Abstract 4833: Inhibiting the mitochondrial RNA degradosome complex SUV3 and PNPase increases dsRNA in the cytoplasm, triggers a viral mimicry response and kills AML cells and progenitors

Eukaryotic cells have two separate genomes; nuclear chromosomal DNA and circular mitochondrial DNA. Mitochondrial DNA lacks introns, and encodes 2 rRNAs, 22 t-RNAs and 13 of the 90 proteins that constitute the mitochondrial respiratory chain. To maintain homeostasis, mitochondrial RNA degradation machinery regulates RNA turnover. ATP-dependent helicase, SUV3 (gene SUPV3L1), and exonuclease PNPase (gene PNPT1) function as a complex to degrade mitochondrial dsRNA. By immunoblotting, PNPase and SUV3 proteins were increased in 7/7 AML patient samples and 13/13 of AML cell lines, compared to the normal hematopoietic cells. Analysis of the TARGET AML dataset revealed AML patients with increased expression of SUPV3L1 (p = 0.051, p= 0.045) and PNPT1 (p = 0.0013, p = 0.018) had decreased overall and event free survival. Genetic knockdown or knockout using shRNA or sgRNA against PNPT1 or SUPV3L1 decreased growth and viability of OCI-AML2, TEX, K562, U937, NB4 and OCI-AML 8227 cells. Furthermore, SUPV3L1 & PNPT1 ranked in the top 5.2% and 7.4% of essential genes in 26 leukemia cell lines in CRISPR screens and 2.7% and 4.9% in RNAi screens (depmap.org). Knockdown of PNPT1 & SUPV3L1 also reduced the clonogenic growth of OCI-AML2, TEX and U937 cells and significantly reduced engraftment of TEX cells into the marrow of immune deficient mice, demonstrating the functional importance on leukemia initiating cells in vivo. SUPV3L1 knockdown in primary AML cells reduced engraftment in marrow of immune deficient mice. Bioinformatics analysis to detect processes associated with PNPT1 and SUPV3L1, we identified associations with Response to exogenous dsRNA, Response to virus, and RNA catabolic process ontologies. Consistent with this, we observed knockdown of PNPT1 or SUPV3L1 increased expression of genes (INFgR1, ICAM, IRF7 & JAK/STAT) suggesting an interferon response. As PNPT1 and SUPV3L1 degrade mitochondrial dsRNA, we measured levels of dsRNA after knockdown of these genes. Knockdown of PNPT1 and SUPV3L1 in OCI-AML2 cells increased levels of cytoplasmic/mitochondrial dsRNA 3-4 fold compared to control. Knockdown of PNPT1 and SUPV3L1 also increased dsRNA in 143B cells, but not Rho (0) 143B cells that lack mitochondrial DNA. Upregulation of inflammatory genes leads to viral mimicry and can increase sensitivity to immune mediated killing. We observed enhanced sensitivity to Double Negative T (DNT) cells mediated killing in PNPT1 and SUPV3L1 knockdown OCI-AML2 cells compared to control cells. In summary, RNA degradosome complex proteins SUPV3L1 and PNPT1 are overexpressed in AML, and are essential for the survival of AML cells and AML stem/progenitors. These enzymes regulate levels of mitochondrial dsRNA, and their inhibition leads to increased cytoplasmic dsRNA triggering a viral mimicry response and enhanced sensitivity to immune-mediated killing.

Citation Format: Geethu Emily Thomas, Kazem Nouri, Jong Bok Lee, Rose Hurren, Yongran Yan, Neil MacLean, Yulia Jitkova, Li Ma, Xiao Ming Wang, Chaitra Sarathy, Andrea Arruda, Mark D. Minden, Li Zhang, Vito Spadavecchio, Aaron Schimmer. Inhibiting the mitochondrial RNA degradosome complex SUV3 and PNPase increases dsRNA in the cytoplasm, triggers a viral mimicry response and kills AML cells and progenitors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4833.

The metabolic enzyme hexokinase 2 localizes to the nucleus in AML and normal haematopoietic stem and progenitor cells to maintain stemness

Mitochondrial metabolites regulate leukaemic and normal stem cells by affecting epigenetic marks. How mitochondrial enzymes localize to the nucleus to control stem cell function is less understood. We discovered that the mitochondrial metabolic enzyme hexokinase 2 (HK2) localizes to the nucleus in leukaemic and normal haematopoietic stem cells. Overexpression of nuclear HK2 increases leukaemic stem cell properties and decreases differentiation, whereas selective nuclear HK2 knockdown promotes differentiation and decreases stem cell function. Nuclear HK2 localization is phosphorylation-dependent, requires active import and export, and regulates differentiation independently of its enzymatic activity. HK2 interacts with nuclear proteins regulating chromatin openness, increasing chromatin accessibilities at leukaemic stem cell-positive signature and DNA-repair sites. Nuclear HK2 overexpression decreases double-strand breaks and confers chemoresistance, which may contribute to the mechanism by which leukaemic stem cells resist DNA-damaging agents. Thus, we describe a non-canonical mechanism by which mitochondrial enzymes influence stem cell function independently of their metabolic function.

Thomas, Egan et al. report that hexokinase 2 localizes to the nucleus of leukaemic and normal haematopoietic cells to maintain stemness by interacting with nuclear proteins and modulating chromatin accessibility independently of its kinase activity.

Venetoclax enhances T cell-mediated antileukemic activity by increasing ROS production

Venetoclax, a Bcl-2 inhibitor, in combination with the hypomethylating agent azacytidine, achieves complete remission with or without count recovery in ∼70% of treatment-naive elderly patients unfit for conventional intensive chemotherapy. However, the mechanism of action of this drug combination is not fully understood. We discovered that venetoclax directly activated T cells to increase their cytotoxicity against acute myeloid leukemia (AML) in vitro and in vivo. Venetoclax enhanced T-cell effector function by increasing reactive oxygen species generation through inhibition of respiratory chain supercomplexes formation. In addition, azacytidine induced a viral mimicry response in AML cells by activating the STING/cGAS pathway, thereby rendering the AML cells more susceptible to T cell-mediated cytotoxicity. Similar findings were seen in patients treated with venetoclax, as this treatment increased reactive oxygen species generation and activated T cells. Collectively, this study presents a new immune-mediated mechanism of action for venetoclax and azacytidine in the treatment of AML and highlights a potential combination of venetoclax and adoptive cell therapy for patients with AML.

Abstract 3098: Leukemia stem cells demonstrate enhanced DNA damage repair and chemoresistance in AML

Leukemia stem cells demonstrate enhanced DNA damage repair and chemoresistance in AML

Relapse of acute myeloid leukemia (AML) is common and the main cause of mortality in this disease. Leukemia stem cells (LSCs) contribute to relapse however the mechanisms underpinning chemoresistance are not well understood. Here, we explored the DNA damage response in AML LSCs to investigate if enhanced DNA repair contributes to relapse and chemoresistance.

We discovered that expression of DNA repair pathway genes were up-regulated in functionally defined LSC vs bulk AML cells (n= 227, accession number GSE76008), NES = 1.74, FDR = 0.057, and undifferentiated (n= 7) vs committed AML samples (n = 4, Princess Margaret Cancer Centre cohort), NES = 2.041, FDR = 0.000. Next, we investigated the expression of DNA damage repair genes and response to DNA damage in FACs sorted stem and bulk fractions of 8227 cells. 8227 cells are low passage primary AML cells that maintain a hierarchical organization with functionally defined stem cells in the CD34+CD38- fraction. Compared to bulk cells, the stem cell fraction of 8227 cells had increased expression of genes associated with DNA repair through homologous recombination (RAD51, XRCC2, XRCC3) and non-homologous end joining (XRCC4, XRCC5, PRKDC). Sorted 8227 cells were treated with daunorubicin, an intercalating anthracycline that causes double stranded breaks. DNA damage and repair were evaluated by measuring foci of 53BP1, RAD51 and γH2AX by fluorescent microscopy and quantified using image J. Compared to bulk cells, 8227 stem cells demonstrated increased DNA damage repair with increased foci of 53BP1 and RAD51 and decreased γH2AX foci.

We recently discovered that the metabolic enzyme hexokinase 2 (HK2) localizes to the nucleus to maintain stem cell number and function. Therefore, to understand how stemness impacts DNA damage repair, we selectively over-expressed HK2 in the nucleus of 8227 and NB4 cells by tagging HK2 with a nuclear localizing sequence. Over-expressing nuclear HK2 increased stem cell function as shown by clonogenic growth assays and engraftment into mouse marrow. We then treated these cells with daunorubicin and measured DNA damage repair. Increasing stem cell number and function by over-expressing nuclear HK2, increased 53BP1 and RAD51 foci and decreased γH2AX foci, similar to the phenotype observed in LSCs. As measured by the COMET assay, these cells had decreased levels of double strand DNA breaks under basal conditions and increased repair of DNA breaks after treatment with daunorubicin treatment. Over-expression of nuclear HK2 also conferred resistance to daunorubicin as measured by clonogenic growth assays.

In summary, LSCs have increased levels of DNA repair genes and increased rates of DNA damage repair after exposure to chemotherapy. The accelerated DNA damage repair seen in LSCs may contribute to chemoresistance and subsequent disease relapse.

Citation Format: Grace Egan, G.E. Thomas, Parasvi Patel, Veronique Voisin, Rose Hurren, Neil MacLean, Razq Hakem, Aaron D. Schimmer. Leukemia stem cells demonstrate enhanced DNA damage repair and chemoresistance in AML [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3098.

The mitochondrial peptidase, neurolysin, regulates respiratory chain supercomplex formation and is necessary for AML viability

Neurolysin (NLN) is a zinc metallopeptidase whose mitochondrial function is unclear. We found that NLN was overexpressed in almost half of patients with acute myeloid leukemia (AML), and inhibition of NLN was selectively cytotoxic to AML cells and stem cells while sparing normal hematopoietic cells. Mechanistically, NLN interacted with the mitochondrial respiratory chain. Genetic and chemical inhibition of NLN impaired oxidative metabolism and disrupted the formation of respiratory chain supercomplexes (RCS). Furthermore, NLN interacted with the known RCS regulator, LETM1, and inhibition of NLN disrupted LETM1 complex formation. RCS were increased in patients with AML and positively correlated with NLN expression. These findings demonstrate that inhibiting RCS formation selectively targets AML cells and stem cells and highlights the therapeutic potential of pharmacologically targeting NLN in AML.

A genome-wide CRISPR/Cas9 screen in acute myeloid leukemia cells identifies regulators of TAK-243 sensitivity

TAK-243 is a first-in-class inhibitor of ubiquitin-like modifier activating enzyme 1 that catalyzes ubiquitin activation, the first step in the ubiquitylation cascade. Based on its preclinical efficacy and tolerability, TAK-243 has been advanced to phase I clinical trials in advanced malignancies. Nonetheless, the determinants of TAK-243 sensitivity remain largely unknown. Here, we conducted a genome-wide CRISPR/Cas9 knockout screen in acute myeloid leukemia (AML) cells in the presence of TAK-243 to identify genes essential for TAK-243 action. We identified BEN domain-containing protein 3 (BEND3), a transcriptional repressor and a regulator of chromatin organization, as the top gene whose knockout confers resistance to TAK-243 in vitro and in vivo. Knockout of BEND3 dampened TAK-243 effects on ubiquitylation, proteotoxic stress, and DNA damage response. BEND3 knockout upregulated the ATP-binding cassette efflux transporter breast cancer resistance protein (BCRP; ABCG2) and reduced the intracellular levelsof TAK-243. TAK-243 sensitivity correlated with BCRP expression in cancer cell lines of different origins. Moreover, chemical inhibition and genetic knockdown of BCRP sensitized intrinsically resistant high-BCRP cells to TAK-243. Thus, our data demonstrate that BEND3 regulates the expression of BCRP for which TAK-243 is a substrate. Moreover, BCRP expression could serve as a predictor of TAK-243 sensitivity.

Transduction of Primary AML Cells with Lentiviral Vector for In Vitro Study or In Vivo Engraftment

We describe a method to silence genes in primary acute myeloid leukemia cells by transducing them with shRNA in lentiviral vectors. The transduction of primary non-adherent cells is particularly challenging. The protocol will aid in performing such experiments and is particularly helpful to prepare cells for in vivo engraftment studies. Use of a special medium supplemented with cytokines preserves the viability of the leukemic stem cells and their ability to engraft the marrow of immune-deficient mice. For complete details on the use and execution of this protocol, please refer to Singh et al. (2020).

Abstract 6321: BEND3 modulates sensitivity to the UBA1 inhibitor TAK-243 by regulating expression of the multidrug transporter BCRP

TAK-243 (MLN7243) is a first-in-class inhibitor of the ubiquitin-activating enzyme (UBA1) that catalyzes the first step in the ubiquitylation cascade whereby proteins are tagged with mono- or poly-ubiquitin to induce their degradation or modify their functions. Based on its preclinical efficacy and tolerability, TAK-243 has entered phase 1 clinical trials in advanced malignancies. However, the determinants of sensitivity to TAK-243 remain largely unknown. Therefore, we conducted a positive-selection, genome-wide CRISPR/Cas9 knockout screen in OCI-AML2 cells followed by selection with lethal TAK-243 concentrations to identify genes essential for TAK-243 action. We identified BEN domain-containing protein 3 (BEND3), a transcriptional repressor and a regulator of chromatin organization, as the top gene whose knockout conferred resistance to TAK-243 (FDR = 0.0012). BEND3-targeting gRNAs were enriched up to 10,000-fold after selection with the drug. To validate the screen results, we independently knocked out BEND3 in OCI-AML2 cells and confirmed the resistance phenotype. In vivo, tumors of BEND3-knockout cells were resistant to TAK243 (20 mg/kg twice weekly) as opposed to control tumors that showed dramatic reductions in tumor growth rate. As assessed by immunoblotting, BEND3 knockout dampened TAK-243 effects on ubiquitylation, proteotoxic stress and DNA damage response. Mechanistically, BEND3 knockout upregulated the ABC efflux transporter breast cancer resistance protein (BCRP; ABCG2), and decreased intracellular levels of TAK-243. It also conferred partial cross-resistance to pevonedistat and TAK-981–related selective inhibitors of the NEDD8-activating enzyme (NAE) and the SUMO-activating enzyme (SAE), respectively, as well as known substrates of BCRP (mitoxantrone and doxorubicin). Finally, TAK-243 sensitivity strongly correlated with BCRP expression in a panel of 30 cancer cell lines of different origin, and chemical inhibition of BCRP but not P-gp sensitized intrinsically resistant high-BCRP cells to TAK-243. Thus, our data demonstrate that BEND3 regulates the expression of BCRP for which TAK-243 is a substrate. Moreover, BCRP expression could serve as a predictor of TAK-243 sensitivity.

Citation Format: Samir H. Barghout, Ahmed Aman, Zachary Blatman, Karen Arevalo, Geethu Thomas, Neil MacLean, Xiaoming Wang, Rose Hurren, Troy Ketela, Moustafa Abohawya, Taira Kiyota, Rima Al-Awar, Aaron D. Schimmer. BEND3 modulates sensitivity to the UBA1 inhibitor TAK-243 by regulating expression of the multidrug transporter BCRP [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6321.

Abstract 3784: The metabolic enzyme Hexokinase 2 localizes to the nucleus and regulates stemness in AML through a kinase independent mechanism

Leukemia stem cells are responsible for the initiation and recurrence of AML. Cell differentiation requires the coordination of metabolic state and gene expression programs. It is known that metabolic intermediates can serve as cofactors in epigenetic modifications in the nucleus. Whether metabolic enzymes can directly localize to the nucleus, influence gene expression and regulate stemness in AML is unknown. To identify mitochondrial metabolic enzymes that localize to the nucleus of stem cells we analyzed stem and bulk fractions of 8227 leukemia cells, which are arranged in a hierarchy with functionally defined stem cells in the CD34+CD38- fraction. Hexokinase 2 (HK2) was detected in the nuclear fraction of 8227 cells and nuclear HK2 was increased in 8227 stem cells compared to bulk cells. Conversely, the metabolic enzymes aconitase, citrate synthesase, enolase, fumarase, GAPDH, glucose-6-phosphate isomerase, phosphofructokinase, pyruvate kinase and succinate dehydrogenase A were not detectable in the nuclear fraction of either stem or bulk cells. We confirmed that HK2 was present in the nuclear fraction of OCI-AML2, NB4, HL60 and TEX AML cell lines and 7/9 primary patient samples. To determine whether nuclear HK2 was functionally important for AML stem cells, we overexpressed HK2 tagged with a nuclear localizing sequence (PAAKRVKLD). Over-expression of nuclear localized HK2 enhanced clonogenic growth and engraftment into immune deficient mice. Likewise, over-expression of nuclear localized HK2 blocked differentiation after treatment with all-trans retinoic acid (ATRA). Next, we investigated whether the kinase activity of HK2 was necessary for its nuclear effects on AML stemness and differentiation. We generated a kinase dead mutant of HK2 (D209A, D657A) tagged with a nuclear localizing signal (PAAKRVKLD). Over-expression of nuclear-localized kinase dead HK2 exerted a similar phenotype to overexpressed nuclear HK2 without manipulation of the kinase domain as it enhanced clonogenic growth and blocked cell differentiation after ATRA treatment. To understand the mechanism by which nuclear HK2 influenced AML stemness, we identified proteins that interacted with nuclear HK2 using proximity-dependent biotin labeling (BioID) and mass spectrometry. Proteins involved in DNA damage repair and chromatin remodeling were identified, including exonuclease 3′-5′ domain-containing 2 (EXD2), sirtuin 1 (SIRT1), E3 ubiquitin-protein ligase (URB5) and tyrosyl-DNA phosphodiesterase 2 (TDP2). Thus, our data suggest that nuclear HK2 influences DNA repair, which has been linked to stemness and differentiation. In support of this hypothesis, we identified a PAR binding motif in HK2 and over-expression of nuclear HK2 conferred resistance to the PARP inhibitor, olaparib. In summary, HK2 localizes to the nucleus in AML stem cells and maintains stemness. These effects are independent of its kinase activity. Rather, HK2 may regulate DNA damage repair through a PAR dependent mechanism. Thus, we have identified a new role for metabolic enzymes in the regulation of stemness and differentiation.

Citation Format: Grace Egan, Geethu E. Thomas, Parasvi S. Patel, Jordan Chin, Aaron Botham, Rose Hurren, Neil MacLean, Razq Hakem, Aaron D. Schimmer. The metabolic enzyme Hexokinase 2 localizes to the nucleus and regulates stemness in AML through a kinase independent mechanism [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3784.

Disrupting Mitochondrial Copper Distribution Inhibits Leukemic Stem Cell Self-Renewal

Leukemic stem cells (LSCs) rely on oxidative metabolism and are differentially sensitive to targeting mitochondrial pathways, which spares normal hematopoietic cells. A subset of mitochondrial proteins is folded in the intermembrane space via the mitochondrial intermembrane assembly (MIA) pathway. We found increased mRNA expression of MIA pathway substrates in acute myeloid leukemia (AML) stem cells. Therefore, we evaluated the effects of inhibiting this pathway in AML. Genetic and chemical inhibition of ALR reduces AML growth and viability, disrupts LSC self-renewal, and induces their differentiation. ALR inhibition preferentially decreases its substrate COX17, a mitochondrial copper chaperone, and knockdown of COX17 phenocopies ALR loss. Inhibiting ALR and COX17 increases mitochondrial copper levels which in turn inhibit S-adenosylhomocysteine hydrolase (SAHH) and lower levels of S-adenosylmethionine (SAM), DNA methylation, and chromatin accessibility to lower LSC viability. These results provide insight into mechanisms through which mitochondrial copper controls epigenetic status and viability of LSCs.

Abstract 2720: Mitochondrial ClpP-mediated proteolysis induces selective cancer cell lethality

ClpP is a mitochondrial protease and a major protein quality control mediator that primarily interacts with metabolic enzymes in mitochondria. Here, we demonstrate that activation of this protease results in prominent anti-cancer activity, and propose ClpP activation as a novel therapeutic strategy for cancer and hematologic malignancies. We used genetic and chemical tools to activate ClpP. In a genetic approach, we tested the anti-cancer effects of ClpP activation by expressing a constitutively active ClpP mutant. Indeed, induction of the active ClpP mutant induced apoptosis in vitro and inhibited tumor progression in vivo. To further explore the antineoplastic effects of ClpP activation, we then performed a chemical screen of an in-house library of on-patent and off-patent drugs and identified imipridones (ONC201 and ONC212) as potent ClpP agonists. Imipridones are first-in-class antineoplastic agents and have shown preclinical efficacy in various malignancies in vitro and in vivo and are currently being evaluated in clinical trials in a diverse spectrum of cancers. Importantly, we and others have shown that their activity is agnostic to TP53 mutational status. Of note, molecular targets of imipridones that bind the drugs and are functionally important for their cytotoxicity have never been identified. Through extensive chemical investigations, including analysis of binding mechanism of the compounds to ClpP in cell free (ITC) and cell based assays (CETSA) as well as molecular analysis of the crystal structure, we demonstrate that these molecules bind ClpP non-covalently, and activate the protease by stabilizing the ClpP 14-mer, enlarging the axial pores of the complex, and inducing structural changes in the residues surrounding and including the catalytic triad. In leukemia, lymphoma and colon cancer cells including primary acute myeloid leukemia (AML) cells, both compounds displayed potent ClpP-dependent cytotoxicity with IC50s in low micro- or nanomolar ranges. Importantly, in primary AML samples, pretreatment ClpP levels correlated with response to imipridones. In lymphoma and AML xenograft models, both genetic and chemical activation of ClpP resulted in antitumor effects, while expression of inactive D190A ClpP mutant induced resistance. Mechanistically, ClpP activation leads to increased degradation of substrates of the enzyme including respiratory chain complex subunits and mitochondrial translation system. The resultant impaired mitochondrial structure and reduction in oxygen consumption is selectively cytotoxic to malignant cells that rely highly on mitochondrial energy production for their survival, whereas normal cells are not affected. In conclusion, ClpP activation is an entirely novel therapeutic strategy for malignant tumors. Our findings also suggest a general concept of inducing TP53-independent cancer cell lethality through activation of mitochondrial proteolysis.

Citation Format: Jo Ishizawa, Sarah F. Zarabi, R Eric Davis, Ondrej Halgas, Takenobu Nii, Yulia Jitkova, Ran Zhao, Jonathan St-Germain, Lauren E. Heese, Grace Egan, Vivian R. Ruvolo, Samir H. Barghout, Yuki Nishida, Rose Hurren, Wencai Ma, Marcela Gronda, Todd Link, Keith Wong, Mark Mabanglo, Kensuke Kojima, Gautam Borthakur, Neil MacLean, John Man Chun Ma, Andrew B. Leber, Mark D. Minden, Walid Houry, Hagop Kantarjian, Martin Stogniew, Brian Raught, Emil F. Pai, Aaron D. Schimmer, Michael Andreeff. Mitochondrial ClpP-mediated proteolysis induces selective cancer cell lethality [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2720.

Abstract 3003: Inhibiting the mitochondrial enzyme phosphatidylserine decarboxylase (PISD) reduces stemness and increases differentiation in acute myeloid leukemia (AML)

Acute myeloid leukemia (AML) is a hematopoietic malignancy characterized by the accumulation of malignant myeloid cells that have arrested maturation. Most therapeutic regimens approved or under development are cytotoxics. An alternate, but less explored therapeutic approach, is to induce terminal differentiation of AML cells. Upon differentiation, AML cells cease to proliferate or die.

Phosphatidylserine decarboxylase (PISD) is a mitochondrial enzyme that converts phosphatidylserine (PS) to phosphatidylethanolamine (PE). Here, we explored the effects of inhibiting PISD on AML growth, stemness and differentiation.

Knockout of PISD by CRISPR reduced the growth and clonogenic growth of OCI-AML2 cells. The reported chemical PISD inhibitor, 7-chloro-N-(4-ethoxyphenyl)-4-quinolinamine (aka: MMV007285), reduced growth and viability of OCI-AML2 cells (IC50 = 4.741 μM) and TEX cells (IC50 = 4.868 μM). Using the 8227 primary AML cell culture model, we showed that inhibiting PISD induced cell death in the functionally defined stem cell fraction (CD34+CD38-). MMV007285 also preferentially inhibited the clonogenic growth of primary AML cells (n = 7) over normal hematopoietic cells (n= 3). Moreover, MMV007285 induced AML cell differentiation as evidenced by increased CD11b expression and staining for non-specific esterase.

Using high-performance thin layer chromatography (HPTLC), we found that inhibition of PISD with MMV007285 increased intracellular PS. To determine whether increased PS was functionally important, OCI-AML2 cells were treated with PS, resulting in reduced growth and clonogenic growth. Furthermore, PS supplementation targeted AML progenitor cells as it decreased engraftment of TEX cells in mice.

Mechanistically, inhibiting PISD induced differentiation and decreased stemness in AML by activating Toll-like receptor (TLR) signaling. Specifically, inhibiting PISD upregulated TLR4 and 8 expression and increased expression of cytokines downstream of TLR activation. We also showed that TLR activation was functionally important to induce AML differentiation.

Finally, we evaluated the effects of PISD inhibition in AML mouse models. MMV007285 (300 mg/kg/5 of 7 days orally for 10 days) decreased the growth of OCI-AML2 cells in SCID mice. Moreover, MMV007285 (150 mg/kg/5 of 7 days orally for 5 weeks) impeded the leukemic engraftment of primary AML cell in NOD/SCID mice without toxicity. Using secondary transplants, we showed that MMV007285 also targeted the leukemic stem cells.

Taken together, inhibition of PISD altered phospholipid metabolism, inhibited growth and stemness, and increased differentiation in AML cells. Our findings reveal a previously undescribed link between mitochondrial phospholipid metabolism and AML stemness and differentiation, highlighting a potential new therapeutic strategy for AML.

Citation Format: Mingjing Xu, Ayesh Seneviratne, Val A. Fajardo, Geethu E. Thomas, G. Wei Xu, Rose Hurren, S. Kim, Neil MacLean, Xiaoming Wang, Marcela Gronda, Danny Jeyaraju, Yulia Jitkova, David Sharon, Ahmed Aman, Rima Al-awar, Steven Chan, Mark D. Minden, Paul LeBlanc, Aaron D. Schimmer. Inhibiting the mitochondrial enzyme phosphatidylserine decarboxylase (PISD) reduces stemness and increases differentiation in acute myeloid leukemia (AML) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3003.

Mitochondrial ClpP-Mediated Proteolysis Induces Selective Cancer Cell Lethality

The mitochondrial caseinolytic protease P (ClpP) plays a central role in mitochondrial protein quality control by degrading misfolded proteins. Using genetic and chemical approaches, we showed that hyperactivation of the protease selectively kills cancer cells, independently of p53 status, by selective degradation of its respiratory chain protein substrates and disrupts mitochondrial structure and function, while it does not affect non-malignant cells. We identified imipridones as potent activators of ClpP. Through biochemical studies and crystallography, we show that imipridones bind ClpP non-covalently and induce proteolysis by diverse structural changes. Imipridones are presently in clinical trials. Our findings suggest a general concept of inducing cancer cell lethality through activation of mitochondrial proteolysis.

The Mitochondrial Transacylase, Tafazzin, Regulates for AML Stemness by Modulating Intracellular Levels of Phospholipids

Tafazzin (TAZ) is a mitochondrial transacylase that remodels the mitochondrial cardiolipin into its mature form. Through a CRISPR screen, we identified TAZ as necessary for the growth and viability of acute myeloid leukemia (AML) cells. Genetic inhibition of TAZ reduced stemness and increased differentiation of AML cells both in vitro and in vivo. In contrast, knockdown of TAZ did not impair normal hematopoiesis under basal conditions. Mechanistically, inhibition of TAZ decreased levels of cardiolipin but also altered global levels of intracellular phospholipids, including phosphatidylserine, which controlled AML stemness and differentiation by modulating toll-like receptor (TLR) signaling.

The thymidine dideoxynucleoside analog, alovudine, inhibits the mitochondrial DNA polymerase γ, impairs oxidative phosphorylation and promotes monocytic differentiation in acute myeloid leukemia

Mitochondrial DNA encodes 13 proteins that comprise components of the respiratory chain that maintain oxidative phosphorylation. The replication of mitochondrial DNA is performed by the sole mitochondrial DNA polymerase γ. As acute myeloid leukemia (AML) cells and stem cells have an increased reliance on oxidative phosphorylation, we sought to evaluate polymerase γ inhibitors in AML. The thymidine dideoxynucleoside analog, alovudine, is an inhibitor of polymerase γ. In AML cells, alovudine depleted mitochondrial DNA, reduced mitochondrial encoded proteins, decreased basal oxygen consumption, and decreased cell proliferation and viability. To evaluate the effects of polymerase γ inhibition with alovudine in vivo, mice were xenografted with OCI-AML2 cells and then treated with alovudine. Systemic administration of alovudine reduced leukemic growth without evidence of toxicity and decreased levels of mitochondrial DNA in the leukemic cells. We also showed that alovudine increased the monocytic differentiation of AML cells. Genetic knockdown and other chemical inhibitors of polymerase γ also promoted AML differentiation, but the effects on AML differentiation were independent of reductions in oxidative phosphorylation or respiratory chain proteins. Thus, we have identified a novel mechanism by which mitochondria regulate AML fate and differentiation independent of oxidative phosphorylation. Moreover, we highlight polymerase γ inhibitors, such as alovudine, as novel therapeutic agents for AML.

Abstract 5489: Characterization of mitochondrial STAT3 (mitostat3) function and the mitoStat3 interactome as a therapeutic strategy for multiple myeloma

The oncogenic transcription factor STAT3 is an appealing therapeutic target in cancer including multiple myeloma (MM) where its inhibition has the potential to downregulate aberrant signaling from various upstream molecules. STAT3 has been studied extensively as a transcription factor however, much less is known about its non-classical functions in the mitochondria and in turn, the role of mitochondrial STAT3 (mitoStat3) in cancer biology. Data suggests that mitoStat3 is critical for mediating Ras-induced oncogenic transformation. As activating mutations of the MAPK pathway are reported in over 50% of myeloma patients, we sought to characterize the function of mitoStat3 in MM.

We first confirmed the presence of STAT3 in the mitochondria of myeloma cell lines, AMO1 and XG6 by Western blot analysis. We next used CRISPR/CAS9 to knockdown STAT3 in XG6 and AMO1 cells, which resulted in inhibition of cell proliferation (XG6 and AMO1), apoptosis (XG6) and reduced oxygen consumption rate as measured by extracellular flux analysis (Seahorse assay). To better define the role of mitoStat3 and to identify indirect strategies to interfere with STAT3 activity, we employed a proximity-dependent Biotin Identification (BioID) method to discover mitoStat3 interacting proteins. BioID is a unique method to screen for physiologically relevant protein interactions that occur in living cells. First, wild-type STAT3 was fused to a mitochondrial localization Signal (MLS-Stat3), cloned into pcDNA5 FRT/TO [MCS]-BirAR118G-FLAG plasmid and transfected into HEK293 TRE-x Flp-In cells. BioID identified 225 high confidence mitoStat3-interacting partners in MLS-Stat3 transfected cells. The most abundant proteins in the mitoStat3 interactome included those with roles in mitochondrial translation and mitochondrial electron transport. Futhermore, mitoStat3 was found to interact with the translocase of inner membrane protein Tim44, which together with Tim23 complex facilitates translocation of proteins into the mitochondrial matrix. Genetic knockdown of Tim23 in XG6 cells resulted in decreased mitoStat3 suggesting that this complex may be involved in the import of STAT3 into the mitochondria. Additional mitoStat3 interacting proteins identified by BioID are currently being validated and will be presented.

Taken together, results support the further exploration of the role of mitoStat3 in myeloma cells. Further, identification of mitoStat3 interacting proteins including Tim44 and others may inform alternative strategies to therapeutically target oncogenic STAT3.

Citation Format: Serges P. Tsofack, Aaron Botham, Zhihua Li, Ellen Nong Wei, Danielle Croucher, Ioulia Jitkova, Neil MacLean, Aaron D. Schimmer, Brian Raught, Suzanne Trudel. Characterization of mitochondrial STAT3 (mitostat3) function and the mitoStat3 interactome as a therapeutic strategy for multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5489.

A novel isoflavone, ME-344, targets the cytoskeleton in acute myeloid leukemia

The isoflavone ME-344 is a potent anti-cancer agent with preclinical and clinical efficacy in solid tumors. Yet, the mechanism of action of ME-344 has not been fully defined and the preclinical efficacy in leukemia has not been established. Therefore, we investigated the anti-leukemic properties and mechanism of action of ME-344. In a panel of 7 leukemia cell lines, ME-344 was cytotoxic with an IC₅₀ in the range of 70–260 nM. In addition, ME-344 was cytotoxic to primary AML patient samples over normal hematopoietic cells. In an OCI-AML2 xenograft model, ME-344 reduced tumor growth by up to 95% of control without evidence of toxicity. Mechanistically, ME-344 increased mitochondrial ROS generation in leukemic cells. However, antioxidant treatment did not rescue cell death, suggesting that ME-344 had additional targets beyond the mitochondria. We demonstrated that ME-344 inhibited tubulin polymerization by interacting with tubulin near the colchicine-binding site. Furthermore, inhibition of tubulin polymerization was functionally important for ME-344 induced death. Finally, we showed that ME-344 synergizes with vinblastine in leukemia cells. Thus, our study demonstrates that ME-344 displays preclinical efficacy in leukemia through a mechanism at least partly related to targeting tubulin polymerization.

Ibrutinib synergizes with poly(ADP-ribose) glycohydrolase inhibitors to induce cell death in AML cells via a BTK-independent mechanism

Targeting Bruton's tyrosine kinase (BTK) with the small molecule BTK inhibitor ibrutinib has significantly improved patient outcomes in several B-cell malignancies, with minimal toxicity. Given the reported expression and constitutive activation of BTK in acute myeloid leukemia (AML) cells, there has been recent interest in investigating the anti-AML activity of ibrutinib. We noted that ibrutinib had limited single-agent toxicity in a panel of AML cell lines and primary AML samples, and therefore sought to identify ibrutinib-sensitizing drugs. Using a high-throughput combination chemical screen, we identified that the poly(ADP-ribose) glycohydrolase (PARG) inhibitor ethacridine lactate synergized with ibrutinib in TEX and OCI-AML2 leukemia cell lines. The combination of ibrutinib and ethacridine induced a synergistic increase in reactive oxygen species that was functionally important to explain the observed cell death. Interestingly, synergistic cytotoxicity of ibrutinib and ethacridine was independent of the inhibitory effect of ibrutinib against BTK, as knockdown of BTK did not sensitize TEX and OCI-AML2 cells to ethacridine treatment. Thus, our findings indicate that ibrutinib may have a BTK-independent role in AML and that PARG inhibitors may have utility as part of a combination therapy for this disease.

Select microtubule inhibitors increase lysosome acidity and promote lysosomal disruption in acute myeloid leukemia (AML) cells

To identify new biological vulnerabilities in acute myeloid leukemia, we screened a library of natural products for compounds cytotoxic to TEX leukemia cells. This screen identified the novel small molecule Deoxysappanone B 7,4' dimethyl ether (Deox B 7,4), which possessed nanomolar anti-leukemic activity. To determine the anti-leukemic mechanism of action of Deox B 7,4, we conducted a genome-wide screen in Saccharomyces cerevisiae and identified enrichment of genes related to mitotic cell cycle as well as vacuolar acidification, therefore pointing to microtubules and vacuolar (V)-ATPase as potential drug targets. Further investigations into the mechanisms of action of Deox B 7,4 and a related analogue revealed that these compounds were reversible microtubule inhibitors that bound near the colchicine site. In addition, Deox B 7,4 and its analogue increased lysosomal V-ATPase activity and lysosome acidity. The effects on microtubules and lysosomes were functionally important for the anti-leukemic effects of these drugs. The lysosomal effects were characteristic of select microtubule inhibitors as only the Deox compounds and nocodazole, but not colchicine, vinca alkaloids or paclitaxel, altered lysosome acidity and induced lysosomal disruption. Thus, our data highlight a new mechanism of action of select microtubule inhibitors on lysosomal function.

Abstract A299: Select microtubule inhibitors increase lysosome acidity and promote lysosomal disruption in acute myeloid leukemia (AML) cells

AML is a hematological malignancy for which the standard of care therapy has remained unchanged for almost 30 years. Novel therapeutic approaches are therefore urgently needed for the treatment of this heterogeneous disease. To identify new strategies for the treatment of AML, we screened a natural product library for compounds cytotoxic to AML cells and identified Deoxysappanone B 7,4’-dimethyl ether. Deoxysappanone B is a homoisoflavanoid compound extracted primarily from the dried heartwood of Caesalpinia sappan, a medicinal plant native to South-East Asia. However, anticancer activity of this compound has not been previously described and its molecular targets are largely unknown. In subsequent validation studies, Deoxysappanone B possessed anti-leukemic activity in 6 tested AML cell lines with nanomolar IC50s and was preferentially cytotoxic to primary AML cells and stem/progenitor cells over normal hematopoietic cells. To understand its mechanism of action, we performed chemo-genomic profiling of Deoxysappanone B in S. cerevisiae and identified enrichment of genes related to mitotic cell cycle as well as vacuolar acidification, therefore pointing to microtubules and lysosomes’ proton-pumping vacuolar (V)-ATPase as potential targets. We confirmed Deoxysappanone B's action as a microtubule inhibitor and localized its binding site near to that of colchicine via in-vitro tubulin polymerization and competitive binding assays. We also showed that Deoxysappanone B reversibly induces cell cycle arrest and cell death in a panel of AML cell lines as well as overcomes some mechanisms of resistance to vinca alkaloids. Validating the functional importance of tubulin as a target for Deoxysappanone B-mediated cell death, epidermoid carcinoma cells with a tubulin mutation were more resistant to Deoxysappanone B compared to their parental counterpart. In addition to inhibiting tubulin polymerization, Deoxysappanone B also increased lysosome acidity as measured by a V-ATPase enzymatic assay as well as staining with LysoSensor™ Yellow/Blue DND-160 and confocal microscopy. The sustained increase in lysosome acidity ultimately led to lysosomal disruption as evidenced by acridine orange staining. Supporting a tubulin-mediated effect on lysosomes, nocodazole, although not vinblastine, vincristine, paclitaxel or colchicine, produced a similar increase in lysosome acidity and lysosomal disruption. The effects on lysosomes were functionally relevant as pre-treatment with bafilomycin A1, a lysosomal V-ATPase inhibitor, partially abrogated the cytotoxic effect of Deoxysappanone B. Thus, our data provide insight into a novel mechanism of action of select microtubule inhibitors in the context of AML.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A299.

Citation Format: Dannie Bernard, Marinella Gebbia, Swayam Prabha, Marcela Gronda, Neil MacLean, Xiaoming Wang, Rose Hurren, Mahadeo A. Sukhai, Eunice E. Cho, Morris F. Manolson, Alessandro Datti, Jeffrey Wrana, Rima Al-Awar, Ahmed Aman, Corey Nislow, Guri Giaever, Aaron D. Schimmer. Select microtubule inhibitors increase lysosome acidity and promote lysosomal disruption in acute myeloid leukemia (AML) cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A299.

Lysosomal disruption preferentially targets acute myeloid leukemia cells and progenitors

Despite efforts to understand and treat acute myeloid leukemia (AML), there remains a need for more comprehensive therapies to prevent AML-associated relapses. To identify new therapeutic strategies for AML, we screened a library of on- and off-patent drugs and identified the antimalarial agent mefloquine as a compound that selectively kills AML cells and AML stem cells in a panel of leukemia cell lines and in mice. Using a yeast genome-wide functional screen for mefloquine sensitizers, we identified genes associated with the yeast vacuole, the homolog of the mammalian lysosome. Consistent with this, we determined that mefloquine disrupts lysosomes, directly permeabilizes the lysosome membrane, and releases cathepsins into the cytosol. Knockdown of the lysosomal membrane proteins LAMP1 and LAMP2 resulted in decreased cell viability, as did treatment of AML cells with known lysosome disrupters. Highlighting a potential therapeutic rationale for this strategy, leukemic cells had significantly larger lysosomes compared with normal cells, and leukemia-initiating cells overexpressed lysosomal biogenesis genes. These results demonstrate that lysosomal disruption preferentially targets AML cells and AML progenitor cells, providing a rationale for testing lysosomal disruption as a novel therapeutic strategy for AML.

Abstract A22: A genome-wide shRNA screen identifies α/β hydrolase domain containing 4 (ABHD4) as a novel regulator of anoikis resistance

Acquisition of resistance to anchorage dependant cell death, a process termed anoikis, is a requirement for cancer cell metastasis. However, the molecular determinants of anoikis resistance and sensitivity are poorly understood. To better understand resistance to anoikis we conducted a genome wide lentiviral shRNA screen to identify genes whose knockdown render RWPE-1 prostate cells resistant to anoikis. RWPE-1 cells are a non-malignant prostate cell line that undergo cell death upon detachment from extracellular matrix. To identify genetic regulators of anoikis, RWPE-1 cells were infected with a pooled lentiviral hairpin shRNA library with 54,021 hairpins targeting 11,255 genes. After infection, cells were cultured in suspension conditions for three weeks and an anoikis-resistant cell population was selected. From this population, genomic DNA was isolated and shRNA sequences were amplified and sequenced. Thirty four shRNA sequences reproducibly protected RWPE-1 cells from anoikis after culture under suspension conditions. We selected α/β hydrolase domain containing 4 (ABHD4) for further analysis as it conferred the greatest protection to anoikis in our screening assays. To validate the effects of ABHD4 knockdown on anoikis resistance, we infected RWPE-1 with 2 independent shRNA targeting ABHD4 or control sequences. We also over-expressed ABHD4 in wild type cells. Finally, we co-infected cells with ABDH4 cDNA and shRNA as a rescue experiment to demonstrate on-target activity. Target knockdown or over-expression after infection was confirmed by Q-RTPCR or immunoblotting. Using two independent shRNA, knockdown of ABHD4 inhibited anoikis as evidence by increased clonogenic growth compared to cells infected with control sequences. Demonstrating an on-target effect, rescue of ABHD4 expression returned levels of clonogenic growth to wild type levels. Finally, over-expression of ABHD4 increased sensitivity to anoikis and less clonogenic growth was observed in these cells compared to control cells.

Resistance to anoikis after ABHD4 knockdown was associated with decreased cleavage of PARP and decreased activation of caspases-3, 8 and 9, but was independent in changes of FLIP expression. Interesting, resistance to anoikis after ABHD4 knockdown was independent of the known role of ABHD4 in the anandamide synthesis pathway and the generation of glycerophospho-N-acyl ethanolamines. Thus, reductions in the levels of ABHD4 confer resistance to anoikis while over-expression of the target enhances anoikis in the anoikis-sensitive cell line RWPE-1. As such, we have identified a novel genetic regulator of anoikis sensitivity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A22.

Inhibition of SREBP1 sensitizes cells to death ligands

Evasion of death receptor ligand-induced apoptosis contributs to cancer development and progression. To better understand mechanisms conferring resistance to death ligands, we screened an siRNA library to identify sequences that sensitize resistant cells to fas activating antibody (CH-11). From this screen, we identified the Sterol-Regulatory Element-Binding Protein 1 (SREBP1), a transcription factor, which regulates genes involved in cholesterol and fatty acid synthesis including fatty acid synthase. Inhibition of SREBP1 sensitized PPC-1 and HeLa to the death receptor ligands CH-11 and TRAIL. In contrast, DU145 prostate cancer cells that are resistant to death ligands despite expressing the receptors on their cell surface remained resistant to CH-11 and TRAIL after knockdown of SREBP1. Consistent with the effects on cell viability, the addition of CH-11 activated caspases 3 and 8 in HeLa but not DU145 cells with silenced SREBP1. We demonstrated that knockdown of SREBP1 produced a marked decrease in fatty acid synthase expression. Furthermore, genetic or chemical inhibition of fatty acid synthase with shRNA or orlistat, respectively, recapitulated the effects of SREBP1 inhibition and sensitized HeLa but not DU145 cells to CH-11 and TRAIL. Sensitization to death receptor ligands by inhibition of fatty acid synthase was associated with activation of caspase 8 prior to caspase 9. Neither silencing of SREBP1 or fatty acid synthase changed basal expression of the core death receptor components Fas, caspase 8, FADD, caspase 3 or FLIP. Thus, inhibition of SREBP1 or its downstream target fatty acid synthase sensitizes resistant cells to death ligands.

2-(Anilino)imidazolines and 2-(benzyl)imidazoline derivatives as h5-HT1D serotonin receptor ligands

2-(Anilino)imidazolines were identified as novel human 5-HT(1D) receptor ligands, but offered no particular advantage over previously reported 2-(benzyl)imidazolines. Pharmacokinetic and functional data were obtained for selected 2-(benzyl)imidazoline derivatives.

3-(2-Pyrrolidin-1-ylethyl)-5-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole derivatives as high affinity human 5-HT1B/1D ligands

A series of 3-(2-pyrrolidin-1-ylethyl)-5-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole derivatives (2) has been prepared using parallel synthesis techniques, and their structure-activity relationships studied. High affinity human 5-HT(1B/1D) (h5-HT(1B/1D)) ligands have been identified.

Design, synthesis and biological activity of novel dimethyl-{2-[6-substituted-indol-1-yl]-ethyl}-amine as potent, selective, and orally-Bioavailable 5-HT 1D agonists

A novel series of highly potent human 5-HT(1D) agonists, dimethyl-[2-[6-substituted-indol-1-yl]-ethyl]-amine, was synthesized. Structure-activity relationship (SAR) investigation revealed 4-[1-(2-dimethylamino-ethyl)-1H-indol-6-yl]-tetrahydro-thiopyran-4-ol, 11b (ALX-2732), as a potent (K(i)=2.4 nM) agonist at the human 5-HT(1D) receptor with good selectivity over the other serotonin receptor subtypes. This compound demonstrated favorable in vitro metabolic stability in human and rat liver microsomes and was found to be orally bioavailable in rats (F(po)=51%).

( R )-3-( N -Methylpyrrolidin-2-ylmethyl)-5-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole derivatives as high affinity h5-HT 1B/1D ligands

A series of (R)-3-(N-methylpyrrolidin-2-ylmethyl)-5-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole derivatives (2) have been prepared using parallel synthesis, and their structure-activity relationship studied. High affinity human 5-HT(1B/1D) (h5-HT(1B/1D)) ligands have been identified.

1-(Bicyclopiperazinyl)ethylindoles and 1-(homopiperazinyl)ethyl-indoles as highly selective and potent 5-HT(7) receptor ligands

A novel series of 1-(bicyclopiperazinyl)ethylindole and 1-(homopiperazinyl)ethyl-indole derivatives was synthesized and found to be potent and selective 5-HT(7) receptor ligands.

5,5-Diaryl-2-amino-4-pentenoates as novel, potent, and selective glycine transporter type-2 reuptake inhibitors

A novel series of 5,5-diaryl-2-amino-4-pentenoates was synthesized and found to be potent and selective glycine transporter type-2 reuptake inhibitors.

Allogeneic stem cell transplantation. An economic comparison of bone marrow, peripheral blood, and cord blood technologies

OBJECTIVES

To compare outcome attributes of three available technologies for stem cell transplantation--bone marrow transplantation (BM), peripheral blood cell transplantation (PB), and cord blood transplantation (CB). To compare the cost per recipient for the three technologies, incorporating all donor and antigen matching functions, as well as the transplantation procedures.

METHODS

Review of relevant literature using the CancerLit and HealthSTAR databases (plus earlier searches of MEDLINE and Embase) to summarize outcome differences. Estimations of cost per transplant using models drawing on Canadian experience.

RESULTS

The literature review indicated that PB may have a modest advantage over BM in terms of outcomes. The literature indicated that CB has longer engraftment times (although this may be due to inadequate controls). Our modeling exercise indicated that costs for PB and BM are similar. CB has a higher cost per recipient, due in large part to the higher testing costs for every donated unit.

CONCLUSIONS

Current literature is inadequate to provide an outcomes comparison of CB, PB, and BM. Viewed from a system-wide perspective, CB is a higher cost technique. However, PB and CB are emerging as technologies, and so our results should be viewed alongside the notion that there may be a steep learning curve in these technologies.

N1-(Benzenesulfonyl)tryptamines as novel 5-HT6 antagonists

N-Benzenesulfonyl-5-methoxy-N,N-dimethyltryptamine (BS/5-OMe DMT; 5) was shown to bind at human 5-HT6 serotonin receptors with high affinity (Ki = 2.3 nM) relative to serotonin (Ki = 78 nM). Structural variation failed to result in significantly enhanced affinity. BS/5-OMe DMT acts as an antagonist of 5-HT-stimulated adenylate cyclase (pA2 = 8.88 nM) and may represent the first member of a novel class of 5-HT6 antagonists.

5-Alkyltryptamine derivatives as highly selective and potent 5-HT1D receptor agonists

A series of 5-alkyltryptamines (6) and the corresponding conformationally constrained analogues (8) have been synthesized. The structure activity relationships (SAR) at the 5-position of the indole skeleton and the ethylamine side chain have been studied. Functional activities were assessed using isolated rabbit saphenous vein. Potent, selective ligands were found (6e, Ki 2.5 nM, 5-HT1B/5-HT1D 125-fold) that have potential for treating acute migraine.

6-Bicyclopiperazinyl-1-arylsulfonylindoles and 6-bicyclopiperidinyl-1-arylsulfonylindoles derivatives as novel, potent, and selective 5-HT6 receptor antagonists

A novel series of 6-bicyclopiperazinyl-1-arylsulfonylindoles and 6-bicyclopiperidinyl-1-arylsulfonylindoles derivatives was synthesized and found to be potent and selective 5-HT6 receptor antagonists.

Pyrrolo[3,2,1-ij]quinoline derivatives, a 5-HT2c receptor agonist with selectivity over the 5-HT2a receptor: potential therapeutic applications for epilepsy and obesity

A series of pyrrolo[3,2,1-ij]quinoline derivatives was synthesized, evaluated for their activity against the 5-HT2c and 5-HT2a, receptors and found to be agonists at 5-HT2c with selectivity over 5-HT2a.

Detection of neuron-specific protein gene product (PGP) 9.5 in the rat and zebrafish using anti-human PGP9.5 antibodies

Protein gene product (PGP) 9.5 is a developmentally regulated neuron- and neuroendocrine cell-specific ubiquitin carboxy-terminal hydrolase (UCHL1) expressed throughout the mammalian central and peripheral nervous systems. We have compared the use of monoclonal and polyclonal antibodies raised against human PGP9.5 for immunodetection of the protein in tissues of the zebrafish and rat. We show that a monoclonal antibody 13C4, which recognises an N-terminal epitope, detects PGP9.5 on Western blots as a single 27 kDa band present at high levels in zebrafish and rat brain. By contrast, the polyclonal antisera recognises multiple tissue-specific proteins in the rat and fails to detect PGP9.5 in the zebrafish. Finally, we have developed a specific ELISA assay for detection of cellular PGP9.5 using MAb13C4 and have employed the assay to show that PGP9.5 is not upregulated during nerve growth factor (NGF)-induced differentiation of rat PC12 cells.

Spatial and temporal genetic variation in British field populations of the grain aphid Sitobion avenae (F.) (Hemiptera: Aphididae) studied using RAPD-PCR

The grain aphid Sitobion avenae (F.) was collected from winter wheat and adjacent cocksfoot grass at two locations in southern England and at four times in the year (April-July). Genetic variation between individual aphids was then investigated using random amplified polymorphic DNA polymerase chain reaction. Individuals caught in wheat and cocksfoot during April provided very different and highly diagnostic banding patterns that were independent of location. This host-based genetic differentiability was less evident as the season progressed, largely as a result of genetic drift and local movement between adjacent host species, which appeared to be predominantely in the direction from cocksfoot to wheat. The diversity of putative clones fell significantly, the mean number of individuals per clone rose and clones became more exclusively associated with certain sites which suggests that long-distance migration may have less of a homogenizing effect than hitherto thought for this species.

Geographic and microgeographic genetic differentiation in two aphid species over southern England using the multilocus (GATA)4 probe

Samples of the grain aphid Sitobion avenae (F.) and the rose-grain aphid Metopolophium dirhodum (Walker) were collected in late March from wheat fields and adjacent road-side grasses at a number of locations in southern England. Unparasitized aphids were DNA fingerprinted using the multilocus (GATA)4 probe. Over all locations, the fingerprints of individual S. avenae caught in wheat had lower overall average distances of band migration (ADBM) and shared a higher proportion of bands, than fingerprints of individuals caught in adjacent road-side grasses. The ADBM of fingerprints of S. avenae collected on road-side grasses altered significantly with geographical location, while the ADBM of fingerprints of S. avenae caught on wheat did not. A comparison of the fingerprints of individual M. dirhodum caught in wheat and neighbouring road-side grasses did not reveal any genetic differentiation. Fingerprints of M. dirhodum that were caught in the same host type did however, show significant variation in ADBM between different locations. With both S. avenae and M. dirhodum, spatial autocorrelation revealed that locations that were close together were no more likely to have individuals with similar ADBM than locations that were far apart. Our results suggest that (i) particular clones of S. avenae prefer to colonize wheat, and/or that (ii) particular clones of S. avenae perform better on wheat than other clones. It is unclear why M. dirhodum did not show any genetic structuring according to host type, but this species appears to engage in sexual reproduction much more frequently than S. avenae in southern England.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of semirigid dressings on below-knee amputations

BACKGROUND AND PURPOSE

The effect of using semirigid dressings (SRDs) on the residual limb of individuals who have had below-knee amputations as a consequence of peripheral vascular disease was investigated, with the primary question being: Does the time to readiness for prosthetic fitting for patients treated with the SRDs differ from that of patients treated with soft dressings?

SUBJECTS

Forty patients entered the study and were alternately assigned to one of two groups. Nineteen patients were assigned to the SRD group, and 21 patients were assigned to the soft dressing group.

METHODS

The time from surgery to readiness for prosthetic fitting was recorded for each patient. Kaplan-Meier survival curves were generated for each group, and the results were analyzed with the log-rank test.

RESULTS

There was a difference between the two curves, and an examination of the curves suggests that the expected time to readiness for prosthetic fitting for patients treated with the SRDs would be less than half that of patients treated with soft dressings.

CONCLUSION AND DISCUSSION

The results suggest that a patient may be ready for prosthetic fitting sooner if treated with SRDs instead of soft dressings.

Evaluation of transgenic canola plants under field conditions

Eleven independent transgenic canola (Brassica napus ssp. oleifera L. cv. Westar and Regent) lines were evaluated in the field. The plants carried a neomycin phosphotransferase (NPTII) gene for kanamycin resistance that was introduced via Agrobacterium-mediated transformation. NPTII enzyme assays, Southern blot by hybridizations and progeny analysis, confirmed the stable, heritable integration and expression of the introduced NPTII gene. A number of agronomic characteristics evaluated under field conditions, including maturity yield, and oil and protein content, were all statistically comparable between the transformed and nontransforemd platns. These results indicate that canola can be genetically engineered successfully, and that the Agrobacterium-based transformation system employed does not induced any adverse effects on the intrinsic agronomic and qualitative traits critical to the agricultural industry.

Perinatal mortality in Southland: an ongoing review

A review of Southland's perinatal mortality was undertaken from 1978 to 1983 and included 124 deaths with a postmortem rate of 90%. The perinatal mortality rate has continued to fall during this period, and has more than halved since 1971. Prematurity remains the single most important factor, and there are still a large number of avoidable deaths. Eighty percent of confinements are attended solely by general practitioner obstetricians.

Cat satellite DNA. Isolation using netropsin with CsCl gradients

The absence of centromeric bands in the karyotype of Felis catus is confirmed. It is also confirmed that no satellite band is visible in CsCl density gradients. However, a satellite is observed both by recentrifuging the fraction of the DNA that bands at high density in CsCl and by using netropsin to enhance the resolution of a CsCl gradient containing total F. catus DNA. The satellite, about 0.5% of total DNA, was isolated by repeated centrifugation in CsCl alone and in CsCl with netropsin. Netropsin was removed and a pure satellite DNA obtained. The reassociation kinetics (C0t1/2 less than 10(-3) M . s) show that the satellite is of the simple sequence type and hence a candidate for centromeric heterochromatin. Its cytological localisation awaits in situ hybridisation experiments.