Table of Contents

Volume 11, Issue 2

  January 15, 2012

  Pages 201 - 417

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 Issue Catalogue (MARC XML)

SPECIAL FEATURE

Open Access Article

A new chronological survival assay in mammalian cell culture

Matt Kaeberlein and Brian K. Kennedy
Pages 201 - 202
http://dx.doi.org/10.4161/cc.11.2.18959
PDF




EDITORIALS: CELL CYCLE FEATURES

Open Access Article

Detection of circulating tumor cells in the cerebrospinal fluid: A new frontier

Timothy F. Burns and Antonio C. Wolff
Pages 203 - 204
http://dx.doi.org/10.4161/cc.11.2.18780
Abstract | PDF

Comment on: Patel AS, et al. Oncotarget 2011; 2:752-760

Open Access Article

Sensing senescence in preterm birth

Jeeyeon Cha, Yasushi Hirota and Sudhansu K. Dey
Pages 205 - 206
http://dx.doi.org/10.4161/cc.11.2.18781
Abstract | PDF

Comment on: Hirota Y, et al. Proc Natl Acad Sci USA 2011; 108:18073-8

Open Access Article

The signaling requirements for mouse embryonic stem cells

Dorota Kurek and Derk ten Berge
Pages 207 - 208
http://dx.doi.org/10.4161/cc.11.2.18783
Abstract | PDF

Comment on: ten Berge D, et al. Nat Cell Biol 2011; 13:1070-5. doi:10.1038/ncb2314

Open Access Article

Genetic variability in the PRKCI gene and prostate cancer risk

Daniele Campa, Federico Canzian and Rudolf Kaaks
Page 209
http://dx.doi.org/10.4161/cc.11.2.18898
Abstract | PDF

Comment on: Campa D, et al. PLoS One 2011; 6:e16914.

Open Access Article

Providing the TORC for cell cycle progression in neoplastic mast cells

Daniel Smrž, Todd M. Wilson, Dean D. Metcalfe and Alasdair M. Gilfillan
Pages 210 - 211
http://dx.doi.org/10.4161/cc.11.2.18976
Abstract | PDF

Comment on: Smrž D, et al. Blood 2011; 118:6803–13




CELL CYCLE NEWS & VIEWS

Open Access Article

Bipolar disorder: Kinesin-12 to the rescue

Julien Dumont
Page 212
http://dx.doi.org/10.4161/cc.11.2.18785
Abstract | PDF

Comment on: Florian S, et al. Cell Cycle 2011; 10:3533–44

Open Access Article

Brain and muscle ARNT-like protein BMAL1 regulates ROS homeostasis and senescence: A possible link to hypoxia-inducible factor-mediated pathway

Olga V. Razorenova
Page 213
http://dx.doi.org/10.4161/cc.11.2.18786
Abstract | PDF

Comment on: Khapre RV, et al. Cell Cycle 2011; 10:4162–9

Open Access Article

The evolution of the p53 family of genes

Arnold J. Levine
Page 214
http://dx.doi.org/10.4161/cc.11.2.18899
Abstract | PDF

Comment on: Lane DP, et al. Cell Cycle 2011; 10:4272–9

Open Access Article

MiR-34 and SNAIL: Another double-negative feedback loop controlling cellular plasticity/EMT governed by p53

Thomas Brabletz
Page 215
http://dx.doi.org/10.4161/cc.11.2.18900
Abstract | PDF

Comment on: Siemens H, et al. Cell Cycle 2011; 10:4256–71

Open Access Article

The shark in us: Learning about the evolution of the p53 regulatory circuit

Rachael Rutkowski and Anton Gartner
Page 216
http://dx.doi.org/10.4161/cc.11.2.18901
Abstract | PDF

Comment on: Lane DP, et al. Cell Cycle 2011; 10:4272–9

Open Access Article

Mutant p53 subverts PLK2 function in a novel, reinforced loop of corruption

Sue Haupt and Ygal Haupt
Pages 217 - 218
http://dx.doi.org/10.4161/cc.11.2.18977
Abstract | PDF

Comment on: Valenti F, et al. Cell Cycle 2011; 10:4330–40




EXTRA VIEWS

Open Access Article

The power of MEN in cytokinesis

Franz Meitinger, Saravanan Palani and Gislene Pereira
Pages 219 - 228
http://dx.doi.org/10.4161/cc.11.2.18857
Abstract | PDF

In budding yeast, the mitotic exit network (MEN) is a signaling pathway best known for its role in driving cells out of mitosis through activation of the conserved phosphatase Cdc14. However, work over the past few years show that MEN components and Cdc14 also have a direct role in promoting cytokinesis by acting upon components of the contractile actomyosin ring and cell separation machineries. In this review, we discuss the current view on the role of MEN kinases and Cdc14 in cytokinesis and comment on the cytokinesis-related function of MEN and Cdc14 orthologs in higher eukaryotes.

Open Access Article

The lesser known story of X chromosome reactivation: A closer look into the reprogramming of the inactive X chromosome

Eriona Hysolli, Yoshiaki Tanaka, Kun-Yong Kim, Yong Wook Jung and In-Hyun Park
Pages 229 - 235
http://dx.doi.org/10.4161/cc.11.2.18998
Abstract | PDF

X-chromosome inactivation (XCI) is an important mechanism employed by mammalian XX female cells to level X-linked gene expression with that of male XY cells. XCI occurs early in development as the pluripotent cells of the inner cell mass (ICM) in blastocysts successively differentiate into cells of all three germ layers. X-chromosome reactivation (XCR), the reversal of XCI, is critical for germ cell formation as a mechanism to diversify the X-chromosome gene pool. Here we review the characterization of XCR, and further explore its natural occurrence during development and the in vitro models of cellular reprogramming. We also review the key regulators involved in XCI for their role in suppressing the active histone marks and the genes in the active chromosome for their inhibition of X inactivation signals.

Open Access Article

Deconvoluting mTOR biology

Jason D. Weber and David H. Gutmann
Pages 236 - 248
http://dx.doi.org/10.4161/cc.11.2.19022
Abstract | PDF

In metazoans, TOR is an essential protein that functions as a master regulator of cellular growth and proliferation. Over the past decade, there has been an explosion of information about this critical master kinase, ranging from the composition of the TOR protein complex to its ability to act as an integrator of numerous extracellular signals. Unfortunately, this plethora of information has also raised numerous questions regarding TOR function. Currently, the prevailing view is that mammalian TOR (mTOR) exists in at least two molecular complexes, mTORC1 and mTORC2, which are largely defined by the presence of either RAPTOR or RICTOR. However, additional co-factors have been identified for each complex, and their importance in mediating mTOR signals has been incompletely elucidated. Similarly, there are differences in mTOR function that reflect the tissue of origin. In this review, we present an alternative view to mTOR complex formation and function, which envisions mTOR regulation and signal propagation as a reflection of cell type- and basal state-dependent conditions. The re-interpretation of mTOR biology in this framework may facilitate the design of therapies most likely to effectively inhibit this central regulator of cell behavior.

Open Access Article

What makes the engine hum: Rad6, a cell cycle supercharger

Jorrit M. Enserink and Richard D. Kolodner
Pages 249 - 252
http://dx.doi.org/10.4161/cc.11.2.19023
Abstract | PDF

Deregulated CDK activity drives cell proliferation of the majority of human tumors, making CDKs highly relevant research subjects. Cdc28 controls cell cycle progression in the budding yeast Saccharomyces cerevisiae, but the identity of many genes that function in conjunction with CDC28 to regulate the cell cycle and cell viability remains obscure. In a recent study, we used a chemical-genetic screen to identify the genetic network of CDC28. Through this analysis, we discovered that the Rad6-Bre1 pathway functions in this network and links ubiquitin levels to cell cycle progression by increasing transcription of cyclin genes. Thus, Rad6 boosts the activity of the cell cycle machinery.




PERSPECTIVE

Open Access Article

Is cancer a metabolic rebellion against host aging? In the quest for immortality, tumor cells try to save themselves by boosting mitochondrial metabolism

Adam Ertel, Aristotelis Tsirigos, Diana Whitaker-Menezes, Ruth Birbe, Stephanos Pavlides, Ubaldo E. Martinez-Outschoorn, Richard G. Pestell, Anthony Howell, Federica Sotgia and Michael P. Lisanti
Pages 253 - 263
http://dx.doi.org/10.4161/cc.11.2.19006
Abstract | PDF

Aging drives large systemic reductions in oxidative mitochondrial function, shifting the entire body metabolically towards aerobic glycolysis, a.k.a, the Warburg effect. Aging is also one of the most significant risk factors for the development of human cancers, including breast tumors. How are these two findings connected? One simplistic idea is that cancer cells rebel against the aging process by increasing their capacity for oxidative mitochondrial metabolism (OXPHOS). Then, local and systemic aerobic glycolysis in the aging host would provide energy-rich mitochondrial fuels (such as L-lactate and ketones) to directly “fuel” tumor cell growth and metastasis. This would establish a type of parasite-host relationship or “two-compartment tumor metabolism”, with glycolytic/oxidative metabolic-coupling. The cancer cells (“the seeds”) would flourish in this nutrient-rich microenvironment (“the soil”), which has been fertilized by host aging. In this scenario, cancer cells are only trying to save themselves from the consequences of aging, by engineering a metabolic mutiny, through the amplification of mitochondrial metabolism. We discuss the recent findings of Drs. Ron DePinho (MD Anderson) and Craig Thomspson (Sloan-Kettering) that are also consistent with this new hypothesis, linking cancer progression with metabolic aging. Using data mining and bioinformatics approaches, we also provide key evidence of a role for PGC1a/NRF1 signaling in the pathogenesis of (1) two-compartment tumor metabolism, and (2) mitochondrial biogenesis in human breast cancer cells.




REVIEW

Open Access Article

Fine-tuning of the intracellular canonical Notch signaling pathway

Tilman Borggrefe and Robert Liefke
Pages 264 - 276
http://dx.doi.org/10.4161/cc.11.2.18995
Abstract | PDF

Notch signaling plays a pivotal role in the regulation of many fundamental cellular processes, such as proliferation, stem cell maintenance and differentiation during embryonic and adult development. At the molecular level, ligand binding induces the proteolytic cleavage of the Notch receptor. The intracellular domain of Notch translocates subsequently into the nucleus, associates with the central transcription factor RBP-J and activates transcription. Although, this pathway is remarkably short, with no second messenger involved, it regulates expression of more than hundred target genes in a tissue-specific manner. This review summarizes recent studies on transcriptional and chromatin control mechanisms, which set the stage for specific expression of Notch target genes. Furthermore, we review how the canonical (RBP-J dependent) Notch pathway is fine-tuned by downstream effectors and feedback loops in mammals.




REPORTS

Open Access Article

Differential stimulation of hepatitis C virus RNA translation by microRNA-122 in different cell cycle phases

Carmen Fehr, K. Dominik Conrad and Michael Niepmann
Pages 277 - 285
http://dx.doi.org/10.4161/cc.11.2.18699
Abstract | PDF

Hepatitis C virus (HCV) replicates preferentially in the liver, and in most cases the HCV infection becomes chronic and often results in hepatocellular carcinoma. When the HCV plus-strand RNA genome has been delivered to the cytosol of the infected cell, its translation is directed by the Internal Ribosome Entry Site (IRES) in the 5´-untranslated region (5´-UTR) of the viral RNA. Thereby, IRES activity is modulated by several host factors. In particular, the liver-specific microRNA-122 (miR-122) interacts with two target sites in the HCV 5´-UTR and stimulates HCV translation, thereby most likely contributing to HCV liver tropism. Here we show that HCV IRES-dependent translation efficiency in the hepatoma cell line Huh7 is highest during the G₀ and G₁ phases of the cell cycle but significantly drops during the S phase and even more in the G₂/M phase. The superimposed stimulation of HCV translation by ectopic miR-122 works best during the G₀, G₁ and G₂/M phases but is lower during the S phase. However, the levels of Ago2 protein do not substantially change during cell cycle phases, indicating that other cellular factors involved in HCV translation stimulation by miR-122 may be differentially expressed in different cell cycle phases. Moreover, the levels of endogenously expressed miR-122 in Huh7 cells are lowest in the S phase, indicating that the predominant G₀/G₁ state of non-dividing hepatocytes in the liver facilitates high expression of the HCV genome and stimulation by miR-122, with yet unknown factors involved in the differential extent of stimulation by miR-122.

Open Access Article

The BRAFV600E causes widespread alterations in gene methylation in the genome of melanoma cells

Peng Hou, Dingxie Liu, Jianli Dong and Mingzhao Xing
Pages 286 - 295
http://dx.doi.org/10.4161/cc.11.2.18707
Abstract | PDF

Although BRAF^V600E is well known to play an important role in the tumorigenesis of melanoma, its molecular mechanism, particularly the epigenetic aspect, has been incompletely understood. Here, we investigated the role of BRAF^V600E signaling in altering gene methylation in the genome of melanoma cells using a methylated CpG island amplification/CpG island microarray system and searched for genes coupled to the BRAF^V600Esignaling through methylation aberrations. The results indicated that a wide range of genes with broad functions were linked to BRAF^V600E signaling through their hyper- or hypomethylation. Expression of 59 genes hypermethylated upon BRAF knockdown was selectively tested and found to be largely correspondingly underexpressed, suggesting that these genes were naturally hypomethylated, and overexpressed with BRAF^V600E in melanoma. This BRAF^V600E-promoted hypomethylation was confirmed on genes selectively examined in primary melanoma tumors. Some of these genes were functionally tested and demonstrated to play a role in melanoma cell proliferation and invasion. As a mechanism of aberrant gene methylation driven by BRAF^V600E, expression of the DNA methyltransferase 1 and histone methyltransferase EZH2 was profoundly affected by BRAF^V600E. We have thus uncovered a previously unrecognized prominent epigenetic mechanism in the tumorigenesis of melanoma driven by BRAF^V600E. Many of the functionally important genes controlled by the BRAF^V600E signaling through aberrant methylation may prove to be novel therapeutic targets for melanoma.

Open Access Article

A functional cooperativity between Aurora A kinase and LIM kinase1: Implication in the mitotic process

Lisa Ritchey, Richard Ottman, Michael Roumanos and Ratna Chakrabarti
Pages 296 - 309
http://dx.doi.org/10.4161/cc.11.2.18734
Abstract | PDF

Aurora kinase A (Aur-A), a mitotic kinase, regulates initiation of mitosis through centrosome separation and proper assembly of bipolar spindles. LIM kinase 1 (LIMK1), a modulator of actin and microtubule dynamics, is involved in the mitotic process through inactivating phosphorylation of cofilin. Phosphorylated LIMK1 is recruited to the centrosomes during early prophase, where it colocalizes with γ-tubulin. Here, we report a novel functional cooperativity between Aur-A and LIMK1 through mutual phosphorylation. LIMK1 is recruited to the centrosomes during early prophase and then to the spindle poles, where it colocalizes with Aur-A. Aur-A physically associates with LIMK1 and activates it through phosphorylation, which is important for its centrosomal and spindle pole localization. Aur-A also acts as a substrate of LIMK1, and the function of LIMK1 is important for its specific localization and regulation of spindle morphology. Taken together, the novel molecular interaction between these two kinases and their regulatory roles on one another’s function may provide new insight on the role of Aur-A in manipulation of actin and microtubular structures during spindle formation.

Open Access Article

Monitoring APC/C activity in the presence of chromosomal misalignment in unperturbed cell populations

Dominik Schnerch, Marie Follo, Julika Krohs, Julia Felthaus, Monika Engelhardt and Ralph Wäsch
Pages 310 - 321
http://dx.doi.org/10.4161/cc.11.2.18737
Abstract | PDF

Chromosome segregation is under strict control of the spindle assembly checkpoint (SAC). The SAC regulates anaphase-promoting complex/cyclosome (APC/C)-dependent proteolysis of securin and cyclin B. Unattached or misaligned chromosomes trigger SAC-mediated mitotic delay by stabilizing securin and cyclin B due to inhibition of APC/C until the problem is solved. Here we present a hitherto unavailable model facilitating the simultaneous depiction of chromosome movements and pulse-chased cyclin B proteolysis in every single cell within a cell population. During chromosome misalignment, we observed slow cyclin B degradation, which changed to fast degradation once the SAC was satisfied, initiating chromosome separation and mitotic exit. Slow degradation during a SAC-mediated mitotic delay is part of a tightly regulated balance between cyclin B synthesis and degradation. Since chromosomal misalignment is a rare event, the ability to study entire cell populations enabled us to monitor for the first time SAC surveillance in living cells without the need of highly artificial perturbation by spindle poisons.

Open Access Article

Interaction between ZBP-89 and p53 mutants and its contribution to effects of HDACi on hepatocellular carcinoma

Chris Z.Y. Zhang, George G. Chen, Juanita L. Merchant and Paul B.S. Lai
Pages 322 - 334
http://dx.doi.org/10.4161/cc.11.2.18758
Abstract | PDF

ZBP-89, a zinc finger transcription factor, participates in histone deacetylases inhibitors (HDACi)-mediated growth arrest and apoptosis in cancer cells. p53 mutants may interact with ZBP-89 that transcriptionally regulates p21^Waf1 (p21). However, this interaction and its consequence in cancer treatments are poorly understood. In this study, we demonstrate that ZBP‑89 is essentially required in HDACi-mediated p21 upregulation in hepetocellular carcinoma (HCC). Overexpression of ZBP-89 protein enhanced the lethal effectiveness of Trichostatin A (TSA). p53 mutant p53^G245D, but not p53^R249S, directly bound to ZBP-89 and prevented its translocation from cytoplasm to nucleus. Furthermore, p53^G245D was shown to have a similar pattern of subcellular localization to ZBP-89 in tissues of HCC patients in Hong Kong. Functionally, the cytoplasmic accumulation of ZBP-89 by p53^G245D significantly abrogated the induction of p21 caused by sodium butyrate (NaB) treatment and protected cells from TSA-induced death. The activations of several apoptotic proteins, such as Bid and PARP, were involved in p53^G245D-mediated protection. Moreover, the resistance to HDACi in p53^G245D-expressing cells was reversed by overexpression of ZBP-89. Taken together, these data suggest a potential mechanism via which mutant p53 enables tumor cells to resist chemotherapy and, therefore, establish a plausible link between mutant p53 binding to ZBP-89 and a decreased chemosensitivity of HCC cells.

Open Access Article

Combined effect of cyclin D3 expression and abrogation of cyclin D1 prevent mouse skin tumor development

Xian Wang, Christopher Sistrunk, Paula L. Miliani de Marval, Yongbaek Kim and Marcelo L. Rodriguez-Puebla
Pages 335 - 342
http://dx.doi.org/10.4161/cc.11.2.18774
Abstract | PDF

We have previously demonstrated that ras-mediated skin tumorigenesis depends on signaling pathways that act preferentially through cyclin D1 and D2. Interestingly, the expression of cyclin D3 inhibits skin tumor development, an observation that conflicts with the oncogenic role of D-type cyclins in the mouse epidermis. Here, we show that simultaneous up and downregulation of particular members of the D-type cyclin family is a valuable approach to reduce skin tumorigenesis. We developed the K5D3/cyclin D1^-/- compound mouse, which overexpresses cyclin D3 but lacks expression of cyclin D1 in the skin. Similar to K5D3 transgenic mice, keratinocytes from K5D3/cyclin D1^-/- compound mice show a significant reduction of cyclin D2 levels. Therefore, this model allows us to determine the effect of cyclin D3 expression when combined with reduced or absent expression of the remaining two members of the D-type cyclin family in mouse epidermis. Our data show that induced expression of cyclin D3 compensates for the reduced level of cyclin D1 and D2, resulting in normal keratinocyte proliferation. However, simultaneous ablation of cyclin D1 and downregulation of cyclin D2 via cyclin D3 expression resulted in a robust reduction in ras-mediated skin tumorigenesis. We conclude that modulation of the levels of particular members of the D-type cyclin family could be useful to inhibit tumor development and, in particular, ras-mediated tumorigenesis.

Open Access Article

Aging reverses the role of the transient receptor potential vanilloid-1 channel in systemic inflammation from anti-inflammatory to proinflammatory

Samuel P. Wanner, Andras Garami, Eszter Pakai, Daniela L. Oliveira, Narender R. Gavva, Cândido C. Coimbra and Andrej A. Romanovsky
Pages 343 - 349
http://dx.doi.org/10.4161/cc.11.2.18772
Abstract | PDF

Studies in young rodents have shown that the transient receptor potential vanilloid-1 (TRPV1) channel plays a suppressive role in the systemic inflammatory response syndrome (SIRS) by inhibiting production of tumor necrosis factor (TNF)α and possibly by other mechanisms. We asked whether the anti-inflammatory role of TRPV1 changes with age. First, we studied the effect of AMG517, a selective and potent TRPV1 antagonist, on aseptic, lipopolysaccharide (LPS)-induced SIRS in young (12 wk) mice. In agreement with previous studies, AMG517 increased LPS-induced mortality in the young. We then studied the effects of TRPV1 antagonism (AMG517 or genetic deletion of TRPV1) on SIRS in middle-aged (43–44 wk) mice. Both types of TRPV1 antagonism delayed and decreased LPS-induced mortality, indicating a reversal of the anti-inflammatory role of TRPV1 with aging. In addition, deletion of TRPV1 decreased the serum TNFα response to LPS, suggesting that the suppressive control of TRPV1 on TNFα production is also reversed with aging. In contrast to aseptic SIRS, polymicrobial sepsis (induced by cecal ligation and puncture) caused accelerated mortality in aged TRPV1-deficient mice as compared with wild-type littermates. The recovery of TRPV1-deficient mice from hypothermia associated with the cecal ligation and puncture procedure was delayed. Hence, the reversal of the anti-inflammatory role of TRPV1 found in the aged and their decreased systemic inflammatory response are coupled with suppressed defense against microbial infection. These results caution that TRPV1 antagonists, widely viewed as new-generation painkillers, may decrease the resistance of older patients to infection and sepsis.

Open Access Article

Entrainment of breast (cancer) epithelial cells detects distinct circadian oscillation patterns for clock and hormone receptor genes

Stefano Rossetti, Joseph Esposito, Francesca Corlazzoli, Alex Gregorski and Nicoletta Sacchi
Pages 350 - 360
http://dx.doi.org/10.4161/cc.11.2.18792
Abstract | PDF

Most physiological and biological processes are regulated by endogenous circadian rhythms under the control of both a master clock, which acts systemically and individual cellular clocks, which act at the single cell level. The cellular clock is based on a network of core clock genes, which drive the circadian expression of non-clock genes involved in many cellular processes. Circadian deregulation of gene expression has emerged to be as important as deregulation of estrogen signaling in breast tumorigenesis. Whether there is a mutual deregulation of circadian and hormone signaling is the question that we address in this study. Here we show that, upon entrainment by serum shock, cultured human mammary epithelial cells maintain an inner circadian oscillator, with key clock genes oscillating in a circadian fashion. In the same cells, the expression of the estrogen receptor α (ER A) gene also oscillates in a circadian fashion. In contrast, ER A-positive and -negative breast cancer epithelial cells show disruption of the inner clock. Further, ER A-positive breast cancer cells do not display circadian oscillation of ER A expression. Our findings suggest that estrogen signaling could be affected not only in ER A-negative breast cancer, but also in ER A-positive breast cancer due to lack of circadian availability of ER A. Entrainment of the inner clock of breast epithelial cells, by taking into consideration the biological time component, provides a novel tool to test mechanistically whether defective circadian mechanisms can affect hormone signaling relevant to breast cancer.

Open Access Article

KRAS alleles: The LCS6 3′UTR variant and KRAS coding sequence mutations in the NCI-60 panel

Samrat T. Kundu, Sunitha Nallur, Trupti Paranjape, Marta Boeke, Joanne Barnes Weidhaas and Frank J. Slack
Pages 361 - 366
http://dx.doi.org/10.4161/cc.11.2.18794
Abstract | PDF

The KRAS-variant is a germline single nucleotide polymorphism (SNP) within the 3′ UTR of the KRAS gene predicted to disrupt a complementary binding site (LCS6) for the let-7 microRNA (miRNA). The KRAS-variant is associated with increased risk of various cancers, including lung cancer, ovarian cancer and triple-negative breast cancer, and is associated with altered tumor biology in head and neck cancer, colon cancer and melanoma. To better understand the molecular pathways that may be regulated or affected by the presence of the KRAS-variant allele in cancer cells, we examined its prevalence in the NCI-60 panel of cell lines and sought to identify common features of the cell lines that carry the variant allele. This study provides a step forward towards understanding the molecular and pathological significance of the KRAS-variant.

Open Access Article

Metformin targets Stat3 to inhibit cell growth and induce apoptosis in triple-negative breast cancers

Xin-Sheng Deng, Shuiliang Wang, Anlong Deng, Bolin Liu, Susan M. Edgerton, Stuart E. Lind, Reema Wahdan-Alaswad and Ann D. Thor
Pages 367 - 376
http://dx.doi.org/10.4161/cc.11.2.18813
Abstract | PDF

A distinct group of breast cancers, called “basal” or “triple-negative” (TN) cancers express both basal cytokeratins and the epidermal growth factor receptor, but fail to express estrogen receptors, progesterone receptors or HER2 and have stem-like or mesenchymal features. They are particularly aggressive, are frequently chemo-resistant, with p53 mutation, up-regulation of IL-6 and Stat3. Because TN cells are particularly sensitive to the anti-diabetic agent metformin, we hypothesized that it may target JAK2/Stat3 signaling. The effects of metformin upon Stat3 expression and activation were examined in four human TN cell lines. Metformin’s effects were also studied in sublines with forced over-expression of constitutively active (CA) Stat3, as well as lines with stable knockdown of Stat3. Metformin inhibited Stat3 activation (P-Stat3) at Tyr705 and Ser727 and downstream signaling in each of the four parental cell lines. CA-Stat3 transfection attenuated, whereas Stat3 knockdown enhanced, the effects of metformin upon growth inhibition and apoptosis induction. A Stat3 specific inhibitor acted synergistically with metformin in reducing cell growth and inducing apoptosis. An mTOR inhibitor showed no significant interaction with metformin. In summary, Stat3 is a critical regulator of metformin action in TN cancer cells, providing the potential for enhancing metformin’s efficacy in the clinical setting.

Open Access Article

Bone marrow- and subcutaneous adipose tissue-derived mesenchymal stem cells: Differences and similarities

Renata I. Dmitrieva, Izida R. Minullina, Anna A. Bilibina, Olga V. Tarasova, Sergey V. Anisimov and Andrey Y. Zaritskey
Pages 377 - 383
http://dx.doi.org/10.4161/cc.11.2.18858
Abstract | PDF

Bone marrow (BM) and subcutaneous adipose tissue (Ad) are both considered being prospective sources of MSC for therapeutic applications. However, functional properties and therapeutic efficacy of MSC derived from different tissues of the same patient are still poorly investigated. In our study, BM-MSC and F-MSC cultures from 43 adult donors were evaluated in successive passages for immunophenotype, secretion of VEGF, SDF1, MCP1, IL6 and TGFβ1, frequency of colony-forming units (CFU-F), frequency of adipo- and osteo-progenitors (CFU-Ad, CFU-Ost), and for onset of in vitro replicative senescence. We have demonstrated that at early passages (P2-P4 or up to 14-15 in vitro population doublings) BM- and Ad- derived MSC cultures are comparable in such important characteristics as proliferation rate (population doubling time: 3,4±0,2% in BM-MSC, 3±0,3 % in F-MSC), clonogenity (CFU-F frequency: 32±5% in BM-MSC, 31±5% in F-MSC), differentiation potential (CFU-Ad frequency: 10,4±2% in BM-MSC, 13±3% in F-MSC; CFU-Ost frequency: 18,5±5,5% in BM-MSC, 18±5% in F-MSC), but differ significantly in abundance of CD146+ fraction within the sample (25±5% in BM-MSC, 7±3 % in F-MSC) and in a level of VEGF, SDF-1, MCP1 and TGFβ1 secretion. We have also demonstrated that BM-MSC enter senescence after P3-4 while most of F-MSC did not show senescence features up to P6-8. Together, these data demonstrate that specific properties of MSC from different sources should be always taken into account, when developing and optimizing the specific protocols for MSC expansion and evaluation for each particular clinical application.

Open Access Article

Acm1 contributes to nuclear positioning by inhibiting Cdh1-substrate interactions

Juan S. Martinez, Hana Hall, Matthew D. Bartolowits and Mark C. Hall
Pages 384 - 394
http://dx.doi.org/10.4161/cc.11.2.18944
Abstract | PDF

The anaphase-promoting complex (APC) is tightly regulated during cell division, often by pseudosubstrate binding to its coactivators Cdh1 and Cdc20. Budding yeast Acm1 is a Cdh1 pseudosubstrate inhibitor whose biological function is unknown. We show here that cells lacking Acm1 have defects in nuclear positioning and spindle morphology during mitosis. However, Cdh1 substrates are not destabilized in the absence of Acm1 and expression of inactive Cdh1 mutants that retain substrate binding is sufficient for the acm1 phenotype. We conclude that Acm1 is not required to inhibit APC^Cdh1 activity but rather prevents untimely Cdh1-substrate interactions. We further provide evidence suggesting that the substrate primarily responsible for the acm1 phenotype is the bud neck-localized kinase, Hsl1. Our results imply that at least some coactivator-substrate interactions require regulation. Several unrelated APC pseudosubstrates have been identified in diverse eukaryotes and their ability to simultaneously inhibit enzymatic activity and substrate binding may partly explain why this regulatory mechanism has been selected repeatedly during evolution.

Open Access Article

Differential targeting of androgen and glucocorticoid receptors induces ER stress and apoptosis in prostate cancer cells: A novel therapeutic modality

Alexander Yemelyanov, Pankaj Bhalla, Ximing Yang, Andrey Ugolkov, Kenichi Iwadate, Apollon Karseladze and Irina Budunova
Pages 395 - 406
http://dx.doi.org/10.4161/cc.11.2.18945
Abstract | PDF

Androgen (AR) and glucocorticoid (GR) receptor signaling play opposing roles in prostate tumorigenesis: in prostate, AR acts as an oncogene, and GR is a tumor suppressor. Recently, we found that non-steroidal phyto-chemical Compound A (CpdA) is AR/GR modulator acting as anti-inflammatory anti-androgen. CpdA inhibits AR and prevents GR transactivation while enhancing GR transrepression. GR and AR are controlled by proteasomal degradation. We found that prolonged exposure of LNCaP, LNCaP-GR, DU145 and PC3 prostate carcinoma (PCa) cells to proteasome inhibitor Bortezomib (BZ) caused AR degradation and GR accumulation. BZ enhanced CpdA ability to inhibit AR and to augment GR transrepression. We also found that CpdA+BZ differentially regulated GR/AR to cooperatively suppress PCa cell growth and survival and to induce endoplasmic reticulum stress (ERS). Importantly, CpdA+BZ differentially regulated GR-responsive genes. CpdA+BZ blocked activation of glucocorticoid-responsive pro-survival genes, including SGK1, but activated BZ-induced ERS-related genes BIP/HSPA5 and CHOP /GADD153. Using ChIP, we showed that SGK1, BIP/HSPA5 and CHOP regulation was due to effects of CpdA and CpdA+BZ on GR loading on their promoters. We also found that AR and GR are abundant in advanced PCa from patients treated by androgen ablation and/or chemotherapy: 56% of carcinomas from treated patients expressed both receptors, and the other 27% expressed either GR or AR. Overall, our data validate the concept of dual AR/GR targeting in prostate cancer (PC) and suggest that BZ combination with dual-target steroid receptor modulator CpdA has high potential for PC therapy.

Open Access Article

The RAX/PACT-PKR stress response pathway promotes p53 sumoylation and activation, leading to G₁ arrest

Richard Bennett, Yu Pan, Jaime Christian, Teng Hui and W. Stratford May Jr.
Pages 407 - 417
http://dx.doi.org/10.4161/cc.11.2.18999
Abstract | PDF

Cellular stresses, including growth factor deprivation, inflammatory cytokines or viral infection promote RAX/PACTdependent activation of the double-stranded RNA-dependent protein kinase, PKR, to phosphorylate eIF2α, resulting in translation inhibition and apoptosis. In addition, PKR has been reported to regulate p53, STAT1 and NFκB. Here, we report that RAX/PACT interacts with the SUMO E2 ligase Ubc9 to stimulate p53-Ubc9 association and reversible p53 sumoylation on lysine 386. In addition, expression of RAX/PACT in a variety of cell lines promotes p53 stability and activity to increase p53 target gene expression. Significantly, while the expression of RAX/PACT, PKR or p53 alone has little effect on the cell cycle of p53-null H1299 cells, co-expression of p53 with either RAX/PACT or PKR promotes a 25–35% increase of cells in G₁. In contrast, co-expression of RAX/PACT with the sumoylation-deficient p53(K386R) mutant or with the desumoylase SENP1 fails to induce such a G1 arrest. Furthermore, co-expression of p53, RAX/PACT and the dominantnegative PKR(K296R) mutant inhibits RAX/PACT-induced, p53-dependent G₁ growth arrest and expression of RAX/PACT in pkr+/+ but not pkr-/- MEF cells promotes p53 and p21 expression following gamma irradiation. Significantly, p53 stability is decreased in cells with reduced RAX/PACT or PKR following doxorubicin treatment, and expression of exogenous RAX/ PACT promotes phosphorylation of wild-type but not p53(K386R) on serine 392. Collectively, results indicate that, in response to stress, the RAX/PACT-PKR signaling pathway may inhibit p53 protein turnover by a sumoylation-dependent mechanism with promotion of p53 phosphorylation and translational activation leading to G₁ cell cycle arrest.