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Sasine JP, Himburg HA, Termini CM, Roos M, Tran E, Zhao L, Kan J, Li M, Zhang Y, de Barros SC, Rao DS, Counter CM, Chute JP. Wild-type Kras expands and exhausts hematopoietic stem cells. JCI Insight 2018; 3:98197. [PMID: 29875320 DOI: 10.1172/jci.insight.98197] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 04/19/2018] [Indexed: 12/14/2022] Open
Abstract
Oncogenic Kras expression specifically in hematopoietic stem cells (HSCs) induces a rapidly fatal myeloproliferative neoplasm in mice, suggesting that Kras signaling plays a dominant role in normal hematopoiesis. However, such a conclusion is based on expression of an oncogenic version of Kras. Hence, we sought to determine the effect of simply increasing the amount of endogenous wild-type Kras on HSC fate. To this end, we utilized a codon-optimized version of the murine Kras gene (Krasex3op) that we developed, in which silent mutations in exon 3 render the encoded mRNA more efficiently translated, leading to increased protein expression without disruption to the normal gene architecture. We found that Kras protein levels were significantly increased in bone marrow (BM) HSCs in Krasex3op/ex3op mice, demonstrating that the translation of Kras in HSCs is normally constrained by rare codons. Krasex3op/ex3op mice displayed expansion of BM HSCs, progenitor cells, and B lymphocytes, but no evidence of myeloproliferative disease or leukemia in mice followed for 12 months. BM HSCs from Krasex3op/ex3op mice demonstrated increased multilineage repopulating capacity in primary competitive transplantation assays, but secondary competitive transplants revealed exhaustion of long-term HSCs. Following total body irradiation, Krasex3op/ex3op mice displayed accelerated hematologic recovery and increased survival. Mechanistically, HSCs from Krasex3op/ex3op mice demonstrated increased proliferation at baseline, with a corresponding increase in Erk1/2 phosphorylation and cyclin-dependent kinase 4 and 6 (Cdk4/6) activation. Furthermore, both the enhanced colony-forming capacity and in vivo repopulating capacity of HSCs from Krasex3op/ex3op mice were dependent on Cdk4/6 activation. Finally, BM transplantation studies revealed that augmented Kras expression produced expansion of HSCs, progenitor cells, and B cells in a hematopoietic cell-autonomous manner, independent from effects on the BM microenvironment. This study provides fundamental demonstration of codon usage in a mammal having a biological consequence, which may speak to the importance of codon usage in mammalian biology.
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Affiliation(s)
- Joshua P Sasine
- Division of Hematology/Oncology, Department of Medicine.,Molecular, Cellular and Integrative Physiology.,Jonsson Comprehensive Cancer Center.,Eli and Edythe Broad Center for Stem Cell Research, and
| | | | | | - Martina Roos
- Division of Hematology/Oncology, Department of Medicine.,Jonsson Comprehensive Cancer Center.,Eli and Edythe Broad Center for Stem Cell Research, and
| | - Evelyn Tran
- Division of Hematology/Oncology, Department of Medicine
| | - Liman Zhao
- Division of Hematology/Oncology, Department of Medicine
| | - Jenny Kan
- Division of Hematology/Oncology, Department of Medicine
| | - Michelle Li
- Division of Hematology/Oncology, Department of Medicine
| | - Yurun Zhang
- Division of Hematology/Oncology, Department of Medicine
| | | | - Dinesh S Rao
- Division of Hematology/Oncology, Department of Medicine.,Jonsson Comprehensive Cancer Center.,Eli and Edythe Broad Center for Stem Cell Research, and.,Department of Pathology and Laboratory Medicine, UCLA, Los Angeles, California, USA
| | - Christopher M Counter
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North California, USA
| | - John P Chute
- Division of Hematology/Oncology, Department of Medicine.,Jonsson Comprehensive Cancer Center.,Eli and Edythe Broad Center for Stem Cell Research, and
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Sun HY, Liu BB, Hu JY, Xu LJ, Chan SW, Chan CO, Mok DKW, Zhang DM, Ye WC, Chen SB. Novel cycloartane triterpenoid from Cimicifuga foetida (Sheng ma) induces mitochondrial apoptosis via inhibiting Raf/MEK/ERK pathway and Akt phosphorylation in human breast carcinoma MCF-7 cells. Chin Med 2016; 11:1. [PMID: 26759603 PMCID: PMC4709995 DOI: 10.1186/s13020-015-0073-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 12/09/2015] [Indexed: 11/29/2022] Open
Abstract
Background Cycloartane triterpenoids exhibited anticancer effects. This study aims to identify any potential novel anticancer cycloartane triterpenoids from Cimicifuga foetida L. rhizome (Sheng ma) and the mode of actions. Methods Cycloartane triterpenoids were isolated from the C. foetida rhizome by a series of column chromatography and identified by IR, MS and NMR. Their anticancer effects on several human cancer cell lines, MCF-7, HepG2, HepG2/ADM, HeLa, and PC3, and normal human mammary epithelial cells MCF10A were investigated by colony formation and MTT assays. Morphological analysis of apoptosis induction was performed by acridine orange/ethidium bromide dual-staining and Hoechst 33258 nuclear staining. The cell-cycle profile and annexin V staining were evaluated by flow cytometry. Apoptosis were investigated by measuring changes in mitochondrial membrane potential and analyzing expression of cell cycle- and apoptosis-related proteins in MCF-7 cells by Western blotting. Results A novel cycloartane triterpenoid, 25-O-acetyl-7,8-didehydrocimigenol-3-O-β-d-(2-acetyl)xylopyranoside (ADHC-AXpn), together with the known 7,8-didehydrocimigenol-3-O-β-d-xylopyranoside (DHC-Xpn) were isolated. MCF-7 growth was significantly inhibited by ADHC-AXpn in a dose- and time-dependent manner (IC50: 27.81 µM at 48 h; P = 0.004 vs. control at 25 μM for 48 h treatment), and ADHC-AXpn was selectively cytotoxic for cancerous cells (MCF-7, HepG2/ADM, HepG2 and HELA cells) based on its higher IC50 values for normal cells MCF10A (IC50: 78.63 µM at 48 h) than for tumor cells. In MCF-7 cells, ADHC-AXpn induced G2/M cell cycle arrest by mediating cyclin-B1, and CDK1 and its phosphorylation; and induced apoptosis through the mitochondrial-mediated apoptotic pathway, with inhibition of Akt activation. As ADHC-AXpn suppressed phosphorylation of ERK1/2, Raf and Akt proteins in MCF-7 cells, its apoptotic effect might be associated with Raf/MEK/ERK signaling and Akt activation. Conclusions ADHC-AXpn significantly suppressed the growth of MCF-7 cells, induced mitochondrial apoptosis and cell-cycle arrest, and inhibited Raf/MEK/ERK signaling pathway and Akt phosphorylation.
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Affiliation(s)
- Hai-Yan Sun
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China ; State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Hong Kong Polytechnic University, Hong Kong, China
| | - Bei-Bei Liu
- State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Hong Kong Polytechnic University, Hong Kong, China
| | - Jian-Yang Hu
- College of Pharmacy, Jinan University, Guangzhou, China
| | - Li-Jia Xu
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Shun-Wan Chan
- State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Hong Kong Polytechnic University, Hong Kong, China
| | - Chi-On Chan
- State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Hong Kong Polytechnic University, Hong Kong, China
| | - Daniel K W Mok
- State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Hong Kong Polytechnic University, Hong Kong, China
| | | | - Wen-Cai Ye
- College of Pharmacy, Jinan University, Guangzhou, China
| | - Si-Bao Chen
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China ; State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Hong Kong Polytechnic University, Hong Kong, China
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Santulli P, Marcellin L, Tosti C, Chouzenoux S, Cerles O, Borghese B, Batteux F, Chapron C. MAP kinases and the inflammatory signaling cascade as targets for the treatment of endometriosis? Expert Opin Ther Targets 2015; 19:1465-83. [PMID: 26389657 DOI: 10.1517/14728222.2015.1090974] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
INTRODUCTION The pathogenesis of endometriosis, a common benign disease, remains ill-defined, although it is clear that chronic inflammation plays a crucial role through mitogen-activated protein kinase (MAPK) signaling pathways. All current medical therapies for endometriosis are antigonadotropic, and therefore have a contraceptive effect. A concerted research effort is hence warranted with the aim of delivering novel therapeutics that reduces disease symptoms without blocking ovulation. AREAS COVERED The authors review the complex pathogenic mechanisms of chronic inflammation in endometriosis and their relationships with MAPK pathways. The authors conducted a literature search of descriptive and functional targeted validation of MAPK in the pathogenesis of endometriosis. The effects of MAPK inhibitors, which constitute potential agents for future treatments, are also described. EXPERT OPINION Preliminary studies have highlighted a crucial role for MAPK in driving endometriosis-related inflammation. MAPK inhibitors exhibit potent activity in terms of controlling growth of endometriosis lesions both in vitro and in animal models. As MAPK inhibitors are known to have a multitude of undesirable side effects, their use in humans has to be approached with great care. Indeed, use of these drugs would probably be limited to short exposures prior to surgery in cases involving the most severe disease phenotypes.
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Affiliation(s)
- Pietro Santulli
- a 1 Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Assistance Publique - Hôpitaux de Paris (AP- HP), Groupe Hospitalier Universitaire (GHU) Ouest, Centre Hospitalier Universitaire (CHU) Cochin, Department of Gynecology Obstetrics II and Reproductive Medicine , 75679 Paris, France +33 1 58 41 36 72 ; .,b 2 Université Paris Descartes, Sorbonne Paris Cité, Department "Development, Reproduction and Cancer," Institut Cochin , INSERM U1016, Equipe Pr Batteux, Paris, France
| | - Louis Marcellin
- a 1 Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Assistance Publique - Hôpitaux de Paris (AP- HP), Groupe Hospitalier Universitaire (GHU) Ouest, Centre Hospitalier Universitaire (CHU) Cochin, Department of Gynecology Obstetrics II and Reproductive Medicine , 75679 Paris, France +33 1 58 41 36 72 ; .,b 2 Université Paris Descartes, Sorbonne Paris Cité, Department "Development, Reproduction and Cancer," Institut Cochin , INSERM U1016, Equipe Pr Batteux, Paris, France
| | - Claudia Tosti
- c 3 University of Siena, Obstetrics and Gynecology, Department of Molecular and Developmental Medicine , Siena, Italy
| | - Sandrine Chouzenoux
- b 2 Université Paris Descartes, Sorbonne Paris Cité, Department "Development, Reproduction and Cancer," Institut Cochin , INSERM U1016, Equipe Pr Batteux, Paris, France
| | - Olivier Cerles
- b 2 Université Paris Descartes, Sorbonne Paris Cité, Department "Development, Reproduction and Cancer," Institut Cochin , INSERM U1016, Equipe Pr Batteux, Paris, France
| | - Bruno Borghese
- a 1 Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Assistance Publique - Hôpitaux de Paris (AP- HP), Groupe Hospitalier Universitaire (GHU) Ouest, Centre Hospitalier Universitaire (CHU) Cochin, Department of Gynecology Obstetrics II and Reproductive Medicine , 75679 Paris, France +33 1 58 41 36 72 ; .,b 2 Université Paris Descartes, Sorbonne Paris Cité, Department "Development, Reproduction and Cancer," Institut Cochin , INSERM U1016, Equipe Pr Batteux, Paris, France
| | - Frédéric Batteux
- b 2 Université Paris Descartes, Sorbonne Paris Cité, Department "Development, Reproduction and Cancer," Institut Cochin , INSERM U1016, Equipe Pr Batteux, Paris, France.,d 4 Hôpital Cochin, Department of Immunology , AP-HP, 75679 Paris cedex 14, France
| | - Charles Chapron
- a 1 Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Assistance Publique - Hôpitaux de Paris (AP- HP), Groupe Hospitalier Universitaire (GHU) Ouest, Centre Hospitalier Universitaire (CHU) Cochin, Department of Gynecology Obstetrics II and Reproductive Medicine , 75679 Paris, France +33 1 58 41 36 72 ; .,b 2 Université Paris Descartes, Sorbonne Paris Cité, Department "Development, Reproduction and Cancer," Institut Cochin , INSERM U1016, Equipe Pr Batteux, Paris, France
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YANG GE, WU DAOQUAN, ZHU JING, JIANG OU, SHI QIONG, TIAN JIE, WENG YAGUANG. Upregulation of miR-195 increases the sensitivity of breast cancer cells to Adriamycin treatment through inhibition of Raf-1. Oncol Rep 2013; 30:877-89. [DOI: 10.3892/or.2013.2532] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 05/08/2013] [Indexed: 11/05/2022] Open
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Expression of EGFR, HER2, phosphorylated ERK and phosphorylated MEK in colonic neoplasms of familial adenomatous polyposis patients. J Gastrointest Cancer 2013; 43:444-55. [PMID: 21989899 DOI: 10.1007/s12029-011-9330-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
PURPOSE The expression of epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) is associated with poor prognosis in sporadic colorectal carcinoma (CRC). EGFR inhibitors are approved for the treatment of refractory CRC. The aim of this study was to investigate the expression of EGFR and HER2 and downstream extracellular signal regulated kinase (ERK) and mitogen activated protein kinase (MAPK) in non-neoplastic colonic mucosa, adenomas and carcinomas from familial adenomatous polyposis coli (FAP) patients, exploring the expression along the adenoma-carcinoma sequence. METHODS The expression of EGFR, HER2, phosphorylated MAPK/ERK kinase (pMEK) and phosphorylated ERK (pERK) proteins was studied by immunohistochemistry in samples of colonic non-neoplastic mucosa (n = 65), adenomas (n = 149) and adenocarcinomas (n = 16) from each of the 16 FAP patients. RESULTS For HER2, only weak cytoplasmic expression was seen in 8% of adenomas, 6% of carcinomas and 3% of the non-neoplastic mucosa. EGFR was expressed in non-neoplastic mucosa, adenomas and carcinomas with a statistically significant increase in expression in adenomas compared with non-neoplastic mucosa (p < 0.001). There was also a statistically significant increase in nuclear staining intensity for pERK (p < 0.001) and pMEK (p < 0.001) in adenomas compared to non-neoplastic mucosa. CONCLUSIONS This is the first study investigating the expression of these receptors in non-neoplastic mucosa, adenomas and carcinomas from FAP patients. HER2 is not upregulated in the tumours of FAP patients, while EGFR appears to be upregulated in most adenomas and carcinomas, with associated upregulation of pERK and pMEK. We conclude that EGFR and downstream members of its signalling pathway, but not HER2, may be potential therapeutic targets in FAP patients.
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Chattergoon NN, Giraud GD, Louey S, Stork P, Fowden AL, Thornburg KL. Thyroid hormone drives fetal cardiomyocyte maturation. FASEB J 2011; 26:397-408. [PMID: 21974928 DOI: 10.1096/fj.10-179895] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Tri-iodo-l-thyronine (T(3)) suppresses the proliferation of near-term serum-stimulated fetal ovine cardiomyocytes in vitro. Thus, we hypothesized that T(3) is a major stimulant of cardiomyocyte maturation in vivo. We studied 3 groups of sheep fetuses on gestational days 125-130 (term ∼145 d): a T(3)-infusion group, to mimic fetal term levels (plasma T(3) levels increased from ∼0.1 to ∼1.0 ng/ml; t(1/2)∼24 h); a thyroidectomized group, to produce low thyroid hormone levels; and a vehicle-infusion group, to serve as intact controls. At 130 d of gestation, sections of left ventricular freewall were harvested, and the remaining myocardium was enzymatically dissociated. Proteins involved in cell cycle regulation (p21, cyclin D1), proliferation (ERK), and hypertrophy (mTOR) were measured in left ventricular tissue. Evidence that elevated T(3) augmented the maturation rate of cardiomyocytes included 14% increased width, 31% increase in binucleation, 39% reduction in proliferation, 150% reduction in cyclin D1 protein, and 500% increase in p21 protein. Increased expression of phospho-mTOR, ANP, and SERCA2a also suggests that T(3) promotes maturation and hypertrophy of fetal cardiomyocytes. Thyroidectomized fetuses had reduced cell cycle activity and binucleation. These findings support the hypothesis that T(3) is a prime driver of prenatal cardiomyocyte maturation.
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Cell cycle reactivation in mature neurons: a link with brain plasticity, neuronal injury and neurodegenerative diseases? Neurosci Bull 2011; 27:185-96. [PMID: 21614101 DOI: 10.1007/s12264-011-1002-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Although the cell cycle machinery is essentially linked to cellular proliferation, recent findings suggest that neuronal cell death is frequently concurrent with the aberrant expression of cell cycle proteins in post-mitotic neurons. The present work reviews the evidence of cell cycle reentry and expression of cell cycle-associated proteins as a complex response of neurons to insults in the adult brain but also as a mechanism underlying brain plasticity. The basic aspects of cell cycle mechanisms, as well as the evidence showing cell cycle protein expression in the injured brain, are reviewed. The discussion includes recent experimental work attempting to establish a correlation between altered brain plasticity and neuronal death, and an analysis of recent evidence on how neural cell cycle dysregulation is related to neurodegenerative diseases especially the Alzheimer's disease. Understanding the mechanisms that control reexpression of proteins required for cell cycle progression which is involved in brain remodeling, may shed new light into the mechanisms involved in neuronal demise under diverse pathological circumstances. This would provide valuable clues about the possible therapeutic targets, leading to potential treatment of presently challenging neurodegenerative diseases.
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Zhang J, Chen YH, Lu Q. Pro-oncogenic and anti-oncogenic pathways: opportunities and challenges of cancer therapy. Future Oncol 2010; 6:587-603. [PMID: 20373871 DOI: 10.2217/fon.10.15] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Carcinogenesis is the uncontrolled growth of cells gaining the potential to invade and disrupt vital tissue functions. This malignant process includes the occurrence of 'unwanted' gene mutations that induce the transformation of normal cells, for example, by overactivation of pro-oncogenic pathways and inactivation of tumor-suppressive or anti-oncogenic pathways. It is now recognized that the number of major signaling pathways that control oncogenesis is not unlimited; therefore, suppressing these pathways can conceivably lead to a cancer cure. However, the clinical application of cancer intervention has not matched up to scientific expectations. Increasing numbers of studies have revealed that many oncogenic-signaling elements show double faces, in which they can promote or suppress cancer pathogenesis depending on tissue type, cancer stage, gene dosage and their interaction with other players in carcinogenesis. This complexity of oncogenic signaling poses challenges to traditional cancer therapy and calls for considerable caution when designing an anticancer drug strategy. We propose future oncology interventions with the concept of integrative cancer therapy.
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Affiliation(s)
- Jiao Zhang
- Department of Anatomy & Cell Biology, The Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
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Bidzhekov K, Hautmann M, Semisch M, Weber C, Engelmann B, Hatzopoulos AK. Rafs constitute a nodal point in the regulation of embryonic endothelial progenitor cell growth and differentiation. J Cell Mol Med 2008; 11:1395-407. [PMID: 18205709 PMCID: PMC4401289 DOI: 10.1111/j.1582-4934.2007.00123.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mouse embryonic endothelial progenitor cells (eEPCs) acquire a mature phenotype after treatment with cyclic adenosine monophosphate (cAMP), suggesting an involvement of Raf serine/threonine kinases in the differentiation process. To test this idea, we investigated the role of B-Raf and C-Raf in proliferation and differentiation of eEPCs by expressing fusion proteins consisting of the kinase domains from Raf molecules and the hormone binding site of the estrogen receptor (ER), or its variant, the tamoxifen receptor. Our findings show that both B- and C-Raf kinase domains, when lacking adjacent regulatory parts, are equally effective in inducing eEPC differentiation. In contrast, the C-Raf kinase domain is a more potent stimulator of eEPC proliferation than B-Raf. In a complimentary approach, we used siRNA silencing to knockdown endogenously expressed B-Raf and C-Raf in eEPCs. In this experimental setting, we found that eEPCs lacking B-Raf failed to differentiate, whereas loss-of C-Raf function primarily slowed cell growth without impairing cAMP-induced differentiation. These findings were further corroborated in B-Raf null eEPCs, isolated from the corresponding knockout embryos, which failed to differentiate in vitro. Thus, gain- and loss-of-function experiments point to distinct roles of B-Raf and C-Raf in regulating growth and differentiation of endothelial progenitor cells, which may harbour therapeutic implications.
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Affiliation(s)
- Kiril Bidzhekov
- GSF-National Research Center for Environment and Health, Institute of Clinical Molecular Biology and Tumor Genetics, Munich, Germany
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McCubrey JA, Steelman LS, Chappell WH, Abrams SL, Wong EWT, Chang F, Lehmann B, Terrian DM, Milella M, Tafuri A, Stivala F, Libra M, Basecke J, Evangelisti C, Martelli AM, Franklin RA. Roles of the Raf/MEK/ERK pathway in cell growth, malignant transformation and drug resistance. BIOCHIMICA ET BIOPHYSICA ACTA 2007; 1773:1263-84. [PMID: 17126425 PMCID: PMC2696318 DOI: 10.1016/j.bbamcr.2006.10.001] [Citation(s) in RCA: 1651] [Impact Index Per Article: 97.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 10/02/2006] [Accepted: 10/03/2006] [Indexed: 02/07/2023]
Abstract
Growth factors and mitogens use the Ras/Raf/MEK/ERK signaling cascade to transmit signals from their receptors to regulate gene expression and prevent apoptosis. Some components of these pathways are mutated or aberrantly expressed in human cancer (e.g., Ras, B-Raf). Mutations also occur at genes encoding upstream receptors (e.g., EGFR and Flt-3) and chimeric chromosomal translocations (e.g., BCR-ABL) which transmit their signals through these cascades. Even in the absence of obvious genetic mutations, this pathway has been reported to be activated in over 50% of acute myelogenous leukemia and acute lymphocytic leukemia and is also frequently activated in other cancer types (e.g., breast and prostate cancers). Importantly, this increased expression is associated with a poor prognosis. The Ras/Raf/MEK/ERK and Ras/PI3K/PTEN/Akt pathways interact with each other to regulate growth and in some cases tumorigenesis. For example, in some cells, PTEN mutation may contribute to suppression of the Raf/MEK/ERK cascade due to the ability of activated Akt to phosphorylate and inactivate different Rafs. Although both of these pathways are commonly thought to have anti-apoptotic and drug resistance effects on cells, they display different cell lineage specific effects. For example, Raf/MEK/ERK is usually associated with proliferation and drug resistance of hematopoietic cells, while activation of the Raf/MEK/ERK cascade is suppressed in some prostate cancer cell lines which have mutations at PTEN and express high levels of activated Akt. Furthermore the Ras/Raf/MEK/ERK and Ras/PI3K/PTEN/Akt pathways also interact with the p53 pathway. Some of these interactions can result in controlling the activity and subcellular localization of Bim, Bak, Bax, Puma and Noxa. Raf/MEK/ERK may promote cell cycle arrest in prostate cells and this may be regulated by p53 as restoration of wild-type p53 in p53 deficient prostate cancer cells results in their enhanced sensitivity to chemotherapeutic drugs and increased expression of Raf/MEK/ERK pathway. Thus in advanced prostate cancer, it may be advantageous to induce Raf/MEK/ERK expression to promote cell cycle arrest, while in hematopoietic cancers it may be beneficial to inhibit Raf/MEK/ERK induced proliferation and drug resistance. Thus the Raf/MEK/ERK pathway has different effects on growth, prevention of apoptosis, cell cycle arrest and induction of drug resistance in cells of various lineages which may be due to the presence of functional p53 and PTEN and the expression of lineage specific factors.
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Affiliation(s)
- James A McCubrey
- Department of Microbiology and Immunology, Leo Jenkins Cancer Center, Brody School of Medicine at East Carolina University, Greenville, NC 27858, USA.
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McCubrey JA, Steelman LS, Abrams SL, Lee JT, Chang F, Bertrand FE, Navolanic PM, Terrian DM, Franklin RA, D'Assoro AB, Salisbury JL, Mazzarino MC, Stivala F, Libra M. Roles of the RAF/MEK/ERK and PI3K/PTEN/AKT pathways in malignant transformation and drug resistance. ACTA ACUST UNITED AC 2006; 46:249-79. [PMID: 16854453 DOI: 10.1016/j.advenzreg.2006.01.004] [Citation(s) in RCA: 486] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The Ras/Raf/MEK/ERK and PI3K/PTEN/AKT signaling cascades play critical roles in the transmission of signals from growth factor receptors to regulate gene expression and prevent apoptosis. Components of these pathways are mutated or aberrantly expressed in human cancer (e.g., Ras, B-Raf, PI3K, PTEN, Akt). Also, mutations occur at genes encoding upstream receptors (e.g., EGFR and Flt-3) and chimeric chromosomal translocations (e.g., BCR-ABL) which transmit their signals through these cascades. These pathways interact with each other to regulate growth and in some cases tumorigenesis. For example, in some cells, PTEN mutation may contribute to suppression of the Raf/MEK/ERK cascade due to the ability of elevated activated Akt levels to phosphorylate and inactivate Raf-1. We have investigated the genetic structures and functional roles of these two signaling pathways in the malignant transformation and drug resistance of hematopoietic, breast and prostate cancer cells. Although both of these pathways are commonly thought to have anti-apoptotic and drug resistance effects on cells, they display different cell-lineage-specific effects. Induced Raf expression can abrogate the cytokine dependence of certain hematopoietic cell lines (FDC-P1 and TF-1), a trait associated with tumorigenesis. In contrast, expression of activated PI3K or Akt does not abrogate the cytokine dependence of these hematopoietic cell lines, but does have positive effects on cell survival. However, activated PI3K and Akt can synergize with activated Raf to abrogate the cytokine dependence of another hematopoietic cell line (FL5.12) which is not transformed by activated Raf expression by itself. Activated Raf and Akt also confer a drug-resistant phenotype to these cells. Raf is more associated with proliferation and the prevention of apoptosis while Akt is more associated with the long-term clonogenicity. In breast cancer cells, activated Raf conferred resistance to the chemotherapeutic drugs doxorubicin and paclitaxel. Raf induced the expression of the drug pump Mdr-1 (a.k.a., Pgp) and the Bcl-2 anti-apoptotic protein. Raf did not appear to induce drug resistance by altering p53/p21Cip-1 expression, whose expression is often linked to regulation of cell cycle progression and drug resistance. Deregulation of the PI3K/PTEN/Akt pathway was associated with resistance to doxorubicin and 4-hydroxyl tamoxifen, a chemotherapeutic drug and estrogen receptor antagonist used in breast cancer therapy. In contrast to the drug-resistant breast cancer cells obtained after overexpression of activated Raf, cells expressing activated Akt displayed altered (decreased) levels of p53/p21Cip-1. Deregulated expression of the central phosphatase in the PI3K/PTEN/Akt pathway led to breast cancer drug resistance. Introduction of mutated forms of PTEN, which lacked lipid phosphatase activity, increased the resistance of the MCF-7 cells to doxorubicin, suggesting that these lipid phosphatase deficient PTEN mutants acted as dominant negative mutants to suppress wild-type PTEN activity. Finally, the PI3K/PTEN/Akt pathway appears to be more prominently involved in prostate cancer drug resistance than the Raf/MEK/ERK pathway. Some advanced prostate cancer cells express elevated levels of activated Akt which may suppress Raf activation. Introduction of activated forms of Akt increased the drug resistance of advanced prostate cancer cells. In contrast, introduction of activated forms of Raf did not increase the drug resistance of the prostate cancer cells. In contrast to the results observed in hematopoietic cells, Raf may normally promote differentiation in prostate cells which is suppressed in advanced prostate cancer due to increased expression of activated Akt arising from PTEN mutation. Thus in advanced prostate cancer it may be advantageous to induce Raf expression to promote differentiation, while in hematopoietic cancers it may be beneficial to inhibit Raf/MEK/ERK-induced proliferation. These signaling and anti-apoptotic pathways can have different effects on growth, prevention of apoptosis and induction of drug resistance in cells of various lineages which may be due to the expression of lineage-specific factors.
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Affiliation(s)
- James A McCubrey
- Department of Microbiology & Immunology, Brody School of Medicine at East Carolina University, Greenville, NC 27858, USA.
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McCubrey JA, Shelton JG, Steelman LS, Franklin RA, Sreevalsan T, McMahon M. Effects of a conditionally active v-ErbB and an EGF-R inhibitor on transformation of NIH-3T3 cells and abrogation of cytokine dependency of hematopoietic cells. Oncogene 2004; 23:7810-20. [PMID: 15361836 DOI: 10.1038/sj.onc.1208055] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Epidermal growth factor (EGF) and its cognate receptor (EGF-R) are often dysregulated in human neoplasia. Moreover, EGF-R-transformed cell lines have constitutive EGF-R activity, which makes elucidation of its effects difficult to determine. In the following studies, the effects of a novel conditionally activated form of EGF-R, v-ErbB:ER, on the morphological transformation of NIH-3T3 cells and the abrogation of hematopoietic cell cytokine dependence were investigated. The v-ErbB ES-4 oncogene was fused to the hormone binding domain of the estrogen receptor (ER). This construct, v-ErbB:ER, requires beta-estradiol or 4-OH tamoxifen for activation. v-ErbB:ER conditionally transformed NIH-3T3 cells and abrogated cytokine dependence of hematopoietic cells. Stimulation of v-ErbB:ER activity resulted in the activation of the phosphatidylinositol 3-kinase (PI3K)/Akt and Raf/MEK/ERK kinase cascades. To determine the importance of these signal transduction pathways, the conditionally transformed hematopoietic cells were treated with EGF-R, PI3K and MEK inhibitors. The EGF-R inhibitor AG1478 effectively inhibited MEK, ERK and Akt activation, and induced apoptosis when the cells were grown in response to v-ErbB:ER. Apoptosis was observed at 100- to 1000-fold lower concentrations of AG1478 when the cells were grown in response to v-ErbB:ER as opposed to IL-3. Furthermore, the parental, BCR-ABL- and Raf-transformed cells were only susceptible to the apoptosis-inducing effects of AG1478 at the highest concentrations demonstrating the specificity of these inhibitors. MEK or PI3K inhibitors suppressed ERK or Akt activation, respectively, and induced apoptosis in the v-ErbB:ER-responsive cells. However, MEK and PI3K inhibitors only induced apoptosis at 1000-fold higher concentrations than the EGFR inhibitor. This novel v-ErbB:ER construct and these conditionally transformed cell lines will be useful to further elucidate ErbB-mediated signal transduction and to determine the effectiveness of various inhibitors in targeting different aspects of EGF-R-mediated signal transduction and malignant transformation.
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Affiliation(s)
- James A McCubrey
- Department of Microbiology and Immunology, Brody School of Medicine at East Carolina University, Greenville, NC 27858, USA.
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13
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Douglas EJ, Fiegler H, Rowan A, Halford S, Bicknell DC, Bodmer W, Tomlinson IPM, Carter NP. Array comparative genomic hybridization analysis of colorectal cancer cell lines and primary carcinomas. Cancer Res 2004; 64:4817-25. [PMID: 15256451 DOI: 10.1158/0008-5472.can-04-0328] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Array comparative genomic hybridization, with a genome-wide resolution of approximately 1 Mb, has been used to investigate copy number changes in 48 colorectal cancer (CRC) cell lines and 37 primary CRCs. The samples were divided for analysis according to the type of genomic instability that they exhibit, microsatellite instability (MSI) or chromosomal instability (CIN). Consistent copy number changes were identified, including gain of chromosomes 20, 13, and 8q and smaller regions of amplification such as chromosome 17q11.2-q12. Loss of chromosome 18q was a recurrent finding along with deletion of discrete regions such as chromosome 4q34-q35. The overall pattern of copy number change was strikingly similar between cell lines and primary cancers with a few obvious exceptions such as loss of chromosome 6 and gain of chromosomes 15 and 12p in the former. A greater number of aberrations were detected in CIN+ than MSI+ samples as well as differences in the type and extent of change reported. For example, loss of chromosome 8p was a common event in CIN+ cell lines and cancers but was often found to be gained in MSI+ cancers. In addition, the target of amplification on chromosome 8q appeared to differ, with 8q24.21 amplified frequently in CIN+ samples but 8q24.3 amplification a common finding in MSI+ samples. A number of genes of interest are located within the frequently aberrated regions, which are likely to be of importance in the development and progression of CRC.
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Affiliation(s)
- Eleanor J Douglas
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
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14
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Raza SM, Fuller GN, Rhee CH, Huang S, Hess K, Zhang W, Sawaya R. Identification of Necrosis-Associated Genes in Glioblastoma by cDNA Microarray Analysis. Clin Cancer Res 2004; 10:212-21. [PMID: 14734472 DOI: 10.1158/1078-0432.ccr-0155-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE In the field of cancer research, there has been a paucity of interest in necrosis, whereas studies focusing on apoptosis abound. In neuro-oncology, this is particularly surprising because of the importance of necrosis as a hallmark of glioblastoma (GBM), the most malignant and most common primary brain tumor, and the fact that the degree of necrosis has been shown to be inversely related to patient survival. It is therefore of considerable interest and importance to identify genes and gene products related to necrosis formation. EXPERIMENTAL DESIGN We used a nylon cDNA microarray to analyze mRNA expression of 588 universal cellular genes in 15 surgically resected human GBM samples with varying degrees of necrosis. Gene expression was correlated with the degree of necrosis using rank correlation coefficients. The expression of identified genes was compared with their expression in tissue samples from 5 anaplastic astrocytomas (AAs). Immunostaining was used to determine whether genes showing the most positive correlation with necrosis were increasingly expressed in tumor tissues, as grade of necrosis increased. RESULTS The hybridization results indicated that 26 genes showed significant correlation with the amount of necrosis. All 26 genes had functions associated with either Ras, Akt, tumor necrosis factor alpha, nuclear factor kappaB, apoptosis, procoagulation, or hypoxia. Nine genes were positively correlated with necrosis grade, and 17 genes were negatively correlated with necrosis grade. There were significant differences in the median expression levels of 3 of the 26 genes between grade III necrosis GBM and anaplastic astrocytoma (AA) samples; all but 1 of the genes had elevated expression when comparing necrosis grade III with AA samples. Two factors, the ephrin type A receptor 1 and the prostaglandin E(2) receptor EP4 subtype, not previously considered in this context, were highlighted because of their particularly high (positive) correlation coefficients; immunostaining showed the products of these two genes to be localized in perinecrotic and necrotic regions and to be overexpressed in grade III GBMs, but not AAs. These two molecules also showed significant correlation with survival of GBM patients (P = 0.0034) in a combined model. CONCLUSIONS The application of cDNA expression microarray analysis has identified specific genes and patterns of gene expression that may help elucidate the molecular basis of necrogenesis in GBM. Additional studies will be required to further investigate and confirm these findings.
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Affiliation(s)
- Shaan M Raza
- Departments of Neurosurgery, Brain Tumor Center, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA
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15
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Shelton JG, Moye PW, Steelman LS, Blalock WL, Lee JT, Franklin RA, McMahon M, McCubrey JA. Differential effects of kinase cascade inhibitors on neoplastic and cytokine-mediated cell proliferation. Leukemia 2003; 17:1765-82. [PMID: 12970777 DOI: 10.1038/sj.leu.2403052] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The Raf/MEK/ERK and PI3K/Akt pathways regulate proliferation and prevent apoptosis, and their altered expression is commonly observed in human cancer due to the high mutation frequency of upstream regulators. In this study, the effects of Raf, MEK, and PI3K inhibitors on conditionally transformed hematopoietic cells were examined to determine if they would display cytotoxic differences between cytokine- and oncogene-mediated proliferation, and whether inhibition of both pathways was a more effective means to induce apoptosis. In the hematopoietic model system employed, proliferation was conditional and occurred when either interleukin-3 (IL-3) or the estrogen receptor antagonist 4-hydroxytamoxifen (4HT), which activates the conditional oncoprotein (DeltaRaf:ER), were provided. Thus, upon the addition of the signal transduction inhibitors and either IL-3 or 4HT, the effects of these drugs were examined in the same cell under 'cytokine-' and 'oncoprotein' -mediated growth conditions avoiding genetic and differentiation stage heterogeneity. At drug concentrations around the reported IC(50) for the Raf inhibitor L-779,450, it suppressed DNA synthesis and induced apoptosis in hematopoietic FDC-P1 cells transformed to grow in response to either Raf-1 or A-Raf (FD/DeltaRaf-1:ER and FD/DeltaA-Raf:ER), but it displayed less effects on DNA synthesis and apoptosis when the cells were cultured in IL-3. This Raf inhibitor was less effective on B-Raf- or MEK1-responsive cells, demonstrating the specificity of this drug. MEK inhibitors also suppressed DNA synthesis and induced apoptosis in Raf-responsive cells and the effects were more significant on Raf-responsive compared to cytokine-mediated growth. The PI3K inhibitor LY294002 suppressed Raf-mediated growth, indicating that part of the long-term proliferative effects mediated by Raf are PI3K dependent. Simultaneous inhibition of both Raf/MEK/ERK and PI3K/Akt pathways proved a more efficient means to suppress DNA synthesis and induce apoptosis at lower drug concentrations.
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Affiliation(s)
- J G Shelton
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville 27858, USA
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16
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Chang F, Steelman LS, Lee JT, Shelton JG, Navolanic PM, Blalock WL, Franklin RA, McCubrey JA. Signal transduction mediated by the Ras/Raf/MEK/ERK pathway from cytokine receptors to transcription factors: potential targeting for therapeutic intervention. Leukemia 2003; 17:1263-93. [PMID: 12835716 DOI: 10.1038/sj.leu.2402945] [Citation(s) in RCA: 513] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The Ras/Raf/Mitogen-activated protein kinase/ERK kinase (MEK)/extracellular-signal-regulated kinase (ERK) cascade couples signals from cell surface receptors to transcription factors, which regulate gene expression. Depending upon the stimulus and cell type, this pathway can transmit signals, which result in the prevention or induction of apoptosis or cell cycle progression. Thus, it is an appropriate pathway to target for therapeutic intervention. This pathway becomes more complex daily, as there are multiple members of the kinase and transcription factor families, which can be activated or inactivated by protein phosphorylation. The diversity of signals transduced by this pathway is increased, as different family members heterodimerize to transmit different signals. Furthermore, additional signal transduction pathways interact with the Raf/MEK/ERK pathway to regulate positively or negatively its activity, or to alter the phosphorylation status of downstream targets. Abnormal activation of this pathway occurs in leukemia because of mutations at Ras as well as genes in other pathways (eg PI3K, PTEN, Akt), which serve to regulate its activity. Dysregulation of this pathway can result in autocrine transformation of hematopoietic cells since cytokine genes such as interleukin-3 and granulocyte/macrophage colony-stimulating factor contain the transacting binding sites for the transcription factors regulated by this pathway. Inhibitors of Ras, Raf, MEK and some downstream targets have been developed and many are currently in clinical trials. This review will summarize our current understanding of the Ras/Raf/MEK/ERK signal transduction pathway and the downstream transcription factors. The prospects of targeting this pathway for therapeutic intervention in leukemia and other cancers will be evaluated.
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Affiliation(s)
- F Chang
- Department of Microbiology and Immunology, Brody School of Medicine at East Carolina University, Greenville, NC 27858, USA
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17
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Shelton JG, Steelman LS, Lee JT, Knapp SL, Blalock WL, Moye PW, Franklin RA, Pohnert SC, Mirza AM, McMahon M, McCubrey JA. Effects of the RAF/MEK/ERK and PI3K/AKT signal transduction pathways on the abrogation of cytokine-dependence and prevention of apoptosis in hematopoietic cells. Oncogene 2003; 22:2478-92. [PMID: 12717425 DOI: 10.1038/sj.onc.1206321] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The Raf/MEK/ERK kinase cascade is pivotal in transmitting signals from membrane receptors to transcription factors that control gene expression culminating in the regulation of cell cycle progression. This cascade can prevent cell death through ERK2 and p90(Rsk) activation and phosphorylation of apoptotic and cell cycle regulatory proteins. The PI3K/Akt kinase cascade also controls apoptosis and can phosphorylate many apoptotic and cell cycle regulatory proteins. These pathways are interwoven as Akt can phosphorylate Raf and result in its inactivation, and Raf can be required for the antiapoptotic effects of Akt. In this study, the effects of activated Raf (Raf-1, A-Raf and B-Raf) and PI3K/Akt proteins on abrogation of cytokine dependence in FL5.12 hematopoietic cells were examined. Activated Raf, PI3K or Akt expression, by themselves, did not readily relieve cytokine dependence. The presence of activated Raf and PI3K/Akt increased the isolation of factor-independent cells from 400- to 2500-fold depending upon the particular combination examined. The individual effects of activated Raf and Akt on proliferation, apoptosis and autocrine growth factor synthesis were further examined with hormone-inducible constructs (Delta Raf-1:AR and Delta Akt:ER*(Myr(+)). Activation of either Raf or Akt hindered cell death; however, both proliferation and maximal synthesis of autocrine cytokines were dependent upon activation of both signaling pathways. The effects of small molecular weight inhibitors on DNA synthesis and cytokine gene expression were also examined. The PI3K inhibitor, LY294002, inhibited growth and cytokine gene expression. This effect could be synergistically increased by addition of the MEK inhibitor UO126. These cells will be useful in elucidating the interactions between Raf/MEK/ERK and PI3K/Akt cascades in proliferation, apoptosis, and leukemogenesis, as well as evaluating the efficacy of signal transduction inhibitors that target these cascades.
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Affiliation(s)
- John G Shelton
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC 27858, USA
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Blagosklonny MV. Cell senescence and hypermitogenic arrest. EMBO Rep 2003; 4:358-62. [PMID: 12671679 PMCID: PMC1319162 DOI: 10.1038/sj.embor.embor806] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2002] [Accepted: 01/30/2003] [Indexed: 11/09/2022] Open
Abstract
A diverse range of conditions, from mitogenic stimuli to cytotoxic stress, can induce cell senescence. Here, I propose that simultaneous stimulation of mitogen-activated pathways and downstream inhibition of cyclin-dependent kinases leads, ultimately, to cell senescence. This model distinguishes between two types of growth arrest: first, exit to G0 phase, which is caused by the withdrawal of mitogens and can lead to apoptosis; and second, hypermitogenic arrest, which is stimulated by mitogens and can lead to senescence. The concept of hypermitogenic arrest defines cell senescence as a functionally active, stable and conditionally reversible state.
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Affiliation(s)
- Mikhail V Blagosklonny
- Brander Cancer Research Institute, New York Medical College, Hawthorne, New York 10532, USA.
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Chang F, Lee JT, Navolanic PM, Steelman LS, Shelton JG, Blalock WL, Franklin RA, McCubrey JA. Involvement of PI3K/Akt pathway in cell cycle progression, apoptosis, and neoplastic transformation: a target for cancer chemotherapy. Leukemia 2003; 17:590-603. [PMID: 12646949 DOI: 10.1038/sj.leu.2402824] [Citation(s) in RCA: 890] [Impact Index Per Article: 42.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The PI3K/Akt signal transduction cascade has been investigated extensively for its roles in oncogenic transformation. Initial studies implicated both PI3K and Akt in prevention of apoptosis. However, more recent evidence has also associated this pathway with regulation of cell cycle progression. Uncovering the signaling network spanning from extracellular environment to the nucleus should illuminate biochemical events contributing to malignant transformation. Here, we discuss PI3K/Akt-mediated signal transduction including its mechanisms of activation, signal transducing molecules, and effects on gene expression that contribute to tumorigenesis. Effects of PI3K/Akt signaling on important proteins controlling cellular proliferation are emphasized. These targets include cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors. Furthermore, strategies used to inhibit the PI3K/Akt pathway are presented. The potential for cancer treatment with agents inhibiting this pathway is also addressed.
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Affiliation(s)
- F Chang
- Department of Microbiology & Immunology, Brody School of Medicine at East Carolina University, Greenville 27858, USA
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