Table of Contents

Volume 10, Issue 23

  December 1, 2011

  Pages 3983 - 4171

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 Issue Catalogue (MARC XML)

EDITORIALS: CELL CYCLE FEATURES

Open Access Article

Expanding NFκB and SUMO ties

Moon-Hee Lee and Shigeki Miyamoto
Pages 3983 - 3984
http://dx.doi.org/10.4161/cc.10.23.18248
Abstract | PDF

Comment on: Lee MH, et al. Mol Cell 2011; 43:180-91.

Open Access Article

Coloring skin with pluripotent stem cells

Xavier Nissan, Gilles Lemaitre, Marc Peschanski and Christine Baldeschi
Pages 3985 - 3986
http://dx.doi.org/10.4161/cc.10.23.18249
Abstract | PDF

Comment on: Nissan X, et al. Proc Natl Acad Sci USA 2011; 108:14861-6.

Open Access Article

TFEB, a novel mTORC1 effector implicated in lysosome biogenesis, endocytosis and autophagy

Samuel Peña-Llopis and James Brugarolas
Pages 3987 - 3988
http://dx.doi.org/10.4161/cc.10.23.18251
Abstract | PDF

Comment on: Peña-Llopis S, et al. EMBO J 2011; 30:3242-58.

Open Access Article

Spindle centricity

Andrew D. McAinsh and Anne Straube
Pages 3989 - 3991
http://dx.doi.org/10.4161/cc.10.23.18252
Abstract | PDF

Comment on: Samora CP, et al. Nat Cell Biol 2011; 13:1040-50.

Open Access Article

The “X factor” in cellular reprogramming and proliferation

Oz Pomp, Oliver Dreesen and Alan Colman
Pages 3992 - 3993
http://dx.doi.org/10.4161/cc.10.23.18253
Abstract | PDF

Comment on: Pomp O, et al. Cell Stem Cell 2011; 9:156-65.




CELL CYCLE NEWS & VIEWS

Open Access Article

Coordinate inactivation of zinc finger transcription factors at mitosis

William F. Marzluff
Pages 3994 - 3998
http://dx.doi.org/10.4161/cc.10.23.18235
Abstract | PDF

Comment on: Rizkallah R, et al. Cell Cycle 2011; 10:3327-36.

Open Access Article

DNA damage responses in the prostate: Implications for cancer formation?

William Bonner

http://dx.doi.org/10.4161/cc.10.23.18236
Abstract | PDF

Comment on: Zhewei Z, et al. Cell Cycle 2011; 10:3545-53.

Open Access Article

Identification and functional annotation of GWAS risk SNPs

Houtan Noushmehr and Gerhard A. Coetzee

http://dx.doi.org/10.4161/cc.10.23.18237
Abstract | PDF

Comment on: Glinskii AB, et al. Cell Cycle 2011; 10:3016-30.

Open Access Article

The Jab1-E2F1 interaction: A matter of life and death

Srikumar P. Chellappan

http://dx.doi.org/10.4161/cc.10.23.18355
Abstract | PDF

Comment on: Huarui Lu, et al. Cell Cycle 2011; 10:3317-26.

Open Access Article

Cockayne syndrome, underlying molecular defects and p53

Brian R. Berquist and Vilhelm A. Bohr

http://dx.doi.org/10.4161/cc.10.23.18352
Abstract | PDF

Comment on: Latini P, et al. Cell Cycle 2011; 10:3719-30.




EXTRA VIEWS

Open Access Article

Orchestrating the nucleases involved in DNA interstrand cross-link (ICL) repair

Blanka Sengerová, Anderson T. Wang and Peter J. McHugh
Pages 3999 - 4008
http://dx.doi.org/10.4161/cc.10.23.18385
Abstract | PDF

DNA interstrand cross-links (ICLs) pose a significant threat to genomic and cellular integrity by blocking essential cellular processes, including replication and transcription. In mammalian cells, much ICL repair occurs in association with DNA replication during S phase, following the stalling of a replication fork at the block caused by an ICL lesion. Here, we review recent work showing that the XPF-ERCC1 endonuclease and the hSNM1A exonuclease act in the same pathway, together with SLX4, to initiate ICL repair, with the MUS81-EME1 fork incision activity becoming important in the absence of the XPF-SNM1A-SLX4-dependent pathway. Another nuclease, the Fanconi anemia-associated nuclease (FAN1), has recently been implicated in the repair of ICLs, and we discuss the possible ways in which the activities of different nucleases at the ICL-stalled replication fork may be coordinated. In relation to this, we briefly speculate on the possible role of SLX4, which contains XPF and MUS81- interacting domains, in the coordination of ICL repair nucleases.

Open Access Article

Insights into phosphorylation-dependent mechanisms regulating USP1 protein stability during the cell cycle

Xiomaris M. Cotto Rios, Mathew J.K. Jones and Tony T. Huang
Pages 4009 - 4016
http://dx.doi.org/10.4161/cc.10.23.18501
Abstract | PDF

Tight regulation of the cell cycle and DNA repair machinery is essential for maintaining genome stability. The APC/CCdh1 ubiquitin ligase complex is a key regulator of protein stability during the G₁ phase of the cell cycle. APC/CCdh1 regulates and promotes the degradation of proteins involved in both cell cycle regulation and DNA repair. In a recent study, we identified a novel APC/CCdh1 substrate, the ubiquitin protease USP1. USP1 is a critical regulator of both the Fanconi anemia (FA) and translesion synthesis (TLS) DNA repair pathways. Here, we provide additional mechanistic insights into the regulation of USP1 during the cell cycle. Specifically, we demonstrate that USP1 is phosphorylated in mitosis by cyclin-dependent kinases (Cdks), and that this phosphorylation event may prevent premature degradation of USP1 during normal cell cycle progression. Finally, we provide a unifying hypothesis integrating the role of G₁-specific proteolysis of USP1 with the regulation of the transcriptional repressors, Inhibitor of DNA-binding (ID) proteins.

Open Access Article

Keeping chromatin quiet: How nucleosome remodeling restores heterochromatin after replication

Jacqueline E. Mermoud, Samuel P. Rowbotham and Patrick D. Varga-Weisz
Pages 4017 - 4025
http://dx.doi.org/10.4161/cc.10.23.18558
Abstract | PDF

Disruption of chromatin organization during replication poses a major challenge to the maintenance and integrity of genome organization. It creates the need to accurately reconstruct the chromatin landscape following DNA duplication but there is little mechanistic understanding of how chromatin based modifications are restored on newly synthesized DNA. ATP-dependent chromatin remodeling activities serve multiple roles during replication and recent work underscores their requirement in the maintenance of proper chromatin organization. A new component of chromatin replication, the SWI/SNF-like chromatin remodeler SMARCAD1, acts at replication sites to facilitate deacetylation of newly assembled histones. Deacetylation is a pre-requisite for the restoration of epigenetic signatures in heterochromatin regions following replication. In this way, SMARCAD1, in concert with histone modifying activities and transcriptional repressors, reinforces epigenetic instructions to ensure that silenced loci are correctly perpetuated in each replication cycle. The emerging concept is that remodeling of nucleosomes is an early event imperative to promote the re-establishment of histone modifications following DNA replication.

Open Access Article

Old and new functions of proneural factors revealed by the genome-wide characterization of their transcriptional targets

Diogo S. Castro and François Guillemot
Pages 4026 - 4031
http://dx.doi.org/10.4161/cc.10.23.18578
Abstract | PDF

In the developing vertebrate nervous system, bHLH proneural factors such as Ascl1 are known to play important regulatory roles at different stages of the neurogenic differentiation process. In spite of the wealth of information gathered on the cellular functions of proneural factors, little was known of the molecular basis for their activities, and in particular of the identity of their target genes. The development of genomic approaches is making possible the characterization of transcriptional programs at an unprecedented scale. Recently, we have used a combination of genomic location analysis by ChIP-on-chip and expression profiling in order to characterize the proneural transcription program regulated by Ascl1 in the ventral telencephalon of the mouse embryonic brain. Our results demonstrate that Ascl1 directly controls successive steps of neurogenesis and provide a molecular frame for previously described Ascl1 functions. In addition, we uncovered an important but previously unrecognized role for Ascl1 in promoting the proliferation of neural progenitors. Here we discuss our recent findings and review them in light of efforts from other laboratories to characterize the transcriptional programs downstream various proneural factors.




REVIEWS

Open Access Article

Mechanisms of mitochondria and autophagy crosstalk

Angelika S. Rambold and Jennifer Lippincott-Schwartz
Pages 4032 - 4038
http://dx.doi.org/10.4161/cc.10.23.18384
Abstract | PDF

Autophagy is a cellular survival pathway that recycles intracellular components to compensate for nutrient depletion and ensures the appropriate degradation of organelles. Mitochondrial number and health are regulated by mitophagy, a process by which excessive or damaged mitochondria are subjected to autophagic degradation. Autophagy is thus a key determinant for mitochondrial health and proper cell function. Mitophagic malfunction has been recently proposed to contribute to progressive neuronal loss in Parkinson's disease. In addition to autophagy's significance in mitochondrial integrity, several lines of evidence suggest that mitochondria can also substantially influence the autophagic process. The mitochondria's ability to influence and be influenced by autophagy places both elements (mitochondria and autophagy) in a unique position where defects in one or the other system could increase the risk to various metabolic and autophagic related diseases.

Open Access Article

Understanding the molecular basis of common fragile sites instability: Role of the proteins involved in the recovery of stalled replication forks

Annapaola Franchitto and Pietro Pichierri
Pages 4039 - 4046
http://dx.doi.org/10.4161/cc.10.23.18409
Abstract | PDF

Common fragile sites (CFS) are difficult-to-replicate genomic regions that show a high propensity to breakage following certain forms of DNA replication stress. Long considered a fascinating component of human chromosome structure, their relevance for biology is proven by the fact that they are frequently rearranged in cancer cells. Furthermore, CFS were found to be the preferential targets for genome instability in the early stages of human tumorigenesis. In recent years, much progress has been made in understanding the structural features of CFS and the mechanisms that monitor and regulate their integrity. From these studies it has emerged that the reason for their fragility may depend on the abnormal high-frequency of fork stalling events occurring at CFS during DNA replication. Consistently, the ATR-dependent checkpoint together with several proteins involved in response to replication fork stalling have been implicated in maintaining CFS stability. Furthermore, more recent findings propose that the scarcity of replication initiation events within CFS may contribute to their expression upon replication perturbation. This review will focus on the molecular determinants responsible for genomic instability at CFS and the systems used by cells to address this eventuality.




REPORTS

Open Access Article

Hyperactivation of oxidative mitochondrial metabolism in epithelial cancer cells in situ: Visualizing the therapeutic effects of metformin in tumor tissue

Diana Whitaker-Menezes, Ubaldo E. Martinez-Outschoorn, Neal Flomenberg, Ruth Birbe, Agnieszka K. Witkiewicz, Anthony Howell, Stephanos Pavlides, Aristotelis Tsirigos, Adam Ertel, Richard G. Pestell, Paolo Broda, Carlo Minetti, Michael P. Lisanti and Federica Sotgia
Pages 4047 - 4064
http://dx.doi.org/10.4161/cc.10.23.18151
Abstract | PDF

We have recently proposed a new mechanism for explaining energy transfer in cancer metabolism.  In this scenario, cancer cells behave as metabolic parasites, by extracting nutrients from normal host cells, such as fibroblasts, via the secretion of hydrogen peroxide as the initial trigger. Oxidative stress in the tumor microenvironment then leads to autophagy-driven catabolism, mitochondrial dys-function, and aerobic glycolysis. This, in turn, produces high-energy nutrients (such as L-lactate, ketones, and glutamine) that drive the anabolic growth of tumor cells, via oxidative mitochondrial metabolism. A logical prediction of this new “parasitic” cancer model is that tumor-associated fibroblasts should show evidence of mitochondrial dys-function (mitophagy and aerobic glycolysis). In contrast, epithelial cancer cells should increase their oxidative mitochondrial capacity. To further test this hypothesis, here we subjected frozen sections from human breast tumors to a staining procedure that only detects functional mitochondria. This method detects the in situ enzymatic activity of cytochrome C oxidase (COX), also known as Complex IV.  Remarkably, cancer cells show an over-abundance of COX activity, while adjacent stromal cells remain essentially negative. Adjacent normal ductal epithelial cells also show little or no COX activity, relative to epithelial cancer cells. Thus, oxidative mitochondrial activity is selectively amplified in cancer cells. Although COX activity staining has never been applied to cancer tissues, it could now be used routinely to distinguish cancer cells from normal cells, and to establish negative margins during cancer surgery. Similar results were obtained with NADH activity staining, which measures Complex I activity, and succinate dehydrogenase (SDH) activity staining, which measures Complex II activity. COX and NADH activities were blocked by electron transport inhibitors, such as Metformin. This has mechanistic and clinical implications for using Metformin as an anti-cancer drug, both for cancer therapy and chemo-prevention. We also immuno-stained human breast cancers for a series of well-established protein biomarkers of metabolism. More specifically, we now show that cancer-associated fibroblasts over-express markers of autophagy (cathepsin B), mitophagy (BNIP3L), and aerobic glycolysis (MCT4). Conversely, epithelial cancer cells show the over-expression of a mitochondrial membrane marker (TOMM20), as well as key components of Complex IV (MT-CO1) and Complex II (SDH-B).  We also validated our observations using a bioinformatics approach with data from >2,000 breast cancer patients, which showed the transcriptional upregulation of mitochondrial oxidative phosphorylation (OXPHOS) in human breast tumors (p < 10^-20), and a specific association with metastasis. Therefore, upregulation of OXPHOS in epithelial tumor cells is a common feature of human breast cancers. In summary, our data provide the first functional in vivo evidence that epithelial cancer cells perform enhanced mitochondrial oxidative phosphorylation, allowing them to produce high amounts of ATP. Thus, we believe that mitochondria are both the “powerhouse” and “Achilles’ heel” of cancer cells.

Open Access Article

Mitochondrial oxidative stress in cancer-associated fibroblasts drives lactate production, promoting breast cancer tumor growth: Understanding the aging and cancer connection

Renee M. Balliet, Claudia Capparelli, Carmela Guido, Timothy G. Pestell, Ubaldo E. Martinez-Outschoorn, Zhao Lin, Diana Whitaker-Menezes, Barbara Chiavarina, Richard G. Pestell, Anthony Howell, Federica Sotgia and Michael P. Lisanti
Pages 4065 - 4073
http://dx.doi.org/10.4161/cc.10.23.18254
Abstract | PDF

Increasing chronological age is the most significant risk factor for cancer. Recently, we proposed a new paradigm for understanding the role of the aging and the tumor microenvironment in cancer onset. In this model, cancer cells induce oxidative stress in adjacent stromal fibroblasts. This, in turn, causes several changes in the phenotype of the fibroblast including mitochondrial dysfunction, hydrogen peroxide production, and aerobic glycolysis, resulting in high levels of L-lactate production. L-lactate is then transferred from these glycolytic fibroblasts to adjacent epithelial cancer cells and used as “fuel” for oxidative mitochondrial metabolism.  Here, we created a new pre-clinical model system to directly test this hypothesis experimentally. To synthetically generate glycolytic fibroblasts, we genetically-induced mitochondrial dysfunction by knocking down TFAM using an sh-RNA approach.  TFAM is mitochondrial transcription factor A, which is important in functionally maintaining the mitochondrial respiratory chain. Interestingly, TFAM-deficient fibroblasts showed evidence of mitochondrial dysfunction and oxidative stress, with the loss of certain mitochondrial respiratory chain components, and the over-production of hydrogen peroxide and L-lactate. Thus, TFAM-deficient fibroblasts underwent metabolic reprogramming towards aerobic glycolysis.  Most importantly, TFAM-deficient fibroblasts significantly promoted tumor growth, as assayed using a human breast cancer (MDA-MB-231) xenograft model. These increases in glycolytic fibroblast driven tumor growth were independent of tumor angiogenesis. Mechanistically, TFAM-deficient fibroblasts increased the mitochondrial activity of adjacent epithelial cancer cells in a co-culture system, as seen using MitoTracker. Finally, TFAM-deficient fibroblasts also showed a loss of caveolin-1 (Cav-1), a known breast cancer stromal biomarker. Loss of stromal fibroblast Cav-1 is associated with early tumor recurrence, metastasis, and treatment failure, resulting in poor clinical outcome in breast cancer patients. Thus, this new experimental model system, employing glycolytic fibroblasts, may be highly clinically relevant. These studies also have implications for understanding the role of hydrogen peroxide production in oxidative damage and “host cell aging,” in providing a permissive metabolic microenvironment for promoting and sustaining tumor growth.

Open Access Article

Poly(ADP-ribose) polymerase inhibition enhances p53-dependent and -independent DNA damage responses induced by DNA damaging agent

Diana Nguyen, Maria Zajac-Kaye, Larry Rubinstein, Donna Voeller, Joseph E. Tomaszewski, Shivaani Kummar, Alice P. Chen, Yves Pommier, James H. Doroshow and Sherry X. Yang
Pages 4074 - 4082
http://dx.doi.org/10.4161/cc.10.23.18170
Abstract | PDF

Targeting DNA repair with poly(ADP-ribose) polymerase (PARP) inhibitors has shown a broad range of anti-tumor activity in patients with advanced malignancies with and without BRCA deficiency. It remains unclear what role p53 plays in response to PARP inhibition in BRCA-proficient cancer cells treated with DNA damaging agents. Using gene expression microarray analysis, we find that DNA damage response (DDR) pathways elicited by veliparib (ABT-888), a PARP inhibitor, plus topotecan comprise the G1/S checkpoint, ATM, and p53 signaling pathways in p53-wildtype cancer cell lines and BRCA1, BRCA2 and ATR pathway in p53-mutant lines. In contrast, topotecan alone induces the G1/S checkpoint pathway in p53-wildtype lines and not in p53-mutant cells. These responses are coupled with G2/G1 checkpoint effectors p21CDKN1A upregulation, and Chk1 and Chk2 activation. The drug combination enhances G2 cell cycle arrest, apoptosis and a marked increase in cell death relative to topotecan alone in p53-wildtype and p53-mutant or -null cells. We also show that the checkpoint kinase inhibitor UCN-01 abolishes the G2 arrest induced by the veliparib and topotecan combination and further increases cell death in both p53-wildtype and -mutant cells. Collectively, PARP inhibition by veliparib enhances DDR and cell death in BRCA-proficient cancer cells in a p53-dependent and -independent fashion. Abrogating the cell-cycle arrest induced by PARP inhibition plus chemotherapeutics may be a strategy in the treatment of BRCA-proficient cancer.

Open Access Article

Phosphorylation of NuSAP by Cdk1 regulates its interaction with microtubules in mitosis

Han-Yi Chou, Ting-Huang Wang, Sheng-Chung Lee, Pang-Hung Hsu, Ming-Daw Tsai, Chih-Ling Chang and Yung-Ming Jeng
Pages 4083 - 4089
http://dx.doi.org/10.4161/cc.10.23.18200
Abstract | PDF

Cell division in eukaryotes depends on a fine control of the dynamic changes of microtubules. Nucleolar and spindle-associated protein (NuSAP) is a microtubule-binding and -bundling protein essential for the integrity of the anaphase spindle and cell division. NuSAP contains two consensus cdk phosphorylation sites in its microtubule-binding domain. Here we show NuSAP is phosphorylated by cdk1 in early mitosis. This phosphorylation inhibits the binding of NuSAP to microtubules. During metaphase-to anaphase transition, NuSAP is dephosphorylated to promote spindle midzone formation and cell cycle progression. Expression of cdk1 phosphorylation-null mutant causes extensive bundling of microtubules in the prometaphase spindle. Our results suggest that phosphorylation and dephosphorylation of NuSAP during progression of mitosis regulate spindle organization through modulation of the dynamics of microtubules.

Open Access Article

Sensitivity of acute myeloid leukemia Kasumi-1 cells to binase toxic action depends on the expression of KIT and АML1-ETO oncogenes

Vladimir A. Mitkevich, Irina Y. Petrushanko, Pavel V. Spirin, Tatiana V. Fedorova, Olga V. Kretova, Nickolai A. Tchurikov, Vladimir S. Prassolov, Olga N. Ilinskaya and Alexander A. Makarov
Pages 4090 - 4097
http://dx.doi.org/10.4161/cc.10.23.18210
Abstract | PDF

Some RNases selectively attack malignant cells, triggering an apoptotic response, and therefore are considered as alternative chemotherapeutic drugs. Here we studied the effects of Bacillus intermedius RNase (binase) on murine myeloid progenitor cells FDC-P1; transduced FDC-P1 cells ectopically expressing mutated human KIT N822K oncogene and/or human AML1-ETO oncogene; and human leukemia Kasumi-1 cells expressing both of these oncogenes. Expression of both KIT and AML1-ETO oncogenes makes FDC-P1 cells sensitive to the toxic effects of binase. Kasumi-1 cells were the most responsive to the toxic actions of binase among the cell lines used in this work with an IC50 value of 0.56 µM. Either blocking the functional activity of the KIT protein with imatinib or knocking-down oncogene expression using lentiviral vectors producing shRNA against AML1-ETO or KIT eliminated the sensitivity of Kasumi-1 cells to binase toxic action and promoted their survival, even in the absence of KIT-dependent proliferation and antiapoptotic pathways. Here we provide evidence that the cooperative effect of the expression of mutated KIT and AML1-ETO oncogenes is crucial for selective toxic action of binase on malignant cells. These findings can facilitate clinical applications of binase providing a useful screen based on the presence of the corresponding target oncogenes in malignant cells.

Open Access Article

Artemis interacts with the Cul4A-DDB1^DDB2 ubiquitin E3 ligase and regulates degradation of the CDK inhibitor p27

Yiyi Yan, Xiaoshan Zhang and Randy J. Legerski
Pages 4098 - 4109
http://dx.doi.org/10.4161/cc.10.23.18227
Abstract | PDF

Artemis, a member of the SNM1 gene family, is a multifunctional phospho-protein that has been shown to have important roles in V(D)J recombination, DNA double strand break repair, and stress-induced cell-cycle checkpoint regulation. We show here that Artemis interacts with the Cul4A-DDB1 E3 ubiquitin ligase via a direct interaction with the substrate-specificity receptor DDB2. Furthermore, Artemis also interacts with the CDK inhibitor and tumor suppressor p27, a substrate of the Cul4A-DDB1 ligase, and both DDB2 and Artemis are required for the degradation of p27 mediated by this complex. We also show that the regulation of p27 by Artemis and DDB2 is important for cell cycle progression in normally proliferating cells and in response to serum deprivation. These findings thus define a function for Artemis as an effector of Cullin-based E3 ligase-mediated ubiquitylation, demonstrate a novel pathway for the regulation of p27, and show that Cul4A-DDB1^DDB2-Artemis regulates G₁ phase cell cycle progression in mammalian cells.

Open Access Article

Drosophila endocytic neoplastic tumor suppressor genes regulate Sav/Wts/Hpo signaling and the c-Jun N-terminal kinase pathway

Brian S. Robinson and Kenneth H. Moberg
Pages 4110 - 4118
http://dx.doi.org/10.4161/cc.10.23.18243
Abstract | PDF

Genetic screens in the fruit fly Drosophila melanogaster have identified a class of neoplastic tumor suppressor genes (endocytic nTSGs), which encode proteins that localize to endosomes and facilitate the trafficking of membrane-bound receptors and adhesion molecules into the degradative lysosome. Loss of endocytic nTSGs transforms imaginal disc epithelia into highly proliferative, invasive tissues that fail to differentiate and display defects in cellular apicobasal polarity, adhesion and tissue architecture. As vertebrate homologs of some Drosophila nTSGs are linked to tumor formation, identifying molecular changes in signaling associated with nTSG loss could inform understanding of neoplastic transformation in vertebrates. Here we show that mutations in genes that act at multiple steps of the endolysosomal pathway lead to autonomous activation of the Sav/Wts/Hpo (SWH) transcriptional effector Yki (YAP/TAZ in vertebrates) and the Jun N-terminal kinase (JNK), which is known to promote Yki activity in cells with disrupted polarity. Yki and JNK activity are elevated by mutations at multiple steps in the endolysosomal pathway including mutations in the AP-2σ gene, which encodes a component of the AP-2 adaptor complex that recruits cargoes into clathrin-coated pits for subsequent internalization. Moreover, reduction of JNK activity can decrease elevated Yki-signaling caused by altered endocytosis. These studies reveal a broad requirement for components of the endocytic pathway in regulating SWH and JNK outputs, and place Drosophila endocytic nTSGs into a network that involving two major signaling pathways implicated in oncogenesis.

Open Access Article

The mitochondrial protein C1qbp promotes cell proliferation, migration and resistance to cell death

Allison M. McGee, Diana L. Douglas, Yayun Liang, Salman M. Hyder and Christopher P. Baines
Pages 4119 - 4127
http://dx.doi.org/10.4161/cc.10.23.18287
Abstract | PDF

Complement 1q-Binding Protein (C1qbp) is a mitochondrial protein reported to be upregulated in cancer. However, whether C1qbp plays a tumor suppressive or tumorigenic role in the progression of cancer is controversial. Moreover, the exact effects of C1qbp on cell proliferation, migration, and death/survival have not been definitely proven. To this end, we comprehensively examined the effects of C1qbp on mitochondrial-dependent cell death, proliferation, and migration in both normal and breast cancer cells using genetic gain- and loss-of-function approaches. In normal fibroblasts, overexpression of C1qbp protected the cells against staurosporine-induce apoptosis, increased proliferation, decreased cellular ATP, and increased cell migration in a wound-healing assay. In contrast, the opposite effects were observed in fibroblasts depleted of C1qbp by RNA interference. C1qbp expression was found to be markedly elevated in 4 different human breast cancer cell lines as well as in ductal and adenocarcinoma tumors from breast cancer patients. Stable knockdown of C1qbp by shRNA in the aggressive MDA-MB-231 breast cancer cell line greatly reduced cell proliferation, increased ATP levels, and decreased cell migration compared to control shRNA-transfected cells. Moreover, C1qbp knockdown elicited a significant increase in doxorubicin-induced apoptosis in the MDA-MB-231 cells. Finally, C1qbp upregulation was not restricted to breast cancer cells and tumors, as levels of C1qbp were also found to be significantly elevated in both human lung and colon cancer cell lines and carcinomas. Together, these results establish a pro-tumor, rather than anti-tumor, role for C1qbp, and indicate that C1qbp could serve as a molecular target for cancer therapeutics.

Open Access Article

Curcumin induces Apaf-1-dependent, p21-mediated caspase activation and apoptosis

Raghu Gogada, Michael Amadori, Honghao Zhang, Anthony Jones, Alissa Verone, Jason Pitarresi, Sirisha Jandhyam, Varun Prabhu, Jennifer D. Black and Dhyan Chandra
Pages 4128 - 4137
http://dx.doi.org/10.4161/cc.10.23.18292
Abstract | PDF

Previous studies have demonstrated that curcumin induces mitochondria-mediated apoptosis. However, understanding of the molecular mechanisms underlying curcumin-induced cell death remains limited. In this study, we demonstrate that curcumin treatment of cancer cells caused dose- and time-dependent caspase-3 activation, which is required for apoptosis as confirmed using the pan caspase inhibitor, z-VAD. Knockdown experiments and knockout cells excluded a role of caspase-8 in curcumin-induced caspase-3 activation. In contrast, Apaf-1 deficiency or silencing inhibited the activity of caspase-3, pointing to a requisite role of Apaf-1 in curcumin-induced apoptotic cell death. Curcumin treatment led to Apaf-1 upregulation both at the protein and mRNA levels. Cytochrome c release from mitochondria to the cytosol in curcumin-treated cells was associated with upregulation of proapoptotic proteins such as Bax, Bak, Bid, and Bim. Crosslinking experiments demonstrated Bax oligomerization during curcumin-induced apoptosis, suggesting that induced expression of Bax, Bid, and Bim causes Bax-channel formation on the mitochondrial membrane. The release of cytochrome c was unaltered in p53-deficient cells, whereas absence of p21 blocked cytochrome c release, caspase activation, and apoptosis. Importantly, p21-deficiency resulted in reduced expression of Apaf-1 during curcumin treatment, indicating a requirement of p21 in Apaf-1 dependent caspase activation and apoptosis. Together, our findings demonstrate that Apaf-1, Bax, and p21 as novel potential targets for curcumin or curcumin-based anticancer agents.

Open Access Article

Mechanism of action of the multikinase inhibitor Foretinib

Maeva Dufies, Arnaud Jacquel, Guillaume Robert, Thomas Cluzeau, Alexandre Puissant, Nina Fenouille, Laurence Legros, Sophie Raynaud, Jill-Patrice Cassuto, Fréderic Luciano and Patrick Auberger
Pages 4138 - 4148
http://dx.doi.org/10.4161/cc.10.23.18323
Abstract | PDF

Mitotic catastrophe (MC) is induced when stressed cells enter prematurely or inappropriately into mitosis and can be caused by ionizing radiation and anticancer drugs. Foretinib is a multikinase inhibitor whose mechanism of action is incompletely understood. We investigated here the effect of Foretinib on chronic myelogenous leukemia (CML) cell lines either sensitive (IM-S) or resistant (IM-R) to the tyrosine kinase inhibitor Imatinib. Foretinib decreased viability and clonogenic potential of IM-S and IM-R CML cells as well. Foretinib-treated cells exhibited increased size, spindle assembly checkpoint anomalies and enhanced ploidy that collectively evoked mitotic catastrophe (MC). Accordingly, Foretinib-stimulated CML cells displayed decreased expression of Cdk1, Cyclin B1 and Plk1. In addition, Foretinib triggered caspase-2 activation that precedes mitochondrial membrane permeabilization. Accordingly, z-VAD-fmk and a caspase-2 siRNA abolished Foretinib-mediated cell death but failed to affect MC, indicating that Foretinib-mediated apoptosis and MC are two independent events. Anisomycin, a JNK activator, impaired Foretinib-induced MC and inhibition or knockdown of JNK phenotyped its effect on MC. Moreover, we found that Foretinib acted as a potent inhibitor of JNK. Importantly, Foretinib exhibited no or very little effect on normal peripheral blood mononuclear cells, monocytes or melanocytes cells but efficiently inhibited the clonogenic potential of CD34+ cell from CML patients. Collectively, our data show that the multikinase inhibitor Foretinib induces MC in CML cells and other cell lines via JNK-dependent inhibition of Plk1 expression and triggered apoptosis by a caspase 2-mediated mechanism. This unusual mechanism of action may have important implications for the treatment of cancer.

Open Access Article

TGFβ-induced c-Myb affects the expression of EMT-associated genes and promotes invasion of ER⁺ breast cancer cells

Vincenzo Cesi, Arianna Casciati, Fabiola Sesti, Barbara Tanno, Bruno Calabretta and Giuseppe Raschellà
Pages 4149 - 4161
http://dx.doi.org/10.4161/cc.10.23.18346
Abstract | PDF

Advanced breast cancer cells acquire metastatic properties in response to TGFβ. We show here that the expression of c-Myb increases in TGFβ-treated ER⁺ breast cancer cells by protein stabilization, transcription activation and release from miR200-dependent down-regulation. In particular, we mapped 2 sites for miR200b, miR200c and miR429 binding in the 3’ UTR of the human c-myb gene. These microRNAs decreased the expression of c-Myb when transfected in MCF-7 cells. In addition, luciferase activity from a vector containing the 3’ UTR of the c-myb gene was inhibited by miR200s through a binding-dependent mechanism. siRNA- and shRNA-mediated down-regulation was used to investigate the role of c-Myb for the effects induced by TGFβ in ER⁺ breast cancer MCF-7 and ZR-75.1 cells. Transfection with c-Myb siRNAs blocked the increase of Slug (SNAI2) and Bcl-2 expression and reversed the decrease in E-cadherin expression induced by TGF−β treatment. Conversely, c-Myb down-regulation decreased invasion and anchorage-independent growth of breast cancer cells expressing a constitutively active TGFβ receptor I. Finally, apoptosis induced by etoposide increased in c-Myb-silenced TGFβ−treated ER⁺ cell lines. In summary, exposure of ER⁺ breast cancer cells to TGFβ induces an increase of c-Myb expression which is required for expression of EMT-associated markers, in vitro invasion and anchorage-independent growth. Furthermore, our findings suggest a potentially detrimental effect of TGFβ and c-Myb co-expression in breast cancer.

Open Access Article

Circadian clock protein BMAL1 regulates cellular senescence in vivo

Rohini V. Khapre, Anna A. Kondratova, Olga Susova and Roman V. Kondratov
Pages 4162 - 4169
http://dx.doi.org/10.4161/cc.10.23.18381
Abstract | PDF

Deficiency of the circadian clock transcriptional factor BMAL1 results in the development of premature aging in mice. In agreement with the accelerated aging phenotype, we observed an increase in the number of senescent cells in different tissues (lungs, liver and spleen) of Bmal1^-/- mice, which suggests the important role of BMAL1 in the control of senescence in vivo. However, no difference in the rate of proliferation and senescence between primary fibroblasts isolated from wild-type and Bmal1^-/- mice has been detected, suggesting that BMAL1 does not play a significant role in replicative senescence in vitro. BMAL1 deficient fibroblasts had an increased sensitivity to hydrogen peroxide treatment, and reduced sensitivity to DNA damaging anticancer drugs etoposide and daunorubicin. Increased sensitivity of Bmal1^-/- cells to oxidative stress was p53 independent and correlated with the disrupted regulation of reactive oxygen species (ROS) homeostasis in BMAL1 deficient cells: indeed, circadian oscillations of ROS level can be induced in wild-type but not in Bmal1^-/- cells. We propose that BMAL1 is important for the regulation of oxidative stress and DNA damage responses, while deregulation of these processes upon BMAL1 deficiency leads to development of stress induced senescence in vivo.




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Open Access Article

HIF-1α localization with mitochondria: A new role for an old favorite?

Thomas Briston, Jun Yang and Margaret Ashcroft
Pages 4170 - 4171
http://dx.doi.org/10.4161/cc.10.23.18565
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