Prognostic Mutations in Myelodysplastic Syndrome after Stem-Cell Transplantation

PPM1D Mutations Drive Clonal Hematopoiesis in Response to Cytotoxic Chemotherapy

Clonal hematopoiesis (CH), in which stem cell clones dominate blood production, becomes increasingly common with age and can presage malignancy development. The conditions that promote ascendancy of particular clones are unclear. We found that mutations in PPM1D (protein phosphatase Mn2+/Mg2+-dependent 1D), a DNA damage response regulator that is frequently mutated in CH, were present in one-fifth of patients with therapy-related acute myeloid leukemia or myelodysplastic syndrome and strongly correlated with cisplatin exposure. Cell lines with hyperactive PPM1D mutations expand to outcompete normal cells after exposure to cytotoxic DNA damaging agents including cisplatin, and this effect was predominantly mediated by increased resistance to apoptosis. Moreover, heterozygous mutant Ppm1d hematopoietic cells outcompeted their wild-type counterparts in vivo after exposure to cisplatin and doxorubicin, but not during recovery from bone marrow transplantation. These findings establish the clinical relevance of PPM1D mutations in CH and the importance of studying mutation-treatment interactions. VIDEO ABSTRACT.

An update on treatment of higher risk myelodysplastic syndromes

INTRODUCTION

Myelodysplastic syndromes (MDS) are clonal stem cell disorders mostly affecting the elderly. They are classified into lower and higher risk MDS according to prognostic scoring systems. In higher risk patients, treatments should aim to modify the disease course by avoiding progression to acute myeloid leukemia and, therefore, to improve survival. Areas covered: Stem cell transplantation remains the only curative treatment when feasible, but this concerns a small minority of patients. Treatment is principally based on hypomethylating agents (HMAs). Our understanding of MDS biology has led to the development of drugs targeting key cellular processes such as apoptosis or posttranslational protein changes, microenvironment-like immunotherapy, and gene mutations. Currently, new drugs are mainly being tested in combination with HMAs in several clinical trials. Expert commentary: Significant advances have been made in the field of MDS, especially in molecular typing, which are improving our ability to offer patients risk-adapted therapies. The current challenge in the management of higher risk MDS is to improve outcome by combining classical HMAs with novel drugs.

Low clinical trial accrual of patients with myelodysplastic syndromes: Causes and potential solutions

Despite few effective therapies, only a small percentage of patients diagnosed with myelodysplastic syndromes (MDS) in the United States are enrolled in prospective, interventional clinical trials. MDS-specific barriers to trial accrual include a high frequency of elderly patients with comorbid conditions, atypical disease features and uncertainty regarding the diagnosis (because other nonclonal processes also can cause dysplasia and cytopenias), a history of another nonmyeloid neoplasm resulting in therapy-related MDS, rapid disease recurrence after allogeneic stem cell transplantation, and an arbitrary division between MDS and acute myeloid leukemia. In addition, barriers to accrual that are common to other oncology populations, such as difficulty traveling to clinical trial enrollment sites and narrow trial eligibility criteria, also prevent patients with MDS from enrolling in studies. Collectively these barriers must be assessed systematically, and creative solutions are needed to improve outcomes for this needy patient population.

The genetic basis and cell of origin of mixed phenotype acute leukaemia

Mixed phenotype acute leukaemia (MPAL) is a high-risk subtype of leukaemia with myeloid and lymphoid features, limited genetic characterization, and a lack of consensus regarding appropriate therapy. Here we show that the two principal subtypes of MPAL, T/myeloid (T/M) and B/myeloid (B/M), are genetically distinct. Rearrangement of ZNF384 is common in B/M MPAL, and biallelic WT1 alterations are common in T/M MPAL, which shares genomic features with early T-cell precursor acute lymphoblastic leukaemia. We show that the intratumoral immunophenotypic heterogeneity characteristic of MPAL is independent of somatic genetic variation, that founding lesions arise in primitive haematopoietic progenitors, and that individual phenotypic subpopulations can reconstitute the immunophenotypic diversity in vivo. These findings indicate that the cell of origin and founding lesions, rather than an accumulation of distinct genomic alterations, prime tumour cells for lineage promiscuity. Moreover, these findings position MPAL in the spectrum of immature leukaemias and provide a genetically informed framework for future clinical trials of potential treatments for MPAL.

Mutation Clearance after Transplantation for Myelodysplastic Syndrome

BACKGROUND

Allogeneic hematopoietic stem-cell transplantation is the only curative treatment for patients with myelodysplastic syndrome (MDS). The molecular predictors of disease progression after transplantation are unclear.

METHODS

We sequenced bone marrow and skin samples from 90 adults with MDS who underwent allogeneic hematopoietic stem-cell transplantation after a myeloablative or reduced-intensity conditioning regimen. We detected mutations before transplantation using enhanced exome sequencing, and we evaluated mutation clearance by using error-corrected sequencing to genotype mutations in bone marrow samples obtained 30 days after transplantation. In this exploratory study, we evaluated the association of a mutation detected after transplantation with disease progression and survival.

RESULTS

Sequencing identified at least one validated somatic mutation before transplantation in 86 of 90 patients (96%); 32 of these patients (37%) had at least one mutation with a maximum variant allele frequency of at least 0.5% (equivalent to 1 heterozygous mutant cell in 100 cells) 30 days after transplantation. Patients with disease progression had mutations with a higher maximum variant allele frequency at 30 days than those who did not (median maximum variant allele frequency, 0.9% vs. 0%; P<0.001). The presence of at least one mutation with a variant allele frequency of at least 0.5% at day 30 was associated with a higher risk of progression (53.1% vs. 13.0%; conditioning regimen-adjusted hazard ratio, 3.86; 95% confidence interval [CI], 1.96 to 7.62; P<0.001) and a lower 1-year rate of progression-free survival than the absence of such a mutation (31.3% vs. 59.3%; conditioning regimen-adjusted hazard ratio for progression or death, 2.22; 95% CI, 1.32 to 3.73; P=0.005). The rate of progression-free survival was lower among patients who had received a reduced-intensity conditioning regimen and had at least one persistent mutation with a variant allele frequency of at least 0.5% at day 30 than among patients with other combinations of conditioning regimen and mutation status (P≤0.001). Multivariate analysis confirmed that patients who had a mutation with a variant allele frequency of at least 0.5% detected at day 30 had a higher risk of progression (hazard ratio, 4.48; 95% CI, 2.21 to 9.08; P<0.001) and a lower 1-year rate of progression-free survival than those who did not (hazard ratio for progression or death, 2.39; 95% CI, 1.40 to 4.09; P=0.002).

CONCLUSIONS

The risk of disease progression was higher among patients with MDS in whom persistent disease-associated mutations were detected in the bone marrow 30 days after transplantation than among those in whom these mutations were not detected. (Funded by the Leukemia and Lymphoma Society and others.).

PPM1D-truncating mutations confer resistance to chemotherapy and sensitivity to PPM1D inhibition in hematopoietic cells

Truncating mutations in the terminal exon of protein phosphatase Mg2+/Mn2+ 1D (PPM1D) have been identified in clonal hematopoiesis and myeloid neoplasms, with a striking enrichment in patients previously exposed to chemotherapy. In this study, we demonstrate that truncating PPM1D mutations confer a chemoresistance phenotype, resulting in the selective expansion of PPM1D-mutant hematopoietic cells in the presence of chemotherapy in vitro and in vivo. Clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein-9 nuclease mutational profiling of PPM1D in the presence of chemotherapy selected for the same exon 6 mutations identified in patient samples. These exon 6 mutations encode for a truncated protein that displays elevated expression and activity due to loss of a C-terminal degradation domain. Global phosphoproteomic profiling revealed altered phosphorylation of target proteins in the presence of the mutation, highlighting multiple pathways including the DNA damage response (DDR). In the presence of chemotherapy, PPM1D-mutant cells have an abrogated DDR resulting in altered cell cycle progression, decreased apoptosis, and reduced mitochondrial priming. We demonstrate that treatment with an allosteric, small molecule inhibitor of PPM1D reverts the phosphoproteomic, DDR, apoptotic, and mitochondrial priming changes observed in PPM1D-mutant cells. Finally, we show that the inhibitor preferentially kills PPM1D-mutant cells, sensitizes the cells to chemotherapy, and reverses the chemoresistance phenotype. These results provide an explanation for the enrichment of truncating PPM1D mutations in the blood of patients exposed to chemotherapy and in therapy-related myeloid neoplasms, and demonstrate that PPM1D can be a targeted in the prevention of clonal expansion of PPM1D-mutant cells and the treatment of PPM1D-mutant disease.

How I use molecular genetic tests to evaluate patients who have or may have myelodysplastic syndromes

Myelodysplastic syndromes (MDS) can be difficult to diagnose, especially when morphological changes in blood and marrow cells are minimal, myeloblast proportion is not increased, and the karyotype is normal. The discovery of >40 genes that are recurrently somatically mutated in MDS patients raised hope that molecular genetic testing for these mutations might help clarify the diagnosis in ambiguous cases where patients present with cytopenias and nondiagnostic marrow morphological findings. However, many older healthy individuals also harbor somatic mutations in leukemia-associated driver genes, especially in DNMT3A, TET2, and ASXL1, and detection of common aging-associated mutations in a cytopenic patient can cause diagnostic uncertainty. Despite this potential confounding factor, certain somatic mutation patterns when observed in cytopenic patients confer a high likelihood of disease progression and may allow a provisional diagnosis of MDS even if morphologic dysplasia and other diagnostic criteria are absent. A subset of acquired mutations also influences risk stratification of patients with an established MDS diagnosis and can inform treatment selection. Many unanswered questions remain about the implications of specific mutations, and clinicians also vary widely in their comfort with interpreting sequencing results. Here, I review the use of molecular genetic assays in patients with possible MDS or diagnosed MDS.

Significance of Clonal Mutations in Bone Marrow Failure and Inherited Myelodysplastic Syndrome/Acute Myeloid Leukemia Predisposition Syndromes

Clonal hematopoiesis as a hallmark of myelodysplastic syndrome (MDS) is mediated by the selective advantage of clonal hematopoietic stem cells in a context-specific manner. Although primary MDS emerges without known predisposing cause and is associated with advanced age, secondary MDS may develop in younger patients with bone marrow failure syndromes or after exposure to chemotherapy, respectively. This article discusses recent advances in the understanding of context-dependent clonal hematopoiesis in MDS with focus on clonal evolution in inherited and acquired bone marrow failure syndromes.

Epigenetics in myelodysplastic syndromes

Epigenetic regulators are the largest group of genes mutated in MDS patients. Most mutated genes belong to one of three groups of genes with normal functions in DNA methylation, in H3K27 methylation/acetylation or in H3K4 methylation. Mutations in the majority of epigenetic regulators disrupt their normal function and induce a loss-of-function phenotype. The transcriptional consequences are often failure to repress differentiation programs and upregulation of self-renewal pathways. However, the mechanisms how different epigenetic regulators result in similar transcriptional consequences are not well understood. Hypomethylating agents are active in higher risk MDS patients, but their efficacy does not correlate with mutations in epigenetic regulators and the median duration of hematologic response is limited to 10-13 months. Inhibitors of histone deacetylases (HDAC) yielded disappointing results so far, questioning this approach in MDS patients. We review the clinical relevance of epigenetic mutations in MDS, discuss their functional consequences and highlight the role of epigenetic therapies in this difficult to treat disease.

The genetic and molecular pathogenesis of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) comprise a diverse group of clonal and malignant myeloid disorders characterized by ineffective hematopoiesis, resultant peripheral cytopenias, and a meaningful increased risk of progression to acute myeloid leukemia. A wide array of recurring genetic mutations involved in RNA splicing, histone manipulation, DNA methylation, transcription factors, kinase signaling, DNA repair, cohesin proteins, and other signal transduction elements has been identified as important substrates for the development of MDS. Cytogenetic abnormalities, namely those characterized by loss of genetic material (including 5q- and 7q-), have also been strongly implicated and may influence the clonal architecture which predicts such mutations and may provoke an inflammatory bone marrow microenvironment as the substrate for clonal expansion. Other aspects of the molecular pathogenesis of MDS continue to be further elucidated, predicated upon advances in gene expression profiling and the development of new, and improved high-throughput techniques. More accurate understanding of the genetic and molecular basis for the development of MDS directly provides additional opportunity for treatment, which to date remains limited. In this comprehensive review, we examine the current understanding of the molecular pathogenesis and pathophysiology of MDS, as well as review future prospects which may enhance this understanding, treatment strategies, and hopefully outcomes.

Diagnostic algorithm for lower-risk myelodysplastic syndromes

Rapid advances over the past decade have uncovered the heterogeneous genomic and immunologic landscape of myelodysplastic syndromes (MDS). This has led to notable improvements in the accuracy and timing of diagnosis and prognostication of MDS, as well as the identification of possible novel targets for therapeutic intervention. For the practicing clinician, however, this increase in genomic, epigenomic, and immunologic knowledge needs consideration in a "real-world" context to aid diagnostic specificity. Although the 2016 revision to the World Health Organization classification for MDS is comprehensive and timely, certain limitations still exist for day-to-day clinical practice. In this review, we describe an up-to-date diagnostic approach to patients with suspected lower-risk MDS, including hypoplastic MDS, and demonstrate the requirement for an "integrated" diagnostic approach. Moreover, in the era of rapid access to massive parallel sequencing platforms for mutational screening, we suggest which patients should undergo such analyses, when such screening should be performed, and how those data should be interpreted. This is particularly relevant given the recent findings describing age-related clonal hematopoiesis.

Overcoming mutational complexity in acute myeloid leukemia by inhibition of critical pathways

Numerous variant alleles are associated with human acute myeloid leukemia (AML). However, the same variants are also found in individuals with no hematological disease, making their functional relevance obscure. Through NOD.Cg-Prkdc^scidIl2rg^tmlWjl/Sz (NSG) xenotransplantation, we functionally identified preleukemic and leukemic stem cell populations present in FMS-like tyrosine kinase 3 internal tandem duplication-positive (FLT3-ITD)⁺ AML patient samples. By single-cell DNA sequencing, we identified clonal structures and linked mutations with in vivo fates, distinguishing mutations permissive of nonmalignant multilineage hematopoiesis from leukemogenic mutations. Although multiple somatic mutations coexisted at the single-cell level, inhibition of the mutation strongly associated with preleukemic to leukemic stem cell transition eliminated AML in vivo. Moreover, concurrent inhibition of BCL-2 (B cell lymphoma 2) uncovered a critical dependence of resistant AML cells on antiapoptotic pathways. Co-inhibition of pathways critical for oncogenesis and survival may be an effective strategy that overcomes genetic diversity in human malignancies. This approach incorporating single-cell genomics with the NSG patient-derived xenograft model may serve as a broadly applicable resource for precision target identification and drug discovery.

Society of Hematologic Oncology (SOHO) State of the Art Updates and Next Questions: Myelodysplastic Syndromes

In the past few months, 2 main streams of research have dominated the panorama of myelodysplastic syndrome (MDS) investigations: deepening the insight into the pathogenic role, hierarchy, and prognostic effect of somatic mutations and, as a consequence, into the effect of inherited congenital predisposing conditions and the second, quite interlinked with the first, analyzing inflammation and innate immunity in patients with MDS. The research devoted to clarifying the mechanisms of action and mechanisms of resistance to hypomethylating agents has also advanced, mostly resulting from different approaches to the study of DNA methylation. Recent observations have reinforced support for targeted therapies for selected subgroups of MDS patients.

Efficacy of azacitidine is independent of molecular and clinical characteristics - an analysis of 128 patients with myelodysplastic syndromes or acute myeloid leukemia and a review of the literature

Azacitidine is the first drug to demonstrate a survival benefit for patients with MDS. However, only half of patients respond and almost all patients eventually relapse. Limited and conflicting data are available on predictive factors influencing response. We analyzed 128 patients from two institutions with MDS or AML treated with azacitidine to identify prognostic indicators. Genetic mutations in ASXL1, RUNX1, DNMT3A, IDH1, IDH2, TET2, TP53, NRAS, KRAS, FLT3, KMT2A-PTD, EZH2, SF3B1, and SRSF2 were assessed by next-generation sequencing. With a median follow up of 5.6 years median survival was 1.3 years with a response rate of 49%. The only variable with significant influence on response was del(20q). All 6 patients responded (p = 0.012) but survival was not improved. No other clinical, cytogenetic or molecular marker for response or survival was identified. Interestingly, patients from poor-risk groups as high-risk cytogenetics (55%), t-MDS/AML (54%), TP53 mutated (48%) or relapsed after chemotherapy (60%) showed a high response rate. Factors associated with shorter survival were low platelets, AML vs. MDS, therapy-related disease, TP53 and KMT2A-PTD. In multivariate analysis anemia, platelets, FLT3-ITD, and therapy-related disease remained in the model. Poor-risk factors such as del(7q)/-7, complex karyotype, ASXL1, RUNX1, EZH2, and TP53 did not show an independent impact. Thus, no clear biomarker for response and survival can be identified. Although a number of publications on predictive markers for response to AZA exist, results are inconsistent and improved response rates did not translate to improved survival. Here, we provide a comprehensive overview comparing the studies published to date.

Concise Review: Age-Related Clonal Hematopoiesis: Stem Cells Tempting the Devil

The recent characterization of clonal hematopoiesis in a large segment of the aging population has raised tremendous interest and concern alike. Mutations have been documented in genes associated with hematological cancers and in non-driver candidates. These mutations are present at low frequency in the majority of individuals after middle-age, and principally affect the epigenetic modifiers DNMT3A and TET2. In 10%-40% of cases, the clone will progress to meet the diagnostic criteria for Clonal Hematopoiesis of Indeterminate Potential, which is associated with an increased risk of hematological cancer and cardiovascular mortality. Blood cell parameters appear unmodified in these individuals, but a minority of them will develop a hematologic malignancy. At this time, the factors put forward as potentially influencing the risk of cancer development are clone size, specific gene, specific mutation, and the number of mutations. Specific stress on hematopoiesis also gives rise to clonal expansion. Genotoxic exposure (such as chemotherapy), or immune attack (as in aplastic anemia) selects/provides a fitness advantage to clones with a context-specific signature. Clonal hematopoiesis offers a new opportunity to understand the biology and adaptation mechanisms of aging hematopoiesis and provides insight into the mechanisms underlying malignant transformation. Furthermore, it might shed light on common denominators of age-associated medical conditions and help devise global strategies that will impact the prevention of hematologic cancers and promote healthy aging. Stem Cells 2018;36:1287-1294.

Clinical Utility of Next-generation Sequencing in the Management of Myeloproliferative Neoplasms: A Single-Center Experience

Supplemental Digital Content is available in the text

Although next-generation sequencing (NGS) has helped characterize the complex genomic landscape of myeloid malignancies, its clinical utility remains undefined. This has resulted in variable funding for NGS testing, limiting its accessibility. At our center, targeted sequencing (TAR-SEQ) using a 54-gene NGS myeloid panel is offered to all new patients referred for myeloid malignancies, as part of a prospective observational study. Here, we evaluated the diagnostic, prognostic, and potential therapeutic utility of clinical grade TAR-SEQ in the routine workflow of 179 patients with myeloproliferative neoplasms (MPN).

Of 13 patients with triple negative (TN) MPN, who lacked driver mutations in JAK2, CALR, and MPL, TAR-SEQ confirmed clonal hematopoiesis in 8 patients. In patients with intermediate-risk myelofibrosis (MF), TAR-SEQ helped optimize clinical decisions in hematopoietic cell transplant (HCT)-eligible patients through identifying a high molecular risk (HMR) mutation profile. The presence of an HMR profile favored HCT in 9 patients with intermediate-1 risk MF. Absence of an HMR profile resulted in a delayed HCT strategy in 10 patients with intermediate-2 risk MF, 7 of which were stable at the last follow-up. Finally, TAR-SEQ identified patients with various targetable mutations in IDH1/2 (4%), spliceosome genes (28%), and EZH2 (7%). Some of these patients can be potential candidates for future targeted therapy trials.

In conclusion, we have demonstrated that TAR-SEQ improves the characterization of TN MPN, can be integrated in clinical practice as an additional tool to refine decision making in HCT, and has the potential to identify candidates for future targeted therapy trials.

Mutations and prognosis in myelodysplastic syndromes: karyotype-adjusted analysis of targeted sequencing in 300 consecutive cases and development of a genetic risk model

To develop a genetic risk model for primary myelodysplastic syndromes (MDS), we queried the prognostic significance of next-generation sequencing (NGS)-derived mutations, in the context of the Mayo cytogenetic risk stratification, which includes high-risk (monosomal karyotype; MK), intermediate-risk (non-MK, classified as intermediate/poor/very poor, per the revised international prognostic scoring system; IPSS-R), and low-risk (classified as good/very good, per IPSS-R). Univariate analysis in 300 consecutive patients with primary MDS identified TP53, RUNX1, U2AF1, ASXL1, EZH2, and SRSF2 mutations as "unfavorable" and SF3B1 as "favorable" risk factors for survival; for the purposes of the current study, the absence of SF3B1 mutation was accordingly dubbed as an "adverse" mutation. Analysis adjusted for age and MK, based on our previous observation of significant clustering between MK and TP53 mutations, confirmed independent prognostic contribution from RUNX1, ASXL1, and SF3B1 mutations. Multivariable analysis that included age, the Mayo cytogenetics risk model and the number of adverse mutations resulted in HRs (95% CI) of 5.3 (2.5-10.3) for presence of three adverse mutations, 2.4 (1.6-3.7) for presence of two adverse mutations, 1.5 (1.02-2.2) for presence of one adverse mutation, 5.6 (3.4-9.1) for high-risk karyotype, 1.5 (1.1-2.2) for intermediate-risk karyotype and 2.4 (1.8-3.3) for age >70 years; HR-weighted risk point assignment generated a three-tiered genetic risk model: high (N = 65; 5-year survival 2%), intermediate (N = 100; 5-year survival 18%), and low (N = 135; 5-year survival 56%). The current study provides a practically simple risk model in MDS that is based on age, karyotype, and mutations only.

Prognostic scoring systems for myelodysplastic syndromes (MDS) in a population-based setting: a report from the Swedish MDS register

The myelodysplastic syndromes (MDS) have highly variable outcomes and prognostic scoring systems are important tools for risk assessment and to guide therapeutic decisions. However, few population-based studies have compared the value of the different scoring systems. With data from the nationwide Swedish population-based MDS register we validated the International Prognostic Scoring System (IPSS), revised IPSS (IPSS-R) and the World Health Organization (WHO) Classification-based Prognostic Scoring System (WPSS). We also present population-based data on incidence, clinical characteristics including detailed cytogenetics and outcome from the register. The study encompassed 1329 patients reported to the register between 2009 and 2013, 14% of these had therapy-related MDS (t-MDS). Based on the MDS register, the yearly crude incidence of MDS in Sweden was 2·9 per 100 000 inhabitants. IPSS-R had a significantly better prognostic power than IPSS (P < 0·001). There was a trend for better prognostic power of IPSS-R compared to WPSS (P = 0·05) and for WPSS compared to IPSS (P = 0·07). IPSS-R was superior to both IPSS and WPSS for patients aged ≤70 years. Patients with t-MDS had a worse outcome compared to de novo MDS (d-MDS), however, the validity of the prognostic scoring systems was comparable for d-MDS and t-MDS. In conclusion, population-based studies are important to validate prognostic scores in a 'real-world' setting. In our nationwide cohort, the IPSS-R showed the best predictive power.

New Insights from Studies of Clonal Hematopoiesis

Clonal hematopoiesis (CH) describes an asymptomatic expansion of blood cells descended from a single hematopoietic stem cell. Recent studies have shown that CH increases in frequency with aging and is often driven by somatic mutations in genes that are recurrently mutated in hematologic malignancies. When CH is associated with a mutation in a leukemia-associated gene at a variant allele frequency of 0.02 or greater, it is termed "clonal hematopoiesis of indeterminate potential" (CHIP). CHIP has a 0.5% to 1% risk per year of progression to hematologic neoplasia, and increases both all-cause mortality and the risk of myocardial infarction and ischemic stroke due to a proinflammatory interaction between clonally derived leukocytes and vascular endothelium. CH frequently emerges in the context of immune-mediated marrow failure syndromes such as aplastic anemia, whereas CH emerging after cytotoxic cancer therapy is strongly associated with subsequent development of a therapy-related myeloid neoplasm, especially if a TP53 mutation is present. However, risk factors for developing CH other than aging, marrow failure, and cytotoxic radiotherapy or chemotherapy are poorly defined. In this review, we discuss the epidemiology, molecular mechanisms, and clinical consequences of this common and clinically important biological state. Clin Cancer Res; 24(19); 4633-42. ©2018 AACR.

Impact of mutational studies on the diagnosis and the outcome of high-risk myelodysplastic syndromes and secondary acute myeloid leukemia patients treated with 5-azacytidine

Myelodysplastic syndromes (MDS) are stem cell disorders caused by various gene abnormalities. We performed targeted deep sequencing in 39 patients with high-risk MDS and secondary acute myeloid leukemia (sAML) at diagnosis and follow-up (response and/or relapse), with the aim to define their mutational status, to establish if specific mutations are biomarkers of response to 5-azacytidine (AZA) and/or may have impact on survival. Overall, 95% of patients harbored at least one mutation. TP53, DNMT3A and SRSF2 were the most frequently altered genes. Mutations in TP53 correlated with higher risk features and shorter overall survival (OS) and progression free survival (PFS) in univariate analysis. Patients with SRSF2 mutations were associated with better OS and PFS. Response rate was 55%; but we could not correlate the presence of TET2 and TP53 mutations with AZA response. Patients with sAML presented more variations than patients with high-risk MDS, and usually at relapse the number of mutations increased, supporting the idea that in advanced stages of the disease there is a greater genomic complexity. These results confirm that mutation analysis can add prognostic value to high-risk MDS and sAML patients, not only at diagnosis but also at follow-up.

Delayed diagnosis of Shwachman diamond syndrome with short telomeres and a review of cases in Asia

Inherited bone marrow failure syndrome (IBMFS) including Shwachman Diamond Syndrome (SDS) can present initially to the hematologist with myelodysplastic syndrome (MDS). Accurate diagnosis affects choice of chemotherapy, donor selection, and transplant conditioning. We report a case of delayed diagnosis of SDS in a family with another child with aplastic anemia, and review reported cases of SDS in Asia. This highlights the gap in identifying inherited bone marrow failure syndromes in adults with hematologic malignancies.

Molecular Minimal Residual Disease in Acute Myeloid Leukemia

BACKGROUND

Patients with acute myeloid leukemia (AML) often reach complete remission, but relapse rates remain high. Next-generation sequencing enables the detection of molecular minimal residual disease in virtually every patient, but its clinical value for the prediction of relapse has yet to be established.

METHODS

We conducted a study involving patients 18 to 65 years of age who had newly diagnosed AML. Targeted next-generation sequencing was carried out at diagnosis and after induction therapy (during complete remission). End points were 4-year rates of relapse, relapse-free survival, and overall survival.

RESULTS

At least one mutation was detected in 430 out of 482 patients (89.2%). Mutations persisted in 51.4% of those patients during complete remission and were present at various allele frequencies (range, 0.02 to 47%). The detection of persistent DTA mutations (i.e., mutations in DNMT3A, TET2, and ASXL1), which are often present in persons with age-related clonal hematopoiesis, was not correlated with an increased relapse rate. After the exclusion of persistent DTA mutations, the detection of molecular minimal residual disease was associated with a significantly higher relapse rate than no detection (55.4% vs. 31.9%; hazard ratio, 2.14; P<0.001), as well as with lower rates of relapse-free survival (36.6% vs. 58.1%; hazard ratio for relapse or death, 1.92; P<0.001) and overall survival (41.9% vs. 66.1%; hazard ratio for death, 2.06; P<0.001). Multivariate analysis confirmed that the persistence of non-DTA mutations during complete remission conferred significant independent prognostic value with respect to the rates of relapse (hazard ratio, 1.89; P<0.001), relapse-free survival (hazard ratio for relapse or death, 1.64; P=0.001), and overall survival (hazard ratio for death, 1.64; P=0.003). A comparison of sequencing with flow cytometry for the detection of residual disease showed that sequencing had significant additive prognostic value.

CONCLUSIONS

Among patients with AML, the detection of molecular minimal residual disease during complete remission had significant independent prognostic value with respect to relapse and survival rates, but the detection of persistent mutations that are associated with clonal hematopoiesis did not have such prognostic value within a 4-year time frame. (Funded by the Queen Wilhelmina Fund Foundation of the Dutch Cancer Society and others.).

Gene dosage effect of CUX1 in a murine model disrupts HSC homeostasis and controls the severity and mortality of MDS

Monosomy 7 (-7) and del(7q) are high-risk cytogenetic abnormalities common in myeloid malignancies. We previously reported that CUX1, a homeodomain-containing transcription factor encoded on 7q22, is frequently inactivated in myeloid neoplasms, and CUX1 myeloid tumor suppressor activity is conserved from humans to Drosophila. CUX1-inactivating mutations are recurrent in clonal hematopoiesis of indeterminate potential as well as myeloid malignancies, in which they independently carry a poor prognosis. To determine the role for CUX1 in hematopoiesis, we generated 2 short hairpin RNA-based mouse models with ∼54% (Cux1^mid) or ∼12% (Cux1^low) residual CUX1 protein. Cux1^mid mice develop myelodysplastic syndrome (MDS) with anemia and trilineage dysplasia, whereas CUX1^low mice developed MDS/myeloproliferative neoplasms and anemia. In diseased mice, restoration of CUX1 expression was sufficient to reverse the disease. CUX1 knockdown bone marrow transplant recipients exhibited a transient hematopoietic expansion, followed by a reduction of hematopoietic stem cells (HSCs), and fatal bone marrow failure, in a dose-dependent manner. RNA-sequencing after CUX1 knockdown in human CD34⁺ cells identified a -7/del(7q) MDS gene signature and altered differentiation, proliferative, and phosphatidylinositol 3-kinase (PI3K) signaling pathways. In functional assays, CUX1 maintained HSC quiescence and repressed proliferation. These homeostatic changes occurred in parallel with decreased expression of the PI3K inhibitor, Pik3ip1, and elevated PI3K/AKT signaling upon CUX1 knockdown. Our data support a model wherein CUX1 knockdown promotes PI3K signaling, drives HSC exit from quiescence and proliferation, and results in HSC exhaustion. Our results also demonstrate that reduction of a single 7q gene, Cux1, is sufficient to cause MDS in mice.

The identification of fibrosis-driving myofibroblast precursors reveals new therapeutic avenues in myelofibrosis

Myofibroblasts are fibrosis-driving cells and are well characterized in solid organ fibrosis, but their role and cellular origin in bone marrow fibrosis remains obscure. Recent work has demonstrated that Gli1⁺ and LepR⁺ mesenchymal stromal cells (MSCs) are progenitors of fibrosis-causing myofibroblasts in the bone marrow. Genetic ablation of Gli1⁺ MSCs or pharmacologic targeting of hedgehog (Hh)-Gli signaling ameliorated fibrosis in mouse models of myelofibrosis (MF). Moreover, pharmacologic or genetic intervention in platelet-derived growth factor receptor α (Pdgfrα) signaling in Lepr⁺ stromal cells suppressed their expansion and ameliorated MF. Improved understanding of cellular and molecular mechanisms in the hematopoietic stem cell niche that govern the transition of MSCs to myofibroblasts and myofibroblast expansion in MF has led to new paradigms in the pathogenesis and treatment of MF. Here, we highlight the central role of malignant hematopoietic clone-derived megakaryocytes in reprogramming the hematopoietic stem cell niche in MF with potential detrimental consequences for hematopoietic reconstitution after allogenic stem cell transplantation, so far the only therapeutic approach in MF considered to be curative. We and others have reported that targeting Hh-Gli signaling is a therapeutic strategy in solid organ fibrosis. Data indicate that targeting Gli proteins directly inhibits Gli1⁺ cell proliferation and myofibroblast differentiation, which results in reduced fibrosis severity and improved organ function. Although canonical Hh inhibition (eg, smoothened [Smo] inhibition) failed to improve pulmonary fibrosis, kidney fibrosis, or MF, the direct inhibition of Gli proteins ameliorated fibrosis. Therefore, targeting Gli proteins directly might be an interesting and novel therapeutic approach in MF.

Ribosomopathies: There's strength in numbers

Ribosomopathies are a group of human disorders most commonly caused by ribosomal protein haploinsufficiency or defects in ribosome biogenesis. These conditions manifest themselves as physiological defects in specific cell and tissue types. We review current molecular models to explain ribosomopathies and attempt to reconcile the tissue specificity of these disorders with the ubiquitous requirement for ribosomes in all cells. Ribosomopathies as a group are diverse in their origins and clinical manifestations; we use the well-described Diamond-Blackfan anemia (DBA) as a specific example to highlight some common features. We discuss ribosome homeostasis as an overarching principle that governs the sensitivity of specific cells and tissue types to ribosomal protein mutations. Mathematical models and experimental insights rationalize how even subtle shifts in the availability of ribosomes, such as those created by ribosome haploinsufficiency, can drive messenger RNA-specific effects on protein expression. We discuss recently identified roles played by ribosome rescue and recycling factors in regulating ribosome homeostasis.

Subclones dominate at MDS progression following allogeneic hematopoietic cell transplant

Allogeneic hematopoietic cell transplantation (alloHCT) is a potentially curative treatment for myelodysplastic syndromes (MDS), but patients who relapse after transplant have poor outcomes. In order to understand the contribution of tumor clonal evolution to disease progression,we applied exome and error-corrected targeted sequencing coupled with copy number analysis to comprehensively define changes in the clonal architecture of MDS in response to therapy using 51 serially acquired tumor samples from 9 patients who progressed after an alloHCT. We show that small subclones before alloHCT can drive progression after alloHCT. Notably, at least one subclone expanded or emerged at progression in all patients. Newly acquired structural variants (SVs) were present in an emergent/expanding subclone in 8 of 9 patients at progression, implicating the acquisition of SVs as important late subclonal progression events. In addition, pretransplant therapy with azacitidine likely influenced the mutation spectrum and evolution of emergent subclones after alloHCT. Although subclone evolution is common, founding clone mutations are always present at progression and could be detected in the bone marrow as early as 30 and/or 100 days after alloHCT in 6 of 8 (75%) patients, often prior to clinical progression. In conclusion, MDS progression after alloHCT is characterized by subclonal expansion and evolution, which can be influenced by pretransplant therapy.

Therapeutic choices after hypomethylating agent resistance for myelodysplastic syndromes

PURPOSE OF REVIEW

Hypomethylating agents (HMAs) are the standard of care for patients with myelodysplastic syndromes (MDS). Although these agents induce responses in up to 40% of patients, most patients ultimately experience loss of response. The purpose of this review is to provide an overview of the different therapies under development for MDS after HMA therapy.

RECENT FINDINGS

Recent advances in the understanding of MDS pathogenesis have led to the development of new potential therapies after HMA failure. Newer HMAs, less susceptible to in-vivo deamination, such as guadecitabine or ASTX727 have shown activity. Alterations of immune checkpoints in MDS have led to multiple clinical trials evaluating the activity of monoclonal antibodies targeting these proteins (pembrolizumab, nivolumab, ipilimumab). Different combinations and new formulations of cytotoxic agents, such as clofarabine or CPX-351, are newer options for specific subsets of patients. Finally, targeted agents inhibiting multiple kinases (rigosertib), BCL2 (venetoclax) or mutant IDH1 (ivosidenib), IDH2 (enasidenib), FLT3 (sorafenib, midostaurin) or spliceosome components (H3B-8800) are other novel options.

SUMMARY

Despite the poor prognosis associated with HMA failure, clinical trials, new cytotoxic agents and allogeneic stem-cell transplantation, can offer therapeutic opportunities for these patients for whom there is no standard of care.

Universal genetic testing for inherited susceptibility in children and adults with myelodysplastic syndrome and acute myeloid leukemia: are we there yet?

Comprehensive genomic profiling of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) cases have enabled the detection and differentiation of driver and subclonal mutations, informed risk prognostication, and defined targeted therapies. These insights into disease biology, and management have made multigene-acquired mutation testing a critical part of the diagnostic assessment of patients with sporadic MDS and AML. More recently, our understanding of the role of an increasing number of inherited genetic factors on MDS/AML risk and management has rapidly progressed. In recognition of the growing impact of this field, clinical guidelines and disease classification systems for both MDS and AML have recently incorporated familial MDS/AML predisposition syndromes into their diagnostic algorithms. In this perspective piece, we contemplate the advantages, disadvantages, and barriers that would need to be overcome to incorporate inherited MDS/AML genetic testing into the upfront molecular diagnostic work-up of every MDS/AML patient. For centers already performing panel-based tumor-only testing, including genes associated with familial forms of MDS/AML (e.g., RUNX1, CEBPA, GATA2, TP53), we advocate optimizing these tests to detect all types of germline variants in these genes and moving toward upfront paired tumor/germline testing to maximize detection and streamline patient care.

Computational Modeling and Treatment Identification in the Myelodysplastic Syndromes

Purpose of Review

This review discusses the need for computational modeling in myelodysplastic syndromes (MDS) and early test results.

Recent Findings

As our evolving understanding of MDS reveals a molecularly complicated disease, the need for sophisticated computer analytics is required to keep track of the number and complex interplay among the molecular abnormalities. Computational modeling and digital drug simulations using whole exome sequencing data input have produced early results showing high accuracy in predicting treatment response to standard of care drugs. Furthermore, the computational MDS models serve as clinically relevant MDS cell lines for pre-clinical assays of investigational agents.

Summary

MDS is an ideal disease for computational modeling and digital drug simulations. Current research is focused on establishing the prediction value of computational modeling. Future research will test the clinical advantage of computer-informed therapy in MDS.

Cellular stressors contribute to the expansion of hematopoietic clones of varying leukemic potential

Hematopoietic clones harboring specific mutations may expand over time. However, it remains unclear how different cellular stressors influence this expansion. Here we characterize clonal hematopoiesis after two different cellular stressors: cytotoxic therapy and hematopoietic transplantation. Cytotoxic therapy results in the expansion of clones carrying mutations in DNA damage response genes, including TP53 and PPM1D. Analyses of sorted populations show that these clones are typically multilineage and myeloid-biased. Following autologous transplantation, most clones persist with stable chimerism. However, DNMT3A mutant clones often expand, while PPM1D mutant clones often decrease in size. To assess the leukemic potential of these expanded clones, we genotyped 134 t-AML/t-MDS samples. Mutations in non-TP53 DNA damage response genes are infrequent in t-AML/t-MDS despite several being commonly identified after cytotoxic therapy. These data suggest that different hematopoietic stressors promote the expansion of distinct long-lived clones, carrying specific mutations, whose leukemic potential depends partially on the mutations they harbor.

Myelodysplastic syndromes: 2018 update on diagnosis, risk-stratification and management

DISEASE OVERVIEW

The myelodysplastic syndromes (MDS) are a very heterogeneous group of myeloid disorders characterized by peripheral blood cytopenias and increased risk of transformation to acute myelogenous leukemia (AML). MDS occurs more frequently in older males and in individuals with prior exposure to cytotoxic therapy.

DIAGNOSIS

Diagnosis of MDS is based on morphological evidence of dysplasia upon visual examination of a bone marrow aspirate and biopsy. Information obtained from additional studies such as karyotype, flow cytometry or molecular genetics is usually complementary and may help refine diagnosis.

RISK-STRATIFICATION

Prognosis of patients with MDS can be calculated using a number of scoring systems. In general, all these scoring systems include analysis of peripheral cytopenias, percentage of blasts in the bone marrow and cytogenetic characteristics. The most commonly used system is probably the International Prognostic Scoring System (IPSS). IPSS is now replaced by the revised IPSS-R score. Although not systematically incorporated into new validated prognostic systems, somatic mutations can help define prognosis and should be considered as new prognostic factors.

RISK-ADAPTED THERAPY

Therapy is selected based on risk, transfusion needs, percent of bone marrow blasts and cytogenetic and mutational profiles. Goals of therapy are different in lower risk patients than in higher risk. In lower risk, the goal is to decrease transfusion needs and transformation to higher risk disease or AML, as well as to improve survival. In higher risk, the goal is to prolong survival. Current available therapies include growth factor support, lenalidomide, hypomethylating agents, intensive chemotherapy and allogeneic stem cell transplantation. The use of lenalidomide has significant clinical activity in patients with lower risk disease, anemia and a chromosome 5 alteration. 5-azacitidine and decitabine have activity in both lower and higher-risk MDS. 5-azacitidine has been shown to improve survival in higher risk MDS. A number of new molecular lesions have been described in MDS that may serve as new therapeutic targets or aid in the selection of currently available agents. Additional supportive care measures may include the use of prophylactic antibiotics and iron chelation.

MANAGEMENT OF PROGRESSIVE OR REFRACTORY DISEASE

At the present time there are no approved interventions for patients with progressive or refractory disease particularly after hypomethylating based therapy. Options include participation in a clinical trial or cytarabine based therapy and stem cell transplantation.

Molecular basis of the human ribosomopathy Shwachman-Diamond syndrome

Mutations that target the ubiquitous process of ribosome assembly paradoxically cause diverse tissue-specific disorders (ribosomopathies) that are often associated with an increased risk of cancer. Ribosomes are the essential macromolecular machines that read the genetic code in all cells in all kingdoms of life. Following pre-assembly in the nucleus, precursors of the large 60S and small 40S ribosomal subunits are exported to the cytoplasm where the final steps in maturation are completed. Here, I review the recent insights into the conserved mechanisms of ribosome assembly that have come from functional characterisation of the genes mutated in human ribosomopathies. In particular, recent advances in cryo-electron microscopy, coupled with genetic, biochemical and prior structural data, have revealed that the SBDS protein that is deficient in the inherited leukaemia predisposition disorder Shwachman-Diamond syndrome couples the final step in cytoplasmic 60S ribosomal subunit maturation to a quality control assessment of the structural and functional integrity of the nascent particle. Thus, study of this fascinating disorder is providing remarkable insights into how the large ribosomal subunit is functionally activated in the cytoplasm to enter the actively translating pool of ribosomes.

Recent advances in the cellular and molecular understanding of myelodysplastic syndromes: implications for new therapeutic approaches

It has been more than 10 years since any new disease-modifying therapies have received regulatory approval for indications related to myelodysplastic syndromes (MDS). Advances in our collective biological understanding of MDS in the last decade, however, have made it possible to hope that effective therapeutics can be designed to improve MDS-associated cytopenias and patients' quality of life, and perhaps even delay clonal progression and extend survival. Classes of MDS-associated mutations and disordered biological pathways targeted by developmental therapeutics include the following: aberrant messenger RNA splicing, neomorphic enzymes in the citric acid cycle with oncogenic activity, overactivated tyrosine and serine-threonine kinases, epigenetic and chromatin remodeling alterations, abnormal telomere dynamics, and failed protection of DNA integrity. At present, treatments for MDS are usually administered as sequential monotherapy, but there is a trend toward clinical trials of combination therapies-in which new agents are added to a DNA hypomethylating agent backbone-for both upfront treatment and the treatment of relapsed/refractory disease. Agents in clinical trials for subsets of MDS include luspatercept, antibodies targeting CD33, isocitrate dehydrogenase inhibitors, deacetylase inhibitors, venetoclax, and immunotherapies designed to overcome immune checkpoint inhibition. These biologically based therapeutics, as well as the encouraging precedent of 7 new approvals by the US Food and Drug Administration in 2017 for the treatment of acute leukemia, offer the prospect that 10 more years will not elapse before another new therapy is approved for MDS.

Inherited bone marrow failure syndromes: considerations pre- and posttransplant

Patients with inherited bone marrow failure syndromes are usually identified when they develop hematologic complications such as severe bone marrow failure, myelodysplastic syndrome, or acute myeloid leukemia. They often have specific birth defects or other physical abnormalities that suggest a syndrome, and sequencing of specific genes or next-generation sequencing can determine or confirm the particular syndrome. The 4 most frequent syndromes are Fanconi anemia, dyskeratosis congenita, Diamond Blackfan anemia, and Shwachman Diamond syndrome. This review discusses the major complications that develop as the patients with these syndromes age, as well as additional late effects following hematopoietic stem cell transplantation. The most common complications are iron overload in transfused patients and syndrome-specific malignancies in untransplanted patients, which may occur earlier and with higher risks in those who have received transplants.