validation in a larger cohort of patients.

Neutrophil metabolomics in severe COVID-19 reveal GAPDH as a suppressor of neutrophil extracellular trap formation.

Severe COVID-19 is characterized by an increase in the number and changes in the function of innate immune cells including neutrophils. However, it is not known how the metabolome of immune cells changes in patients with COVID-19. To address these questions, we analyzed the metabolome of neutrophils from patients with severe or mild COVID-19 and healthy controls. We identified widespread dysregulation of neutrophil metabolism with disease progression including in amino acid, redox, and central carbon metabolism. Metabolic changes in neutrophils from patients with severe COVID-19 were consistent with reduced activity of the glycolytic enzyme GAPDH. Inhibition of GAPDH blocked glycolysis and promoted pentose phosphate pathway activity but blunted the neutrophil respiratory burst. Inhibition of GAPDH was sufficient to cause neutrophil extracellular trap (NET) formation which required neutrophil elastase activity. GAPDH inhibition increased neutrophil pH, and blocking this increase prevented cell death and NET formation. These findings indicate that neutrophils in severe COVID-19 have an aberrant metabolism which can contribute to their dysfunction. Our work also shows that NET formation, a pathogenic feature of many inflammatory diseases, is actively suppressed in neutrophils by a cell-intrinsic mechanism controlled by GAPDH.

Post-transplant cyclophosphamide and early mixed donor Chimerism in myeloid malignancies; a single-center experience.

BACKGROUND: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative option for high-risk myeloid malignancies. Post-transplant cyclophosphamide (PT-Cy) has proven to be effective for graft versus host disease (GVHD) prophylaxis. Given that graft-versus-tumor (GVT) effect plays a major role in reducing the risk of disease relapse, the application of PT-Cy must balance the risk of relapse. Mixed chimerism (MC) refers to a state of concurrent presence of recipient and donor cells post allo-HSCT which may precede relapse disease. OBJECTIVE: We investigated the impact of PT-Cy on early MC (EMC) and disease relapse in patients with a myeloid malignancy post allo-HSCT. STUDY DESIGN: This retrospective single-center study included patients that underwent allo-HSCT between 2015 and 2021. Patient and disease characteristics were collected from the electronic health records. EMC was defined as <95% donor cells at day 90-120 post allo-HSCT. RESULTS: A total of 144 patient that received an allo-HSCT were included in the study. One hundred and eight (75%) patients received PT-Cy as part of the GVHD prophylaxis regimen. The majority underwent allo-HSCT for acute myeloid leukemia (62%) or myelodysplastic syndrome (31%). Sixty-five percent received allo-HSCT from a matched unrelated donor transplant and 65% received a myeloablative conditioning regimen. A lower rate of chronic GVHD (p = 0.03) and a higher rate of EMC (p = 0.04) were observed in patients that received PT-Cy. PT-Cy was not associated with overall survival (OS) and relapse-free survival (RFS). Multivariable analysis identified measurable residual disease status (p = 0.003), hematopoietic cell transplantation-specific comorbidity index (p = 0.012) and chronic GVHD (p = 0.006) as independent prognostic variables for OS. AML-adverse risk (p = 0.004) and EMC (p = 0.018) were independently prognostic for RFS. While EMC overall was not significantly associated with higher risk of relapse, EMC was associated with shorter RFS within adverse-risk AML patients. CONCLUSION: Our study shows that PT-Cy was associated with an increased risk of EMC. The predictive value of EMC for relapse remains unclear and may depend on the underlying disease, which should be validated in a larger cohort.

Clinical and molecular characteristics associated with Vitamin C deficiency in myeloid malignancies; real world data from a prospective cohort.

Vitamin C is an essential vitamin that acts as a co-factor for many enzymes involved in epigenetic regulation in humans. Low vitamin C levels in hematopoietic stem cells (HSC) promote self-renewal and vitamin C supplementation retards leukaemogenesis in vitamin C-deficient mouse models. Studies on vitamin C levels in patients with myeloid malignancies are limited. We thus conducted a retrospective analysis on a prospective cohort of patients with myeloid malignancies on whom plasma vitamin C levels were measured serially at diagnosis and during treatment. Baseline characteristics including hematological indices, cytogenetics, and molecular mutations are described in this cohort. Among 64 patients included in our study, 11 patients (17%) had low vitamin C levels. We noted a younger age at diagnosis for patients with myeloid malignancies who had low plasma vitamin C levels. Patients with low plasma vitamin C levels were more likely to have acute myeloid leukemia compared to other myeloid malignancies. Low vitamin C levels were associated with ASXL1 mutations. Our study calls for further multi-institutional studies to understand the relevance of low plasma vitamin C level in myeloid neoplasms, the role of vitamin C deficiency in leukemogenesis, and the potential benefit of vitamin C supplementation.

Disabling Uncompetitive Inhibition of Oncogenic IDH Mutations Drives Acquired Resistance.

Mutations in IDH genes occur frequently in acute myeloid leukemia (AML) and other human cancers to generate the oncometabolite R-2HG. Allosteric inhibition of mutant IDH suppresses R-2HG production in a subset of patients with AML; however, acquired resistance emerges as a new challenge, and the underlying mechanisms remain incompletely understood. Here we establish isogenic leukemia cells containing common IDH oncogenic mutations by CRISPR base editing. By mutational scanning of IDH single amino acid variants in base-edited cells, we describe a repertoire of IDH second-site mutations responsible for therapy resistance through disabling uncompetitive enzyme inhibition. Recurrent mutations at NADPH binding sites within IDH heterodimers act in cis or trans to prevent the formation of stable enzyme-inhibitor complexes, restore R-2HG production in the presence of inhibitors, and drive therapy resistance in IDH-mutant AML cells and patients. We therefore uncover a new class of pathogenic mutations and mechanisms for acquired resistance to targeted cancer therapies. SIGNIFICANCE: Comprehensive scanning of IDH single amino acid variants in base-edited leukemia cells uncovers recurrent mutations conferring resistance to IDH inhibition through disabling NADPH-dependent uncompetitive inhibition. Together with targeted sequencing, structural, and functional studies, we identify a new class of pathogenic mutations and mechanisms for acquired resistance to IDH-targeting cancer therapies. This article is highlighted in the In This Issue feature, p. 1.

Epo-IGF1R cross talk expands stress-specific progenitors in regenerative erythropoiesis and myeloproliferative neoplasm.

We found that in regenerative erythropoiesis, the erythroid progenitor landscape is reshaped, and a previously undescribed progenitor population with colony-forming unit-erythroid (CFU-E) activity (stress CFU-E [sCFU-E]) is expanded markedly to restore the erythron. sCFU-E cells are targets of erythropoietin (Epo), and sCFU-E expansion requires signaling from the Epo receptor (EpoR) cytoplasmic tyrosines. Molecularly, Epo promotes sCFU-E expansion via JAK2- and STAT5-dependent expression of IRS2, thus engaging the progrowth signaling from the IGF1 receptor (IGF1R). Inhibition of IGF1R and IRS2 signaling impairs sCFU-E cell growth, whereas exogenous IRS2 expression rescues cell growth in sCFU-E expressing truncated EpoR-lacking cytoplasmic tyrosines. This sCFU-E pathway is the major pathway involved in erythrocytosis driven by the oncogenic JAK2 mutant JAK2(V617F) in myeloproliferative neoplasm. Inability to expand sCFU-E cells by truncated EpoR protects against JAK2(V617F)-driven erythrocytosis. In samples from patients with myeloproliferative neoplasm, the number of sCFU-E-like cells increases, and inhibition of IGR1R and IRS2 signaling blocks Epo-hypersensitive erythroid cell colony formation. In summary, we identified a new stress-specific erythroid progenitor cell population that links regenerative erythropoiesis to pathogenic erythrocytosis.

Convergence of oncogenic cooperation at single-cell and single-gene levels drives leukemic transformation.

Cancers develop from the accumulation of somatic mutations, yet it remains unclear how oncogenic lesions cooperate to drive cancer progression. Using a mouse model harboring NRasG12D and EZH2 mutations that recapitulates leukemic progression, we employ single-cell transcriptomic profiling to map cellular composition and gene expression alterations in healthy or diseased bone marrows during leukemogenesis. At cellular level, NRasG12D induces myeloid lineage-biased differentiation and EZH2-deficiency impairs myeloid cell maturation, whereas they cooperate to promote myeloid neoplasms with dysregulated transcriptional programs. At gene level, NRasG12D and EZH2-deficiency independently and synergistically deregulate gene expression. We integrate results from histopathology, leukemia repopulation, and leukemia-initiating cell assays to validate transcriptome-based cellular profiles. We use this resource to relate developmental hierarchies to leukemia phenotypes, evaluate oncogenic cooperation at single-cell and single-gene levels, and identify GEM as a regulator of leukemia-initiating cells. Our studies establish an integrative approach to deconvolute cancer evolution at single-cell resolution in vivo.

Safety and activity of selinexor in patients with myelodysplastic syndromes or oligoblastic acute myeloid leukaemia refractory to hypomethylating agents: a single-centre, single-arm, phase 2 trial.

BACKGROUND: The median overall survival of patients with high-risk myelodysplastic syndromes refractory to hypomethylating agents is less than 6 months. Currently, no standard therapy for such patients exists. Preclinical studies have shown that inhibition of the nuclear export protein exportin 1 (XPO1) causes nuclear accumulation of p53 and disruption of NF-κB signalling, both relevant targets for myelodysplastic syndromes. We therefore aimed to assess the safety and activity of selinexor in patients with myelodysplastic syndromes or oligoblastic acute myeloid leukaemia refractory to hypomethylating agents. METHODS: We did a single-centre, single-arm, phase 2 trial at the Memorial Sloan Kettering Cancer Center in the USA. We included patients 18 years or older with high-risk myelodysplastic syndromes or oligoblastic acute myeloid leukaemia (defined as blasts ≥20% but ≤30%) refractory to hypomethylating agents and with an Eastern Cooperative Oncology Group performance status score of 0-2. Eligible patients received 3-week long cycles of oral selinexor (60 mg twice per week for 2 weeks, followed by 1 week off). The primary outcome was overall response rate. Complete remission, partial remission, marrow complete remission, or haematological improvement were included in the response categories for assessing the primary endpoint. The activity analysis included all patients who completed at least one full-scheduled post-treatment disease assessment. All patients who were given selinexor were included in the safety analysis. This study is registered with ClinicalTrials.gov, NCT02228525. FINDINGS: Between Sept 23, 2014, and March 13, 2018, 25 patients were enrolled on this study. The median follow-up was 8·5 months (IQR 3·1-12·2). Two patients did not meet the full eligibility criteria after baseline assessment; therefore, 23 patients were evaluable for activity assessment. In the 23 evaluable patients, overall response rate was 26% (95% CI 10-48) in six patients with marrow complete remission, with an additional 12 patients (52%, 95% CI 31-73) achieving stable disease. The most common grade 3 or 4 adverse events were thrombocytopenia (eight [32%] of 25 patients) and hyponatraemia (five [20%]). There were no drug-related serious adverse events and no treatment-related deaths. INTERPRETATION: Selinexor showed responses in patients with myelodysplastic syndromes or oligoblastic acute myeloid leukaemia refractory to hypomethylating agents. Adverse events were manageable with supportive care implementation. Further studies are needed to compare selinexor with supportive care alone, and to identify patient subgroups that might benefit the most from selinexor treatment. FUNDING: Karyopharm Therapeutics.

CD97 is a critical regulator of acute myeloid leukemia stem cell function.

Despite significant efforts to improve therapies for acute myeloid leukemia (AML), clinical outcomes remain poor. Understanding the mechanisms that regulate the development and maintenance of leukemic stem cells (LSCs) is important to reveal new therapeutic opportunities. We have identified CD97, a member of the adhesion class of G protein-coupled receptors (GPCRs), as a frequently up-regulated antigen on AML blasts that is a critical regulator of blast function. High levels of CD97 correlate with poor prognosis, and silencing of CD97 reduces disease aggressiveness in vivo. These phenotypes are due to CD97's ability to promote proliferation, survival, and the maintenance of the undifferentiated state in leukemic blasts. Collectively, our data credential CD97 as a promising therapeutic target on LSCs in AML.

Oncogenic TRK fusions are amenable to inhibition in hematologic malignancies.

Rearrangements involving the neurotrophic receptor kinase genes (NTRK1, NTRK2, and NTRK3; hereafter referred to as TRK) produce oncogenic fusions in a wide variety of cancers in adults and children. Although TRK fusions occur in fewer than 1% of all solid tumors, inhibition of TRK results in profound therapeutic responses, resulting in Breakthrough Therapy FDA approval of the TRK inhibitor larotrectinib for adult and pediatric patients with solid tumors, regardless of histology. In contrast to solid tumors, the frequency of TRK fusions and the clinical effects of targeting TRK in hematologic malignancies are unknown. Here, through an evaluation for TRK fusions across more than 7,000 patients with hematologic malignancies, we identified TRK fusions in acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), histiocytosis, multiple myeloma, and dendritic cell neoplasms. Although TRK fusions occurred in only 0.1% of patients (8 of 7,311 patients), they conferred responsiveness to TRK inhibition in vitro and in vivo in a patient-derived xenograft and a corresponding AML patient with ETV6-NTRK2 fusion. These data identify that despite their individual rarity, collectively, TRK fusions are present in a wide variety of hematologic malignancies and predict clinically significant therapeutic responses to TRK inhibition.

Do preclinical studies suggest that CD99 is a potential therapeutic target in acute myeloid leukemia and the myelodysplastic syndromes?

INTRODUCTION: Acute myeloid leukemia (AML) and the myelodysplastic syndromes (MDS) are clonal hematopoietic neoplasms that arise from leukemia stem cells (LSCs) and hematopoietic stem cells (HSCs), respectively. Standard chemotherapy can efficiently eliminate the bulk of neoplastic cells, however, LSCs and MDS HSCs are relatively resistant to these therapies and can reinitiate and maintain disease. CD99 is a 32-kDa transmembrane polypeptide that is highly expressed on disease stem cells in the vast majority of AML and MDS. Areas covered: In this editorial, we focus on the current literature surrounding the identification of CD99 as a marker of MDS and AML stem cells and preclinical studies revealing the therapeutic efficacy of targeting CD99 in these diseases. Expert opinion/commentary: Cytotoxic CD99 monoclonal antibodies represent promising stem cell-directed therapies that have the potential to markedly improve clinical outcomes for these difficult-to-treat hematologic malignancies.

Aging, hematopoiesis, and the myelodysplastic syndromes.

The aging hematopoietic system undergoes numerous changes, including reduced production of red blood cells and lymphocytes as well as a relative increase in the production of myeloid cells. Emerging evidence indicates that many of these changes are due to selection pressures from cell-intrinsic and cell-extrinsic factors that result in clonal shifts in the hematopoietic stem cell (HSC) pool, resulting in predominant HSC clones that exhibit the functional characteristics associated with HSC aging. Given the recent descriptions of clonal hematopoiesis in aged populations, the increased risk of developing hematologic malignancies in individuals with clonal hematopoiesis, and the many similarities in hematopoietic aging and acquired bone marrow failure (BMF) syndromes, such as myelodysplastic syndromes (MDS), this raises significant questions regarding the relationship between aging hematopoiesis and MDS, including the factors that regulate HSC aging, whether clonal hematopoiesis is required for the development of MDS, and even whether BMF is an inevitable consequence of aging. In this article, we will review our current understanding of these processes and the potential intersections among them.

Genomic analysis of hairy cell leukemia identifies novel recurrent genetic alterations.

Classical hairy cell leukemia (cHCL) is characterized by a near 100% frequency of the BRAFV600E mutation, whereas ∼30% of variant HCLs (vHCLs) have MAP2K1 mutations. However, recurrent genetic alterations cooperating with BRAFV600E or MAP2K1 mutations in HCL, as well as those in MAP2K1 wild-type vHCL, are not well defined. We therefore performed deep targeted mutational and copy number analysis of cHCL (n = 53) and vHCL (n = 8). The most common genetic alteration in cHCL apart from BRAFV600E was heterozygous loss of chromosome 7q, the minimally deleted region of which targeted wild-type BRAF, subdividing cHCL into those hemizygous versus heterozygous for the BRAFV600E mutation. In addition to CDKN1B mutations in cHCL, recurrent inactivating mutations in KMT2C (MLL3) were identified in 15% and 25% of cHCLs and vHCLs, respectively. Moreover, 13% of vHCLs harbored predicted activating mutations in CCND3 A change-of-function mutation in the splicing factor U2AF1 was also present in 13% of vHCLs. Genomic analysis of de novo vemurafenib-resistant cHCL identified a novel gain-of-function mutation in IRS1 and losses of NF1 and NF2, each of which contributed to resistance. These data provide further insight into the genetic bases of cHCL and vHCL and mechanisms of RAF inhibitor resistance encountered clinically.

CD99 is a therapeutic target on disease stem cells in myeloid malignancies.

Acute myeloid leukemia (AML) and the myelodysplastic syndromes (MDS) are initiated and sustained by self-renewing malignant stem cells; thus, eradication of AML and MDS stem cells is required for cure. We identified CD99 as a cell surface protein frequently overexpressed on AML and MDS stem cells. Expression of CD99 allows for prospective separation of leukemic stem cells (LSCs) from functionally normal hematopoietic stem cells in AML, and high CD99 expression on AML blasts enriches for functional LSCs as demonstrated by limiting dilution xenotransplant studies. Monoclonal antibodies (mAbs) targeting CD99 induce the death of AML and MDS cells in a SARC family kinase-dependent manner in the absence of immune effector cells or complement, and anti-CD99 mAbs exhibit antileukemic activity in AML xenografts. These data establish CD99 as a marker of AML and MDS stem cells, as well as a promising therapeutic target in these disorders.

Aldose reductase deficiency leads to oxidative stress-induced dopaminergic neuronal loss and autophagic abnormality in an animal model of Parkinson's disease.

Fungicide exposure causes degeneration of dopaminergic neurons and contributes to Parkinson's disease (PD). Benomyl inhibits enzymes responsible for detoxifying the reactive dopamine metabolite 3,4-dihydroxyphenylacetaldehyde. Aldose reductase (AR) is known as tetrahydrobiopterin (BH4) reductase that generates BH4, a cofactor for tyrosine hydroxylase (TH) involved in dopamine synthesis. AR also acts as an aldehyde reductase involved in detoxifying 3,4-dihydroxyphenylacetaldehyde. In PD patients, the level of AR is significantly lower in the cerebellum. To determine if AR deficiency contributes to PD, AR wild-type (AR+/+) and knockout (AR-/-) mice were administrated with 1-methyl-4-phenyl -1,2,3,6- tetrahydropyridine (MPTP). The MPTP-treated AR-/- mice showed more severe behavioral deficits and brain damage than that of AR+/+ mice. Contrary to expectation, under normal or MPTP-treated condition, AR-/- mice showed a significant elevation of BH4 and dopamine in the midbrain, suggesting that either AR does not contribute to BH4 production, or other BH4 synthetic pathways are induced. The AR-/- brain showed upregulation of peroxynitrite, inducible nitric oxide synthase and downregulation of antioxidant enzymes, Cu/Zn superoxide dismutase (SOD) and peroxiredoxin 2 (Prx2), which indicate an increase in oxidative stress. In line with the animal data, pretreating the SH-SY5Y cells with AR inhibitors (Fidarestat or Epalrestat) before MPP+ treatment, increased severe cell death and mitochondrial fragmentation with downregulation of SOD were observed when compared to the MPP+ treatment alone. Cycloxygenase 2 (COX2), which can lead to the oxidation of dopamine, was upregulated in AR-/- brains. Autophagic proteins, beclin-1 and LC3B were also downregulated. The loss of dopaminergic neurons was associated with activation of p-ERK1/2. These findings suggest that AR plays an important role in protecting dopaminergic neuron against neurotoxic metabolites in PD.

Aging, hematopoiesis, and the myelodysplastic syndromes.

The aging hematopoietic system undergoes numerous changes, including reduced production of red blood cells and lymphocytes as well as a relative increase in the production of myeloid cells. Emerging evidence indicates that many of these changes are due to selection pressures from cell-intrinsic and cell-extrinsic factors that result in clonal shifts in the hematopoietic stem cell (HSC) pool, resulting in predominant HSC clones that exhibit the functional characteristics associated with HSC aging. Given the recent descriptions of clonal hematopoiesis in aged populations, the increased risk of developing hematologic malignancies in individuals with clonal hematopoiesis, and the many similarities in hematopoietic aging and acquired bone marrow failure (BMF) syndromes, such as myelodysplastic syndromes (MDS), this raises significant questions regarding the relationship between aging hematopoiesis and MDS, including the factors that regulate HSC aging, whether clonal hematopoiesis is required for the development of MDS, and even whether BMF is an inevitable consequence of aging. In this article, we will review our current understanding of these processes and the potential intersections among them.