PPM1D modulates hematopoietic cell fitness and response to DNA damage and is a therapeutic target in myeloid malignancy

PPM1D encodes a phosphatase that is recurrently activated across cancer, most notably in therapy-related myeloid neoplasms. However, the function of PPM1D in hematopoiesis and its contribution to tumor cell growth remain incompletely understood. Using conditional mouse models, we uncover a central role for Ppm1d in hematopoiesis and validate its potential as a therapeutic target. We find that Ppm1d regulates the competitive fitness and self-renewal of hematopoietic stem cells (HSCs) with and without exogenous genotoxic stresses. We also show that although Ppm1d activation confers cellular resistance to cytotoxic therapy, it does so to a lesser degree than p53 loss, informing the clonal competition phenotypes often observed in human studies. Notably, loss of Ppm1d sensitizes leukemias to cytotoxic therapies in vitro and in vivo, even in the absence of a Ppm1d mutation. Vulnerability to PPM1D inhibition is observed across many cancer types and dependent on p53 activity. Importantly, organism-wide loss of Ppm1d in adult mice is well tolerated, supporting the tolerability of pharmacologically targeting PPM1D. Our data link PPM1D gain-of-function mutations to the clonal expansion of HSCs, inform human genetic observations, and support the therapeutic targeting of PPM1D in cancer.

Malic enzyme 2 connects the Krebs cycle intermediate fumarate to mitochondrial biogenesis

Mitochondria have an independent genome (mtDNA) and protein synthesis machinery that coordinately activate for mitochondrial generation. Here, we report that the Krebs cycle intermediate fumarate links metabolism to mitobiogenesis through binding to malic enzyme 2 (ME2). Mechanistically, fumarate binds ME2 with two complementary consequences. First, promoting the formation of ME2 dimers, which activate deoxyuridine 5'-triphosphate nucleotidohydrolase (DUT). DUT fosters thymidine generation and an increase of mtDNA. Second, fumarate-induced ME2 dimers abrogate ME2 monomer binding to mitochondrial ribosome protein L45, freeing it for mitoribosome assembly and mtDNA-encoded protein production. Methylation of the ME2-fumarate binding site by protein arginine methyltransferase-1 inhibits fumarate signaling to constrain mitobiogenesis. Notably, acute myeloid leukemia is highly dependent on mitochondrial function and is sensitive to targeting of the fumarate-ME2 axis. Therefore, mitobiogenesis can be manipulated in normal and malignant cells through ME2, an unanticipated governor of mitochondrial biomass production that senses nutrient availability through fumarate.

Abstract PO085: Cryogel-based cancer vaccine to treat acute myeloid leukemia

Acute myeloid leukemia (AML) is a hematopoietic malignancy with limited therapeutic options. Standard-of-care chemotherapy depletes AML cells to induce remission, but often precedes disease relapse. To promote robust and durable immunity against AML, we developed a macroporous cryogel-based vaccine which provided a sustained release of GM-CSF to concentrate dendritic cells (DCs), TLR agonist CpG-ODN, and leukemia antigen. Prophylactic vaccination in mice against AML cell lysates or peptide antigen induced a potent anti-tumor adaptive immune response and prevented the engraftment of AML cells. This immunity was transferable, as bone marrow transplanted from vaccinated mice immunized recipients against AML. In models of established disease, only the combination of chemotherapy and biomaterial vaccination entirely eradicated AML in all mice and generated long-term T cell immunity preventing relapse. Notably, in combination with chemotherapy, a cryogel vaccine delivering no antigen (only GM-CSF and CpG-ODN) generated robust AML-specific T cell immunity, depleted leukemia, and enabled long-term survival. In this setting, tumor antigens were likely sourced from chemotherapy-induced AML cell death, as AML cells expressing high levels of apoptotic markers were found in the vaccine site and draining lymph node, co-localizing with DCs activated by the vaccine. These results demonstrate the capacity of a biomaterial-based vaccine to induce a potent immune response depleting AML and preventing relapse, even without defined antigen targets.

Citation Format: Alexander J. Najibi, Nisarg J. Shah, Ting-Yu Shih, Angelo S Mao, Azeem Sharda, David T. Scadden, David J. Mooney. Cryogel-based cancer vaccine to treat acute myeloid leukemia [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO085.

Aldehyde dehydrogenase 3a2 protects AML cells from oxidative death and the synthetic lethality of ferroptosis inducers

Metabolic alterations in cancer represent convergent effects of oncogenic mutations. We hypothesized that a metabolism-restricted genetic screen, comparing normal primary mouse hematopoietic cells and their malignant counterparts in an ex vivo system mimicking the bone marrow microenvironment, would define distinctive vulnerabilities in acute myeloid leukemia (AML). Leukemic cells, but not their normal myeloid counterparts, depended on the aldehyde dehydrogenase 3a2 (Aldh3a2) enzyme that oxidizes long-chain aliphatic aldehydes to prevent cellular oxidative damage. Aldehydes are by-products of increased oxidative phosphorylation and nucleotide synthesis in cancer and are generated from lipid peroxides underlying the non-caspase-dependent form of cell death, ferroptosis. Leukemic cell dependence on Aldh3a2 was seen across multiple mouse and human myeloid leukemias. Aldh3a2 inhibition was synthetically lethal with glutathione peroxidase-4 (GPX4) inhibition; GPX4 inhibition is a known trigger of ferroptosis that by itself minimally affects AML cells. Inhibiting Aldh3a2 provides a therapeutic opportunity and a unique synthetic lethality to exploit the distinctive metabolic state of malignant cells.

Induction of a Timed Metabolic Collapse to Overcome Cancer Chemoresistance

Cancer relapse begins when malignant cells pass through the extreme metabolic bottleneck of stress from chemotherapy and the byproducts of the massive cell death in the surrounding region. In acute myeloid leukemia, complete remissions are common, but few are cured. We tracked leukemia cells in vivo, defined the moment of maximal response following chemotherapy, captured persisting cells, and conducted unbiased metabolomics, revealing a metabolite profile distinct from the pre-chemo growth or post-chemo relapse phase. Persisting cells used glutamine in a distinctive manner, preferentially fueling pyrimidine and glutathione generation, but not the mitochondrial tricarboxylic acid cycle. Notably, malignant cell pyrimidine synthesis also required aspartate provided by specific bone marrow stromal cells. Blunting glutamine metabolism or pyrimidine synthesis selected against residual leukemia-initiating cells and improved survival in leukemia mouse models and patient-derived xenografts. We propose that timed cell-intrinsic or niche-focused metabolic disruption can exploit a transient vulnerability and induce metabolic collapse in cancer cells to overcome chemoresistance.

An injectable bone marrow-like scaffold enhances T cell immunity after hematopoietic stem cell transplantation

The use of allogeneic hematopoietic stem cell transplantation (HSCT) to cure multiple disorders is limited by deficiency and dysregulation of T-cells. Here we report a biomaterial-based scaffold that mimics features of T-cell lymphopoiesis in the bone marrow. The bone marrow cryogel (BMC) releases bone morphogenetic protein-2 to recruit stromal cells, and presents the Notch ligand Delta-like ligand-4 to facilitate T-cell lineage specification of mouse and human hematopoietic progenitor cells. BMCs subcutaneously injected in mice at the time of HSCT enhanced T-cell progenitor seeding of the thymus, T-cell neogenesis and diversification of the T-cell receptor repertoire. Peripheral T-cell reconstitution increased ~6-fold in mouse HSCT and ~2-fold in human xenogeneic HSCT. Furthermore, BMCs promoted donor CD4⁺ regulatory T-cell generation and improved survival after allogeneic HSCT. Compared with adoptive transfer of T-cell progenitors, BMCs increased donor chimerism, T-cell generation and antigen-specific T-cell responses to vaccination. BMCs may provide an off-the-shelf approach for enhancing T-cell regeneration and mitigating graft-versus-host disease in HSCT.

A purinergic P2Y6 receptor agonist prodrug modulates airway inflammation, remodeling, and hyperreactivity in a mouse model of asthma

Background

Purinergic receptors control cell proliferation, apoptosis, migration, inflammation, and cytokine secretion. Increased expression of specific purinergic receptors is reported in asthma. The role of purinergic P2Y6 receptors (P2Y6R) in asthma is controversial.

Hypothesis

P2Y6R activation in asthma improves pulmonary function and reduces inflammation and smooth muscle amount.

Methods

Female mice (C57/BL6, age 30 days) were randomly assigned to receive intranasal house dust mite (HDM) antigen (40 or 80 µg) or saline, 5 days/week, for 6 weeks. Randomly selected subgroups received intraperitoneal P2Y6R agonist prodrug (GC021109; 10 or 100 µg/kg weight/dose) simultaneously with HDM. After 6 weeks, lung function was measured. Lung lavage fluid (LLF) was used to measure total cell count, total protein, and cytokines. Immunohistochemistry for alpha smooth muscle actin (α-SMA) was done. Airway wall thickness was measured on micro-computed tomography (micro-CT) images.

Results

Pulmonary function testing revealed a HDM dose-dependent airway hyperresponsiveness. Airway resistance was increased 2-fold while compliance was decreased by 50% at the higher HDM dose (P<0.05). GC021109 prevented these changes. HDM-exposed mice had elevated inflammatory cell and total protein levels in LLF which were prevented by GC021109 (P<0.05). HDM mice also had elevated LLF levels of interleukin (IL)-4, IL-5, IL-12, granulocyte colony stimulating factor, chemokine (C-X-C) motif ligand 1, and leukemia inhibitory factor that were reduced by GC021109 with a dose-dependent pattern. HDM mice had increased peribronchial and perivascular inflammatory cell infiltration and increased α-SMA; these changes were absent with GC021109. Airway wall thickness measured on micro-CT images was increased after HDM exposure and significantly reduced by GC021109 treatment.

Conclusion

The P2Y6R prodrug GC021109 inhibited allergen-induced changes in pulmonary function, inflammatory responses, and airway and vascular smooth muscle mass. P2Y6R activation may be an effective therapeutic maintenance strategy in asthma.

IgE mediates broncho-vascular remodeling after neonatal sensitization in mice

The temporal origins of childhood asthma are incompletely understood. We hypothesize that allergen sensitization which begins in early infancy causes IgE-mediated airway and vascular remodeling, and airway hyper-responsiveness. Mice were sensitized with ovalbumin (OVA) without or with anti-IgE antibody from postnatal day (P) 10 through P42. We studied airway resistance in response to Methacholine (MCh) challenge, bronchoalveolar lavage fluid (BAL) inflammatory cell content, immunohistochemistry for inflammation, alpha-smooth muscle actin (alpha-SMA) and platelet/endothelial cell adhesion molecule (PECAM) proteins, and Western blotting for vascular endothelial growth factor (VEGF) protein. Compared to controls, mice treated with OVA had increased airway resistance (baseline: 192% of control; MCH 12 mg/mL 170% of control; P less than 0.0.5). OVA treatment also increased lung alpha-SMA, VEGF and PECAM compared to controls. Inflammatory cells in the BAL and perivascular and peribronchiolar inflammatory cell infiltrates increased over controls with OVA exposure. These changes were counteracted by anti-IgE treatment. We conclude that mice sensitized in early infancy develop an IgE-mediated hyper-reactive airway disease with airway and vascular remodeling. Preventive approaches in early infancy of at-risk individuals may reduce childhood asthma.

Barriers to the utilization of dental services in udaipur, India

OBJECTIVE

Regular home care and yearly dental check-ups are the best means of dental care. In spite of the information on dental care, many people fail to take these precautions. The objective of this study was to determine the barriers in regular dental care and home care and to assess their association with age, sex, education and income.

MATERIALS AND METHODS

A cross-sectional survey was conducted among 427 randomly selected individuals, 248 males and 179 females. Data were collected by a pre-tested, self-administered 14 question questionnaire. The answer "very much" was scored as one, "to some degree" as two and "not at all" as three. The data was described and analyzed by frequency distribution and chi square test with P<0.05 level of significance. Logistic regression was used to investigate the association between dental visits with age, sex and education. Correlation between income and dental visits was determined by Spearman's correlation coefficient.

RESULTS

The male group had more dental visits (P>0.05), but females experienced higher dental fear (P<0.001). The younger age group had more visits within one year in comparison to the older. Increase in education, decreases the barriers for regular dental care. Income had a significantly negative correlation with dental visit (P=0.02).

CONCLUSION

Our findings suggest that males believed in having regular dental care. Cost of the treatment also affected the dental visits, but the distance they had to travel to get the dental treatment was not much significant. Above all, felt need had a major impact on the dental visits.

Awareness of Consumer Protection Act among Doctors in Udaipur City, India

OBJECTIVE

To compare the awareness of provisions of consumer protection act among dental and medical professionals in Udaipur city, Rajasthan, India.

MATERIALS AND METHODS

In a cross sectional study, a total of 448 professionals (253 males, 195 females) belonging to dental (222) and medical (226) categories were surveyed using a self administered structured questionnaire. The questionnaire comprised of 22 questions about the awareness of consumer protection art (CPA) and whether these professionals were following the recommendations of CPA. The student's t-test, ANOVA test, and Scheffe's test were used as tests of significance.

RESULTS

The awareness scores were significantly higher for medical professionals compared with those of dental professionals. Similarly, postgraduates showed more awareness in both the professions and it was found that private practitioners significantly have more awareness than the academic sector.

CONCLUSION

Though medical professionals have more awareness of CPA compared to dental professionals, considering the present scenario, better knowledge of CPA is necessary for both professionals in order to be on the safer side.

Unruptured sinus of valsalva aneurysm presenting as acute coronary syndrome

An unusual presentation of sinus of Valsalva aneurysm causing right ventricular outflow tract obstruction and presenting as acute coronary syndrome is reported. A 38-year-old lady presented with ischemic chest pain, probably due to embolization from an unruptured sinus of Valsalva aneurysm.

Pedicled omental transfer for ischaemic limbs--a 5-year experience

Chronic occlusive arterial diseases form a single largest entity amongst the peripheral vascular diseases. Current operative methods available for improving circulation often elicit poor results and the patient has to undergo an amputation. The technique of pedicled omental transfer has given hope of saving such unsalvageable limbs. Although symptomatic and clinical improvement has been reported by this method of "biological by-pass revascularisation", there are no simple, objective and easily reproducible tests to assess improvement in circulation. In this study pulse oximetry and stress testing have been used to assess revascularisation. This study comprised 56 patients (78 limbs) suffering from chronic occlusive arterial disease, spanning a period of 5 years. Patients were investigated and subjected to pedicled omental transplantation (omentopexy). Symptomatological assessment showed improvement in intermittent claudication in about 85% of patients, relief from rest pain in 86% and healing of chronic ulcers in 73% of patients. Objective tests of stress testing and pulse oximetry also showed improvement in circulation. Relief from ischaemia was more in cases of Buerger's disease (TAO) than in cases of atherosclerosis obliterans (ASO).