Table of Contents

Volume 2, Issue 3

  May/June 2003

  Pages 165 - 265

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 Issue Catalogue (MARC XML)

INFERENCES AND HYPOTHESES

Open Access Article

Hsp90 and Chromatin: Where is the Link?

Todd A. Sangster, Christine Queitsch and Susan Lindquist
Pages 165 - 167
http://dx.doi.org/10.4161/cc.2.3.400
Abstract | PDF

No abstract available.




EXTRA VIEWS

Open Access Article

PARC: A Potential Target for Cancer Therapy

Anatoly Y. Nikolaev and Wei Gu
Pages 168 - 170
http://dx.doi.org/10.4161/cc.2.3.346
Abstract | PDF

no abstract available

Open Access Article

DNA Building Blocks at the Foundation of Better Survival

Andrei Chabes and Lars Thelander
Pages 171 - 172
http://dx.doi.org/10.4161/cc.2.3.354
Abstract | PDF

No abstract available.

Open Access Article

The Spindle-Associated Transmembrane Protein Axs Identifies a New Family of Transmembrane Proteins in Eukaryotes

Joseph Kramer and R. Scott Hawley
Pages 173 - 175
http://dx.doi.org/10.4161/cc.2.3.368
Abstract | PDF

Axs mutations disrupt both the progression of the meiotic cell cycle and meiotic chromosome segregation in Drosophila. Axs protein co-localizes with endoplasmic reticulum components and is present within a novel structure ensheathing the meiotic spindle. We show that Axs encodes the founding member of a eukaryotic family of trans-membrane proteins.

Open Access Article

Altered mRNA Translation: Possible Mechanism for CML Disease Progression

Danilo Perrotti, Rossanna Trotta and Bruno Calabretta
Pages 176 - 179
http://dx.doi.org/10.4161/cc.2.3.374
Abstract | PDF

No abstract available.

Open Access Article

Direct Regulation of RNA Polymerase III Transcription by RB, p53 and c-Myc

Zoë A. Felton-Edkins, Niall S. Kenneth, Timothy R. P. Brown, Nicole L. Daly, Natividad Gomez-Roman, Carla Grandori, Robert N. Eisenman and Robert J. White
Pages 180 - 183
http://dx.doi.org/10.4161/cc.2.3.375
Abstract | PDF

The synthesis of tRNA and 5S rRNA by RNA polymerase (pol) III is cell cycle regulated in higher organisms. Overexpression of pol III products is a general feature of transformed cells. These observations may be explained by the fact that a pol III-specific transcription factor, TFIIIB, is strongly regulated by the tumour suppressors RB and p53, as well as the proto-oncogene product c-Myc. RB and p53 repress TFIIIB, but this restraint can be lost in tumours through a variety of mechanisms. In contrast, c-Myc binds and activates TFIIIB, causing potent induction of pol III transcription. Using chromatin immunoprecipitation and RNA interference, we show that c-Myc interacts with tRNA and 5S rRNA genes in transformed cervical cells, stimulating their expression. Availability of pol III products may be an important determinant of a cell's capacity to grow. The ability to regulate pol III output may therefore be integral to the growth control functions of RB, p53 and c-Myc.

Open Access Article

Coordination of S-Phase Events and Genome Stability

Xiaofen Ye and Peter D. Adams
Pages 184 - 186
http://dx.doi.org/10.4161/cc.2.3.389
Abstract | PDF

No Abstract Available

Open Access Article

The ATR-Independent DNA Replication Checkpoint

Eric J. Brown
Pages 187 - 188
http://dx.doi.org/10.4161/cc.2.3.395
Abstract | PDF

No Abstract Available.

Open Access Article

Gleevec Resistance: Lessons for Target-Directed Drug Development

George Q. Daley
Pages 189 - 190
http://dx.doi.org/10.4161/cc.2.3.401
Abstract | PDF

No abstract available.

Open Access Article

A Novel Role for the Hypoxia Inducible Transcription Factor HIF-1alpha: Critical Regulation of Inflammatory Cell Function

Thorsten Cramer and Randall S. Johnson
Pages 191 - 192
http://dx.doi.org/10.4161/cc.2.3.402
Abstract | PDF

No abstract available.

Open Access Article

Clinical Impact of ATR Checkpoint Signalling Failure in Humans

Mark O’Driscoll and Penny A. Jeggo
Pages 193 - 194
http://dx.doi.org/10.4161/cc.2.3.404
Abstract | PDF

No abstract available.




PERSPECTIVES

Open Access Article

Hedgehog Signaling: Progenitor Phenotype in Small-Cell Lung Cancer

D. Neil Watkins, David M. Berman and Stephen B. Baylin
Pages 195 - 197
http://dx.doi.org/10.4161/cc.2.3.378
Abstract | PDF

Recently, we have shown that small cell lung cancer (SCLC) is dependent on activation of the Hedgehog signaling, an embryonic pathway implicated in development, morphogenesis and the regulation of stem cell fates. These findings form the framework for an emerging view of cancer as a process of aberrant organogenesis in which progenitor/ stem cells escape dependence on niche signaling through mutation in genes such as Ptch, or through persistent activation of progenitor cell pathways. Interestingly, the normally quiescent airway epithelial compartment uses the Hh pathway to repopulate itself when challenged by injury. How Hh signaling works to promote the malignant phenotype promises to be as important biologically as the promise of Hh pathway inhibitors are clinically.

Key words

Cancer, Hedgehog signaling, Morphogenesis, Stem cells

Open Access Article

Role of JNK in Tumor Development


Pages 198 - 200
http://dx.doi.org/10.4161/cc.2.3.388
Abstract | PDF

The c-Jun NH2-terminal kinase (JNK) is implicated in oncogenic transformation. However, studies of the effect of Jnk gene disruption on Ras-induced transformation of murine fibroblasts indicate that JNK may act as a suppressor of Ras transformation and that the JNK signaling pathway contributes to the apoptotic elimination of transformed cells in vivo. The conclusion that JNK can act as a tumor suppressor is consistent with the presence of loss-of-function mutations in JNK pathway components (Jnk3 and Mkk4) in human tumors. Nevertheless, JNK can also contribute to the proliferation and survival responses of some tumors. A key question that remains unresolved concerns the genetic and mechanistic basis for these different roles of JNK in tumors. Indeed, an understanding of this question will be required for the rational use of small molecule inhibitors of JNK for tumor therapy.




REVIEW

Open Access Article

Multistep Carcinogenesis: A Chain Reaction of Aneuploidizations

Peter Duesberg and Ruhong Li
Pages 201 - 209
http://dx.doi.org/10.4161/cc.2.3.382
Abstract | PDF

Carcinogenesis is a multistep process in which new, parasitic and polymorphic cancer cells evolve from a single, normal diploid cell. This normal cell is converted to a prospective cancer cell, alias "initiated", either by a carcinogen or spontaneously. The initiated cell typically does not have a new distinctive phenotype yet, but evolves spontaneously—over months to decades—to a clinical cancer. The cells of a primary cancer also evolve spontaneously towards more and more malignant phenotypes. The outstanding genotype of initiated and cancer cells is aneuploidy, an abnormal balance of chromosomes, which increases and varies in proportion with malignancy. The driving force of the spontaneous evolution of initiated and cancerous cells to ever more abnormal phenotypes is said to be their "genetic instability". However, since neither the instability of cancer phenotypes nor the characteristically slow kinetics of carcinogenesis are compatible with gene mutation, we propose here that the driving force of carcinogenesis is the inherent instability of aneuploid karyotypes. Aneuploidy renders chromosome structure and segregation error-prone, because it unbalances mitosis proteins and the many teams of enzymes that synthesize and maintain chromosomes. Thus, carcinogenesis is initiated by a random aneuploidy, which is induced either by a carcinogen or spontaneously. The resulting karyotype instability sets off a chain reaction of aneuploidizations, which generate ever more abnormal and eventually cancer-specific combinations and rearrangements of chromosomes. According to this hypothesis the many abnormal phenotypes of cancer are generated by abnormal dosages of thousands of aneuploid, but un-mutated genes.




REVIEW: SPOTLIGHT ON CARDIOLOGY

Open Access Article

Break the Cycle: The Role of Cell-Cycle Modulation in the Prevention of Vasculoproliferative Diseases

J.E. Ferguson and Cam Patterson
Pages 210 - 218
http://dx.doi.org/10.4161/cc.2.3.366
Abstract | PDF

Atherosclerosis is a major health problem in the western world, and the effectiveness of interventional therapeutic modalities for symptomatic atherosclerotic lesions is limited by vessel restenosis. Proliferation and migration of smooth muscle cells (SMCs) play a central role in post-interventional restenosis. Accordingly, many therapeutic approaches attempt to inhibit SMC proliferation. As the cell cycle is a final common pathway in SMC proliferation, proteins of the cell cycle have emerged as logical targets for the treatment and prevention of restenotic lesions. In this review we discuss current approaches that target the cell cycle in smooth muscle cells, and also describe recent and ongoing clinical trials that involve cell-cycle manipulation in the treatment of vasculoproliferative diseases.

Open Access Article

Akt and PI 3-Kinase Signaling in Cardiomyocyte Hypertrophy and Survival

Takashi Matsui, Tomohisa Nagoshi and Anthony Rosenzweig
Pages 219 - 222
http://dx.doi.org/10.4161/cc.2.3.381
Abstract | PDF

In many systems, activation of the “protein and lipid kinase” phosphoinositide 3-kinase (PI 3-kinase) and its downstream serine-threonine kinase effector, Akt (or Protein Kinase B), provide a potent stimulus for cell proliferation, growth, and survival. In the heart, constrained by the limited proliferative capacity of cardiomyocytes, this pathway plays a key role in regulating cardiomyocyte growth and survival, with little effect on proliferation. Simultaneously, PI 3-kinase and Akt are important modulators of metabolic substrate utilization and cardiomyocyte function. Thus, the convergent signaling pathways controlling so many clinical important phenotypes of the cardiomyocyte suggest it holds promise as a therapeutic target in a variety of cardiac diseases. However, the similar role of PI 3-kinase/Akt signaling in neoplasia suggests the difficulty of activating this pathway in the heart without invoking adverse consequences elsewhere. Here we review evidence regarding the role of PI 3-kinase/Akt in controlling cardiomyocyte growth and survival, and discuss the implications for therapeutic strategies.

Open Access Article

Genetic Instability, DNA Damage and Atherosclerosis

Maria Grazia Andreassi and Nicoletta Botto
Pages 223 - 226
http://dx.doi.org/10.4161/cc.2.3.403
Abstract | PDF

We review the role of somatic mutations and genetic instability in the pathogenesis of atherosclerosis, suggesting novel therapeutic approaches.




VIEWS AND COMMENTARIES

Open Access Article

Fine Tuning of Kinetochor Function by Phosphorylation

Silke Hauf
Pages 227 - 228
http://dx.doi.org/10.4161/cc.2.3.367
Abstract | PDF

No abstract available.

Open Access Article

Replication-Coupled Topoisomerase II Templates the Mitotic Chromosome Scaffold?

Juan F. Gimenez-Abian and Duncan J. Clarke
Pages 229 - 231
http://dx.doi.org/10.4161/cc.2.3.377
Abstract | PDF

No abstract available.

Open Access Article

p53 in a Crosstalk Between DNA Repair and Cell Cycle Checkpoints

Andrei L. Okorokov
Pages 232 - 234
http://dx.doi.org/10.4161/cc.2.3.394
Abstract | PDF

No abstract available.

Open Access Article

Chk’n Out in Mitosis

Isaac A. Manke and Michael B. Yaffe
Pages 235 - 236
http://dx.doi.org/10.4161/cc.2.3.405
Abstract | PDF

No abstract available.




REPORTS

Open Access Article

Loss of Mitotic Spindle Checkpoint Activity Predisposes to Chromosomal Instability at Early Stages of Fibrosarcoma Development

Duncan M. Gascoyne, Mary L. Hixon, Antonio Gualberto and Maria d.M. Vivanco
Pages 237 - 241
http://dx.doi.org/10.4161/cc.2.3.355
Abstract | PDF

Mice carrying the bovine papillomavirus type I genome develop dermal fibrosarcomas in a multiple step process characterized by distinctive proliferative stages. Chromosomal aberrations are identified early in this tumorigenic pathway, however, the mechanism that originates them is unknown. Using a functional assay, we investigated the status of the mitotic spindle cell cycle checkpoint (MSCCC) that regulates the metaphase to anaphase transition, in cells representing different stages of fibrosarcoma progression. Loss of MSCCC activity was apparent in mild fibromatosis and completely abolished in aggressive fibromatosis and fibrosarcoma lesions. This altered MSCCC status was confirmed biochemically by deregulated expression of Cks1 protein and unscheduled cyclin B metabolism. Immunoprecipitation and sequencing analyses indicated that mutation of p53 was not required for the abrogation of the MSCCC. These results demonstrate that loss of mitotic spindle checkpoint activity predisposes to chromosomal instability at early stages of fibrosarcoma development. To our knowledge, these studies constitute the first report of a transition in MSCCC activity in a tumorigenesis model.

Open Access Article

Flavopiridol Induces Mitochondrial-Mediated Apoptosis in Murine Glioma GL261 Cells via Release of Cytochrome c and Apoptosis Inducing Factor

Elizabeth W. Newcomb, Cristina Tamasdan, Yolanda Entzminger, Judith Alonso, David Friedlander, Diana Crisan, Douglas C. Miller and David Zagzag
Pages 242 - 249
http://dx.doi.org/10.4161/cc.2.3.357
Abstract | PDF

Glioblastoma (GBM) remains one of the most challenging solid cancers to treat due to its highly proliferative, angiogenic and invasive nature. Over 80% of adult high-grade astrocytomas show inactivation of the Rb tumor suppressor pathway. Therefore, one possible therapeutic strategy would be to directly modulate cyclin dependent kinase (CDK) activity resulting in inhibition of Rb phosphorylation and cell cycle progression. The small molecule CDK inhibitor, flavopiridol, has demonstrated antitumor activity in human xenograft models and is currently in clinical trials showing efficacy in patients with advanced disease. We have developed an experimental animal model using the murine glioma GL261 cells as a novel in vivo system to screen potential therapeutic agents for GBM. Results of in vitro testing demonstrate that flavopiridol has several relevant clinical characteristics such as its ability to:

1. inhibit cell growth;

2. inhibit cell migration;

3. decrease expression of CDK inhibitor cyclin D1, CDK4 and p21;

4. induce apoptosis in cells with high levels of p27 expression; and

5. decrease the expression of the anti-apoptotic protein Bcl-2.

The mechanism by which flavopiridol induces apoptosis is mitochondrial-mediated. We demonstrate by electron microscopy and immunohistochemistry that drug treatment induces mitochondrial damage that was accompanied by the release of cytochrome c into the cytosol together with the translocation of apoptosis inducing factor (AIF) into the nucleus. This finding in murine glioma cells differs markedly from the mechanism of flavopiridol-induced apoptosis cell death reported by us for human glioma cells (Alonso et al., Mol Cancer Ther 2003; 2:139) where drug treatment induced a caspase- and cytochrome c-independent pathway in the absence of detectable damage to mitochondria. In apoptotic human glioma cells only translocation of AIF into the nucleus occurred. Thus, the same drug induces apoptosis inkills different types of glioma cells by different mitochondrial-dependent pathways.

Open Access Article

Modulation of Gene Expression by Lentiviral-Mediated Delivery of Small Interfering RNA

Michaela Scherr, Karin Battmer, Arnold Ganser and Matthias Eder
Pages 250 - 256
http://dx.doi.org/10.4161/cc.2.3.376
Abstract | PDF

RNA interference (RNAi) mediates sequence-specific posttranscriptional gene silencing triggered by double-stranded RNA. RNAi is an effective tool for functional genomics in C. elegans, whereas biochemical characteristics of RNAi hamper its use in mammalian cells. We here analyze kinetic and quantitative aspects of mammalian RNAi in different cell lines using novel lentiviral constructs with double H1-shRNA expression cassettes located in the U3 region of the LTR. Using enhanced green fluorescence protein (EGFP) as a target gene for RNAi and red fluorescence protein (RFP) as surrogate marker for intracellular siRNA expression, we show that long-term siRNA expression mediates stable RNAi. Furthermore, RNAi-induced gene silencing varies from minimal to complete loss-of-function phenotypes within homogenous and between different cell populations. Interestingly, the extent of gene silencing correlates to lentiviral integrations as well as siRNA expression levels in target cells. Finally, we demonstrate functional gene silencing of a cytokine receptor gene in normal CD34+ hematopoietic progenitor cells. These data suggest that the use of suitable lentiviral constructs to quantify siRNA expression in living cells may allow analysis of loss-of-function phenotypes in a dose-dependent manner in a wide variety of target cells.

Open Access Article

Pim-1 Phosphorylates the DNA Binding Domain of c-Myb

Louise M. Winn, Wanli Lei and Scott A. Ness
Pages 257 - 261
http://dx.doi.org/10.4161/cc.2.3.383
Abstract | PDF

The c-Myb transcription factor regulates cellular differentiation and proliferation and is regulated by complex mechanisms that control its repressed oncogenic activity. The transcriptional activity of c-Myb is regulated by the serine/threonine protein kinase Pim-1. Here, we show that Pim-1 is able to interact with c-Myb and the closely related transcription factor A-Myb, via direct interactions with the highly conserved Myb DNA binding domain. Pim-1 associated with Myb both in cells and in vitro, and phosphorylated the Myb DNA binding domain, suggesting that it regulates Myb protein activity by direct phosphorylation.

Open Access Article

Phosphorylation of Xenopus Cdc25C at Ser285 Interferes with Ability to Activate a DNA Damage Replication Checkpoint in the Pre-Midblastula Embryos

Dmitry V. Bulavin, Zoya N. Demidenko, Crissy Phillips, Sally A. Moody and Albert J. Fornace, Jr.
Pages 262 - 265
http://dx.doi.org/10.4161/cc.2.3.396
Abstract | PDF

We have recently demonstrated that negative regulation of human Cdc25 protein phosphatases by phosphorylation at their 14-3-3 site can be antagonized through phosphorylation at an adjacent site in the -2 position.1 Based on structural homology for different Cdc25 phosphatases, a similar regulatory pathway also could be conserved in Xenopus embryos, where cell cycle checkpoints are not operational prior to the Midblastula Transition (MBT). Here, we demonstrate that before MBT, XeCdc25C is phosphorylated on Ser285, an analogous site to Ser214 in human Cdc25C or Ser307 in Cdc25B.1 Phosphorylation of Ser285 prevents subsequent inhibitory phosphorylation of XeCdc25C on Ser287, thus maintaining XeCdc25C in an active form. Mutation of Ser285 to alanine allows the reconstitution of a DNA damage replication checkpoint. This effect is completely dependent on Ser287 phosphorylation as additional mutation of Ser287 to alanine fully reversed the cell cycle inhibitory effect of Ser285A XeCdc25C. We propose that phosphorylation of XeCdc25C Ser285 may account for the lack of a DNA replication checkpoint in cleaving Xenopus embryos prior to the MBT.