Musashi2 sustains the mixed-lineage leukemia–driven stem cell regulatory program

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Abstract

Leukemia stem cells (LSCs) are found in most aggressive myeloid diseases and contribute to therapeutic resistance. Leukemia cells exhibit a dysregulated developmental program as the result of genetic and epigenetic alterations. Overexpression of the RNA-binding protein Musashi2 (MSI2) has been previously shown to predict poor survival in leukemia. Here, we demonstrated that conditional deletion of Msi2 in the hematopoietic compartment results in delayed leukemogenesis, reduced disease burden, and a loss of LSC function in a murine leukemia model. Gene expression profiling of these Msi2-deficient animals revealed a loss of the hematopoietic/leukemic stem cell self-renewal program and an increase in the differentiation program. In acute myeloid leukemia patients, the presence of a gene signature that was similar to that observed in Msi2-deficent murine LSCs correlated with improved survival. We determined that MSI2 directly maintains the mixed-lineage leukemia (MLL) self-renewal program by interacting with and retaining efficient translation of Hoxa9, Myc, and Ikzf2 mRNAs. Moreover, depletion of MLL target Ikzf2 in LSCs reduced colony formation, decreased proliferation, and increased apoptosis. Our data provide evidence that MSI2 controls efficient translation of the oncogenic LSC self-renewal program and suggest MSI2 as a potential therapeutic target for myeloid leukemia.

Authors

Sun-Mi Park, Mithat Gönen, Ly Vu, Gerard Minuesa, Patrick Tivnan, Trevor S. Barlowe, James Taggart, Yuheng Lu, Raquel P. Deering, Nir Hacohen, Maria E. Figueroa, Elisabeth Paietta, Hugo F. Fernandez, Martin S. Tallman, Ari Melnick, Ross Levine, Christina Leslie, Christopher J. Lengner, Michael G. Kharas

Inhibition of IRAK1/4 sensitizes T cell acute lymphoblastic leukemia to chemotherapies

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Abstract

Signaling via the MyD88/IRAK pathway in T cells is indispensable for cell survival; however, it is not known whether this pathway functions in the progression of T acute lymphoblastic leukemia (T-ALL). Here, we determined that compared with thymic and peripheral T cells, T-ALL cells from patients have elevated levels of IRAK1 and IRAK4 mRNA as well as increased total and phosphorylated protein. Targeted inhibition of IRAK1 and IRAK4, either with shRNA or with a pharmacological IRAK1/4 inhibitor, dramatically impeded proliferation of T-ALL cells isolated from patients and T-ALL cells in a murine leukemia model; however, IRAK1/4 inhibition had little effect on cell death. We screened several hundred FDA-approved compounds and identified a set of drugs that had enhanced cytotoxic activity when combined with IRAK inhibition. Administration of an IRAK1/4 inhibitor or IRAK knockdown in combination with either ABT-737 or vincristine markedly reduced leukemia burden in mice and prolonged survival. IRAK1/4 signaling activated the E3 ubiquitin ligase TRAF6, increasing K63-linked ubiquitination and enhancing stability of the antiapoptotic protein MCL1; therefore, IRAK inhibition reduced MCL1 stability and sensitized T-ALL to combination therapy. These studies demonstrate that IRAK1/4 signaling promotes T-ALL progression through stabilization of MCL1 and suggest that impeding this pathway has potential as a therapeutic strategy to enhance chemotherapeutic efficacy.

Authors

Zhaoyang Li, Kenisha Younger, Ronald Gartenhaus, Ann Mary Joseph, Fang Hu, Maria R. Baer, Patrick Brown, Eduardo Davila

Recombinant human CD19L-sTRAIL effectively targets B cell precursor acute lymphoblastic leukemia

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Abstract

Patients with B cell precursor acute lymphoblastic leukemia (BPL) respond well to chemotherapy at initial diagnosis; however, therapeutic options are limited for individuals with BPL who relapse. Almost all BPL cells express CD19, and we recently cloned the gene encoding a natural ligand of the human CD19 receptor (CD19L). We hypothesized that fusion of CD19L to the soluble extracellular domain of proapoptotic TNF-related apoptosis-inducing ligand (sTRAIL) would markedly enhance the potency of sTRAIL and specifically induce BPL cell apoptosis due to membrane anchoring of sTRAIL and simultaneous activation of the CD19 and TRAIL receptor (TRAIL-R) apoptosis signaling pathways. Here, we demonstrate that recombinant human CD19L-sTRAIL was substantially more potent than sTRAIL and induced apoptosis in primary leukemia cells taken directly from BPL patients. CD19L-sTRAIL effectively targeted and eliminated in vivo clonogenic BPL xenograft cells, even at femtomolar-picomolar concentrations. In mice, CD19L-sTRAIL exhibited a more favorable pharmacokinetic (PK) profile than sTRAIL and was nontoxic at doses ranging from 32 fmol/kg to 3.2 pmol/kg. CD19L-sTRAIL showed potent in vivo antileukemic activity in NOD/SCID mouse xenograft models of relapsed and chemotherapy-resistant BPL at nontoxic fmol/kg dose levels. Together, these results suggest that recombinant human CD19L-sTRAIL has clinical potential as a biotherapeutic agent against BPL.

Authors

Fatih M. Uckun, Dorothea E. Myers, Sanjive Qazi, Zahide Ozer, Rebecca Rose, Osmond J. D’Cruz, Hong Ma

F-box protein FBXW7 inhibits cancer metastasis in a non-cell-autonomous manner

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Abstract

The gene encoding F-box protein FBXW7 is frequently mutated in many human cancers. Although most previous studies have focused on the tumor-suppressive capacity of FBXW7 in tumor cells themselves, we determined that FBXW7 in the host microenvironment also suppresses cancer metastasis. Deletion of Fbxw7 in murine BM-derived stromal cells induced accumulation of NOTCH and consequent transcriptional activation of Ccl2. FBXW7-deficient mice exhibited increased serum levels of the chemokine CCL2, which resulted in the recruitment of both monocytic myeloid-derived suppressor cells and macrophages, thereby promoting metastatic tumor growth. Administration of a CCL2 receptor antagonist blocked the enhancement of metastasis in FBXW7-deficient mice. Furthermore, in human breast cancer patients, FBXW7 expression in peripheral blood was associated with serum CCL2 concentration and disease prognosis. Together, these results suggest that FBXW7 antagonizes cancer development in not only a cell-autonomous manner, but also a non-cell-autonomous manner, and that modulation of the FBXW7/NOTCH/CCL2 axis may provide a potential approach to suppression of cancer metastasis.

Authors

Kanae Yumimoto, Sayuri Akiyoshi, Hiroki Ueo, Yasuaki Sagara, Ichiro Onoyama, Hiroaki Ueo, Shinji Ohno, Masaki Mori, Koshi Mimori, Keiichi I. Nakayama

Proximity ligation assay evaluates IDH1^R132H presentation in gliomas

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Abstract

For a targeted cancer vaccine to be effective, the antigen of interest needs to be naturally processed and presented on MHC by the target cell or an antigen-presenting cell (APC) in the tumor stroma. The presence of these characteristics is often assumed based on animal models, evaluation of antigen-overexpressing APCs in vitro, or assays of material-consuming immune precipitation from fresh solid tissue. Here, we evaluated the use of an alternative approach that uses the proximity ligation assay (PLA) to identify the presentation of an MHC class II–restricted antigen in paraffin-embedded tissue sections from patients with brain tumors. This approach required a specific antibody directed against the epitope that was presented. We used an antibody that specifically binds an epitope of mutated isocitrate dehydrogenase type 1 (IDH1^R132H), which is frequently expressed in gliomas and other types of tumors. In situ PLA showed that the IDH1^R132H epitope colocalizes with MHC class II in IDH1^R132H-mutated glioma tissue. Moreover, PLA demonstrated colocalization between the class II epitope-containing melanoma antigen New York esophageal 1 and MHC class II. Collectively, our data suggest that PLA may be a useful tool to acquire information on whether an antigen is presented in situ, and this technique has potential to guide clinical studies that use antigen-specific cancer immunotherapy.

Authors

Lukas Bunse, Theresa Schumacher, Felix Sahm, Stefan Pusch, Iris Oezen, Katharina Rauschenbach, Marina Gonzalez, Gergely Solecki, Matthias Osswald, David Capper, Benedikt Wiestler, Frank Winkler, Christel Herold-Mende, Andreas von Deimling, Wolfgang Wick, Michael Platten

TALEN-mediated targeting of HPV oncogenes ameliorates HPV-related cervical malignancy

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Abstract

Persistent HPV infection is recognized as the main etiologic factor for cervical cancer. HPV expresses the oncoproteins E6 and E7, both of which play key roles in maintaining viral infection and promoting carcinogenesis. While siRNA-mediated targeting of E6 and E7 transcripts temporarily induces apoptosis in HPV-positive cells, it does not eliminate viral DNA within the host genome, which can harbor escape mutants. Here, we demonstrated that specifically targeting E6 and E7 within host DNA with transcription activator–like effector nucleases (TALENs) induces apoptosis, inhibits growth, and reduces tumorigenicity in HPV-positive cell lines. TALEN treatment efficiently disrupted E6 and E7 oncogenes, leading to the restoration of host tumor suppressors p53 and retinoblastoma 1 (RB1), which are targeted by E6 and E7, respectively. In the K14-HPV16 transgenic mouse model of HPV-driven neoplasms, direct cervical application of HPV16-E7–targeted TALENs effectively mutated the E7 oncogene, reduced viral DNA load, and restored RB1 function and downstream targets transcription factor E2F1 and cycling-dependent kinase 2 (CDK2), thereby reversing the malignant phenotype. Together, the results from our study suggest that TALENs have potential as a therapeutic strategy for HPV infection and related cervical malignancy.

Authors

Zheng Hu, Wencheng Ding, Da Zhu, Lan Yu, Xiaohui Jiang, Xiaoli Wang, Changlin Zhang, Liming Wang, Teng Ji, Dan Liu, Dan He, Xi Xia, Tao Zhu, Juncheng Wei, Peng Wu, Changyu Wang, Ling Xi, Qinglei Gao, Gang Chen, Rong Liu, Kezhen Li, Shuang Li, Shixuan Wang, Jianfeng Zhou, Ding Ma, Hui Wang

LMP1-deficient Epstein-Barr virus mutant requires T cells for lymphomagenesis

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Abstract

Epstein-Barr virus (EBV) infection transforms B cells in vitro and is associated with human B cell lymphomas. The major EBV oncoprotein, latent membrane protein 1 (LMP1), mimics constitutively active CD40 and is essential for outgrowth of EBV-transformed B cells in vitro; however, EBV-positive diffuse large B cell lymphomas and Burkitt lymphomas often express little or no LMP1. Thus, EBV may contribute to the development and maintenance of human lymphomas even in the absence of LMP1. Here, we found that i.p. injection of human cord blood mononuclear cells infected with a LMP1-deficient EBV into immunodeficient mice induces B cell lymphomas. In this model, lymphoma development required the presence of CD4⁺ T cells in cord blood and was inhibited by CD40-blocking Abs. In contrast, LMP1-deficient EBV established persistent latency but did not induce lymphomas when directly injected into mice engrafted with human fetal CD34⁺ cells and human thymus. WT EBV induced lymphomas in both mouse models and did not require coinjected T cells in the cord blood model. Together, these results demonstrate that LMP1 is not essential for EBV-induced lymphomas in vivo and suggest that T cells supply signals that substitute for LMP1 in EBV-positive B cell lymphomagenesis.

Authors

Shi-Dong Ma, Xuequn Xu, Julie Plowshay, Erik A. Ranheim, William J. Burlingham, Jeffrey L. Jensen, Fotis Asimakopoulos, Weihua Tang, Margaret L. Gulley, Ethel Cesarman, Jenny E. Gumperz, Shannon C. Kenney

Rare codons capacitate Kras-driven de novo tumorigenesis

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Abstract

The KRAS gene is commonly mutated in human cancers, rendering the encoded small GTPase constitutively active and oncogenic. This gene has the unusual feature of being enriched for rare codons, which limit protein expression. Here, to determine the effect of the rare codon bias of the KRAS gene on de novo tumorigenesis, we introduced synonymous mutations that converted rare codons into common codons in exon 3 of the Kras gene in mice. Compared with control animals, mice with at least 1 copy of this Kras^ex3op allele had fewer tumors following carcinogen exposure, and this allele was mutated less often, with weaker oncogenic mutations in these tumors. This reduction in tumorigenesis was attributable to higher expression of the Kras^ex3op allele, which induced growth arrest when oncogenic and exhibited tumor-suppressive activity when not mutated. Together, our data indicate that the inherent rare codon bias of KRAS plays an integral role in tumorigenesis.

Authors

Nicole L.K. Pershing, Benjamin L. Lampson, Jason A. Belsky, Erin Kaltenbrun, David M. MacAlpine, Christopher M. Counter

Preexisting oncogenic events impact trastuzumab sensitivity in ERBB2-amplified gastroesophageal adenocarcinoma

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Abstract

Patients with gastric and esophageal (GE) adenocarcinoma tumors in which the oncogene ERBB2 has been amplified are routinely treated with a combination of cytotoxic chemotherapy and the ERBB2-directed antibody trastuzumab; however, the addition of trastuzumab, even when tested in a selected biomarker-positive patient population, provides only modest survival gains. To investigate the potential reasons for the modest impact of ERBB2-directed therapies, we explored the hypothesis that secondary molecular features of ERBB2-amplified GE adenocarcinomas attenuate the impact of ERBB2 blockade. We analyzed genomic profiles of ERBB2-amplified GE adenocarcinomas and determined that the majority of ERBB2-amplified tumors harbor secondary oncogenic alterations that have the potential to be therapeutically targeted. These secondary events spanned genes involved in cell-cycle regulation as well as phosphatidylinositol-3 kinase and receptor tyrosine kinase signaling. Using ERBB2-amplified cell lines, we demonstrated that secondary oncogenic events could confer resistance to ERBB2-directed therapies. Moreover, this resistance could be overcome by targeting the secondary oncogene in conjunction with ERBB2-directed therapy. EGFR is commonly coamplified with ERBB2, and in the setting of ERBB2 amplification, higher EGFR expression appears to mark tumors with greater sensitivity to dual EGFR/ERBB2 kinase inhibitors. These data suggest that combination inhibitor strategies, guided by secondary events in ERBB2-amplified GE adenocarcinomas, should be evaluated in clinical trials.

Authors

Jihun Kim, Cameron Fox, Shouyong Peng, Mark Pusung, Eirini Pectasides, Eric Matthee, Yong Sang Hong, In-Gu Do, Jiryeon Jang, Aaron R. Thorner, Paul Van Hummelen, Anil K. Rustgi, Kwok-Kin Wong, Zhongren Zhou, Ping Tang, Kyoung-Mee Kim, Jeeyun Lee, Adam J. Bass

LYN-activating mutations mediate antiestrogen resistance in estrogen receptor–positive breast cancer

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Abstract

Estrogen receptor–positive (ER⁺) breast cancers adapt to hormone deprivation and become resistant to antiestrogen therapy. Here, we performed deep sequencing on ER⁺ tumors that remained highly proliferative after treatment with the aromatase inhibitor letrozole and identified a D189Y mutation in the inhibitory SH2 domain of the SRC family kinase (SFK) LYN. Evaluation of 463 breast tumors in The Cancer Genome Atlas revealed four LYN mutations, two of which affected the SH2 domain. In addition, LYN was upregulated in multiple ER⁺ breast cancer lines resistant to long-term estrogen deprivation (LTED). An RNAi-based kinome screen revealed that LYN is required for growth of ER⁺ LTED breast cancer cells. Kinase assays and immunoblot analyses of SRC substrates in transfected cells indicated that LYN^D189Y has higher catalytic activity than WT protein. Further, LYN^D189Y exhibited reduced phosphorylation at the inhibitory Y507 site compared with LYN^WT. Other SH2 domain LYN mutants, E159K and K209N, also exhibited higher catalytic activity and reduced inhibitory site phosphorylation. LYN^D189Y overexpression abrogated growth inhibition by fulvestrant and/or the PI3K inhibitor BKM120 in 3 ER⁺ breast cancer cell lines. The SFK inhibitor dasatinib enhanced the antitumor effect of BKM120 and fulvestrant against estrogen-deprived ER⁺ xenografts but not LYN^D189Y-expressing xenografts. These results suggest that LYN mutations mediate escape from antiestrogens in a subset of ER⁺ breast cancers.

Authors

Luis J. Schwarz, Emily M. Fox, Justin M. Balko, Joan T. Garrett, María Gabriela Kuba, Mónica Valeria Estrada, Ana María González-Angulo, Gordon B. Mills, Monica Red-Brewer, Ingrid A. Mayer, Vandana Abramson, Monica Rizzo, Mark C. Kelley, Ingrid M. Meszoely, Carlos L. Arteaga