Inhibiting glutaminase in acute myeloid leukemia: metabolic dependency of selected AML subtypes

Metabolic reprogramming has been described as a hallmark of transformed cancer cells. In this study, we examined the role of the glutamine (Gln) utilization pathway in acute myeloid leukemia (AML) cell lines and primary AML samples. Our results indicate that a subset of AML cell lines is sensitive to Gln deprivation. Glutaminase (GLS) is a mitochondrial enzyme that catalyzes the conversion of Gln to glutamate. One of the two GLS isoenzymes, GLS1 is highly expressed in cancer and encodes two different isoforms: kidney (KGA) and glutaminase C (GAC). We analyzed mRNA expression of GLS1 splicing variants, GAC and KGA, in several large AML datasets and identified increased levels of expression in AML patients with complex cytogenetics and within specific molecular subsets. Inhibition of glutaminase by allosteric GLS inhibitor bis-2-(5-phenylacetamido-1, 2, 4-thiadiazol-2-yl) ethyl sulfide or by novel, potent, orally bioavailable GLS inhibitor CB-839 reduced intracellular glutamate levels and inhibited growth of AML cells. In cell lines and patient samples harboring IDH1/IDH2 (Isocitrate dehydrogenase 1 and 2) mutations, CB-839 reduced production of oncometabolite 2-hydroxyglutarate, inducing differentiation. These findings indicate potential utility of glutaminase inhibitors in AML therapy, which can inhibit cell growth, induce apoptosis and/or differentiation in specific leukemia subtypes.

Pastoralism in the drylands of Latin America: Argentina, Chile, Mexico and Peru

This article discusses various aspects of pastoralism in the Latin American countries with the largest dryland areas. The topics covered include: social, economic and institutional issues; grasslands and their carrying capacity; production systems and productivity rates; competition for forage resources between domestic livestock and wildlife; and the health status of livestock and wildlife. Most grasslands exhibit some degree of degradation. The percentage of offspring reaching weaning age is low: 47-66% of calves and 40-80% of lambs. Some pastoralists adopt patterns of transhumance. In the main, pastoralists experience a high poverty rate and have poor access to social services. For many pastoralists, wildlife is a source of food and by-products. Argentina, Chile, Mexico and Peru have animal health control agencies, are members of the World Organisation for Animal Health (OIE) and have signed the United Nations Convention to Combat Desertification. Pastoral systems subsist mainly on income unrelated to pastoral farming. The OIE recognises all four countries as free from infection with peste des petits ruminants virus, and from rinderpest and African horse sickness. It is difficult to predict the future of pastoralism in Latin America because the situation differs from country to country. For instance, pastoralism is more important in Peru than in Argentina, where it is a more marginal activity. In the future, lack of promotion and protection policies could lead to a decline in pastoralism or to an adverse environmental impact on drylands.

Genetic characterization of two gain-of-function alleles of the effector caspase DrICE in Drosophila

Caspases are the executioners of apoptosis. Although much is known about their physiological roles and structures, detailed analyses of missense mutations of caspases are lacking. As mutations within caspases are identified in various human diseases, the study of caspase mutants will help to elucidate how caspases interact with other components of the apoptosis pathway and how they may contribute to disease. DrICE is the major effector caspase in Drosophila required for developmental and stress-induced cell death. Here, we report the isolation and characterization of six de novo drICE mutants, all of which carry point mutations affecting amino acids conserved among caspases in various species. These six mutants behave as recessive loss-of-function mutants in a homozygous condition. Surprisingly, however, two of the newly isolated drICE alleles are gain-of-function mutants in a heterozygous condition, although they are loss-of-function mutants homozygously. Interestingly, they only behave as gain-of-function mutants in the presence of an apoptotic signal. These two alleles carry missense mutations affecting conserved amino acids in close proximity to the catalytic cysteine residue. This is the first time that viable gain-of-function alleles of caspases are described in any intact organism and provides a significant exception to the expectation that mutations of conserved amino acids always abolish the pro-apoptotic activity of caspases. We discuss models about how these mutations cause the gain-of-function character of these alleles.

Functions of TAp63 and p53 in restraining the development of metastatic cancer

Many tumours harbour mutations in the p53 tumour-suppressor gene that result in the expression of a mutant p53 protein. This mutant p53 protein has, in most cases, lost wild-type transcriptional activity and can also acquire novel functions in promoting invasion and metastasis. One of the mechanisms underlying these novel functions involves the ability of the mutant p53 to interfere with other transcription factors, including the p53 family protein TAp63. To investigate whether simultaneous depletion of both p53 and TAp63 can recapitulate the effect of mutant p53 expression in vivo, we used a mouse model of pancreatic cancer in which the expression of mutant p53 resulted in the rapid appearance of primary tumours and metastases. As shown previously, loss of one allele of wild-type (WT) p53 accelerated tumour development. A change of one WT p53 allele into mutant p53 did not further accelerate tumour development, but did promote the formation of metastasis. By contrast, loss of TAp63 did not significantly accelerate tumour development or metastasis. However, simultaneous depletion of p53 and TAp63 led to both rapid tumour development and metastatic potential, although the incidence of metastases remained lower than that seen in mutant p53-expressing tumours. TAp63/p53-null cells derived from these mice also showed an enhanced ability to scatter and invade in tissue culture as was observed in mutant p53 cells. These data suggest that depletion of TAp63 in a p53-null tumour can promote metastasis and recapitulate-to some extent-the consequences of mutant p53 expression.

Abstract 2331: Deletion of ΔNp63 and ΔNp73 in p53 deficient mice results in TAp63 and TAp73 compensation of p53 tumor suppression in vivo

p53 tumor suppressor undergoes mutational loss in majority of cancers contributing to tumor formation. Therapeutic strategies are aimed towards p53 overexpression in tumors or to identify targets that compensate for p53-functional loss. p63 & p73, share structural similarities to p53, making them excellent candidates for therapeutic compensation of p53. Unlike p53, p63 and p73 do not undergo mutational loss and their role in tumorigenesis is being delineated. p63 and p73 have two major isoforms, the transactivation (TA), with activities similar to p53 and the delta (Δ)N- isoform with oncogenic functions. Inhibition of TAp63 and TAp73 is observed in cancers as a consequence of overexpression of ΔN isoforms of p63 and p73. In disparity, recent studies report, tumor suppressive properties of ΔNp63 and ΔNp73 in activating genes involved in DNA repair and apoptosis.

To define the functional roles of ΔNp63 and ΔNp73 in cancer, mouse models targeting the ΔN isoforms were generated. We observed that, ΔNp63+/- and ΔNp73−/− mice on a p53−/− background had lower thymic lymphoma incidence compared to the p53−/− mice. I found TAp63 and TAp73 up regulated in the double mutant mice that correspond with an increase in p53-downstream apoptotic (PUMA, Noxa, BAX) and cell cycle targets (p21, p16, PML). This suggests that ablation of ΔN isoforms mediate TAp63 and TAp73 up regulation inducing apoptosis or cell cycle arrest by activation of p53-downstream targets. To further demonstrate this, I ablated ΔNp63 and ΔNp73 in vivo in p53−/- mice thymic lymphoma by administering adenoviral-CRE specifically to the thymus. The CRE-treated mice had a significant thymic lymphoma regression within 3 weeks as imaged by MRI in comparison to the mock-treated mouse cohorts. Additionally, RNA-Seq analysis from CRE-treated versus untreated mice, has identified novel metabolic genes with apoptotic or cell-cycle functions. We further report, ΔNp63 and ΔNp73 to bind to promoter site of TAp63 and TAp73 by chromatin immunoprecipitation (ChIP). This supports the notion that ablation of ΔN isoforms of p63 and p73 restores the function of TAp63 and TAp73 thus compensating for p53-tumor suppressive function in vivo. To test, if ablation of ΔN isoforms reduces tumorigenesis in human cancers, ΔNp63 and ΔNp73 were knocked down in human cancer cell lines were p53 expression was ablated or mutated. TAp63 and TAp73 were upregulated in ΔNp63/ΔNp73 knock down human cancer cell lines. However, induction of apoptosis or cell-cycle arrest was observed in p53-deleted cancer cell lines in comparison to the p53-mutated cell lines. This highlights the co-repressive effect of mutant p53, preventing activation of TAp63/TAp73 downstream targets. Current work is aimed towards overcoming mutant p53 effect in these cancer cell lines. Thus, targeting the ΔNp63/ΔNp73 compensates for p53-functional loss mediating tumor suppression.

Citation Format: Avinashnarayan Venkatanarayan, Deepavali Chakravarti, Xiaohua Su, Santosh Sandur, Lingzhi Liu, Eliot Fletcher Sananikone, Payal Raulji, Cristian Coarfa, William Norton, Preethi Gunaratne, Elsa Renee Flores. Deletion of ΔNp63 and ΔNp73 in p53 deficient mice results in TAp63 and TAp73 compensation of p53 tumor suppression in vivo. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2331. doi:10.1158/1538-7445.AM2013-2331

Abstract P5-10-03: OncomiR-569 deregulate p53 pathway and initiate breast oncogenesis

Background: The 3q26.2 chromosomal loci is highly amplified in large set of breast cancers, primarily in aggressive basal tumors are difficult to treat in the clinic. Our amplicon data suggests that 3q26.2 is a large structurally complex amplicon and multiple components in the amplicon contribute to tumor initiation and progression either alone or through cooperative activity. Detailed mapping of the 3q26.2 amplicon by us demonstrated a microRNA, miR569 is highly amplified as a part of 3q26.2 amplicon in breast cancer patient's samples. The role of microRNAs amplified at 3q26 loci is not well studied and their molecular functions and targets were not well known. Thus our studies provide novel mechanism underlying miR569 oncogenesis.

Methods: Following the Institutional Review Board approval, tissues obtained from MD Anderson Cancer Center tumor bank were used to exatract DNA and RNA. Human miR-569 was cloned into pEZX-MR06 lentiviral vector used for the production of amphotropic viruses to infect the target cells. The miRIDIAN microRNA mimics were used to overexpress miRs and the antimiRs were used to knock down the miRNAs. All the transfections were performed using Oligofectamine. Trypsinized cells were grown in 5% matrigel for the 3D morphogenesis of epithelial cells.

Results: Our results demonstrated a strong correlation between 3q26.2 amplification and expression of miR569 in patient samples of breast cancer. We subsequently demonstrated that overexpression and knockdown of miR569 in the breast epithelial cells altered their growth, proliferation, and lumen filling in 3-dimensional cultures grown in Matrigel. Importantly ectopic expression of miR569 in breast epithelial cells promoted tumor growth and increased metastatic potential in mouse xenograft models. Seed match based analysis of the microRNA targets, in silico studies and in vitro experiments showed that miR-569 directly target Tumor protein 53-induced nuclear protein1 (TP53INP1) and inhibited the expression of a tumor suppressor gene TP53INP1 expression. Loss of TP53INP1 expression mediated by miR569 altered normal cell growth cycle and subsequently promoted the survival and growth of tumor cells. Our in vitro results showed that knockdown of miR-569 and subsequent increase in TP53INP1 expression enhanced the sensitivity of cancer cell lines to cisplatin. Our immunohistochemical analysis showed that TP53INP1 protein levels were higher in normal tissues compared to cancer tissues. Further, reduced expression of TP53INP1 was observed in invasive cancers as compared to low malignant potential tumors, and decreased TP53INP1 protein levels were associated with worsened outcomes in breast cancer patients.

Disscussion: TP53INP1 had previously been identified as a combined target of p53 and p73; however our studies indicate that miR-569 regulates TP53INP1 levels independently of p53 and p73 expression. Based on our preclinical results of antimiR-569 on cell survival, tumor growth and cisplatin sensitivity, inhibiting miR-569 activity or increasing TP53INP1 expression may be valid therapeutic approaches to treat breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-10-03.

Centrosome abnormalities and genomic instability by episomal expression of human papillomavirus type 16 in raft cultures of human keratinocytes

Primary human keratinocytes with ectopic expression of high-risk human papillomavirus (HPV) E6 and E7 oncoproteins display abnormal centrosome numbers, multipolar mitoses, and aneusomy. However, it has not been explored whether these abnormalities can occur in cells containing HPV episomes where E6 and E7 expression is under viral transcriptional control. Here, we demonstrate that centrosome abnormalities and genomic instability occur in organotypic raft cultures of human keratinocytes with episomal HPV-16 even at low copy numbers. We conclude that HPV-16 DNA, when maintained as an episome, can disturb centrosome homeostasis and subvert genomic integrity of the host cell during early stages of the viral infection.

Role for the p53 homologue p73 in E2F-1-induced apoptosis

The transcription factor E2F-1 induces both cell-cycle progression and, in certain settings, apoptosis. E2F-1 uses both p53-dependent and p53-independent pathways to kill cells. The p53-dependent pathway involves the induction by E2F-1 of the human tumour-suppressor protein p14ARF, which neutralizes HDM2 (human homologue of MDM2) and thereby stabilizes the p53 protein. Here we show that E2F-1 induces the transcription of the p53 homologue p73. Disruption of p73 function inhibited E2F-1-induced apoptosis in p53-defective tumour cells and in p53-/- mouse embryo fibroblasts. We conclude that activation of p73 provides a means for E2F-1 to induce death in the absence of p53.

The human papillomavirus type 16 E7 oncogene is required for the productive stage of the viral life cycle

The production of the human papillomavirus type 16 (HPV-16) is intimately tied to the differentiation of the host epithelium that it infects. Infection occurs in the basal layer of the epithelium at a site of wounding, where the virus utilizes the host DNA replication machinery to establish itself as a low-copy-number episome. The productive stage of the HPV-16 life cycle occurs in the postmitotic suprabasal layers of the epithelium, where the virus amplifies its DNA to high copy number, synthesizes the capsid proteins (L1 and L2), encapsidates the HPV-16 genome, and releases virion particles as the upper layer of the epithelium is shed. Papillomaviruses are hypothesized to possess a mechanism to overcome the block in DNA synthesis that occurs in the differentiated epithelial cells, and the HPV-16 E7 oncoprotein has been suggested to play a role in this process. To determine whether E7 plays a role in the HPV-16 life cycle, an E7-deficient HPV-16 genome was created by inserting a translational termination linker (TTL) in the E7 gene of the full HPV-16 genome. This DNA was transfected into an immortalized human foreskin keratinocyte cell line shown previously to support the HPV-16 life cycle, and stable cell lines were obtained that harbored the E7-deficient HPV-16 genome episomally, the state of the genome found in normal infections. By culturing these cells under conditions which promote the differentiation of epithelial cells, we found E7 to be necessary for the productive stage of the HPV-16 life cycle. HPV-16 lacking E7 failed to amplify its DNA and expressed reduced amounts of the capsid protein L1, which is required for virus production. E7 appears to create a favorable environment for HPV-16 DNA synthesis by perturbing the keratinocyte differentiation program and inducing the host DNA replication machinery. These data demonstrate that E7 plays an essential role in the papillomavirus life cycle.

Establishment of the human papillomavirus type 16 (HPV-16) life cycle in an immortalized human foreskin keratinocyte cell line

The study of human papillomaviruses (HPVs) in cell culture has been hindered because of the difficulty in recreating the three-dimensional structure of the epithelium on which the virus depends to complete its life cycle. Additionally, the study of genetic mutations in the HPV genome and its effects on the viral life cycle are difficult using the current method of transfecting molecularly cloned HPV genomes into early-passage human foreskin keratinocytes (HFKs) because of the limited life span of these cells. Unless the HPV genome transfected into the early-passage HFK extends the life span of the cell, analysis of stable transfectants becomes difficult. In this study, we have used BC-1-Ep/SL cells, an immortalized human foreskin keratinocyte cell line, to recreate the HPV-16 life cycle. This cell line exhibits many characteristics of the early-passage HFKs including the ability to stratify and terminally differentiate in an organotypic raft culture system. Because of their similarity to early-passage HFKs, these cells were tested for their ability to support the HPV-16 life cycle. The BC-1-Ep/SL cells could stably maintain two HPV genotypes, HPV-16 and HPV-31b, episomally. Additionally, when the BC-1-Ep/SL cell line was stably transfected with HPV-16 and cultured using the organotypic raft culture system (rafts), it sustained the HPV-16 life cycle. Evidence for the productive stage of the HPV-16 life cycle was provided by: DNA in situ hybridization demonstrating HPV-16 DNA amplification in the suprabasal layers of the rafts, immunohistochemical staining for L1 showing the presence of capsid protein in the suprabasal layers of the rafts, and electron microscopy indicating the presence of virus like particles (VLPs) in nuclei from cells in the differentiated layers of the rafts.

Evidence for a switch in the mode of human papillomavirus type 16 DNA replication during the viral life cycle

The study of human papillomavirus type 16 (HPV-16) replication has been impaired because of the lack of a cell culture system that stably maintains viral replication. Recently, cervical epithelial cell populations that stably maintain HPV-16 replicons at a copy number of approximately 1,000 per cell were derived from an HPV-16-infected patient (W12 cell clone 20863 [W12-E cells]). We used neutral/neutral and neutral/alkaline two-dimensional gel electrophoretic techniques to characterize HPV-16 DNA replication in these cells. When W12-E cells were maintained in an undifferentiated state mimicking the nonproductive stage of the life cycle, HPV-16 DNA was found to replicate primarily by theta structures in a bidirectional manner. The initiation site of HPV-16 DNA replication was mapped to approximately nucleotide 100, and the termination site was mapped to between nucleotides 3398 and 5990. To study the productive stage of HPV-16 DNA replication, W12-E cells were grown under culture conditions that promote differentiation of epithelial cell types. Under these conditions, where virus-like particles were detected, the mode of viral DNA replication changed from theta structure to what is apparently a rolling circle mode. Additionally, CIN 612-9E cells, which were derived from an HPV-31-infected patient and harbor HPV-31 extrachromosomally, exhibited the same switch in the mode of DNA replication upon induction of differentiation. These data argue that a fundamental switch in the mechanism of viral DNA replication occurs during the life cycle of the papillomavirus.

Effects of different heat treatments during processing of soybean meal on nursery and growing pig performance

Four soybean meals (SBM) were manufactured in a commercial solvent-extraction plant to give a much wider range in heat treatment than is usually found among commercially available SBM. The SBM were designated in ascending order of heat treatment as Under, Normal, Over and Rumen Escape. The nutritive value of the four meals was evaluated in a series of five feeding trials using 458 pigs: two performance and two diet preference trials with pigs weaned at 4 wk of age and one performance trial with growing pigs (17.4 kg initial weight were conducted). In both nursery and grower trials, there were no differences (P greater than .10) in performance of pigs fed the four meals. However, in the nursery trials, the severely heated meal (Rumen Escape) supported slightly lower gains (6.4%) and less desirable feed efficiency (3.5%) than the average of the other three meals. Growing pig performance was essentially the same for all meals. This suggests that older pigs either used the Rumen Escape meal more effectively than nursery pigs, or the Rumen Escape diet contained adequate digestible lysine for 17.4-kg pigs to grow optimally. In the preference studies, pigs selected between Normal- and Rumen Escape-supplemented diets. Pigs consumed 63 and 62% of the Normal diet in preference trials 1 and 2, but these differences were not significant (P greater than .10) due to the large variation among pens. These data suggest that the range of heat treatment normally found among commercially available SBM (Under, Normal and Over meals) has no effect on the nutritive value of the meal for swine.(ABSTRACT TRUNCATED AT 250 WORDS)