Table of Contents

Volume 5, Issue 1

  January 1, 2006

  Pages 3 - 119

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 Issue Catalogue (MARC XML)

EXTRA VIEWS

Open Access Article

The Diverging Roles of Calmodulin and PKC in the Regulation of p21 Intracellular Localization

Neus Agell, Montserrat Jaumot, Aina Rodríguez-Vilarrupla, Sonia Brun, Neus Abella Núria Canela, Josep Mª Estanyol and Oriol Bachs
Pages 3 - 6
http://dx.doi.org/10.4161/cc.5.1.2270
Abstract | PDF

Intracellular localization plays an important role in the functional regulation of the cyclindependent kinase inhibitor p21. While nuclear functions have been linked to the tumor suppressor activity of p21, cytoplasmatic functions are oncogenic. We have recently shown that Ser153 phosphorylation of p21 by PKC contributes to its cytoplasmatic accumulation, and that this phosphorylation is inhibited by Ca2+-dependent calmodulin binding to the Cterminal region of p21. Consequently, PKC and calmodulin/Ca2+ play diverging roles in the regulation of p21 intracellular localization. Other kinases such as AKT and MIRK/dyrk1B also phosphorylate p21 near the nuclear localization signal, thus inhibiting its nuclear accumulation. We discuss here the effects of such phosphorylations on p21 functionality, as well as its relevance to cell cycle progression and differentiation.

Open Access Article

Pancreas Development and Cancer: Wnt/β-Catenin at Issue…

Jessica Dessimoz and Anne Grapin-Botton
Pages 7 - 10
http://dx.doi.org/10.4161/cc.5.1.2293
Abstract | PDF

β-catenin and Adenomatous poliposis coli (APC) have been implicated in non-ductal pancreatic cancers. As for many other organs, several recent publications show that β-catenin and more largely the Wnt pathway appear to function at the level of pancreatic progenitors and endocrine cells during organogenesis. This raises the question of the cell type in which β-catenin is mutated during tumor formation in acinar cell carcinomas, pancreatoblastomas and solid cystic papillary tumors of the pancreas.

Open Access Article

Anaphase Topsy-Turvy: Cdk1 a Securin, Separase a CKI

Olaf Stemmann, Ingo H. Gorr and Dominik Boos
Pages 11 - 13
http://dx.doi.org/10.4161/cc.5.1.2296
Abstract | PDF

Chromosome segregation in mitosis and meiosis is triggered by activation of a large protease, separase. While it has been known for some time that the anaphase inhibitor securin regulates separase activity recent work shows that this is only half the story. In vertebrates Cdk1-dependent inhibition of separase represents a second, securin-independent branch of anaphase regulation. Furthermore, an unanticipated ability of separase to inhibit Cdk1 suggests additional, non-proteolytic functions of separase.

Open Access Article

HOXB4 Inhibits Cell Growth in a Dose-Dependent Manner and Sensitizes Cells Towards Extrinsic Cues

Elke Will, Daniel Speidel, Zheng Wang, Gabriel Ghiaur, Andreas Rimek, Bernhard Schiedlmeier, David A. Williams, Christopher Baum, Wolfram Ostertag and Hannes Klump
Pages 14 - 22
http://dx.doi.org/10.4161/cc.5.1.2304
Abstract | PDF

Ectopic expression of the homeodomain transcription factor HOXB4 expands hematopoietic stem and progenitor cells in vivo and in vitro, making HOXB4 a highly interesting candidate for therapeutic stem cell expansion. However, when expressed at high levels, HOXB4 concomitantly perturbs differentiation and thus likely predisposes the manipulated cells for leukemogenesis. We therefore asked whether the expression level of HOXB4 may be a critical parameter that influences the growth and transformation properties of transduced cells. Using a set of retroviral vectors which covered a 40-fold range of expression levels, we studied the consequences of HOXB4 expression at different levels in the well established Rat-1 fibroblast cell system. HOXB4 transformed Rat-1 fibroblasts beyond a certain threshold level of expression. Further escalation of HOXB4 expression, however, did not enhance transformation. Nevertheless, HOXB4 mediated a dose dependent anti-proliferative effect on Rat-1 and NIH3T3 fibroblasts. This effect was aggravated under reduced serum concentrations and was, at least partially, due to an enhanced sensitivity of HOXB4 overexpressing cells to induction of apoptosis. Based on these results we propose that HOXB4 affects cell growth in a dose-dependent manner by sensitizing cells towards extrinsic signals.

Open Access Article

R-Spondin Proteins: A Novel Link to β-catenin Activation

Kyung-Ah Kim, Jingsong Zhao, Susan Andarmani, Makoto Kakitani, Takeshi Oshima, Minke E. Binnerts, Arie Abo, Kazuma Tomizuka and Walter D. Funk
Pages 23 - 26
http://dx.doi.org/10.4161/cc.5.1.2305
Abstract | PDF

The RSpondin (Rspo) protein family is a recently described group of 4 distinct human secreted proteins. Reported activities for RSpo proteins include essential roles in vertebrate development and their ligand-type activities overlap substantially with those of the canonical Wnt ligands in that both RSpo and canonical Wnt signaling result in the activation of β-catenin. In a general functional screen for human secreted proteins using transgenic mouse models, we identified human Rspondin 1 (hRSpo1) protein as a potent and specific mitogen for the gastrointestinal epithelium and demonstrated potential therapeutic applications for the protein in mouse models of cancer therapy-induced mucositis. In contrast to previous studies, our data indicated only partial overlap between Wnt and RSpo ligand activities, suggesting that there may be independent receptor/signaling pathways for RSpo proteins that intersect those of Wnt at the level of β-catenin. Here we summarize the current reported data on the RSpo family and discuss these results in terms of alternate mechanisms of action. We have extended our observations on the potential therapeutic application of RSpo proteins by showing that all 4 human Rspo family members are capable of inducing epithelial proliferation and report the first non-vertebrate RSpo family member.




PERSPECTIVES

Open Access Article

Cooperation of EB1-Mal3 and the Bub1 Spindle Checkpoint

Kazuhide Asakawa and Takashi Toda
Pages 27 - 30
http://dx.doi.org/10.4161/cc.5.1.2262
Abstract | PDF

EB1 is a conserved microtubule binding protein that preferentially localises to the growing tips of the microtubule plus end. Whilst the function of EB1 in cell polarity control is well established, its role during mitosis remains largely elusive. Here we discuss our recent work of roles for Mal3, the fission yeast EB1 homologue, in mitotic progression and chromosome stability. Our analysis sheds light upon the requirement of Mal3 for bipolar microtubule attachment and its cooperative role with the spindle assembly checkpoint. In particular Mal3 collaborates with a specific branch of this checkpoint pathway, which is dependent upon Bub1, but not Mad2. As malfunctioning of the EB1-mediated pathway might be directly related to chromosome instability in some types of human cancers, a new knowledge of Mal3’s mitotic role would be of direct relevance to understanding the molecular defects in these cancer cells.

Open Access Article

2:1 Stoichiometry of the CED4–CED9 Complex and the Tetrameric CED-4: Insights into the Regulation of CED-3 Activation

Nieng Yan, Yanhui Xu and Yigong Shi
Pages 31 - 34
http://dx.doi.org/10.4161/cc.5.1.2263
Abstract | PDF

Four evolutionally conserved proteins - EGL-1, CED-9, CED-4 and CED-3 – collectively control the initiation of programmed cell death (PCD) in Caenorhabditis elegans. Activation of CED-3, the cell killing caspase, requires CED-4. The pro-death function of CED-4 is inhibited by the mitochondria-bound CED-9. Crystal structure of the 150-kDa CED-4–CED-9 complex at 2.6 Å resolution reveals a 2:1 stoichiometry between CED-4 and CED-9. EGL-1 binding to CED-9 results in the dissociation of CED-4 from the CED-4–CED-9 complex. The freed CED-4 dimer further dimerizes to form a tetramer. Only the CED-4 tetramer, but not dimer or monomer, is capable of activating CED-3. Thus, CED-9 inhibits CED-4-mediated activation of CED-3 by sequestering CED-4 dimer from further dimerization. On the basis of structural and biochemical analyses, working models are proposed to explain the mechanism by which CED-4 facilitates CED-3 activation.

Open Access Article

Hematopoietic Stem Cell Senescence and Long-Term Bone Marrow Injury

Yong Wang, Bradley A. Schulte and Daohong Zhou
Pages 35 - 38
http://dx.doi.org/10.4161/cc.5.1.2280
Abstract | PDF

Radiotherapy and chemotherapy are commonly used for treatment of cancer. Unfortunately, these treatments frequently cause acute and/or long-term bone marrow (BM) injury that can adversely affect the quality of life and the course of treatment. Our recent studies suggest that induction of hematopoietic stem cell (HSC) senescence by ionizing radiation (IR) and certain chemotherapeutic agents may contribute to long-term BM injury by impairing the ability of HSCs to self-renew. This suggestion is in agreement with a growing body of evidence demonstrating that HSCs from Bmi-1-/- and ATM-/- mice can lose their ability to self-renew by undergoing premature senescence. Interestingly, IR and different chemotherapeutic agents may induce HSC senescence and long-term BM injury in an agent-specific manner by activation of the p53-p21 and/or p16-Rb pathways. It will be of a great interest to determine if inhibition of these pathways can ameliorate radiotherapy and chemotherapy induced long-term BM injury.

Open Access Article

Selective Pharmacologic Activation of the p53-Dependent Pathway as a Therapeutic Strategy for Hematologic Malignancies

Thorsten Stühmer and Ralf C. Bargou
Pages 39 - 42
http://dx.doi.org/10.4161/cc.5.1.2281
Abstract | PDF

Most of the drugs currently used to treat hematologic cancers are genotoxic agents that exert some of their antitumor activity through p53-dependent mechanisms. However, this activity is achieved at the price of collateral genotoxic damage, which may lead to generation of more malignant tumor subclones and secondary neoplasias. Because p53 remains wild-type in the majority of hematologic malignancies nongenotoxic induction of the p53-pathway is an attractive therapeutic strategy for this group of cancers. Following the recent development of selective small-molecule MDM2-antagonists (nutlins), we have demonstrated that nutlintreatment of primary tumor cells isolated from patients with multiple myeloma induces p53 target genes and efficiently drives these cells into apoptosis. Because the apoptotic function of p53 appears to be preserved in a number of common hematologic neoplasias it should be used to investigate the utility of nongenotoxic p53-induction therapies.

Open Access Article

Dissecting the Cellular Origins of Pancreatic Cancer

Ben Z. Stanger and Yuval Dor
Pages 43 - 46
http://dx.doi.org/10.4161/cc.5.1.2291
Abstract | PDF

Although putative premalignant lesions like metaplasia – the replacement of one mature cell type with another – have been identified in a variety of cancers, the normal cellular targets of malignant transformation are largely unknown. Pancreatic ductal adenocarcinoma (PDAC) is a particularly aggressive and lethal cancer. Despite its ductal histology, however, it is unknown whether PDAC originates from pancreatic ducts or another cell type within the pancreas. Recent analysis of mice with pancreas-specific deletion of the PTEN tumor suppressor gene has provided new insight into the mechanism of metaplasia and focuses attention on pancreatic centroacinar cells as candidates for the cellular origin of PDAC. Characterization of the “cell-of-origin” could lead to a better understanding of the molecular substrate for tumor initiation and eventually to early diagnosis and treatment.




REVIEW

Open Access Article

Neural Precursor Cycling at Sonic Speed: N-Myc Pedals, GSK-3 Brakes

Paul S. Knoepfler and Anna Marie Kenney
Pages 47 - 52
http://dx.doi.org/10.4161/cc.5.1.2292
Abstract | PDF

Signaling by the sonic hedgehog (Shh) pathway is essential for neural precursor population expansion during normal central nervous system (CNS) development, and is implicated in the childhood brain tumor, medulloblastoma. The proto-oncogene N-myc plays essential roles as a downstream effector of Shh proliferative effects in neural precursors of the cerebellum, where medulloblastomas arise. It is likely that N-Myc has analogous functions in medulloblastomas and other CNS tumors where it is highly expressed due to altered regulation or gene amplification. Myc destabilization occurs in response to phosphorylation by GSK-3β. N-Myc degradation is required for cerebellar neural precursors to exit the cell cycle. During mitosis in cerebellar neural precursors, levels of N-Myc primed for phosphorylation by GSK-3β increase, due to cdk1 complex activity towards N-Myc. GSK-3β is kept in check by insulin-like growth factor signaling, which also plays critical roles in brain development and cancer. These findings indicate that therapeutic strategies targeting N-myc and the IGF pathway might be effective against medulloblastoma.




BRIEF REPORT

Open Access Article

Mitotic Catastrophe Results in Cell Death by Caspase-Dependentand Caspase-Independent Mechanisms

Sylvia Mansilla, Waldemar Priebe and José Portugal
Pages 53 - 60
http://dx.doi.org/10.4161/cc.5.1.2267
Abstract | PDF

Exposure of MDA-MB-231 and MCF-7/VP human breast carcinoma cells to the anthracyclines doxorubicin and WP631 induced polyploidy, formation of multinucleated cells and cell death by mitotic catastrophe through caspase-dependent and caspase-independent mechanisms. In both cell lines, the antiproliferative effect of WP631 was higher than that of doxorubicin and a transient halt in G2/M was observed without cell senescence, while p53- dependent apoptosis did not occur in these cells. Mitotic catastrophe was linked to necrosis, but also to apoptosis-like death, estimated by differential cell staining with Annexin-V-fluorescein and propidium iodide. Drug-induced changes in the expression of c-myc and p21WAF1, and in their respective protein levels, were observed. They depended on the cell line, the anthracycline used and its concentration, and they were consistent with the cell cycle progression through G2 to mitosis. Significant activation of caspase-2 and caspase-3 was only observed in MDA-MB-231 cells treated with doxorubicin but not with WP631, indicating that caspases may be not mandatory for the occurrence of cell death through mitotic catastrophe. In MCF-7/VP cells, which do not express functional caspase-3, mitotic catastrophe was also induced.




REPORTS

Open Access Article

Distinct Specificities of pRb Phosphorylation by CDK4 Activated by Cyclin D1 or Cyclin D3: Differential Involvement in the Distinct Mitogenic Modes of Thyroid Epithelial Cells

Sabine Paternot, Tatjana Arsenijevic, Katia Jacques E. Dumont and Pierre P. Roger
Pages 61 - 70
http://dx.doi.org/10.4161/cc.5.1.2265
Abstract | PDF

Two distinct mitogenic modes coexist in the physiologically relevant model of primary cultures of dog thyroid epithelial cells. The differentiation-associated mitogenic stimulation by TSH and cAMP specifically requires the assembly and activation of cyclin D3- cyclin-dependent kinase (CDK)4 associated to p27kip1, while the dedifferentiating proliferation induced by growth factors is associated with induction of cyclin D1. Here, we suggest that the related CDK “inhibitors” p21cip1 and p27 are differentially utilized as positive CDK4 regulators in these mitogenic stimulations. p21 was induced by EGF+serum, but repressed by TSH, which, as previously shown, up-regulates p27. In response to EGF+serum, p21 supported the nuclear localization, phosphorylation and pRb-kinase activity of CDK4. Unexpectedly, partly different site-specificities of pRb-kinase activity, leading to similar differences in the phosphorylation pattern of pRb in intact cells, were associated with cyclin D3-CDK4 bound to p27 in TSH-stimulated cells, or with CDK4 bound to p21 in growth factor-stimulated cells. These differences were ascribed to the predominant association of the latter complex to cyclin D1. Indeed, in different cell types and species, cyclin D1 varied from cyclin D3 by more efficiently driving the phosphorylation of pRb at sites (Ser807/811 and Thr826) required for its electrophoretic mobility shift. Therefore, different D-type cyclins could differently impact some pRb functions, which should be considered not only in the understanding of the relationships between cell cycle and differentiation expression in the distinct mitogenic modes of thyroid cells, but also in various development or differentiation models associated with dramatic switches in the expression of individual D-type cyclins.

Open Access Article

Involvement of CUL4 Ubiquitin E3 Ligases in Regulating CDK Inhibitors Dacapo/p27Kip1 and Cyclin E Degradation

Leigh Ann Higa, Xiaoming Yang, Jianyu Zheng, Damon Banks, Min Wu, Papia Ghosh, Hong Sun and Hui Zhang
Pages 71 - 77
http://dx.doi.org/10.4161/cc.5.1.2266
Abstract | PDF

The CUL4 (cullin 4) proteins are the core components of a new class of ubiquitin E3 ligases that regulate replication and transcription. To examine the roles of CUL4 in cell cycle regulation, we analyzed the effect of inactivation of CUL4 in both Drosophila and human cells. We found that loss of CUL4 in Drosophila cells causes G1 cell cycle arrest and an increased protein level of the CDK inhibitor Dacapo. Co-elimination of Dacapo with CUL4 abolishes the G1 cell arrest. In human cells, inactivation of CUL4A induces CDK inhibitor p27Kip1 stabilization and G1 cell cycle arrest which is dependent on the presence of p27, suggesting that this regulatory pathway is evolutionarily conserved. In addition, we found that the Drosophila CUL4 also regulates the protein level of cyclin E independent of Dacapo. We provide evidence that human CUL4B, a paralogue of human CUL4A, is involved in cyclin E regulation. Loss of CUL4B causes the accumulation of cyclin E without a concomitant increase of p27. The human CUL4B and cyclin E proteins also interact with each other and the CUL4B complexes can polyubiquitinate the CUL4B-associated cyclin E. Our studies suggest that the CUL4- containing ubiquitin E3 ligases plays a critical role in regulating G1 cell cycle progression in both Drosophila and human cells.

Open Access Article

The Hay Wells Syndrome-Derived TAp63αQ540L Mutant has Impaired Transcriptional and Cell Growth Regulatory Activity

Marco Lo Iacono, Antonella Di Costanzo, Raffaele A. Calogero, Gelsomina Mansueto, Silvia Saviozzi, Stefania Crispi, Alessandra Pollice, Girolama La Mantia and Viola Calabrò
Pages 78 - 87
http://dx.doi.org/10.4161/cc.5.1.2268
Abstract | PDF

P63 mutations have been associated with several human hereditary disorders characterized by ectodermal dysplasia such as EEC (ectrodactyly, ectodermal dysplasia, clefting) syndrome, ADULT (acro, dermato, ungual, lacrimal, tooth) syndrome and AEC (ankyloblepharon, ectodermal dysplasia, clefting) syndrome (also called Hay-Wells syndrome). The location and functional effects of the mutations that underlie these syndromes reveal a striking genotype-phenotype correlation. Unlike EEC and ADULT that result from missense mutations in the DNA-binding domain of p63, AEC is solely caused by missense mutations in the SAM domain of p63. In this paper we report a study on the TAp63α isoform, the first to be expressed during development of the embryonic epithelia, and on its naturally occurring Q540L mutant derived from an AEC patient. To assess the effects of the Q540L mutation, we generated stable cell lines expressing TAp63α wt, δNp63α or the TAp63αQ540L mutant protein and used them to systematically compare the cell growth regulatory activity of the mutant and wt p63 proteins and to generate, by microarray analysis, a comprehensive profile of differential gene expression. We found that the Q540L substitution impairs the transcriptional activity of TAp63α and causes misregulation of genes involved in the control of cell growth and epidermal differentiation.

Open Access Article

ATM is Activated by Default in Mitosis, Localizes at Centrosomes and Monitors Mitotic Spindle Integrity

Elisa Oricchio, Chiara Saladino, Stefano Iacovelli, Silvia Soddu and Enrico Cundari
Pages 88 - 92
http://dx.doi.org/10.4161/cc.5.1.2269
Abstract | PDF

We previously showed that ATM is responsible for p53 phosphorylation at Ser15 and localization at centrosomes during mitosis. When p53 centrosomal localization is prevented by inhibiting polymerization of spindle microtubules, a stabilized form of p53 is transmitted to daughter cells that arrest in the next G1 phase of the cell cycle after exit from mitosis. AT cells are unable to both localize p53 at centrosomes in mitosis and arrest after exposure to mitotic-spindle poisons. Here we show that during mitosis ATM is activated by phosphorylation at Ser1981 and localizes at centosomes. When mitotic spindle is disrupted by nocodazole, ATM is displaced from centrosomes and co-localizes with phospho-Ser15-p53 under the form of spots dispersed in the mitotic cytoplasm. After release from nocodazoleblock, as soon as cells exit mitosis, p53 is redirected to the nucleus and its Ser15 phosphorylation is substituted by phosphorylation at Ser46. We suggest that ATM is activated by default at each mitotic onset and phosphorylates p53 at Ser15 so as to keep it inactive at centrosomes when the spindle is correctly in place or, in case of inactivation of the mitotic spindle, to maintain the memory of a perturbed mitosis.

Open Access Article

Radiation Sensitivity of GL261 Murine Glioma Model and Enhanced Radiation Response by Flavopiridol

Elizabeth W. Newcomb, Stella C. Lymberis, Yevgeniy Lukyanov, Yongzhao Shao, Tona Schnee, Marylou Devitt, Barry S. Rosenstein, David Zagzag and Silvia C. Formenti
Pages 93 - 99
http://dx.doi.org/10.4161/cc.5.1.2271
Abstract | PDF

Response of a solid tumor to radiation treatment depends, in part, on the intrinsic radiosensitivity of tumor cells, the proliferation rate of tumor cells between radiation treatments and the hypoxic state of the tumor cells. A successful radiosensitizing agent would target S-phase cells and hypoxia. Recently, we demonstrated the anti-tumor effects of flavopiridol in the GL261 murine glioma model might involve 1) recruitment of tumor cells to S-phase (Newcomb et al., Cell Cycle 2004; 3:230-234) and 2) an anti-angiogenic effect on the tumor vasculature by downregulation of hypoxia-inducible factor -1? (HIF-1?) (Newcomb et al., Neuro-Oncology 2005; 7:225-235). Given that flavopiridol has demonstrated radiosensitizing activity in several murine tumor models, we tested whether it would enhance the response of GL261 tumors to radiation. In the present study, we evaluated the intrinsic radiation sensitivity of the GL261 glioma model using the tumor control/cure dose of radiation assay (TCD50). We found that a single dose of 65 Gy (CI 57.1-73.1) was required to cure 50% of the tumors locally. Using the tumor growth delay assay, fractionated radiation (5 fractions of 5 Gy over 10 days) combined with flavopiridol (5 mg/kg) given three times weekly for 3 cycles produced a significant growth delay. Our results indicate that the GL261 murine glioma model mimics the radioresistance encountered in human gliomas, and thus should prove useful in identifying promising new investigational radiosensitizers for use in the treatment of glioma patients.

Open Access Article

Mitochondrial Impairment Mediates Cytolysis in Anthrax Lethal Toxin-Treated Murine Macrophages

Abdelkrim Alileche, Raynal C. Squires, Stefan M. Muehlbauer, Michael P. Lisanti and Jürgen Brojatsch
Pages 100 - 106
http://dx.doi.org/10.4161/cc.5.1.2283
Abstract | PDF

Numerous early events in anthrax lethal toxin (LT)-mediated cell killing have been described, including uptake of LT and MAPKK cleavage. However, critical downstream events in LT killing remain to be identified. In this study we show that LT cause mitochondrial dysfunction in murine J774A.1 macrophages, as indicated by a continuous drop in both mitochondrial membrane potential and SDH activity over 90 min of LT exposure. This was further supported by ultrastructural analysis revealing LT-induced swelling of mitochondria. Mitochondrial impairment and cytolysis were controlled by proteasomes: Proteasome inhibitors restored mitochondrial activity and rescued cells from cytolysis, even when added immediately prior to membrane perturbation, suggesting a link between mitochondrial impairment and cytolysis. The addition of KCl delayed LT-mediated cytolysis, but could not block mitochondrial impairment or rescue cells. KCl treatment precluded events linked to cytolysis, including a precipitous drop in ATP levels and ubiquitinated proteins, revealing that they are epiphenomena in LT killing. This is the first study that indicates mitochondrial targeting by anthrax lethal toxin. We present evidence that mitochondrial dysfunction and membrane perturbation are key events in LT killing, and are controlled by proteasomes and KCl.

Open Access Article

Cyclin and Caveolin Expression in an Acute Model of Murine Chagasic Myocarditis


Pages 107 - 112
http://dx.doi.org/10.4161/cc.5.1.2284
Abstract | PDF

Chagas’ disease caused by the parasite, Trypanosoma cruzi, is accompanied by an acute myocarditis which can be fatal. Mice (A/J strain) infected with T. cruzi (Tulahuern strain) develop an acute myocarditis associated with high parasitemia and uniform mortality. Examination of the myocardium demonstrated myonecrosis, vasculitis and parasite pseudocysts. Immunoblot analysis and quantitative real time PCR of heart lysates demonstrated an increased expression of cell cycle regulatory proteins such as cyclins B1, D1, A1 and E1 and an increased expression of cdk2 when compared with uninfected controls. Extracellular signal-regulated kinase (ERK) was activated. Proliferating cell nuclear antigen (PCNA), endothelin-1, endothelin receptor type A (ETA) and endothelin receptor type B (ETB) expression were increased. Caveolin-1 is important in the regulation of ERK and cyclin D1. The expression of caveolin-1 as well as caveolin-2 and caveolin-3 was reduced. These data suggest that acute fatal T. cruzi myocarditis is accompanied by changes in cell cycle proteins such as the cyclins and caveolin and the upregulation of the endothelin pathway which may be important in the myocardial abnormalities and the mortality observed in this mouse model.

Open Access Article

Contrast-Enhanced In Vivo Imaging of Breast and Prostate Cancer Cells by MRI

Olga Rodriguez, Stanley Fricke, Christopher Chien, Luis Dettin, John VanMeter, Erik Shapiro, Hai-Ning Dai, Mathew Casimiro, Lilia Ileva, John Dagata, Michael Johnson, Michael P. Lisanti, Alan Koretsky and Chris Albanese
Pages 113 - 119
http://dx.doi.org/10.4161/cc.5.1.2295
Abstract | PDF

The development of effective cancer therapies has been hampered, in part, by the inability to non-invasively follow tumor progression from the initial cancerous lesion through to metastasis. We have previously shown that superparamagnetic iron oxide particles can be used as magnetic resonance imaging contrast agents to label embryonic, mesenchymal and hematopoietic stem cells in vivo. Improving the capacity to non-invasively image cancer progression is an appealing method that could be useful for assessing the efficacy of anticancer therapies. We have established that human prostate (LNCaP, DU145, PC3), rodent prostate (TRAMPC1, YPEN-1), human breast (MDA-MB-213) and mouse mammary (Myc/VEGF) cancer cell lines were readily labeled by fluorescent superparamagnetic sub-micron particles of iron oxide (MPIOs). The MPIOs were essentially inert with respect to cell proliferation and tumor formation. Fluorescence stereomicroscopy and three dimensional magnetic resonance imaging (MRI) determined that subcutaneous, intramuscular or orthotopically implanted labeled cancer cells could be imaged, in vivo, despite in some cases being undetectable by manual palpation. The MPIO-labeled cancer cells could also be imaged, in vivo, at least 6 weeks after implantation. The fluorescent MPIOs further allowed for the ex vivo identification of tumors cells from histological sections. This study demonstrates the feasibility of using fluorescent MPIOs in prostate and breast cancer cell lines as both a negative contrast agent for in vivo MRI as well as a fluorescent tumor marker for optical imaging in vivo and ex vivo.