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2.
Blood ; 124(11): 1777-89, 2014 Sep 11.
Article in English | MEDLINE | ID: mdl-25006129

ABSTRACT

Postchemotherapy relapse presents a major unmet medical need in acute myeloid leukemia (AML), where treatment options are limited. CD25 is a leukemic stem cell marker and a conspicuous prognostic marker for overall/relapse-free survival in AML. Rare occurrence of genetic alterations among PIM family members imposes a substantial hurdle in formulating a compelling patient stratification strategy for the clinical development of selective PIM inhibitors in cancer. Here we show that CD25, a bona fide STAT5 regulated gene, is a mechanistically relevant predictive biomarker for sensitivity to PIM kinase inhibitors. Alone or in combination with tyrosine kinase inhibitors, PIM inhibitors can suppress STAT5 activation and significantly shorten the half-life of MYC to achieve substantial growth inhibition of high CD25-expressing AML cells. Our results highlight the importance of STAT5 and MYC in rendering cancer cells sensitive to PIM inhibitors. Because the presence of a CD25-positive subpopulation in leukemic blasts correlates with poor overall or relapse-free survival, our data suggest that a combination of PIM inhibitors with chemotherapy and tyrosine kinase inhibitors could improve long-term therapeutic outcomes in CD25-positive AML.


Subject(s)
Antineoplastic Agents/pharmacology , Blast Crisis , Gene Expression Regulation, Leukemic/drug effects , Interleukin-2 Receptor alpha Subunit/metabolism , Proteolysis/drug effects , Proto-Oncogene Proteins c-myc/metabolism , Proto-Oncogene Proteins c-pim-1/antagonists & inhibitors , STAT5 Transcription Factor/metabolism , Antineoplastic Agents/chemistry , Blast Crisis/drug therapy , Blast Crisis/genetics , Blast Crisis/metabolism , Blast Crisis/pathology , Female , HL-60 Cells , Humans , Interleukin-2 Receptor alpha Subunit/genetics , Leukemia, Myeloid, Acute/drug therapy , Leukemia, Myeloid, Acute/genetics , Leukemia, Myeloid, Acute/metabolism , Leukemia, Myeloid, Acute/pathology , Male , Proto-Oncogene Proteins c-myc/genetics , Proto-Oncogene Proteins c-pim-1/genetics , Proto-Oncogene Proteins c-pim-1/metabolism , STAT5 Transcription Factor/genetics
3.
PLoS Comput Biol ; 11(9): e1004350, 2015 Sep.
Article in English | MEDLINE | ID: mdl-26379039

ABSTRACT

The traditional view of cancer as a genetic disease that can successfully be treated with drugs targeting mutant onco-proteins has motivated whole-genome sequencing efforts in many human cancer types. However, only a subset of mutations found within the genomic landscape of cancer is likely to provide a fitness advantage to the cell. Distinguishing such "driver" mutations from innocuous "passenger" events is critical for prioritizing the validation of candidate mutations in disease-relevant models. We design a novel statistical index, called the Hitchhiking Index, which reflects the probability that any observed candidate gene is a passenger alteration, given the frequency of alterations in a cross-sectional cancer sample set, and apply it to a mutational data set in colorectal cancer. Our methodology is based upon a population dynamics model of mutation accumulation and selection in colorectal tissue prior to cancer initiation as well as during tumorigenesis. This methodology can be used to aid in the prioritization of candidate mutations for functional validation and contributes to the process of drug discovery.


Subject(s)
Colorectal Neoplasms/genetics , Computational Biology/methods , Models, Genetic , Mutation/genetics , Cross-Sectional Studies , Evolution, Molecular , Humans , Models, Statistical , Population Dynamics
4.
Nature ; 461(7264): 614-20, 2009 Oct 01.
Article in English | MEDLINE | ID: mdl-19759537

ABSTRACT

The stability of the Wnt pathway transcription factor beta-catenin is tightly regulated by the multi-subunit destruction complex. Deregulated Wnt pathway activity has been implicated in many cancers, making this pathway an attractive target for anticancer therapies. However, the development of targeted Wnt pathway inhibitors has been hampered by the limited number of pathway components that are amenable to small molecule inhibition. Here, we used a chemical genetic screen to identify a small molecule, XAV939, which selectively inhibits beta-catenin-mediated transcription. XAV939 stimulates beta-catenin degradation by stabilizing axin, the concentration-limiting component of the destruction complex. Using a quantitative chemical proteomic approach, we discovered that XAV939 stabilizes axin by inhibiting the poly-ADP-ribosylating enzymes tankyrase 1 and tankyrase 2. Both tankyrase isoforms interact with a highly conserved domain of axin and stimulate its degradation through the ubiquitin-proteasome pathway. Thus, our study provides new mechanistic insights into the regulation of axin protein homeostasis and presents new avenues for targeted Wnt pathway therapies.


Subject(s)
Repressor Proteins/metabolism , Signal Transduction/drug effects , Tankyrases/antagonists & inhibitors , Wnt Proteins/antagonists & inhibitors , Axin Protein , Cell Division/drug effects , Cell Line , Cell Line, Tumor , Colorectal Neoplasms/drug therapy , Colorectal Neoplasms/metabolism , Heterocyclic Compounds, 3-Ring/pharmacology , Humans , Proteasome Endopeptidase Complex/metabolism , Protein Binding , Proteomics , Repressor Proteins/chemistry , Tankyrases/metabolism , Transcription, Genetic/drug effects , Ubiquitin/metabolism , Ubiquitination , Wnt Proteins/metabolism , beta Catenin/antagonists & inhibitors , beta Catenin/metabolism
5.
J Biol Chem ; 288(42): 30125-30138, 2013 Oct 18.
Article in English | MEDLINE | ID: mdl-24003220

ABSTRACT

PRP4 kinase is known for its roles in regulating pre-mRNA splicing and beyond. Therefore, a wider spectrum of PRP4 kinase substrates could be expected. The role of PRP4 kinase in cancer is also yet to be fully elucidated. Attaining specific and potent PRP4 inhibitors would greatly facilitate the study of PRP4 biological function and its validation as a credible cancer target. In this report, we verified the requirement of enzymatic activity of PRP4 in regulating cancer cell growth and identified an array of potential novel substrates through orthogonal proteomics approaches. The ensuing effort in structural biology unveiled for the first time unique features of PRP4 kinase domain and its potential mode of interaction with a low molecular weight inhibitor. These results provide new and important information for further exploration of PRP4 kinase function in cancer.


Subject(s)
Neoplasm Proteins , Neoplasms , Protein Kinase Inhibitors , Ribonucleoprotein, U4-U6 Small Nuclear , Cell Line, Tumor , Humans , Neoplasm Proteins/antagonists & inhibitors , Neoplasm Proteins/chemistry , Neoplasm Proteins/genetics , Neoplasm Proteins/metabolism , Neoplasms/drug therapy , Neoplasms/enzymology , Neoplasms/genetics , Protein Kinase Inhibitors/chemistry , Protein Kinase Inhibitors/pharmacology , Proteomics/methods , Ribonucleoprotein, U4-U6 Small Nuclear/antagonists & inhibitors , Ribonucleoprotein, U4-U6 Small Nuclear/chemistry , Ribonucleoprotein, U4-U6 Small Nuclear/genetics , Ribonucleoprotein, U4-U6 Small Nuclear/metabolism
6.
Bioorg Med Chem Lett ; 24(6): 1506-10, 2014 Mar 15.
Article in English | MEDLINE | ID: mdl-24560540
7.
Sci Transl Med ; 16(749): eabp8334, 2024 May 29.
Article in English | MEDLINE | ID: mdl-38809966

ABSTRACT

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disease driven by gain-of-function variants in activin receptor-like kinase 2 (ALK2), the most common variant being ALK2R206H. In FOP, ALK2 variants display increased and dysregulated signaling through the bone morphogenetic protein (BMP) pathway resulting in progressive and permanent replacement of skeletal muscle and connective tissues with heterotopic bone, ultimately leading to severe debilitation and premature death. Here, we describe the discovery of BLU-782 (IPN60130), a small-molecule ALK2R206H inhibitor developed for the treatment of FOP. A small-molecule library was screened in a biochemical ALK2 binding assay to identify potent ALK2 binding compounds. Iterative rounds of structure-guided drug design were used to optimize compounds for ALK2R206H binding, ALK2 selectivity, and other desirable pharmacokinetic properties. BLU-782 preferentially bound to ALK2R206H with high affinity, inhibiting signaling from ALK2R206H and other rare FOP variants in cells in vitro without affecting signaling of closely related homologs ALK1, ALK3, and ALK6. In vivo efficacy of BLU-782 was demonstrated using a conditional knock-in ALK2R206H mouse model, where prophylactic oral dosing reduced edema and prevented cartilage and heterotopic ossification (HO) in both muscle and bone injury models. BLU-782 treatment preserved the normal muscle-healing response in ALK2R206H mice. Delayed dosing revealed a short 2-day window after injury when BLU-782 treatment prevented HO in ALK2R206H mice, but dosing delays of 4 days or longer abrogated HO prevention. Together, these data suggest that BLU-782 may be a candidate for prevention of HO in FOP.


Subject(s)
Disease Models, Animal , Myositis Ossificans , Ossification, Heterotopic , Animals , Myositis Ossificans/drug therapy , Myositis Ossificans/metabolism , Ossification, Heterotopic/drug therapy , Ossification, Heterotopic/metabolism , Ossification, Heterotopic/prevention & control , Mice , Humans , Activin Receptors, Type II/metabolism , Activin Receptors, Type I/metabolism , Activin Receptors, Type I/antagonists & inhibitors , Signal Transduction/drug effects
8.
Cancer Cell ; 7(6): 561-73, 2005 Jun.
Article in English | MEDLINE | ID: mdl-15950905

ABSTRACT

PIK3CA is mutated in diverse human cancers, but the functional effects of these mutations have not been defined. To evaluate the consequences of PIK3CA alterations, the two most common mutations were inactivated by gene targeting in colorectal cancer (CRC) cells. Biochemical analyses of these cells showed that mutant PIK3CA selectively regulated the phosphorylation of AKT and the forkhead transcription factors FKHR and FKHRL1. PIK3CA mutations had little effect on growth under standard conditions, but reduced cellular dependence on growth factors. PIK3CA mutations resulted in attenuation of apoptosis and facilitated tumor invasion. Treatment with the PI3K inhibitor LY294002 abrogated PIK3CA signaling and preferentially inhibited growth of PIK3CA mutant cells. These data have important implications for therapy of cancers harboring PIK3CA alterations.


Subject(s)
Cell Proliferation , Neoplasm Invasiveness/pathology , Phosphatidylinositol 3-Kinases/genetics , Amino Acid Substitution , Animals , Apoptosis/genetics , Apoptosis Regulatory Proteins , Base Sequence , Cell Line, Tumor , Cell Movement/genetics , Chromones/pharmacology , Class I Phosphatidylinositol 3-Kinases , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Enzyme Inhibitors/pharmacology , Forkhead Box Protein O1 , Forkhead Box Protein O3 , Forkhead Transcription Factors , Gene Targeting , Growth Substances/deficiency , Humans , Insulin/deficiency , Membrane Glycoproteins/physiology , Mice , Mice, Nude , Morpholines/pharmacology , Mutation , Neoplasm Invasiveness/genetics , Neoplasms, Experimental/genetics , Neoplasms, Experimental/metabolism , Neoplasms, Experimental/pathology , Phosphoinositide-3 Kinase Inhibitors , Phosphorylation/drug effects , Protein Serine-Threonine Kinases/genetics , Protein Serine-Threonine Kinases/metabolism , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins/metabolism , Proto-Oncogene Proteins c-akt , Signal Transduction/drug effects , TNF-Related Apoptosis-Inducing Ligand , Transcription Factors/genetics , Transcription Factors/metabolism , Tumor Necrosis Factor-alpha/physiology , Xenograft Model Antitumor Assays/methods
9.
Nat Rev Cancer ; 3(9): 695-701, 2003 09.
Article in English | MEDLINE | ID: mdl-12951588

ABSTRACT

A very large fraction of cancers have an abnormal genetic content, called aneuploidy, which is characterized by changes in chromosome structure and number. One explanation for this aneuploidy is chromosomal instability, in which cancer cells gain or lose whole chromosomes or large fractions of chromosomes at a greatly increased rate compared with normal cells. Here, we explore experimental and theoretical evidence for the initiation of chromosomal instability in very early colorectal cancers, and reflect on the role that chromosomal instability could have in colorectal tumorigenesis.


Subject(s)
Cell Transformation, Neoplastic/genetics , Chromosome Aberrations , Colorectal Neoplasms/genetics , Humans
10.
Gastro Hep Adv ; 2(3): 307-321, 2023.
Article in English | MEDLINE | ID: mdl-39132655

ABSTRACT

Background and Aims: Fibrolamellar carcinoma (FLC) is a rare, difficult-to-treat liver cancer primarily affecting pediatric and adolescent patients, and for which precision medicine approaches have historically not been possible. The DNAJB1-PRKACA gene fusion was identified as a driver of FLC pathogenesis. We aimed to assess whether FLC tumors maintain dependency on this gene fusion and determine if PRKACA is a viable therapeutic target. Methods: FLC patient-derived xenograft (PDX) shRNA cell lines were implanted subcutaneously into female NOD-SCID mice and tumors were allowed to develop prior to randomization to doxycycline (to induce knockdown) or control groups. Tumor development was assessed every 2 days. To assess the effect of treatment with novel selective PRKACA small molecule kinase inhibitors, BLU0588 and BLU2864, FLC PDX tumor cells were implanted subcutaneously into NOD-SCID mice and tumors allowed to develop. Mice were randomized to treatment (BLU0588 and BLU2864, orally, once daily) or control groups and tumor size determined as previously. Results: Knockdown of DNAJB1-PRKACA reversed a FLC-specific gene signature and reduced PDX tumor growth in mice compared to the control group. Furthermore, FLC PDX tumor growth was significantly reduced with BLU0588 and BLU2864 treatment vs control (P = .003 and P = .0005, respectively). Conclusion: We demonstrated, using an inducible knockdown and small molecule approaches, that FLC PDX tumors were dependent upon DNAJB1-PRKACA fusion activity. In addition, this study serves as a proof-of-concept that PRKACA is a viable therapeutic target for FLC and warrants further investigation.

11.
Bioorg Med Chem Lett ; 22(20): 6381-4, 2012 Oct 15.
Article in English | MEDLINE | ID: mdl-22981333

ABSTRACT

From a HTS campaign, a new series of pyrimidone anilides exemplified by compound 1 has been identified with good inhibitory activity for the PI3Kß isoform. The structure of compound 1 in PI3Kγ was solved revealing a binding mode in agreement with the SAR observed on PI3Kß. These compounds displayed inhibition in the nanomolar range in the biochemical assay and were also potent p-Akt inhibitors in a PTEN-deficient PC3 prostate cancer cell line. Optimization of in vitro pharmocokinetic properties led to compound 25 exhibiting 52% bioavailability in mice and target engagement in an acute PK/PD study.


Subject(s)
Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Phosphoinositide-3 Kinase Inhibitors , Prostatic Neoplasms/drug therapy , Pyrimidinones/chemistry , Pyrimidinones/pharmacology , Anilides/chemistry , Anilides/pharmacokinetics , Anilides/pharmacology , Animals , Antineoplastic Agents/pharmacokinetics , Cell Line, Tumor , Class Ia Phosphatidylinositol 3-Kinase/metabolism , Crystallography, X-Ray , Female , Gene Deletion , Humans , Male , Mice , Mice, SCID , Models, Molecular , PTEN Phosphohydrolase/genetics , Prostate/cytology , Prostate/drug effects , Prostatic Neoplasms/enzymology , Prostatic Neoplasms/genetics , Protein Isoforms/antagonists & inhibitors , Protein Isoforms/metabolism , Pyrimidinones/pharmacokinetics , Structure-Activity Relationship
12.
Nat Med ; 11(3): 261-2, 2005 Mar.
Article in English | MEDLINE | ID: mdl-15723071

ABSTRACT

It has been shown that bone marrow-derived stem cells can form a major fraction of the tumor endothelium in mouse tumors. To determine the role of such cells in human tumor angiogenesis, we studied six individuals who developed cancers after bone marrow transplantation with donor cells derived from individuals of the opposite sex. By performing fluorescence in situ hybridization (FISH) with sex chromosome-specific probes in conjunction with fluorescent antibody staining, we found that such stem cells indeed contributed to tumor endothelium, but at low levels, averaging only 4.9% of the total. These results illustrate substantial differences between human tumors and many mouse models with respect to angiogenesis and have important implications for the translation of experimental antiangiogenic therapies to the clinic.


Subject(s)
Bone Marrow Cells/cytology , Bone Marrow Transplantation/adverse effects , Endothelial Cells/cytology , Neoplasms/blood supply , Neovascularization, Pathologic , Stem Cells/physiology , Chromosomes, Human, X , Chromosomes, Human, Y , Endothelial Cells/physiology , Female , Fluorescent Antibody Technique , Humans , In Situ Hybridization, Fluorescence , Male , Neoplasms/pathology , Neovascularization, Pathologic/blood
13.
Nature ; 441(7092): 451-6, 2006 May 25.
Article in English | MEDLINE | ID: mdl-16724057

ABSTRACT

A cancer drug target is only truly validated by demonstrating that a given therapeutic agent is clinically effective and acts through the target against which it was designed. Nevertheless, it is desirable to declare an early-stage drug target as 'validated' before investing in a full-scale drug discovery programme dedicated to it. Although the outcome of validation studies can guide cancer research programmes, strictly defined universal validation criteria have not been established.


Subject(s)
Drug Evaluation, Preclinical/methods , Neoplasms/drug therapy , Neoplasms/metabolism , Animals , Cells/drug effects , Cells/metabolism , Disease Models, Animal , Drug Evaluation, Preclinical/standards , Humans , Neoplasms/genetics , Neoplasms/pathology , Reproducibility of Results , Substrate Specificity
14.
Proc Natl Acad Sci U S A ; 106(11): 4166-70, 2009 Mar 17.
Article in English | MEDLINE | ID: mdl-19237565

ABSTRACT

The cyclin D1-cyclin-dependent kinase 4 (CDK4) complex is a key regulator of the transition through the G(1) phase of the cell cycle. Among the cyclin/CDKs, CDK4 and cyclin D1 are the most frequently activated by somatic genetic alterations in multiple tumor types. Thus, aberrant regulation of the CDK4/cyclin D1 pathway plays an essential role in oncogenesis; hence, CDK4 is a genetically validated therapeutic target. Although X-ray crystallographic structures have been determined for various CDK/cyclin complexes, CDK4/cyclin D1 has remained highly refractory to structure determination. Here, we report the crystal structure of CDK4 in complex with cyclin D1 at a resolution of 2.3 A. Although CDK4 is bound to cyclin D1 and has a phosphorylated T-loop, CDK4 is in an inactive conformation and the conformation of the heterodimer diverges from the previously known CDK/cyclin binary complexes, which suggests a unique mechanism for the process of CDK4 regulation and activation.


Subject(s)
Cyclin D1/chemistry , Cyclin-Dependent Kinase 4/chemistry , Crystallography, X-Ray , Humans , Multiprotein Complexes/chemistry , Protein Binding , Protein Conformation
15.
Br J Haematol ; 152(4): 420-32, 2011 Feb.
Article in English | MEDLINE | ID: mdl-21223249

ABSTRACT

Cell cycle regulators, such as cyclin-dependent kinases (CDKs), are appealing targets for multiple myeloma (MM) therapy given the increased proliferative rates of tumour cells in advanced versus early stages of MM. We hypothesized that a multi-targeted CDK inhibitor with a different spectrum of activity compared to existing CDK inhibitors could trigger distinct molecular sequelae with therapeutic implications for MM. We therefore studied the small molecule heterocyclic compound NVP-LCQ195/AT9311 (LCQ195), which inhibits CDK1, CDK2 and CDK5, as well as CDK3 and CDK9. LCQ195 induced cell cycle arrest and eventual apoptotic cell death of MM cells, even at sub-µmol/l concentrations, spared non-malignant cells, and overcame the protection conferred to MM cells by stroma or cytokines of the bone marrow milieu. In MM cells, LCQ195 triggered decreased amplitude of transcriptional signatures associated with oncogenesis, drug resistance and stem cell renewal, including signatures of activation of key transcription factors for MM cells e.g. myc, HIF-1α, IRF4. Bortezomib-treated MM patients whose tumours had high baseline expression of genes suppressed by LCQ195 had significantly shorter progression-free and overall survival than those with low levels of these transcripts in their MM cells. These observations provide insight into the biological relevance of multi-targeted CDK inhibition in MM.


Subject(s)
Antineoplastic Agents/pharmacology , Cyclin-Dependent Kinases/antagonists & inhibitors , Multiple Myeloma/pathology , Apoptosis/drug effects , Boronic Acids/therapeutic use , Bortezomib , Cell Cycle/drug effects , Cell Survival/drug effects , Coculture Techniques , Cyclin-Dependent Kinases/metabolism , Cytokines/antagonists & inhibitors , Cytokines/pharmacology , Dose-Response Relationship, Drug , Down-Regulation/drug effects , Drug Combinations , Drug Interactions , Drug Screening Assays, Antitumor , Gene Expression Regulation, Neoplastic/drug effects , Humans , Multiple Myeloma/drug therapy , Multiple Myeloma/enzymology , Multiple Myeloma/genetics , Pyrazines/therapeutic use , Signal Transduction/drug effects , Stromal Cells/physiology , Survival Analysis , Transcription, Genetic , Treatment Outcome , Tumor Cells, Cultured
16.
Nature ; 436(7052): 792, 2005 Aug 11.
Article in English | MEDLINE | ID: mdl-16094359

ABSTRACT

Protein kinases are enzymes that are important for controlling cellular growth and invasion, and their malfunction is implicated in the development of some tumours. We analysed human colorectal cancers for genetic mutations in 340 serine/threonine kinases and found mutations in eight genes, including in three members of the phosphatidylinositol-3-OH kinase (PI(3)K) pathway. The discovery of this mutational activation of a key cell-signalling pathway may provide new targets for therapeutic intervention.


Subject(s)
Colorectal Neoplasms/enzymology , Colorectal Neoplasms/genetics , Mutation/genetics , Signal Transduction/genetics , Colorectal Neoplasms/metabolism , DNA Mutational Analysis , Exons/genetics , Humans , Phosphatidylinositol 3-Kinases/metabolism , Polymerase Chain Reaction , Protein Serine-Threonine Kinases/chemistry , Protein Serine-Threonine Kinases/genetics , Protein Serine-Threonine Kinases/metabolism , Protein Structure, Tertiary/genetics
17.
Proc Natl Acad Sci U S A ; 105(35): 13057-62, 2008 Sep 02.
Article in English | MEDLINE | ID: mdl-18755892

ABSTRACT

Deregulation of the PI3K signaling pathway is observed in many human cancers and occurs most frequently through loss of PTEN phosphatase tumor suppressor function or through somatic activating mutations in the Class IA PI3K, PIK3CA. Tumors harboring activated p110alpha, the protein product of PIK3CA, require p110alpha activity for growth and survival and hence are expected to be responsive to inhibitors of its lipid kinase activity. Whether PTEN-deficient cancers similarly depend on p110alpha activity to sustain activation of the PI3K pathway has been unclear. In this study, we used a single-vector lentiviral inducible shRNA system to selectively inactivate the three Class IA PI3Ks, PIK3CA, PIK3CB, and PIK3CD, to determine which PI3K isoforms are responsible for driving the abnormal proliferation of PTEN-deficient cancers. Down-regulation of PIK3CA in colorectal cancer cells harboring mutations in PIK3CA inhibited downstream PI3K signaling and cell growth. Surprisingly, PIK3CA depletion affected neither PI3K signaling nor cell growth in 3 PTEN-deficient cancer cell lines. In contrast, down-regulation of the PIK3CB isoform, which encodes p110beta, resulted in pathway inactivation and subsequent inhibition of growth in both cell-based and in vivo settings. This essential function of PIK3CB in PTEN-deficient cancer cells required its lipid kinase activity. Our findings demonstrate that although p110alpha activation is required to sustain the proliferation of established PIK3CA-mutant tumors, PTEN-deficient tumors are dependent instead on p110beta signaling. This unexpected finding demonstrates the need to tailor therapeutic approaches to the genetic basis of PI3K pathway activation to achieve optimal treatment response.


Subject(s)
Neoplasms/enzymology , PTEN Phosphohydrolase/deficiency , Phosphatidylinositol 3-Kinases/metabolism , Animals , Cell Line, Tumor , Cell Proliferation , Cell Survival , Class I Phosphatidylinositol 3-Kinases , Colonic Neoplasms/enzymology , Colonic Neoplasms/pathology , Down-Regulation , Humans , Male , Mice , Mice, Nude , Mutation/genetics , Neoplasms/pathology , PTEN Phosphohydrolase/metabolism , Phosphatidylinositol 3-Kinases/deficiency , Phosphoproteins/metabolism , Prostatic Neoplasms/enzymology , Prostatic Neoplasms/pathology , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction , Transplantation, Heterologous
18.
Proc Natl Acad Sci U S A ; 105(9): 3443-8, 2008 Mar 04.
Article in English | MEDLINE | ID: mdl-18299561

ABSTRACT

Although the majority of colorectal cancers exhibit chromosome instability (CIN), only a few genes that might cause this phenotype have been identified and no general mechanism underlying their function has emerged. To systematically identify somatic mutations in potential CIN genes in colorectal cancers, we determined the sequence of 102 human homologues of 96 yeast CIN genes known to function in various aspects of chromosome transmission fidelity. We identified 11 somatic mutations distributed among five genes in a panel that included 132 colorectal cancers. Remarkably, all but one of these 11 mutations were in the homologs of yeast genes that regulate sister chromatid cohesion. We then demonstrated that down-regulation of such homologs resulted in chromosomal instability and chromatid cohesion defects in human cells. Finally, we showed that down-regulation or genetic disruption of the two major candidate CIN genes identified in previous studies (MRE11A and CDC4) also resulted in abnormal sister chromatid cohesion in human cells. These results suggest that defective sister chromatid cohesion as a result of somatic mutations may represent a major cause of chromosome instability in human cancers.


Subject(s)
Chromatids , Chromosomal Instability/genetics , Colorectal Neoplasms/genetics , Mutation , Neoplasm Proteins/genetics , Base Sequence , Cell Cycle Proteins/genetics , Chondroitin Sulfate Proteoglycans/genetics , Chromosomal Proteins, Non-Histone/genetics , DNA, Neoplasm , DNA-Binding Proteins/genetics , Down-Regulation/drug effects , Down-Regulation/physiology , F-Box Proteins/genetics , F-Box-WD Repeat-Containing Protein 7 , Genes, Fungal , Humans , MRE11 Homologue Protein , Neoplasm Proteins/physiology , Nuclear Proteins/genetics , Proteins/genetics , RNA, Small Interfering/pharmacology , Ubiquitin-Protein Ligases/genetics
19.
Mol Cell Biol ; 27(13): 4968-79, 2007 Jul.
Article in English | MEDLINE | ID: mdl-17452456

ABSTRACT

Bmi-1 and Mel-18 are structural homologues that belong to the Polycomb group of transcriptional regulators and are believed to stably maintain repression of gene expression by altering the state of chromatin at specific promoters. While a number of clinical and experimental observations have implicated Bmi-1 in human tumorigenesis, the role of Mel-18 in cancer cell growth has not been investigated. We report here that short hairpin RNA-mediated knockdown of either Bmi-1 or Mel-18 in human medulloblastoma DAOY cells results in the inhibition of proliferation, loss of clonogenic survival, anchorage-independent growth, and suppression of tumor formation in nude mice. Furthermore, overexpression of both Bmi-1 and Mel-18 significantly increases the clonogenic survival of Rat1 fibroblasts. In contrast, stable downregulation of Bmi-1 or Mel-18 alone does not affect the growth of normal human WI38 fibroblasts. Proteomics-based characterization of Bmi-1 and Mel-18 protein complexes isolated from cancer cells revealed substantial similarities in their respective compositions. Finally, gene expression analysis identified a number of cancer-relevant pathways that may be controlled by Bmi-1 and Mel-18 and also showed that these Polycomb proteins regulate a set of common gene targets. Taken together, these results suggest that Bmi-1 and Mel-18 may have overlapping functions in cancer cell growth.


Subject(s)
DNA-Binding Proteins/metabolism , Medulloblastoma/pathology , Nuclear Proteins/metabolism , Proto-Oncogene Proteins/metabolism , Repressor Proteins/chemistry , Repressor Proteins/metabolism , Sequence Homology, Amino Acid , Animals , Cell Death , Cell Proliferation , Cell Survival , DNA-Binding Proteins/genetics , Down-Regulation/genetics , Fibroblasts/cytology , Gene Expression , Gene Expression Profiling , Gene Expression Regulation, Neoplastic , HeLa Cells , Humans , Medulloblastoma/genetics , Mice , Nuclear Proteins/genetics , Polycomb Repressive Complex 1 , Polycomb-Group Proteins , Proto-Oncogene Proteins/genetics , RNA, Small Interfering/metabolism , Rats , Repressor Proteins/genetics , Transplantation, Heterologous
20.
Nature ; 432(7015): 338-41, 2004 Nov 18.
Article in English | MEDLINE | ID: mdl-15549096

ABSTRACT

In contrast to normal cells, aneuploidy--alterations in the number of chromosomes--is consistently observed in virtually all cancers. A growing body of evidence suggests that aneuploidy is often caused by a particular type of genetic instability, called chromosomal instability, which may reflect defects in mitotic segregation in cancer cells. A better understanding of the molecular mechanisms leading to aneuploidy holds promise for the development of cancer drugs that target this process.


Subject(s)
Aneuploidy , Chromosomal Instability/genetics , Neoplasms/genetics , Neoplasms/pathology , Animals , Chromosome Segregation , Humans , Mitosis/genetics , Neoplasms/drug therapy , Prognosis
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