bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inactivation of the Myc−Induced DNA Damage Response Promotes Lymphomagenesis and Treatment Resistance In Vivo.
Authors: Reimann Maurice , Loddenkemper Christoph , Rudolph Cornelia , Stein Harald , Schlegelberger Brigitte , Dorken Bernd , Schmitt Clemens A. 
Published: April 2020

Abstract
Activation of the DNA damage response (DDR) was recently claimed to serve as a critical anti−cancer barrier in early human tumorigenesis (Bartkova−J et al., and Gorgoulis−VG et al., Nature, 2005). As a consequence, deregulation of the DDR machinery may be required for tumor manifestation.
Myc activation is an oncogenic event frequently detected in malignant lymphomas. It is known that constitutive Myc expression provokes apoptosis via the ARF/p53 pathway as a cellular failsafe mechanism to counteract malignant transformation, but the potential role of Myc signaling to the DDR machinery, mediated via the Atm (ataxia telangiectasia mutated) kinase, as another putative tumor suppressive restraint remains still elusive.
Utilizing a tamoxifen−regulatable Myc system as well as RNA interference in vitro, we found in cell−based models that acute induction of Myc, associated with an increased production of reactive oxygen species (ROS) and marks of DNA strand breaks, leads to p53 activation which is mainly mediated by Atm and its upstream regulator PP5.
To further examine the role of Atm during Myc−driven tumorigenesis in vivo, we intercrossed Atm knockout mice to Eμ−myc transgenic mice that develop B−cell lymphomas. Lymphomas formed significantly faster in the absence of Atm, mostly due to a significant apoptotic defect in Atm−/− lymphomas compared to Atm+/+ derived (referred to as ‘control’) lymphomas.
In accordance with our in vitro findings, we detected significantly elevated levels of ROS−induced oxidative DNA damage and γ−H2AX foci in Myc−driven lymphomas. Importantly, constitutive expression of Myc selected against components of the Atm−governed DDR in a subset of control lymphomas. Like Atm deficiency, these lesions predetermined a poor response in subsequent cytotoxicity assays in vitro and anticancer therapy in vivo, since DNA damaging treatments also produce apoptosis via PP5/Atm.
The role for ROS as inducers of DNA damage during the execution of Myc−induced apoptosis was further substantiated by the finding that Eμ−myc transgenic mice continuously exposed to the ROS scavenger N−acetylcysteine (starting prenatally) developed lymphomas with significantly reduced levels of spontaneous apoptosis and with less marks of DNA damage (i.e. γ−H2AX foci), but a retained ability to respond to anticancer therapy in vitro and in vivo.
Hence, Atm eliminates pre−neoplastic lesions by converting oncogenic signaling into apoptosis, while selection for an attenuated Atm response permits lymphoma formation, and, in turn, has profound implications for reduced efficacy of DNA damaging therapies.
Evi-1 Is Essential for Expansion and Maintenance of Hematopoietic Stem Cells.
Authors: Goyama Susumu , Yamamoto Go , Sato Tomohiko , Ogawa Seishi , Chiba Shigeru , Kurokawa Mineo 
Published: April 2020

Abstract
The ecotropic viral integration site-1 (Evi-1) was first identified as a gene located at the integration site of an ecotropic retrovirus leading to murine myeloid leukemia. Since its identification, Evi-1 has been recognized as one of the dominant oncogenes associated with human myeloid leukemia and myelodysplastic syndrome. Evi-1 is a member of the SET/PR domain family of transcription factors and it contains two separated zinc-finger DNA-binding domains, which recognize cognate DNA sequences respectively. Recently, it was shown that Evi-1 is predominantly expressed in hematopoietic stem cells (HSCs), and HSC activity is significantly impaired in Evi-1-deficient embryos, which succumb to the multiple organ defects before birth. In order to investigate a role of Evi-1 in adult hematopoiesis, we generated the mutant mice harboring Cre recombinase recognition sites (loxP sites) flanking exon 4 of the Evi-1 gene (Evi1flox/flox), together with the mice in which the same region was completely deleted (Evi-1−/−). Evi-1−/− mice died around embryonic day 13–16. In Evi-1−/− embryos, Lineage−Sca1+cKit+ cells (LSK cells) and colony forming cells were severely reduced. Furthermore, Evi-1−/− fetal liver cells could not reconstitute hematopoiesis of sublethally irradiated mice in the transplantation experiments, indicating an apparent defect in hematopietic stem/progenitor cells. In contrast, more committed cells was unaffected in Evi-1−/− fetal liver. Then, we ablated Evi-1 by breeding Evi-1flox/flox mice with mice expressing Cre-recombinase under the control of the Tie2 promoter and enhancer, a marker of endothelial and hematopoietic stem cells. These mice virtually phenocopied Evi-1−/− mice, demonstrating that Evi-1 function is distinctly required in Tie2+ cells to establish HSCs. Next, we assessed the requirement of Evi-1 in adult hematopoiesis using an interferon (IFN) -inducible Mx-Cre gene-targeting method, in which floxed alleles can be effectively deleted in hematopoietic cells upon injection of IFN-inducer pIpC. Immediately upon injection of pIpC, platelet counts modestly declined in Evi-1flox/flox/Mx-Cre mice, while white blood cell counts or hemoglobin levels were not affected. Platelet recovery after 5FU-treatment is also delayed in Evi-1-deficient mice compared to the control mice. Furthermore, two weeks after pIpC infection, LSK cells in Evi-1-deficient mice decreased to about half the number of those in the control mice. By 10 weeks, however, LSK cells in these mice began to recover. At this time point, a majority of hematopoietic cells in the bone marrow retained the intact Evi-1 alleles, suggesting that HSCs can not maintain hematopoiesis in the absence of Evi-1 and are outcompeted by a fraction of HSCs that escaped Cre-mediated Evi-1 exicision. Together, these results show that Evi-1 plays an indispensable role not only in the establishment of HSCs during embryogenesis but also in the maintenance of HSCs in adults.
Ott1(Rbm15) Is Essential for Pre-B Differentiation and Has an Inhibitory Role in Myeloid and Megakaryocytic Lineages.
Authors: Raffel Glen D. , Mercher Thomas , Shigematsu Hirokazu , Williams Ifor R. , Cullen Dana E. , Akashi Koichi , Bernard Olivier A. , Gilliland D. Gary 
Published: April 2020

Abstract
OTT1(RBM15) is a putative transcriptional repressor related to the spen/Mint/SHARP family of proteins which was originally identified as the 5′ translocation partner of the MAL(MKL1) gene in t(1;22)(p13;q13) infant acute megakaryocytic leukemia (AMKL). OTT1 contains RNA recognition motifs (RRMs) and a transactivation/repression spen paralog and ortholog (SPOC) homology domain however no physiologic function has yet been attributed to it. To define the role of OTT1 in hematopoiesis and help gain an understanding of potential dysregulated pathways in t(1;22) AMKL, a conditional allele of Ott1 was generated in mice. Germline deletion of Ott1 was early embryonic lethal, however, deletion in adult mice utilizing the Mx1-Cre transgene affected multiple lineages within the hematopoietic compartment. Deletion of Ott1 caused a loss of peripheral B cells as a result of block in pro/pre-B differentiation. An expansion myeloid cells was seen in the spleen and bone marrow and increased numbers of myeloid CFU were detected in the bone marrow. Progenitor analysis demonstrated in increase in Lin−Sca-1+c-Kit+ (LSK) cells with an altered clonogenicity shifting towards granulocytic cell fate. Finally, increased numbers of megakaryocytes were found in the bone marrow and spleen suggesting a negative role for Ott1 in megakaryocytic proliferation/survival. These data indicate a requirement for Ott1 in B lymphopoiesis and inhibitory roles within the myeloid, megakaryocytic and progenitor compartments. Accordingly, the ability of Ott1 to affect hematopoietic cell fate and expansion within multiple lineages including megakaryocytes may underlie the mechanism of OTT1-MAL-mediated leukemogenesis.
Ubiquitin Ligase Component Fbw7 Regulates the Quiescence of Hematopoietic Stem Cells.
Authors: Matsuoka Sahoko , Oike Yuichi , Onoyama Ichiro , Takubo Keiyo , Ito Keisuke , Arai Fumio , Ikeda Yasuo , Nakayama Keiko , Nakayama Keiichi , Suda Toshio 
Published: April 2020

Abstract
Fbw7 is a SCF ubiquitin ligase component that catalyzes the ubiquitination of c-Myc, Cyclin E, and Notch. In several human cancer cell lines and primary cancer cells, Fbw7 is mutated and functions as a tumor suppressor gene. Previously we have reported that Fbw7-deficient mice died at embryonic day 10.5–11.5 with deficiencies in hematopoietic and vascular development, indicating that Fbw7 has a pivotal role in hematopoiesis (Tsunematsu R et al. J Biol Chem. 2004). Fbw7 is widely expressed in various hematopoietic lineages in BM of adult mice, but little has been known about the function of Fbw7 in hematopoiesis. To assess the requirement of Fbw7 in adult hematopoietic cells, we generated Fbw7-deficient mice by conditional gene targeting. Fbw7 was conditionally deleted from Mx-1-Cre;Fbw7fl/− adult mice by injection of pIpC over 1 week to induce Cre expression. We examined Fbw7fl/+ littermates as a control. We found progressive pancytopenia in Fbw7-deficient mice. Furthermore, most Fbw7-deficient mice developed leukemia (mainly ALL) within 3 months after pIpC treatment, suggesting that Fbw7 is essential to maintain normal hematopoiesis and loss of Fbw7 accelerates leukemogenesis. The portion of Fbw7-deficient Lin−Sca-1+c-Kit+CD34− hematopoietic stem cells (HSCs) in the G0 phase was 2.5-fold decreased and the frequency of cell division of Fbw7-deficient HSCs markedly increased in culture. These data suggest that Fbw7 promotes quiescence of HSCs. To examine the function of Fbw7-deficient HSCs, we transplanted 1500 Lin−Sca-1+cKit+ BM cells from Fbw7-dificient mice or littermate controls into lethally irradiated recipient mice with 4×105 normal BM mononuclear cells. In the result, Fbw7-deficient HSCs are impaired in long-term repopulating activity and multipotency. It has been reported that c-Myc controls the self-renewal activity of HSCs through the cell adhesion to the osteoblastic niche (Wilson A et al. Genes Dev. 2004). We found that c-Myc is significantly accumulated in Fbw7-deficient Lin−Sca-1+cKit+ BM cells, suggesting that HSCs leave the niche and show the active cell cycling. We propose that a ubiquitin ligase, Fbw7 is a key mediator of HSC quiescence and self renewal capacity.
A New Prognostic Index (MIPI) for Patients with Advanced Stage Mantle Cell Lymphoma.
Authors: Hoster Eva , Dreyling Martin , Unterhalt Michael , Hasford Joerg , Hiddemann Wolfgang 
Published: April 2020

Abstract
On behalf of the German Low Grade Lymphoma Study Group (GLSG) and the European MCL Network.
Background: There is no generally established prognostic classification system for patients with mantle cell lymphoma (MCL), as the International Prognostic Index (IPI) and the Follicular Lymphoma International Prognostic Index (FLIPI) have been developed based on data of patients with diffuse large cell and follicular lymphoma, respectively.
Methods: The data of 455 patients with advanced stage MCL treated first-line within three clinical trials of GLSG and European MCL Network have been analyzed to clarify the prognostic relevance of IPI and FLIPI and to derive a new prognostic index of overall survival (OS). Age, sex, ECOG performance status, Ann Arbor stage, B-symptoms, number of extranodal sites, number of involved nodal areas, tumor size, serum LDH activity, WBC count, platelet count, hemoglobin, albumin, β2-microglobulin and cell proliferation (Ki-67) were considered as candidate prognostic factors. Statistical methods included Kaplan-Meier estimates and logrank test for the validation of IPI and FLIPI and multiple Cox regression with backward variable selection for the derivation of the new prognostic index.
Results: IPI showed a significant impact on OS, but low-intermediate and high-intermediate risk groups comprised more than two thirds of the patients and were not well separated. According to the FLIPI, only 6% of the patients were classified as low risk and almost two thirds of the patients as high risk, and low and intermediate risk groups were not separated. Four of the candidate prognostic factors were independently associated with OS, namely age, ECOG performance status, LDH and WBC count. The relative risk was 1.42 (95% confidence interval 1.18 to 1.72, p = 0.0002) for an increased age by ten years, 2.01 (1.19 to 3.39, p = 0.0088) for an ECOG greater than one, 1.51 (1.13 to 2.02, p = 0.0059) for a 2 fold elevation of LDH and 2.56 (1.66 to 3.95, p &lt; 0.0001) for a 10 fold increase of WBC count. According to these four parameters, patients could be classified into a low risk (44% of the patients, median OS not reached), an intermediate risk (35%, median OS 51 months), and a high risk group (21%, median OS 29 months).
Discussion: IPI and FLIPI showed only modest prognostic discrimination in our external validation data set of patients with advanced stage MCL. In contrast, age, ECOG performance status, LDH and WBC were identified as independent prognostic factors of OS, and three reasonably sized and well separated risk groups were defined. With four clinical prognostic factors readily determined in clinical routine, our new prognostic index (MIPI) is superior to the IPI. Bootstrap validation confirmed the separation of three risk groups, but external validation is still needed. The MIPI may prove to be an important tool to facilitate risk-adapted treatment decisions for patients with advanced stage MCL.
A New Target in Multiple Myeloma: Inhibition of Notch Pathway Induces Apoptosis and Enhances Drug Sensitivity of Myeloma Cells In Vitro and In Vivo.
Authors: Nefedova Yulia , Verali Krista , Sullivan Daniel M. , Dalton William S. , Gabrilovich Dmitry I. 
Published: April 2020

Abstract
Bone marrow (BM) microenvironment and particularly BM stromal cells play a critical role in de novo drug resistance of multiple myeloma (MM) cells. BM stromal cells express Notch ligands and activate Notch signaling in MM cells. We have previously demonstrated that Notch signaling is one of the major mechanisms of BM stroma mediated MM cell protection from chemotherapeutic drugs. Here we investigated whether the pharmacological inhibition of Notch signaling with γ-secretase inhibitor (GSI) could affect viability of MM cells and overcome BM stroma mediated resistance of MM cells to chemotherapy. GSI (6–8 μM) induced apoptosis of MM cells cultured in suspension or on monolayer of BM stroma via specific inhibition of Notch signaling. The effect of GSI was evaluated in four different MM cell lines and primary MM cells isolated from BM of four patients with MM. Treatment with GSI alone significantly reduced the viability of MM cells with IC50 almost 5-fold lower than that for peripheral blood mononuclear cells or BM cells from healthy donors. In addition, treatment of MM cells with GSI reversed BM stroma mediated protection of MM cells from drug-induced apoptosis. This effect of GSI was associated by dramatic up-regulation of pro-apoptotic protein NOXA and down-regulation of anti-apoptotic proteins bcl-xL, bcl-2, and Akt. Inhibition of NOXA with siRNA canceled the cytotoxic effect of GSI on MM cells indicating that NOXA could mediate the direct effect of GSI on MM cells. To test the effect of GSI on MM cells in vivo we used SCID/NOD mouse model. Mice were injected s.c. with human MM RPMI-8226 cells. These cells express both Notch ligands and Notch receptors so Notch signaling is activated by interaction between MM cells themselves. Tumor became visible in ~3 weeks after inoculation and grew as a solid tumor which allowed easily monitoring tumor size. Mice were treated with doxorubicin (1.5 mg/kg, i.p., once a 4 days, 3 times), GSI (5mg/kg/day i.p. for 14 days), combinations of doxorubicin and GSI, or vehicle control (PBS). Tumor size was constantly monitored during treatment and 3 weeks after the treatment. Treatment with doxorubicin and GSI alone resulted in moderate decreased in tumor burden as compared with control group. In contrast, combination of GSI and doxorubicin induced dramatic antitumor effect. Thus, our study, for the first time, demonstrates that inhibition of Notch signaling with GSI can be a new promising approach for therapeutic intervention in MM.
Aurora Kinases as Therapeutic Targets in Multiple Myeloma.
Authors: Reiman Tony , Evans Robert P. , Naber Claudia , Steffler Tara , Keats Jonathan J. , Perry Troy , Maxwell Christopher A. , Chau Heidi , Belch Andrew R. , Pilarski Linda M. 
Published: April 2020

Abstract
BACKGROUND: We have previously found that in multiple myeloma there is amplification of the centrosome, the organelle that nucleates the mitotic spindle. We have reported that RHAMM is a component of the centrosome which interacts with TPX2, the protein that targets Aurora A kinase to the mitotic spindle. We have also shown that RHAMM expression and alternative splicing in myeloma correlate with centrosome amplification, aggressive disease and poor survival. These findings led us to speculate that Aurora A and possibly other Aurora kinases are potential therapeutic targets in myeloma.
METHODS: We examined the expression of Aurora A, B and C kinases in 5 myeloma cell lines and autoMACS-purified CD138+ myeloma bone marrow plasma cells from 20 patients. We assessed the anti-proliferative and pro-apoptotic effects of Aurora A knockdown in myeloma cell lines with RNA interference. We investigated the anti-myeloma activity of two potent, selective Aurora kinase inhibitors, VE-465 (Merck/Vertex) and AZD1152 (AstraZeneca), in 5 myeloma cell lines, in CD138+ bone marrow plasma cells from 2 myeloma patients, and in a NOD/SCID murine xenograft model.
RESULTS: Aurora A, B and C kinases are ubiquitously expressed in both myeloma cell lines and myeloma bone marrow plasma cells. Expression levels vary among patients. Aurora A and B are expressed in myeloma plasma cells at levels comparable to that seen in the CD138- cells from the same marrow sample, and comparable to the levels seen in normal marrow from control individuals. Aurora C, while expressed at low levels, is consistently ectopically overexpressed in myeloma plasma cells relative to coexisting CD138- cells and normal marrow. In myeloma cell lines, Aurora A knockdown with RNA interference induces apoptosis and cell killing. In all five myeloma cell lines tested, and in myeloma bone marrow plasma cells from two patients, both VE-465 and AZD1152 induce apoptosis and myeloma cell killing at nanomolar concentrations, to varying degrees (20–80% reduction in cell viability). VE-465 is known to inhibit all three Aurora kinases with comparable specificity, while AZD1152 is known to inhibit Aurora B and C more selectively than Aurora A. Despite these differences in activity, both compounds have comparable pre-clinical efficacy against myeloma. Myeloma cell lines treated with either agent demonstrate a phenotype consistent with target inhibition. Both drugs show additive effects on killing of cell lines and primary myeloma cells when combined with dexamethasone, even in dexamethasone-resistant cells. Anti-myeloma activity was seen with single agent Aurora kinase inhibition in the murine model, at well tolerated doses.
CONCLUSIONS: Aurora kinases are potential therapeutic targets in myeloma. Aurora kinase inhibitors comprise an emerging class of anti-cancer drug therapy that deserves further evaluation for myeloma patients.
Lenalidomide Up-Regulates SPARC and Inhibits In Vitro Growth of the Malignant Clone in Myelodysplastic Syndrome Patients with 5q Deletion.
Authors: Pellagatti Andrea , Jädersten Martin , Forsblom Ann-Mari , Cattan Helen , Christensson Birger , Emanuelsson Emma K. , Merup Mats , Nilsson Lars , Samuelsson Jan , Sander Birgitta , Wainscoat James S. , Boultwood Jacqueline , Hellström-Lindberg Eva 
Published: April 2020

Abstract
The immunomodulatory drug lenalidomide induces cytogenetic remissions in 75% of patients with myelodysplastic syndrome (MDS) and del(5)(q31) through unknown mechanisms. We investigated the in vitro effects of lenalidomide on growth and maturation in differentiating erythroblasts from MDS patients with del(5)(q31) (n=13) and from healthy controls (n=10). Lenalidomide selectively inhibited growth of del(5q) erythroblasts, while not affecting normal cells, including cytogenetically normal cells from MDS del(5q) patients. The inhibitory effect was more pronounced in erythroid than in myeloid cells. In order to gain insight into the mode of action of lenalidomide and to identify the molecular targets of this drug, we have investigated the gene expression profiles of the lenalidomide-treated and untreated intermediate erythroblasts from MDS del(5q) patients (n=9) and from healthy controls (n=8). GeneChip Human Genome U133 Plus 2.0 arrays (Affymetrix), covering over 47,000 transcripts representing 39,000 human genes, were used. Treatment with lenalidomide significantly influenced the pattern of gene expression in del(5q) intermediate erythroblasts, with up-regulation of VSIG4, PPIC, TPBG, and SPARC in all samples, and down-regulation of many genes involved in erythropoiesis, including HBA2, GYPA, and KLF1, in most samples. Up-regulation of SPARC (median 4.4-fold, range 2.4–9.5) is of particular interest since SPARC, a gene with known tumor suppressor functions, is both anti-proliferative and anti-angiogenic, and is located at 5q31–q32, within the commonly deleted region in MDS 5q- syndrome. Activin A was one of the most significant differentially expressed genes between lenalidomide-treated cells of MDS del(5q) patients and healthy controls. Activin A is a member of the transforming growth factor-beta superfamily, with pleiotropic functions including apoptosis of hemopoietic cells. We conclude that lenalidomide specifically inhibits growth of del(5q) erythroid progenitors, while not affecting cytogenetically normal cells. These novel findings suggest that up-regulation of SPARC and Activin A may underlie the potent effects of lenalidomide, in particular growth inhibition and anti-angiogenesis, in MDS with del(5)(q31). The localization of the SPARC gene to the CDR of the 5q- syndrome is intriguing and, in relation to the findings of the present study, we suggest that SPARC may well play a role in the molecular pathogenesis of the 5q- syndrome.