Hot off the presses! Sep 13 Cancer Cell

The Sep 13 issue of the Cancer Cell is now up on Pubget (About Cancer Cell): if you're at a subscribing institution, just click the link in the latest link at the home page. (Note you'll only be able to get all the PDFs in the issue if your institution subscribes to Pubget.)

Latest Articles Include:

• Cancer Biomarkers: Closer to Delivering on their Promise
  - Cancer Cell 20(3):279-280 (2011)
  Taguchi et al. describe, in this issue of Cancer Cell, a quantitative comparative biomarker discovery approach that integrates animal lung cancer models with validation in well-controlled human clinical study sets. This approach overcomes many of the major barriers that have held back the field of cancer biomarkers in the past.
• Ras, ROS and Proteotoxic Stress: A Delicate Balance
  - Cancer Cell 20(3):281-282 (2011)
  Ras-deregulated cells require reactive oxygen species for proliferation. They survive the resultant proteotoxic stress by maintaining sufficient levels of reduced glutathione and optimally functioning stress response machinery. In this issue of Cancer Cell, De Raedt et al. identify a novel strategy that utilizes this dependency to cause cell death.
• DePICTing p53 Activation: A New Nucleolar Link to Cancer
  - Cancer Cell 20(3):283-284 (2011)
  p53 activation by ribosomal biogenesis stress is important for tumor suppression. In the August issue of Nature Medicine, Sasaki et al. identify PICT1 as a regulator of this process. PICT1 sequesters ribosomal protein RPL11 in the nucleolus, attenuating p53 induction. Excessive PICT1 may dampen the p53 response and promote cancer.
• Tissue States Provide Novel Insights into Attributes that Drive Metastasis
  - Cancer Cell 20(3):285-286 (2011)
  Recently, in Nature Medicine, Schedin and colleagues define attributes within the involuting postpartum breast microenvironment that promote breast cancer metastasis. Cell invasiveness is controlled by a positive feedback loop involving COX-2 and fibrillar collagen. NSAIDs suppress tumor progression during postpartum involution, potentially providing effective agents for intervention in pregnant women.
• Short Hairpin RNA Screen Reveals Bromodomain Proteins as Novel Targets in Acute Myeloid Leukemia
  - Cancer Cell 20(3):287-288 (2011)
  Targeting chromatin regulators for the treatment of malignancies has shown great promise, but also revealed significant challenges. By employing an elegant shRNA screen and a selective pharmacological inhibitor, a recent study published in Nature establishes the bromodomain protein Brd4 as novel target in acute myeloid leukemia (AML).
• Lung Cancer Signatures in Plasma Based on Proteome Profiling of Mouse Tumor Models
  - Cancer Cell 20(3):289-299 (2011)
  We investigated the potential of in-depth quantitative proteomics to reveal plasma protein signatures that reflect lung tumor biology. We compared plasma protein profiles of four mouse models of lung cancer with profiles of models of pancreatic, ovarian, colon, prostate, and breast cancer and two models of inflammation. A protein signature for Titf1/Nkx2-1, a known lineage-survival oncogene in lung cancer, was found in plasmas of mouse models of lung adenocarcinoma. An EGFR signature was found in plasma of an EGFR mutant model, and a distinct plasma signature related to neuroendocrine development was uncovered in the small-cell lung cancer model. We demonstrate relevance to human lung cancer of the protein signatures identified on the basis of mouse models.
• Tumor Entrained Neutrophils Inhibit Seeding in the Premetastatic Lung
  - Cancer Cell 20(3):300-314 (2011)
  Primary tumors have been shown to prepare distal organs for later colonization of metastatic cells by stimulating organ-specific infiltration of bone marrow derived cells. Here we demonstrate that neutrophils accumulate in the lung prior to the arrival of metastatic cells in mouse models of breast cancer. Tumor-entrained neutrophils (TENs) inhibit metastatic seeding in the lungs by generating H2O2 and tumor secreted CCL2 is a critical mediator of optimal antimetastatic entrainment of G-CSF-stimulated neutrophils. TENs are present in the peripheral blood of breast cancer patients prior to surgical resection but not in healthy individuals. Thus, whereas tumor-secreted factors contribute to tumor progression at the primary site, they concomitantly induce a neutrophil-mediated inhibitory process at the metastatic site.
• The Glycolytic Shift in Fumarate-Hydratase-Deficient Kidney Cancer Lowers AMPK Levels, Increases Anabolic Propensities and Lowers Cellular Iron Levels
  - Cancer Cell 20(3):315-327 (2011)
  Inactivation of the TCA cycle enzyme, fumarate hydratase (FH), drives a metabolic shift to aerobic glycolysis in FH-deficient kidney tumors and cell lines from patients with hereditary leiomyomatosis renal cell cancer (HLRCC), resulting in decreased levels of AMP-activated kinase (AMPK) and p53 tumor suppressor, and activation of the anabolic factors, acetyl-CoA carboxylase and ribosomal protein S6. Reduced AMPK levels lead to diminished expression of the DMT1 iron transporter, and the resulting cytosolic iron deficiency activates the iron regulatory proteins, IRP1 and IRP2, and increases expression of the hypoxia inducible factor HIF-1α, but not HIF-2α. Silencing of HIF-1α or activation of AMPK diminishes invasive activities, indicating that alterations of HIF-1α and AMPK contribute to the oncogenic growth of FH-deficient cells.
• Asymmetry-Defective Oligodendrocyte Progenitors Are Glioma Precursors
  - Cancer Cell 20(3):328-340 (2011)
  Postnatal oligodendrocyte progenitor cells (OPC) self-renew, generate mature oligodendrocytes, and are a cellular origin of oligodendrogliomas. We show that the proteoglycan NG2 segregates asymmetrically during mitosis to generate OPC cells of distinct fate. NG2 is required for asymmetric segregation of EGFR to the NG2+ progeny, which consequently activates EGFR and undergoes EGF-dependent proliferation and self-renewal. In contrast, the NG2− progeny differentiates. In a mouse model, decreased NG2 asymmetry coincides with premalignant, abnormal self-renewal rather than differentiation and with tumor-initiating potential. Asymmetric division of human NG2+ cells is prevalent in non-neoplastic tissue but is decreased in oligodendrogliomas. Regulators of asymmetric cell division are misexpressed in low-grade oligodendrogliomas. Our results identify loss of asymmetric division associated with the neoplastic transformation of OPC.
• BikDD Eliminates Breast Cancer Initiating Cells and Synergizes with Lapatinib for Breast Cancer Treatment
  - Cancer Cell 20(3):341-356 (2011)
  Breast cancer initiating cells (BCICs), which can fully recapitulate the tumor origin and are often resistant to chemo- and radiotherapy, are currently considered as a major obstacle for breast cancer treatment. Here, we show that BIKDD, a constitutively active mutant form of proapoptotic gene, BIK, effectively induces apoptosis of breast cancer cells and synergizes with lapatinib. Most importantly, BikDD significantly reduces BCICs through co-antagonism of its binding partners Bcl-2, Bcl-xL, and Mcl-1, suggesting a potential therapeutic strategy targeting BCICs. Furthermore, we developed a cancer-specific targeting approach for breast cancer that selectively expresses BikDD in breast cancer cells including BCICs, and demonstrated its potent antitumor activity and synergism with lapatinib in vitro and in vivo.
• Rho Kinase Regulates the Survival and Transformation of Cells Bearing Oncogenic Forms of KIT, FLT3, and BCR-ABL
  - Cancer Cell 20(3):357-369 (2011)
  We show constitutive activation of Rho kinase (ROCK) in cells bearing oncogenic forms of KIT, FLT3, and BCR-ABL, which is dependent on PI3K and Rho GTPase. Genetic or pharmacologic inhibition of ROCK in oncogene-bearing cells impaired their growth as well as the growth of acute myeloid leukemia patient-derived blasts and prolonged the life span of mice bearing myeloproliferative disease. Downstream from ROCK, rapid dephosphorylation or loss of expression of myosin light chain resulted in enhanced apoptosis, reduced growth, and loss of actin polymerization in oncogene-bearing cells leading to significantly prolonged life span of leukemic mice. In summary we describe a pathway involving PI3K/Rho/ROCK/MLC that may contribute to myeloproliferative disease and/or acute myeloid leukemia in humans.
• Mesenchymal Stem Cells Induce Resistance to Chemotherapy through the Release of Platinum-Induced Fatty Acids
  - Cancer Cell 20(3):370-383 (2011)
  The development of resistance to chemotherapy is a major obstacle for lasting effective treatment of cancer. Here, we demonstrate that endogenous mesenchymal stem cells (MSCs) become activated during treatment with platinum analogs and secrete factors that protect tumor cells against a range of chemotherapeutics. Through a metabolomics approach, we identified two distinct platinum-induced polyunsaturated fatty acids (PIFAs), 12-oxo-5,8,10-heptadecatrienoic acid (KHT) and hexadeca-4,7,10,13-tetraenoic acid (16:4(n-3)), that in minute quantities induce resistance to a broad spectrum of chemotherapeutic agents. Interestingly, blocking central enzymes involved in the production of these PIFAs (cyclooxygenase-1 and thromboxane synthase) prevents MSC-induced resistance. Our findings show that MSCs are potent mediators of resistance to chemotherapy and reveal targets to enhance chemotherapy efficacy in patients.
• An Integrated In Vitro and In Vivo High-Throughput Screen Identifies Treatment Leads for Ependymoma
  - Cancer Cell 20(3):384-399 (2011)
  Using a mouse model of ependymoma—a chemoresistant brain tumor—we combined multicell high-throughput screening (HTS), kinome-wide binding assays, and in vivo efficacy studies, to identify potential treatments with predicted toxicity against neural stem cells (NSC). We identified kinases within the insulin signaling pathway and centrosome cycle as regulators of ependymoma cell proliferation, and their corresponding inhibitors as potential therapies. FDA approved drugs not currently used to treat ependymoma were also identified that posses selective toxicity against ependymoma cells relative to normal NSCs both in vitro and in vivo, e.g., 5-fluorouracil. Our comprehensive approach advances understanding of the biology and treatment of ependymoma including the discovery of several treatment leads for immediate clinical translation.
• Exploiting Cancer Cell Vulnerabilities to Develop a Combination Therapy for Ras-Driven Tumors
  - Cancer Cell 20(3):400-413 (2011)
  Ras-driven tumors are often refractory to conventional therapies. Here we identify a promising targeted therapeutic strategy for two Ras-driven cancers: Nf1-deficient malignancies and Kras/p53 mutant lung cancer. We show that agents that enhance proteotoxic stress, including the HSP90 inhibitor IPI-504, induce tumor regression in aggressive mouse models, but only when combined with rapamycin. These agents synergize by promoting irresolvable ER stress, resulting in catastrophic ER and mitochondrial damage. This process is fueled by oxidative stress, which is caused by IPI-504-dependent production of reactive oxygen species, and the rapamycin-dependent suppression of glutathione, an important endogenous antioxidant. Notably, the mechanism by which these agents cooperate reveals a therapeutic paradigm that can be expanded to develop additional combinations.