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.

TET1 is a tumor suppressor of hematopoietic malignancy.

The methylcytosine dioxygenase TET1 ('ten-eleven translocation 1') is an important regulator of 5-hydroxymethylcytosine (5hmC) in embryonic stem cells. The diminished expression of TET proteins and loss of 5hmC in many tumors suggests a critical role for the maintenance of this epigenetic modification. Here we found that deletion of Tet1 promoted the development of B cell lymphoma in mice. TET1 was required for maintenance of the normal abundance and distribution of 5hmC, which prevented hypermethylation of DNA, and for regulation of the B cell lineage and of genes encoding molecules involved in chromosome maintenance and DNA repair. Whole-exome sequencing of TET1-deficient tumors revealed mutations frequently found in non-Hodgkin B cell lymphoma (B-NHL), in which TET1 was hypermethylated and transcriptionally silenced. Our findings provide in vivo evidence of a function for TET1 as a tumor suppressor of hematopoietic malignancy.

NAC and Zuotin/Hsp70 chaperone systems coexist at the ribosome tunnel exit in vivo.

The area surrounding the tunnel exit of the 60S ribosomal subunit is a hub for proteins involved in maturation and folding of emerging nascent polypeptide chains. How different factors vie for positioning at the tunnel exit in the complex cellular environment is not well understood. We used in vivo site-specific cross-linking to approach this question, focusing on two abundant factors-the nascent chain-associated complex (NAC) and the Hsp70 chaperone system that includes the J-domain protein co-chaperone Zuotin. We found that NAC and Zuotin can cross-link to each other at the ribosome, even when translation initiation is inhibited. Positions yielding NAC-Zuotin cross-links indicate that when both are present the central globular domain of NAC is modestly shifted from the mutually exclusive position observed in cryogenic electron microscopy analysis. Cross-linking results also suggest that, even in NAC's presence, Hsp70 can situate in a manner conducive for productive nascent chain interaction-with the peptide binding site at the tunnel exit and the J-domain of Zuotin appropriately positioned to drive stabilization of nascent chain binding. Overall, our results are consistent with the idea that, in vivo, the NAC and Hsp70 systems can productively position on the ribosome simultaneously.

The human proton pump inhibitors inhibit Mycobacterium tuberculosis rifampicin efflux and macrophage-induced rifampicin tolerance.

Tuberculosis treatment requires months-long combination chemotherapy with multiple drugs, with shorter treatments leading to relapses. A major impediment to shortening treatment is that Mycobacterium tuberculosis becomes tolerant to the administered drugs, starting early after infection and within days of infecting macrophages. Multiple lines of evidence suggest that macrophage-induced drug tolerance is mediated by mycobacterial drug efflux pumps. Here, using assays to directly measure drug efflux, we find that M. tuberculosis transports the first-line antitubercular drug rifampicin through a proton gradient-dependent mechanism. We show that verapamil, a known efflux pump inhibitor, which inhibits macrophage-induced rifampicin tolerance, also inhibits M.tuberculosis rifampicin efflux. As with macrophage-induced tolerance, the calcium channel-inhibiting property of verapamil is not required for its inhibition of rifampicin efflux. By testing verapamil analogs, we show that verapamil directly inhibits M. tuberculosis drug efflux pumps through its human P-glycoprotein (PGP)-like inhibitory activity. Screening commonly used drugs with incidental PGP inhibitory activity, we find many inhibit rifampicin efflux, including the proton pump inhibitors (PPIs) such as omeprazole. Like verapamil, the PPIs inhibit macrophage-induced rifampicin tolerance as well as intramacrophage growth, which has also been linked to mycobacterial efflux pump activity. Our assays provide a facile screening platform for M. tuberculosis efflux pump inhibitors that inhibit in vivo drug tolerance and growth.

Satb1 regulates the self-renewal of hematopoietic stem cells by promoting quiescence and repressing differentiation commitment.

How hematopoietic stem cells (HSCs) coordinate the regulation of opposing cellular mechanisms such as self-renewal and differentiation commitment remains unclear. Here we identified the transcription factor and chromatin remodeler Satb1 as a critical regulator of HSC fate. HSCs lacking Satb1 had defective self-renewal, were less quiescent and showed accelerated lineage commitment, which resulted in progressive depletion of functional HSCs. The enhanced commitment was caused by less symmetric self-renewal and more symmetric differentiation divisions of Satb1-deficient HSCs. Satb1 simultaneously repressed sets of genes encoding molecules involved in HSC activation and cellular polarity, including Numb and Myc, which encode two key factors for the specification of stem-cell fate. Thus, Satb1 is a regulator that promotes HSC quiescence and represses lineage commitment.

NPM1 ablation induces HSC aging and inflammation to develop myelodysplastic syndrome exacerbated by p53 loss.

Myelodysplastic syndrome (MDS) is characterized by ineffective hematopoiesis with morphologic dysplasia and a propensity to transform into overt acute myeloid leukemia (AML). Our analysis of two cohorts of 20 MDS and 49 AML with multi-lineage dysplasia patients shows a reduction in Nucleophosmin 1 (NPM1) expression in 70% and 90% of cases, respectively. A mouse model of Npm1 conditional knockout (cKO) in hematopoietic cells reveals that Npm1 loss causes premature aging of hematopoietic stem cells (HSCs). Mitochondrial activation in Npm1-deficient HSCs leads to aberrant activation of the NLRP3 inflammasome, which correlates with a developing MDS-like phenotype. Npm1 cKO mice exhibit shortened survival times, and expansion of both the intra- and extra-medullary myeloid populations, while evoking a p53-dependent response. After transfer into a p53 mutant background, the resulting Npm1/p53 double KO mice develop fatal leukemia within 6 months. Our findings identify NPM1 as a regulator of HSC aging and inflammation and highlight the role of p53 in MDS progression to leukemia.

Imageable Radioembolization Microspheres for Treatment of Unresectable Hepatocellular Carcinoma: Interim Results from a First-in-Human Trial.

PURPOSE: To Describe 6-Month safety, efficacy and multimodal imageability after imageable glass Yttrium-90 radioembolization for unresectable Hepatocellular Carcinoma (HCC) in a First-in Human Trial METHODS: Eye90 microspheres® (Eye90), an FDA Breakthrough Designated Device, are glass radiopaque Y-90 microspheres visible on CT and SPECT/CT. Six subjects with unresectable HCC underwent selective (≤ 2 segments) Eye90 treatment in a prospective open-label pilot trial. Key inclusion criteria included liver only HCC, ECOG ≤ 1, total lesion length ≤ 9 cm and Child-Pugh A. Prospective partition dosimetry was utilized. Safety, biochemistry, toxicity, adverse events (AE), multimodal imageability on CT and SPECT/CT and 3 and 6-month MRI local modified RECIST (mRECIST) response was evaluated. RESULTS: 6 subjects with HCC (7 lesions) were treated with Eye90 and followed to 180 days. Administration success was 100%. Eye90 CT radiopacity distribution correlated with SPECT/CT. Target lesion complete response was observed in 3 of 6 subjects (50%) and partial response in 2 (33.3%). Two subjects could not be assessed at 180 days. At 180 days, target lesion complete response was maintained in 3 subjects (50%) and partial response in 1 (16.7%). All subjects reported AEs, and 5 reported AEs related to treatment. There were no treatment related serious AEs. CONCLUSIONS: Eye90 was safe and effective in six subjects with unresectable HCC up to 6 months. Eye90 was imageable via CT and SPECT/CT with correlation between CT radiopacity and SPECT/CT radioactivity distribution. Eye90 provided previously unavailable CT based tumor targeting information.

Validation of a Midfacial Scale and Its Use in a Randomized, Evaluator-Blinded Study of CPM-HA-V.

BACKGROUND: Age-related loss of midfacial contour is frequently corrected using dermal fillers. A validated photonumeric scale is beneficial when evaluating post-treatment aesthetic improvement. OBJECTIVE: To present scale-development activities for the Merz Cheek Fullness Assessment Scale (MCFAS) and report pilot-study results of a hyaluronic-acid filler (Belotero Volume with Lidocaine; CPM-HA-V) to treat midfacial volume loss. METHODS: A 5-point photonumeric scale was developed to objectively assess midface volume loss. Rater reliability was evaluated using live assessments. The clinical relevance of a 1-point difference in severity grade was evaluated using photographic comparisons. Pilot-study participants, with moderate-to-severe volume loss on the MCFAS, were randomized 2:1 to treatment or untreated control. Effectiveness was evaluated using the MCFAS, and adverse events were recorded. RESULTS: The MCFAS demonstrated substantial intra- and interrater agreement among physicians (weighted kappa > 0.6). The mean absolute difference (95% confidence interval) in scale ratings was 1.12 (1.00, 1.24) for photographic pairs differing by one grade and was 0.55 (0.48, 0.63) for pairs of the same grade, suggesting a 1-point difference is clinically relevant. In the pilot study, significant  (P < 0.0001) differences were observed in MCFAS response rates between treatment and control. No safety concerns were identified. CONCLUSION: The MCFAS is a validated, reliable, and clinically relevant photonumeric scale for rating midfacial volume loss in males and females of various ages and skin types. In a pilot study, CPM-HA-V was found to be safe and tolerable, and the MCFAS was able to detect clinically meaningful post-treatment changes. J Drugs Dermatol. 2024;23(1):     doi:10.36849/JDD.7981.

Dorsal root ganglion stimulator-A targeted therapy for post-herpetic neuralgia: The Middle East Experience.

BACKGROUND: Post herpetic neuralgia (PHN) is a chronic neuropathic pain syndrome which presents after an episode of herpes zoster caused by the reactivation of varicella zoster virus. Conservative treatment starts with pharmacological measures using Anti-epileptics and Antidepressants. Some patients also respond well to epidural steroid injections too, but the effect is usually short lasting. Dorsal Root Ganglion Stimulator (DRG-S) has recently been suggested as a new treatment modality for PHN due to its selective targeting of the pathophysiologic focus. CASE SERIES: We are reporting three cases, who were suffering from neuropathic pain after an episode of herpes zoster. Pain and pain related suffering scores were high, even with multiple antiepileptics and opioid medications. They underwent DRG-S implant and appreciated more than 50% reduction of their pain score, meaningful reduction in the dose of medications along with significant improvement of their general well being measured using Generalized Anxiety Disorder Questionnaire (GAD-7), pain disability index (PDI), and 9 Question Patient Health Questionnaire (PHQ-9). To our knowledge this is the first report on DRG stimulator from the Middle East Region. CONCLUSION: DRG-S has potential to be a preferable treatment option in patients with refractory PHN and acts as a specific targeted therapy in the treatment of these patients.

Luspatercept in Patients with Lower-Risk Myelodysplastic Syndromes.

BACKGROUND: Patients with anemia and lower-risk myelodysplastic syndromes in whom erythropoiesis-stimulating agent therapy is not effective generally become dependent on red-cell transfusions. Luspatercept, a recombinant fusion protein that binds transforming growth factor ß superfamily ligands to reduce SMAD2 and SMAD3 signaling, showed promising results in a phase 2 study. METHODS: In a double-blind, placebo-controlled, phase 3 trial, we randomly assigned patients with very-low-risk, low-risk, or intermediate-risk myelodysplastic syndromes (defined according to the Revised International Prognostic Scoring System) with ring sideroblasts who had been receiving regular red-cell transfusions to receive either luspatercept (at a dose of 1.0 up to 1.75 mg per kilogram of body weight) or placebo, administered subcutaneously every 3 weeks. The primary end point was transfusion independence for 8 weeks or longer during weeks 1 through 24, and the key secondary end point was transfusion independence for 12 weeks or longer, assessed during both weeks 1 through 24 and weeks 1 through 48. RESULTS: Of the 229 patients enrolled, 153 were randomly assigned to receive luspatercept and 76 to receive placebo; the baseline characteristics of the patients were balanced. Transfusion independence for 8 weeks or longer was observed in 38% of the patients in the luspatercept group, as compared with 13% of those in the placebo group (P<0.001). A higher percentage of patients in the luspatercept group than in the placebo group met the key secondary end point (28% vs. 8% for weeks 1 through 24, and 33% vs. 12% for weeks 1 through 48; P<0.001 for both comparisons). The most common luspatercept-associated adverse events (of any grade) included fatigue, diarrhea, asthenia, nausea, and dizziness. The incidence of adverse events decreased over time. CONCLUSIONS: Luspatercept reduced the severity of anemia in patients with lower-risk myelodysplastic syndromes with ring sideroblasts who had been receiving regular red-cell transfusions and who had disease that was refractory to or unlikely to respond to erythropoiesis-stimulating agents or who had discontinued such agents owing to an adverse event. (Funded by Celgene and Acceleron Pharma; MEDALIST ClinicalTrials.gov number, NCT02631070; EudraCT number, 2015-003454-41.).

Identification of subfunctionalized aggregate-remodeling J-domain proteins in Arabidopsis thaliana.

J-domain proteins (JDPs) are critical components of the cellular protein quality control machinery, playing crucial roles in preventing the formation and, solubilization of cytotoxic protein aggregates. Bacteria, yeast, and plants additionally have large, multimeric heat shock protein 100 (Hsp100)-class disaggregases that resolubilize protein aggregates. JDPs interact with aggregated proteins and specify the aggregate-remodeling activities of Hsp70s and Hsp100s. However, the aggregate-remodeling properties of plant JDPs are not well understood. Here we identify eight orthologs of Sis1 (an evolutionarily conserved Class II JDP of budding yeast) in Arabidopsis thaliana with distinct aggregate-remodeling functionalities. Six of these JDPs associate with heat-induced protein aggregates in vivo and co-localize with Hsp101 at heat-induced protein aggregate centers. Consistent with a role in solubilizing cytotoxic protein aggregates, an atDjB3 mutant had defects in both solubilizing heat-induced aggregates and acquired thermotolerance as compared with wild-type seedlings. Next, we used yeast prions as protein aggregate models to show that the six JDPs have distinct aggregate-remodeling properties. Results presented in this study, as well as findings from phylogenetic analysis, demonstrate that plants harbor multiple, evolutionarily conserved JDPs with capacity to process a variety of protein aggregate conformers induced by heat and other stressors.

Impact of race and ethnicity on early mortality in multiple myeloma: a SEER analysis.

Over the past two decades, there have been significant advances in the treatment of multiple myeloma which has led to an improvement in overall survival (OS) (1,2). However, a notable proportion of patients continue to experience early mortality (EM), defined as two years from the time of diagnosis. This raises the possibility that improvements in myeloma survival have not extended equally to all groups. Using the latest data drawn from the Surveillance Epidemiology and End Results (SEER) database of patients in the United States spanning 2000-2019, we study impact of important sociodemographic factors on EM. Through regression modeling, we demonstrate that patients diagnosed from 2000-2005, of older age, male sex, and of certain racial minority status (non-Hispanic Black and Hispanic) have higher odds of EM. Of these factors, minority status contributed to worse 2-year overall survival as well. We evaluate whether income, as a surrogate to access to care, could potentially explain this finding, but find that race has a distinct relationship with EM that is not modified by income. This is further reinforced by subgroup analysis. After characterizing groups vulnerable to EM, we examine reasons for these disparities and potential avenues to address them.

A Co-Management Model for Myeloid Malignancies That Evolved during the COVID-19 Pandemic.

INTRODUCTION: Myeloid malignancies are a heterogeneous group of clonal bone marrow disorders that are complex to manage in the community and therefore often referred to subspecialists at tertiary oncology referral centers. Many patients do not live in close proximity to tertiary referral centers and are unable to commute long distances due to age, comorbidities, and frailty. Interventions that minimize the travel time burden without compromising quality of care are an area of unmet need. We describe a cancer care delivery model for patients with myeloid malignancies that is built around telehealth and enables this vulnerable population access to care at an NCI-designated cancer center while receiving majority of their care close to home. METHODS AND MATERIALS: We report on a cohort of patients with myeloid malignancies who were co-managed by a general community oncologist and an academic leukemia subspecialist at Montefiore Einstein Cancer Center in New York. Patients were initially referred to our institute for a second opinion by community practices that are in partnership with Montefiore Health System, and initial visits were in-person or via telehealth. Treatment plans were made after discussion with patient's local community oncologist. Patients then continued to receive majority of their treatment and supportive care including transfusion support with their local oncologist, and follow-up visits were mainly via telehealth with the academic leukemia subspecialist. RESULTS: Our cohort of 12 patients had a median age of 81 years (range, 59-88 years). Patients remained on active treatment for a median time of 357 days (range, 154-557 days). Most of our patients had a performance status of ECOG 2 or higher. Three patients had myelodysplastic syndromes, 7 patients had acute myeloid leukemia, and 2 patients had myelofibrosis. The median number of hospitalizations over the total treatment time period was one. CONCLUSION: We demonstrate a shared academic and community care co-management model for the treatment of myeloid malignancies in elderly, frail patients using telehealth as a backbone with a very low hospitalization rate.

Histone Variant H2A.Z.2 Mediates Proliferation and Drug Sensitivity of Malignant Melanoma.

Histone variants are emerging as key regulatory molecules in cancer. We report a unique role for the H2A.Z isoform H2A.Z.2 as a driver of malignant melanoma. H2A.Z.2 is highly expressed in metastatic melanoma, correlates with decreased patient survival, and is required for cellular proliferation. Our integrated genomic analyses reveal that H2A.Z.2 controls the transcriptional output of E2F target genes in melanoma cells. These genes are highly expressed and display a distinct signature of H2A.Z occupancy. We identify BRD2 as an H2A.Z-interacting protein, levels of which are also elevated in melanoma. We further demonstrate that H2A.Z.2-regulated genes are bound by BRD2 and E2F1 in an H2A.Z.2-dependent manner. Importantly, H2A.Z.2 deficiency sensitizes melanoma cells to chemotherapy and targeted therapies. Collectively, our findings implicate H2A.Z.2 as a mediator of cell proliferation and drug sensitivity in malignant melanoma, holding translational potential for novel therapeutic strategies.

Development and Validation of a Photonumeric Scale for Evaluation of Lip Fullness.

BACKGROUND: The shape, proportion, and fullness of one's lips are associated with overall facial beauty and attractiveness. Lip augmentation, due to personal preference or to reverse natural aging, has become a standard clinical procedure to improve lip volume or proportion. Several options are available to redefine the lips. To objectively evaluate treatment-related improvements in clinical practice and research, a validated photonumeric scale is needed. OBJECTIVE: To present scale-development methods for the Merz Lip Fullness Assessment Scale (MLFAS) and establish its reliability. METHODS: A 5-point photonumeric scale was developed to objectively assess loss of lip volume using male and female subjects of various ages and skin types. To establish intra- and interrater reliability, 8 board-certified dermatologists and plastic surgeons evaluated 64 subjects live in 2 sessions, 2 weeks apart. RESULTS: The weighted kappa for intra- and interrater agreement were ≥ 0.6 in all cases. Intrarater agreement between the 2 rating sessions was nearly perfect (median weighted kappa = 0.911 and 0.930 for the upper lip and lower lip, respectively). Substantial interrater agreement between each rater pair was also demonstrated for both rating sessions, and ratings of upper and lower lip fullness showed comparable reliability. CONCLUSION: The MLFAS is a validated and reliable photonumeric scale for rating loss in lip volume. The scale maintains its reliability with reproducible results across a diverse group of males and females of various ages and Fitzpatrick skin types. J Drugs Dermatol. 2023;22(3): doi:10.36849/JDD.7309.

Development and Validation of a Photonumeric Scale for Evaluation of Infraorbital Hollowing.

BACKGROUND: The infraorbital hollow is characterized by a sunken hollowing appearance of the junction between the lower eyelid and the cheek. Dermal fillers provide a suitable option to reduce the appearance of infraorbital hollowing. To objectively evaluate treatmentrelated improvements in clinical practice and research, a validated photonumeric scale is needed. OBJECTIVE: To present the scale development methods for the Merz Infraorbital Hollow Assessment Scale and establish its reliability and clinical relevance. METHODS: A 5-point photonumeric scale was developed to objectively assess the infraorbital hollowing among subjects of varying sex, age, and skin type. Intra- and inter-rater reliability was evaluated using live assessments conducted 2 weeks apart. The clinical relevance of a 1-point difference in scale-severity grade was evaluated through side by-side comparisons of photographs with either same grade or a one-grade difference. RESULTS: The scale demonstrated excellent reliability when used by trained physicians and other healthcare practitioners. Intra-rater agreement between the 2 live-subject rating sessions was nearly perfect. Substantial inter-rater agreement between the raters from both live sessions was also demonstrated. The mean absolute difference (95% confidence interval) in scale ratings was 1.08 (1.02, 1.14) for "clinically different" pairs and was 0.34 (0.27, 0.41) for "clinically same" pairs, suggesting a 1-point difference is clinically relevant. CONCLUSION: The Merz Infraorbital Hollow Assessment Scale is a validated, reliable, and clinically relevant photonumeric scale for rating infraorbital hollowing. The scale maintains its validity and reliability with reproducible results across a diverse group of males and females of various ages and Fitzpatrick Skin Types. J Drugs Dermatol. 2023;22(1):74-81.doi:10.36849/JDD.7191.

Development and Validation of a Photonumeric Scale for Evaluation of Jawline Contour.

BACKGROUND: A naturally aged face is often characterized by a noticeable lack of jawline contour and decreased volume in the lower region. Several options are available to redefine the jawline. To objectively evaluate treatment-related improvements in clinical practice and research, a validated photonumeric scale is needed. OBJECTIVE: To present scale-development methods for the Merz Jawline Assessment Scale and establish its reliability. METHODS: A 5-point photonumeric scale was developed to objectively assess jawline volume loss and contour disruption using male and female subjects of various ages and skin types. Seven board-certified dermatologists and plastic surgeons evaluated 90 subjects live in 2 sessions, 3 weeks apart to establish intra- and interrater reliability. RESULTS: The weighted kappa for intra- and interrater agreement were ≥ 0.7 in all cases. Intrarater agreement between the 2 rating sessions was nearly perfect (median weighted kappa = 0.908). Substantial interrater agreement between each rater pair was also demonstrated for both rating sessions. CONCLUSION: The Merz Jawline Assessment Scale is a validated and reliable photonumeric scale for rating loss of jawline volume and contour. The scale maintains its validity and reliability with reproducible results across a diverse group of males and females of various ages and Fitzpatrick skin types. J Drugs Dermatol. 2023;22(2):203-209. doi:10.36849/JDD.7193.

High-dose ascorbic acid synergizes with anti-PD1 in a lymphoma mouse model.

Major efforts are underway to identify agents that can potentiate effects of immune checkpoint inhibition. Here, we show that ascorbic acid (AA) treatment caused genomewide demethylation and enhanced expression of endogenous retroviral elements in lymphoma cells. AA also increased 5-hydroxymethylcytosine (5hmC) levels of CD8+ T cells and enhanced their cytotoxic activity in a lymphoma coculture system. High-dose AA treatment synergized with anti-PD1 therapy in a syngeneic lymphoma mouse model, resulting in marked inhibition of tumor growth compared with either agent alone. Analysis of the intratumoral epigenome revealed increased 5hmC with AA treatment, consistent with in vitro findings. Analysis of the tumor immune microenvironment revealed that AA strikingly increased intratumoral infiltration of CD8+ T cells and macrophages, suggesting enhanced tumor immune recognition. The combination treatment markedly enhanced intratumoral infiltration of macrophages and CD8+ T lymphocytes, granzyme B production by cytotoxic cells (cytotoxic T cells and natural killer cells), and interleukin 12 production by antigen-presenting cells compared with single-agent anti-PD1. These data indicate that AA potentiates anti-PD1 checkpoint inhibition through synergistic mechanisms. The study provides compelling rationale for testing combinations of high-dose AA and anti-PD1 agents in patients with aggressive B cell lymphoma as well as in preclinical models of other malignancies.

HDAC11 deficiency disrupts oncogene-induced hematopoiesis in myeloproliferative neoplasms.

Protein acetylation is an important contributor to cancer initiation. Histone deacetylase 6 (HDAC6) controls JAK2 translation and protein stability and has been implicated in JAK2-driven diseases best exemplified by myeloproliferative neoplasms (MPNs). By using novel classes of highly selective HDAC inhibitors and genetically deficient mouse models, we discovered that HDAC11 rather than HDAC6 is necessary for the proliferation and survival of oncogenic JAK2-driven MPN cells and patient samples. Notably, HDAC11 is variably expressed in primitive stem cells and is expressed largely upon lineage commitment. Although Hdac11is dispensable for normal homeostatic hematopoietic stem and progenitor cell differentiation based on chimeric bone marrow reconstitution, Hdac11 deficiency significantly reduced the abnormal megakaryocyte population, improved splenic architecture, reduced fibrosis, and increased survival in the MPLW515L-MPN mouse model during primary and secondary transplantation. Therefore, inhibitors of HDAC11 are an attractive therapy for treating patients with MPN. Although JAK2 inhibitor therapy provides substantial clinical benefit in MPN patients, the identification of alternative therapeutic targets is needed to reverse MPN pathogenesis and control malignant hematopoiesis. This study establishes HDAC11 as a unique type of target molecule that has therapeutic potential in MPN.