Transcription elongation defects link oncogenic SF3B1 mutations to targetable alterations in chromatin landscape.

Transcription and splicing of pre-messenger RNA are closely coordinated, but how this functional coupling is disrupted in human diseases remains unexplored. Using isogenic cell lines, patient samples, and a mutant mouse model, we investigated how cancer-associated mutations in SF3B1 alter transcription. We found that these mutations reduce the elongation rate of RNA polymerase II (RNAPII) along gene bodies and its density at promoters. The elongation defect results from disrupted pre-spliceosome assembly due to impaired protein-protein interactions of mutant SF3B1. The decreased promoter-proximal RNAPII density reduces both chromatin accessibility and H3K4me3 marks at promoters. Through an unbiased screen, we identified epigenetic factors in the Sin3/HDAC/H3K4me pathway, which, when modulated, reverse both transcription and chromatin changes. Our findings reveal how splicing factor mutant states behave functionally as epigenetic disorders through impaired transcription-related changes to the chromatin landscape. We also present a rationale for targeting the Sin3/HDAC complex as a therapeutic strategy.

The FANCI/FANCD2 complex links DNA damage response to R-loop regulation through SRSF1-mediated mRNA export.

Fanconi anemia (FA) is characterized by congenital abnormalities, bone marrow failure, and cancer susceptibility. The central FA protein complex FANCI/FANCD2 (ID2) is activated by monoubiquitination and recruits DNA repair proteins for interstrand crosslink (ICL) repair and replication fork protection. Defects in the FA pathway lead to R-loop accumulation, which contributes to genomic instability. Here, we report that the splicing factor SRSF1 and FANCD2 interact physically and act together to suppress R-loop formation via mRNA export regulation. We show that SRSF1 stimulates FANCD2 monoubiquitination in an RNA-dependent fashion. In turn, FANCD2 monoubiquitination proves crucial for the assembly of the SRSF1-NXF1 nuclear export complex and mRNA export. Importantly, several SRSF1 cancer-associated mutants fail to interact with FANCD2, leading to inefficient FANCD2 monoubiquitination, decreased mRNA export, and R-loop accumulation. We propose a model wherein SRSF1 and FANCD2 interaction links DNA damage response to the avoidance of pathogenic R-loops via regulation of mRNA export.

Transcription elongation defects link oncogenic splicing factor mutations to targetable alterations in chromatin landscape.

Transcription and splicing of pre-messenger RNA are closely coordinated, but how this functional coupling is disrupted in human disease remains unexplored. Here, we investigated the impact of non-synonymous mutations in SF3B1 and U2AF1, two commonly mutated splicing factors in cancer, on transcription. We find that the mutations impair RNA Polymerase II (RNAPII) transcription elongation along gene bodies leading to transcription-replication conflicts, replication stress and altered chromatin organization. This elongation defect is linked to disrupted pre-spliceosome assembly due to impaired association of HTATSF1 with mutant SF3B1. Through an unbiased screen, we identified epigenetic factors in the Sin3/HDAC complex, which, when modulated, normalize transcription defects and their downstream effects. Our findings shed light on the mechanisms by which oncogenic mutant spliceosomes impact chromatin organization through their effects on RNAPII transcription elongation and present a rationale for targeting the Sin3/HDAC complex as a potential therapeutic strategy. HIGHLIGHTS: Oncogenic mutations of SF3B1 and U2AF1 cause a gene-body RNAPII elongation defectRNAPII transcription elongation defect leads to transcription replication conflicts, DNA damage response, and changes to chromatin organization and H3K4me3 marksThe transcription elongation defect is linked to disruption of the early spliceosome formation through impaired interaction of HTATSF1 with mutant SF3B1.Changes to chromatin organization reveal potential therapeutic strategies by targeting the Sin3/HDAC pathway.

A phase 1 study to evaluate the safety, pharmacology, and feasibility of continuous infusion nelarabine in patients with relapsed and/or refractory lymphoid malignancies.

BACKGROUND: Nelarabine is a purine nucleoside analogue prodrug approved for the treatment of relapsed and refractory T-cell acute lymphoblastic leukemia (R/R T-ALL) and lymphoblastic lymphoma (T-LBL). Although effective in R/R T-ALL, significant neurotoxicity is dose-limiting and such neurotoxicity associated with nucleoside analogues can be related to dosing schedule. METHODS: The authors conducted a phase 1 study to evaluate the pharmacokinetics and toxicity of nelarabine administered as a continuous infusion (CI) for 5 days (120 hours), rather than the standard, short-infusion approach. RESULTS: Twenty-nine patients with R/R T-ALL/LBL or T-cell prolymphocytic leukemia (T-PLL) were treated, with escalating doses of nelarabine from 100 to 800 mg/m2 /day × 5 days. The median age of the patients was 39 years (range, 14-77 years). The overall response rate was 31%, including 27% complete remission (CR) or CR with incomplete platelet recovery (CRp). Peripheral neuropathy was observed in 34% of patients, including four ≥grade 3 events related to nelarabine. Notably, there was no nelarabine-related central neurotoxicity on study. The maximum tolerated dose was not reached. Pharmacokinetic data suggested no relationship between dose of nelarabine and accumulation of active intracellular ara-GTP metabolite. Higher intracellular ara-GTP concentrations were statistically associated with a favorable clinical response. CONCLUSION: Preliminary evaluation of continuous infusion schedule of nelarabine suggests that the safety profile is acceptable for this patient population, with clinical activity observed even at low doses and could broaden the use of nelarabine both as single agent and in combinations by potentially mitigating the risk of central nervous system toxicities.

Generation of scalable cancer models by combining AAV-intron-trap, CRISPR/Cas9, and inducible Cre-recombinase.

Scalable isogenic models of cancer-associated mutations are critical to studying dysregulated gene function. Nonsynonymous mutations of splicing factors, which typically affect one allele, are common in many cancers, but paradoxically confer growth disadvantage to cell lines, making their generation and expansion challenging. Here, we combine AAV-intron trap, CRISPR/Cas9, and inducible Cre-recombinase systems to achieve >90% efficiency to introduce the oncogenic K700E mutation in SF3B1, a splicing factor commonly mutated in multiple cancers. The intron-trap design of AAV vector limits editing to one allele. CRISPR/Cas9-induced double stranded DNA breaks direct homologous recombination to the desired genomic locus. Inducible Cre-recombinase allows for the expansion of cells prior to loxp excision and expression of the mutant allele.  Importantly, AAV or CRISPR/Cas9 alone results in much lower editing efficiency and the edited cells do not expand due to toxicity of SF3B1-K700E. Our approach can be readily adapted to generate scalable isogenic systems where mutant oncogenes confer a growth disadvantage.

Special considerations in the management of adult patients with acute leukaemias and myeloid neoplasms in the COVID-19 era: recommendations from a panel of international experts.

The ongoing COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 is a global public health crisis. Multiple observations indicate poorer post-infection outcomes for patients with cancer than for the general population. Herein, we highlight the challenges in caring for patients with acute leukaemias and myeloid neoplasms amid the COVID-19 pandemic. We summarise key changes related to service allocation, clinical and supportive care, clinical trial participation, and ethical considerations regarding the use of lifesaving measures for these patients. We recognise that these recommendations might be more applicable to high-income countries and might not be generalisable because of regional differences in health-care infrastructure, individual circumstances, and a complex and highly fluid health-care environment. Despite these limitations, we aim to provide a general framework for the care of patients with acute leukaemias and myeloid neoplasms during the COVID-19 pandemic on the basis of recommendations from international experts.

Distinct Immunophenotypes of T Cells in Bronchoalveolar Lavage Fluid From Leukemia Patients With Immune Checkpoint Inhibitors-Related Pulmonary Complications.

Patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) treated with immune checkpoint inhibitors (ICIs) are at risk of pneumonitis as well as pneumonia (combined henceforth as ICI-related pulmonary complications). Little is known about the cellular and molecular mechanisms underlying ICI-related pulmonary complications. We characterized lymphocytes from bronchoalveolar lavage (BAL) fluid and peripheral blood from seven AML/MDS patients with pulmonary symptoms after ICI-based therapy (ICI group) and four ICI-naïve AML/MDS patients with extracellular bacterial or fungal pneumonias (controls). BAL T cells in the ICI group were clonally expanded, and BAL IFNγ+ IL-17- CD8+ T and CXCR3+ CCR6+ Th17/Th1 cells were enriched in the ICI group. Our data suggest that these cells may play a critical role in the pathophysiology of ICI-related pulmonary complications. Understanding of these cell populations may also provide predictive and diagnostic biomarkers of ICI-related pulmonary complications, eventually enabling differentiation of pneumonitis from pneumonia in AML/MDS patients receiving ICI-based therapies.

Gut Microbiome Signatures Are Predictive of Infectious Risk Following Induction Therapy for Acute Myeloid Leukemia.

BACKGROUND: The majority of studies that provide insights into the influence of the microbiome on the health of hematologic malignancy patients have concentrated on the transplant setting. Here, we sought to assess the predictive capacity of the gastrointestinal microbiome and its relationship to infectious outcomes in patients with acute myeloid leukemia (AML). METHODS: 16s rRNA-based analysis was performed on oral swabs and stool samples obtained biweekly from baseline until neutrophil recovery following induction chemotherapy (IC) in 97 AML patients. Microbiome characteristics were correlated with clinical outcomes both during and after IC completion. RESULTS: At the start of IC, higher stool Shannon diversity (hazard ratio [HR], 0.36; 95% confidence interval [CI], .18-.74) and higher relative abundance of Porphyromonadaceae (HR, 0.36; 95% CI, .18-.73) were associated with increased probability of remaining infection-free during neutropenia. A baseline stool Shannon diversity cutoff of <2 had optimal operating characteristics for predicting infectious complications during neutropenia. Although 56 patients received therapy >72 hours with a carbapenem, none of the patients had an infection with an extended spectrum ß-lactamase-producing organism. Patients who received carbapenems for >72 hours had significantly lower α-diversity at neutrophil recovery (P = .001) and were approximately 4 times more likely to have infection in the 90 days following neutrophil recovery (HR, 4.55; 95% CI, 1.73-11.93). CONCLUSIONS: Our results suggest that gut microbiome evaluation could assist with infectious risk stratification and that improved targeting of antibiotic administration during IC could decrease subsequent infectious complications in AML patients.Baseline microbiome diversity is a strong independent predictor of infection during acute myeloid leukemia induction chemotherapy (IC) among clinical and microbiome covariates. Higher baseline levels of Porphyromonadaceae appear protective against infection, while carbapenem use is associated with consequences to the microbiome and infection susceptibility post-IC.

The minimal that kills: Why defining and targeting measurable residual disease is the "Sine Qua Non" for further progress in management of acute myeloid leukemia.

Patients with acute myeloid leukemia (AML) who achieve morphologic remission in the bone marrow after initial treatment often continue to harbor residual leukemic cells that can give rise to disease relapse. Achievement of a deeper remission has been associated with a reduced risk of relapse and improved event-free and overall survival in several studies. However, standardization of diagnostic techniques, sample acquisition and test timing are needed before minimal, also known as measurable, residual disease (MRD) quantification can be used to guide treatment decision making. Furthermore, clinical trial evidence that preemptive intervention at MRD level can alter the natural history of AML is required. Herein, we outline the current landscape of MRD assessment in AML, summarize the available evidence and challenges, and highlight the potential for MRD status to serve as a surrogate endpoint for hard clinical outcomes and as an approvable endpoint in clinical trials for regulatory purposes.

The golden age for patients in their golden years: The progressive upheaval of age and the treatment of newly-diagnosed acute myeloid leukemia.

Most acute myeloid leukemia (AML) patients will be aged more than 65 years. Chronological aging is accompanied by decreasing stem cell and solid organ reserve as well as an increased incidence of medical comorbidity. For the older patient with AML, these patient-specific factors are compounded by an association with complexity of disease biology, chemoresistance, poor tolerance and early mortality with intensive induction therapy. However, the investigation and availability of therapies targeted against various molecular drivers of leukemogenesis, leukemic stem cell persistence, and chemoresistance have provided more options for the patient ineligible for intensive or classical induction therapy, often guided by age >60-65 years by some treatment algorithms. Many providers remain appropriately optimistic that such therapies may overtake the longstanding recommendation for frontline intensive therapy in certain circumstances. Traditional algorithms dichotomizing the optimal treatment modality based on AML patient age are aging themselves and are very likely to soon be outdated.

Hedgehog pathway inhibition as a therapeutic target in acute myeloid leukemia.

Introduction: The Hedgehog (HH) pathway constitutes a collection of signaling molecules which critically influence embryogenesis. In adults, however, the HH pathway remains integral to the proliferation, maintenance, and apoptosis of adult stem cells including hematopoietic stem cells. Areas covered: We discuss the current understanding of the HH pathway as it relates to normal hematopoiesis, the pathology of acute myeloid leukemia (AML), the rationale for and data from combination therapies including HH pathway inhibitors, and ultimately the prospects that might offer promise in targeting this pathway in AML. Expert opinion: Efforts to target the HH pathway have been focused on impeding this disposition and restoring chemosensitivity to conventional myeloid neoplasm therapies. The year 2018 saw the first approval of a HH pathway inhibitor (glasdegib) for AML, though for an older population and in combination with an uncommonly-used therapy. Several other clinical trials with agents targeting modulators of HH signaling in AML and MDS are underway. Further study and understanding of the interplay between the numerous aspects of HH signaling and how it relates to the augmented survival of AML will provide a more reliable substrate for therapeutic strategies in patients with this poor-risk disease.

Outcomes of patients with chronic phase chronic myeloid leukemia (CML-CP) after discontinuation of frontline ponatinib therapy.

Considering the risk of arterio-thrombotic adverse events (AEs), ponatinib trials in previously untreated chronic myeloid leukemia chronic phase (CML-CP) were terminated. We conducted a retrospective CML-CP outcome study of patients who discontinued frontline-ponatinib. Among 51 patients who received frontline ponatinib, 38 discontinued because of FDA request and 13 due to AEs. At ponatinib discontinuation, all patients remained in CP with deepest response being CCyR, n = 7; PCyR, n = 4; MMR, n = 14; MR4.5, n = 26. Of the four patients in PCyR at ponatinib discontinuation, two improved response to CCyR on subsequent TKI. Of seven patients, in CCyR at discontinuation, five improved response to MMR or deeper, one was inevaluable, and another lost response due to treatment noncompliance. With a median follow-up of 39 months, 3-year EFS and OS were 92% and 96%, respectively, indicating favorable long-term outcomes. The cardiac/vascular system AEs with subsequent TKI occurred in patients with prior similar events on ponatinib. AEs occurred up to 9 months post-ponatinib.

Myeloid disorders after autoimmune disease.

Autoimmune diseases (ADs) are associated with an increased risk not only of lymphoproliferative disorders but also of myeloid malignancies. The excess risk of myelodysplastic syndromes and/or acute myeloid leukemia is observed across several AD types, including systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disorders, multiple sclerosis, among others. The risk of developing myeloid neoplasms (MNs) is dependent on several variables, including the specific AD type, chronicity and severity of the AD, type and duration of exposure of disease modifying anti-rheumatic drugs or cytotoxics/immunosuppressives, and genetic predisposition risk. Putative triggering factors linking AD to elevated MN risk include AD-directed medications, shared genetic susceptibilities between the two disease entities, and chronic immune stimulation or bone marrow infiltration by the AD. Molecular mechanisms underpinning leukemogenesis remain largely speculative and warrant further investigation. Leukemias arising in patients with AD are not always 'therapy-related' in that MNs may develop in certain AD subtypes even among patients with no prior therapy exposure. Only a few studies have attempted to determine factors associated with MN development in AD but failed to demonstrate consistent characteristic clinical or paraclinical features. These reports have failed to demonstrate a clear correlation between individual agent exposure and subsequent leukemia development due to the low rates of therapy exposure compounded by the rarity of MN occurrence. Notwithstanding, the leukemogenic potential is best documented with agents such as azathioprine, cyclophosphamide, and mitoxantrone; this risk of MN development does not appear to be shared by biologic approaches such as anti-tumor necrosis factors-alpha inhibitors. In this article, we discuss plausible biologic mechanisms underlying MN pathogenesis in AD and review the data available on the development of MNs in patients with AD.

Analysis of cardiovascular and arteriothrombotic adverse events in chronic-phase CML patients after frontline TKIs.

Cardiovascular or arteriothrombotic adverse events (CV- or AT-AEs) are reported in chronic myeloid leukemia (CML) patients treated with tyrosine kinase inhibitors (TKIs). The incidence and characteristics across different TKI have not been systematically analyzed. We analyzed 531 patients treated with frontline TKIs in different prospective trials: imatinib 400 mg (n = 71) and 800 mg (n = 203), nilotinib (n = 108), dasatinib (n = 106), and ponatinib (n = 43). Characteristics and incidence of new-onset CV-AEs and AT-AEs were analyzed. Poisson regression models assessed factors associated with AE incidence. Median follow-up was 94 months (range, 2-195). Overall, 237 patients (45%) developed CV-AEs and 46 (9%) developed AT-AEs. Hypertension was the most common AE seen in 175 patients (33%; grade 3/4 in 17%). CV-AE and AT-AE incidence ratios (IRs) with 95% confidence intervals (CIs) were 8.6 (7.6-9.8) and 1.7 (1.2-2.2) per 100 person-years. Among the TKIs, ponatinib showed the highest IR (95% CI) for CV-AEs and AT-AEs at 40.7 (27.9-59.4) and 9.0 (4.1-20.1). In multivariate analysis, ponatinib therapy was associated with increased incidence rate ratio (IRR) for CV-AEs (4.62; 95% CI, 2.7-7.7; P < .0001) and AT-AEs (6.38; 95% CI, 1.8-21.8; P < .0001) compared with imatinib 400. In summary, there is an increased risk of CV-AEs (except hypertension) and AT-AEs in CML patients treated with newer TKIs, particularly with ponatinib. Patients on TKIs must be informed and closely monitored for vascular AEs. These studies were registered at www.clinicaltrials.gov as #NCT00048672, #NCT00038649, #NCT00050531, #NCT00254423, #NCT00129740, and #NCT01570868.

SMAC mimetics as potential cancer therapeutics in myeloid malignancies.

Evasion of apoptosis has been identified as one of the essential hallmarks of cancer. Inhibitor of apoptosis proteins (IAPs) are implicated in a host of myeloid malignancies, providing the rationale for strategies aimed at neutralizing IAPs to lower the cancer cell apoptosis threshold. Modes of IAP antagonism may include down-regulating IAP expression, up-regulating endogenous pro-apoptotic proteins, such as tumour necrosis factor-α or Fas ligand, or directly antagonizing IAP activity against caspases. Direct targeting of IAPs using mimetics of the second mitochondria-derived activator of caspase (SMAC) protein has shown therapeutic promise by sensitizing the effect of chemotherapy on malignant cells. In pre-clinical studies, SMAC mimetics have demonstrated broad synergistic activity with a wide range of therapeutics, including cytotoxic chemotherapy, receptor tyrosine kinase inhibitors, agents targeting death receptors and alternative mechanisms of cell death, such as necroptosis or autophagy and immune check point blockade. SMAC mimetics represent a novel approach for further investigation in patients with high-risk, chemo-refractory blood cancers, as single agents or in thoughtfully selected combinations. In this review, we discuss the development and therapeutic rationale of small molecule SMAC mimetics, with an emphasis on agents in clinical development for myeloid malignancies.

Janus kinase 2 variants associated with the transformation of myeloproliferative neoplasms into acute myeloid leukemia.

BACKGROUND: Canonical Janus kinase 2 (JAK2) V617F and exon 12 mutations in myeloid neoplasms are well described. There are limited reports of other JAK2 variants of potential clinical relevance. This study was designed to survey JAK2 variants in patients with myeloproliferative neoplasms (MPNs) and acute myeloid leukemia (AML) and to determine their contributions to disease pathogenesis. METHODS: Next-generation sequencing of the coding region of JAK2 and 27 other genes was performed on bone marrow DNA samples. The study population was classified into 3 cohorts: chronic MPNs only (the MPN cohort); MPNs transformed into AML (the MPN>>AML cohort); and AML only, with MPN>>AML patients excluded (the AML cohort). RESULTS: Testing was performed for 2154 patients, and non-V617F/non-exon 12 JAK2 sequence variants were identified in 114 (5.3%). They included 35 unique JAK2 variants across all functional domains. Sixteen of the 114 JAK2 variants occurred without somatic mutations in the remaining 27 genes. JAK2 variants were detected at a higher frequency in the MPN>>AML cohort (15.3%) in comparison with the MPN (4.6%; P < .001) and AML cohorts (5.2%; P < .001). Detected variants occurred at higher than expected frequencies in patients with MPNs and AML in comparison with the population, and N1108S had a significantly increased prevalence in patients with AML. A JAK2 variant in addition to JAK2 V617F (n = 13) in myelofibrosis was associated with an increased cumulative risk of transformation into AML (P = .003). CONCLUSIONS: Specific JAK2 variants detected in MPNs may be predictors for transformation into AML.

Leukemic Involvement in the Thorax.

Leukemias are malignancies in which abnormal white blood cells are produced in the bone marrow, resulting in compromise of normal bone marrow hematopoiesis and subsequent cytopenias. Leukemias are classified as myeloid or lymphoid depending on the type of abnormal cells produced and as acute or chronic according to cellular maturity. The four major types of leukemia are acute myeloid leukemia, chronic myeloid leukemia, acute lymphoblastic leukemia, and chronic lymphocytic leukemia. Clinical manifestations are due to either bone marrow suppression (anemia, thrombocytopenia, or neutropenia) or leukemic organ infiltration. Imaging manifestations of leukemia in the thorax are myriad. While lymphadenopathy is the most common manifestation of intrathoracic leukemia, leukemia may also involve the lungs, pleura, heart, and bones and soft tissues. Myeloid sarcomas occur in 5%-7% of patients with acute myeloid leukemia and represent masses of myeloid blast cells in an extramedullary location. ©RSNA, 2019.

What are the most promising new agents in myelodysplastic syndromes?

PURPOSE OF REVIEW: Myelodysplastic syndromes (MDS) are a diverse group of clonal disorders of hematopoietic stem or progenitor cells that represent the most common class of acquired bone marrow failure syndromes in adults. Despite significant improvement in the pathologic insight into this group of disorders, therapeutic options remain limited and allogeneic hematopoietic stem-cell transplantation is the only treatment that can induce long-term remission in patients with MDS. The goals of therapy for MDS are based on disease prognostication, with a focus of minimizing transfusion dependence and preserving quality of life in low-risk groups and preventing progression of disease to acute myeloid leukemia in high-risk groups. Given the dearth of approved treatment options, there is a marked need for novel therapies across the board, and there are several novel agents currently in the pipeline. RECENT FINDINGS: Among the promising agents with preclinical and early phase efficacy in higher risk MDS, apoptosis targeting with BCL-2 inhibitors have been a standout. There is also a keen interest in immunotherapy, and targeted agents (genetic, signaling pathways, bispecific antibodies, antibody-drug conjugates, and others described in this review). SUMMARY: In this review, we will highlight some of the promising new agents currently under investigation for the management of MDS.