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Shang Z, Xi S, Lai Y, Cheng H. Single-cell transcriptomics and Mendelian randomization reveal LUCAT1's role in right-sided colorectal cancer risk. Front Genet 2024; 15:1357704. [PMID: 38711918 PMCID: PMC11070547 DOI: 10.3389/fgene.2024.1357704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 03/22/2024] [Indexed: 05/08/2024] Open
Abstract
Background: Colorectal cancer (CRC) is a malignancy with high incidence and mortality rates globally, categorized into left-sided and right-sided CRC, each exhibiting significant differences in molecular characteristics, clinical manifestations, and prognosis. Methods: This study employed single-cell transcriptomic data and various bioinformatics approaches, such as two-sample Mendelian randomization, reverse Mendelian randomization, colocalization analysis, directed filtering, pseudotime analysis, and intercellular communication analysis. It analyzed cellular-level disparities between left-sided and right-sided CRC, identifying distinct subpopulations with characteristic variations. For these cells, two-sample Mendelian randomization was utilized to explore gene-to-one-sided CRC causality. Results: LUCAT1 was enriched in high-abundance monocyte subpopulations in right-sided CRC and demonstrated potential risk factor status through Mendelian randomization analysis. The specific single-nucleotide polymorphism (SNP) rs10774624 was associated with an increased risk of CRC. Moreover, metabolic pathway analysis revealed that LUCAT1+ monocytes exhibit lower communication activity in the tumor microenvironment and heightened activity in metabolic functions like glycosaminoglycan degradation. Its biological functions are related to the positive regulation of interleukin-6 production and NF-kappa B signaling, among others. Conclusion: This study confirmed a potential causal relationship between LUCAT1 and right-sided CRC risk through Mendelian randomization analysis. These findings provide novel insights into the pathogenesis of right-sided CRC and may aid in developing early detection and treatment strategies for right-sided CRC.
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Affiliation(s)
- Zhihao Shang
- Jiangsu Collaborative Innovation Center of Traditional Chinese Medicine Prevention and Treatment of Tumor, Nanjing University of Chinese Medicine, Nanjing, China
- The First School of Clinical Medicine, Nanjing University of Chinese Medicine, Nanjing, China
| | - Songyang Xi
- Jiangsu Collaborative Innovation Center of Traditional Chinese Medicine Prevention and Treatment of Tumor, Nanjing University of Chinese Medicine, Nanjing, China
- The First School of Clinical Medicine, Nanjing University of Chinese Medicine, Nanjing, China
- Zhenjiang Hospital of Chinese Traditional and Western Medicine, Zhenjiang, Jiangsu, China
| | - Yueyang Lai
- Jiangsu Collaborative Innovation Center of Traditional Chinese Medicine Prevention and Treatment of Tumor, Nanjing University of Chinese Medicine, Nanjing, China
- The First School of Clinical Medicine, Nanjing University of Chinese Medicine, Nanjing, China
| | - Haibo Cheng
- Jiangsu Collaborative Innovation Center of Traditional Chinese Medicine Prevention and Treatment of Tumor, Nanjing University of Chinese Medicine, Nanjing, China
- The First School of Clinical Medicine, Nanjing University of Chinese Medicine, Nanjing, China
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Lu JW, Raghuram D, Fong PSA, Gong Z. Inducible Intestine-Specific Expression of kras V12 Triggers Intestinal Tumorigenesis In Transgenic Zebrafish. Neoplasia 2018; 20:1187-1197. [PMID: 30390498 PMCID: PMC6215966 DOI: 10.1016/j.neo.2018.10.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2018] [Revised: 10/10/2018] [Accepted: 10/11/2018] [Indexed: 02/06/2023] Open
Abstract
KRAS mutations are a major risk factor in colorectal cancers. In particular, a point mutation of KRAS of amino acid 12, such as KRASV12, renders it stable activity in oncogenesis. We found that krasV12 promotes intestinal carcinogenesis by generating a transgenic zebrafish line with inducible krasV12 expression in the intestine, Tg(ifabp:EGFP-krasV12). The transgenic fish generated exhibited significant increases in the rates of intestinal epithelial outgrowth, proliferation, and cross talk in the active Ras signaling pathway involving in epithelial-mesenchymal transition (EMT). These results provide in vivo evidence of Ras pathway activation via krasV12 overexpression. Long-term transgenic expression of krasV12 resulted in enteritis, epithelial hyperplasia, and tubular adenoma in adult fish. This was accompanied by increased levels of the signaling proteins p-Erk and p-Akt and by downregulation of the EMT marker E-cadherin. Furthermore, we also observed a synergistic effect of krasV12 expression and dextran sodium sulfate treatment to enhance intestinal tumor in zebrafish. Our results demonstrate that krasV12 overexpression induces intestinal tumorigenesis in zebrafish, which mimics intestinal tumor formation in humans. Thus, our transgenic zebrafish may provide a valuable in vivo platform that can be used to investigate tumor initiation and anticancer drugs for gastrointestinal cancers.
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Affiliation(s)
- Jeng-Wei Lu
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Divya Raghuram
- Department of Biological Sciences, National University of Singapore, Singapore
| | | | - Zhiyuan Gong
- Department of Biological Sciences, National University of Singapore, Singapore.
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Zolfaghari N, Shahbazi S, Torfeh M, Khorasani M, Hashemi M, Mahdian R. Identification of Differentially Expressed K-Ras Transcript Variants in Patients With Leiomyoma. Reprod Sci 2017; 24:1438-1443. [PMID: 28122482 DOI: 10.1177/1933719116689596] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
PURPOSE Molecular studies have demonstrated a wide range of gene expression variations in uterine leiomyoma. The rat sarcoma virus/rapidly accelerated fibrosarcoma/mitogen-activated protein kinase (RAS/RAF/MAPK) is the crucial cellular pathway in transmitting external signals into nucleus. Deregulation of this pathway contributes to excessive cell proliferation and tumorigenesis. The present study aims to investigate the expression profile of the K-Ras transcripts in tissue samples from patients with leiomyoma. METHODS The patients were leiomyoma cases who had no mutation in mediator complex subunit 12 ( MED12) gene. A quantitative approach has been applied to determine the difference in the expression of the 2 main K-Ras messenger RNA (mRNA) variants. The comparison between gene expression levels in leiomyoma and normal myometrium group was performed using relative expression software tool. RESULTS The expression of K-Ras4B gene was upregulated in leiomyoma group ( P = .016), suggesting the involvement of K-Ras4B in the disease pathogenesis. Pairwise comparison of the K-Ras4B expression between each leiomyoma tissue and its matched adjacent normal myometrium revealed gene upregulation in 68% of the cases. The expression of K-Ras4A mRNA was relatively upregulated in leiomyoma group ( P = .030). In addition, the mean expression of K-Ras4A gene in leiomyoma tissues relative to normal samples was 4.475 (95% confidence interval: 0.10-20.42; standard error: 0.53-12.67). In total, 58% of the cases showed more than 2-fold increase in K-Ras4A gene expression. CONCLUSION Our results demonstrated increased expression of both K-Ras mRNA splicing variants in leiomyoma tissue. However, the ultimate result of KRAS expression on leiomyoma development depends on the overall KRAS isoform balance and, consequently, on activated signaling pathways.
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Affiliation(s)
- Nooshin Zolfaghari
- 1 Department of Molecular Genetics, Tehran Medical Branch, Islamic Azad University, Tehran, Iran
| | - Shirin Shahbazi
- 2 Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Mahnaz Torfeh
- 3 Molecular Medicine Department, Pasteur Institute of Iran, Tehran, Iran
| | - Maryam Khorasani
- 3 Molecular Medicine Department, Pasteur Institute of Iran, Tehran, Iran
| | - Mehrdad Hashemi
- 1 Department of Molecular Genetics, Tehran Medical Branch, Islamic Azad University, Tehran, Iran
| | - Reza Mahdian
- 3 Molecular Medicine Department, Pasteur Institute of Iran, Tehran, Iran
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Madison BB, Liu Q, Zhong X, Hahn CM, Lin N, Emmett MJ, Stanger BZ, Lee JS, Rustgi AK. LIN28B promotes growth and tumorigenesis of the intestinal epithelium via Let-7. Genes Dev 2013; 27:2233-45. [PMID: 24142874 PMCID: PMC3814644 DOI: 10.1101/gad.224659.113] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The RNA-binding proteins LIN28A and LIN28B have diverse functions in cellular reprogramming, growth, and oncogenesis. Madison et al. discover that intestine targeted expression of LIN28B causes intestinal hypertrophy, crypt expansion, and adenocarcinoma formation. Modulation of Let-7 levels via deletion of the mirLet7c2/mirLet7b genes recapitulated these effects, and intestine-specific Let-7 expression reversed the hypertrophy and Paneth cell depletion caused by Lin28b. These results demonstrate that Let-7 miRNAs are critical for repressing intestinal tissue growth and that LIN28B can act as an oncogene. The RNA-binding proteins LIN28A and LIN28B have diverse functions in embryonic stem cells, cellular reprogramming, growth, and oncogenesis. Many of these effects occur via direct inhibition of Let-7 microRNAs (miRNAs), although Let-7-independent effects have been surmised. We report that intestine targeted expression of LIN28B causes intestinal hypertrophy, crypt expansion, and Paneth cell loss. Furthermore, LIN28B fosters intestinal polyp and adenocarcinoma formation. To examine potential Let-7-independent functions of LIN28B, we pursued ribonucleoprotein cross-linking, immunoprecipitation, and high-throughput sequencing (CLIP-seq) to identify direct RNA targets. This revealed that LIN28B bound a substantial number of mRNAs and modestly augmented protein levels of these target mRNAs in vivo. Conversely, Let-7 had a profound effect; modulation of Let-7 levels via deletion of the mirLet7c2/mirLet7b genes recapitulated effects of Lin28b overexpression. Furthermore, intestine-specific Let-7 expression could reverse hypertrophy and Paneth cell depletion caused by Lin28b. This was independent of effects on insulin–PI3K–mTOR signaling. Our study reveals that Let-7 miRNAs are critical for repressing intestinal tissue growth and promoting Paneth cell differentiation. Let-7-dependent effects of LIN28B may supersede Let-7-independent effects on intestinal tissue growth. In summary, LIN28B can definitively act as an oncogene in the absence of canonical genetic alterations.
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Affiliation(s)
- Blair B Madison
- Division of Gastroenterology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA
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5
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Functional interplay between the DNA-damage-response kinase ATM and ARF tumour suppressor protein in human cancer. Nat Cell Biol 2013; 15:967-77. [DOI: 10.1038/ncb2795] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 05/24/2013] [Indexed: 12/25/2022]
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Abstract
AbstractRas genes are pre-eminent genes that are frequently linked with cancer biology. The functional loss of ras protein caused by various point mutations within the gene, is established as a prognostic factor for the genesis of a constitutively active Ras-MAPK pathway leading to cancer. Ras signaling circuit follows a complex pathway, which connects many signaling molecules and cells. Several strategies have come up for targeting mutant ras proteins for cancer therapy, however, the clinical benefits remain insignificant. Targeting the Ras-MAPK pathway is extremely complicated due its intricate networks involving several upstream and downstream regulators. Blocking oncogenic Ras is still in latent stage and requires alternative approaches to screen the genes involved in Ras transformation. Understanding the mechanism of Ras induced tumorigenesis in diverse cancers and signaling networks will open a path for drug development and other therapeutic approaches.
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Fan J, Ou YW, Wu CY, Yu CJ, Song YM, Zhan QM. Migfilin sensitizes cisplatin-induced apoptosis in human glioma cells in vitro. Acta Pharmacol Sin 2012; 33:1301-10. [PMID: 22983390 DOI: 10.1038/aps.2012.123] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
AIM Filamin binding LIM protein 1, also known as migfilin, is a skeleton organization protein that binds to mitogen-inducible gene 2 at cell-extracellular matrix adhesions. The aim of this study was to investigate the role of migfilin in cisplatin-induced apoptosis in human glioma cells, to determine the functional domains of migfilin, and to elucidate the molecular mechanisms underlying the regulation of cisplatin-related chemosensitivity. METHODS The human glioma cell lines Hs683, H4, and U-87 MG were transfected with pEGFP-C2-migfilin to elevate the expression level of migfilin. RNA interference was used to reduce the expression of migfilin. To determine the functional domains of migfilin, U-87 MG cells were transfected with plasmids of migfilin deletion mutants. After treatment with cisplatin (40 μmol/L) for 24 h, the cell viability was assessed using the MTS assay, and the cell apoptotic was examined using the DAPI staining assay and TUNEL analysis. Expression levels of apoptosis-related proteins were detected by Western blot analysis. RESULTS Overexpression of migfilin significantly enhanced cisplatin-induced apoptosis in Hs683, H4, and U-87 MG cells, whereas downregulation of migfilin expression inhibited the chemosensitivity of these cell lines. The N-terminal region of migfilin alone was able to enhance the cisplatin-induced apoptosis. However, despite the existence of the N-terminal region, mutants of migfilin with any one of three LIM domains deleted led to a function loss. Furthermore, apoptotic proteins (PARP and caspase-3) and the anti-apoptotic protein Bcl-xL were modulated by the expression level of migfilin in combination with cisplatin. CONCLUSION The LIM1-3 domains of migfilin play a key role in sensitizing glioma cells to cisplatin-induced apoptosis through regulation of apoptosis-related proteins.
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Hsp90 Inhibitors NVP-AUY922 and NVP-BEP800 May Exert a Significant Radiosensitization on Tumor Cells along with a Cell Type-Specific Cytotoxicity. Transl Oncol 2012; 5:356-69. [PMID: 23066444 DOI: 10.1593/tlo.12211] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 06/28/2012] [Accepted: 07/04/2012] [Indexed: 02/04/2023] Open
Abstract
Targeting heat shock protein 90 (Hsp90) provides a promising therapeutic approach to enhance the sensitivity of tumor cells to ionizing radiation (IR). To explore the impact of scheduling drug-IR administration, in the present study, we analyzed the response of lung carcinoma A549 and glioblastoma SNB19 cells to simultaneous drug-IR treatment followed by a long-term drug administration. Cellular response was evaluated at different time intervals after IR-alone, drug-alone, or combined drug-IR treatments by colony counts and expression profiles of Hsp90 and its clients, along with several apoptotic markers and cell cycle-related proteins, as well as by IR-drug-induced cell cycle arrest, DNA damage, and repair. A short 30-minute exposure to either Hsp90 inhibitor did not affect the radiosensitivity of both tumor cell lines. Increasing the duration of post-IR-drug treatment progressively enhanced the sensitivity of SNB19 cells to IR. In contrast, the response of A549 cells to drug-IR combination was largely determined by the cytotoxic effects of both drugs without radiosensitization. Combined drug-IR treatment induced more severe DNA damage in both tumor cell lines than each treatment alone and also protracted the kinetics of DNA damage repair in SNB19 cells. In addition to large cell cycle disturbances, drug-IR treatment also caused depletion of the antiapoptotic proteins Akt and Raf-1 in both cell lines, along with a decrease of survivin in A549 cells in case of NVP-AUY922. The data show that simultaneous Hsp90 inhibition and irradiation may induce cell type-specific radiosensitization as well as cytotoxicity against tumor cells.
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Deshpande AM, Khalid O, Kim JJ, Kim Y, Lindgren A, Clark AT, Wong DTW. Cdk2ap2 is a novel regulator for self-renewal of murine embryonic stem cells. Stem Cells Dev 2012; 21:3010-8. [PMID: 22548356 DOI: 10.1089/scd.2012.0007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In this study we present data to support the role for Cdk2ap2 in regulating self-renewal of mouse embryonic stem cells (mESCs) under permissive conditions, and cell survival during differentiation of the mESCs into terminally differentiated cell types. To understand the function of Cdk2ap2 during early development, we generated mESCs with homozygous disruption of the endogenous Cdk2ap2 locus (Cdk2ap2(tr/tr)). The Cdk2ap2(tr/tr) mESCs, when grown in a complete growth medium containing leukemia inhibitory factor (LIF), showed an early differentiation phenotype characterized by flattened colonies and a distinct intercellular boundary. We also observed downregulation of Nanog and upregulation in markers of mesoderm and endoderm differentiation, including Brachyury (T), Afp, and S100a, when compared to Wt mESCs. Cdk2ap2(tr/tr) mESCs were able to form embryoid bodies (EBs); however, those EBs were unhealthy and had an increased level of apoptosis. Furthermore, Cdk2ap2(tr/tr) mESCs were unable to form teratomas in severe combined immunodeficiency (SCID) mice. Cdk2ap2 under normal conditions has a biphasic expression, suggesting regulatory roles in early-versus-late stem cell differentiation. These data begin to add to our understanding of how Cdk2ap2 may be involved in the regulation of self-renewal of stem cells during early embryogenesis.
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Affiliation(s)
- Amit M Deshpande
- School of Dentistry and Dental Research Institute, UCLA, Los Angeles, California 90095, USA.
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Synthesis and biological validation of novel pyrazole derivatives with anticancer activity guided by 3D-QSAR analysis. Bioorg Med Chem 2012; 20:2101-10. [DOI: 10.1016/j.bmc.2012.01.032] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 01/18/2012] [Accepted: 01/19/2012] [Indexed: 12/21/2022]
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Filippakis H, Dimitropoulou P, Eliopoulos AG, Spandidos DA, Sourvinos G. The enhanced host-cell permissiveness of human cytomegalovirus is mediated by the Ras signaling pathway. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1872-82. [PMID: 21782855 DOI: 10.1016/j.bbamcr.2011.07.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 07/08/2011] [Accepted: 07/08/2011] [Indexed: 12/14/2022]
Abstract
Human cytomegalovirus utilizes cellular signal transduction pathways to activate viral or cellular transcription factors involved in the control of viral gene expression and DNA replication. In the present study, we demonstrate that Harvey-ras-transformed cells show increased permissiveness to human cytomegalovirus when compared to their parental non-transformed cells. Both the progeny viral yield and the protein levels were elevated in the human cytomegalovirus-infected Harvey-ras-transformed cells requiring active viral gene replication, as shown by the infection with UV-inactivated human cytomegalovirus. Inhibition of Ras or of key molecules of the Ras pathway, effectively suppressed viral infection in the Harvey-ras-transformed cells. On a cellular level, the human cytomegalovirus-infected Harvey-ras-transformed cells formed larger cellular foci, which were significantly higher in number, compared to the uninfected cells and preferentially recruited human cytomegalovirus virions, thereby incriminating human cytomegalovirus infection for the increased transformation of these cells. Furthermore, proliferation assays revealed a higher rate for the human cytomegalovirus-infected Harvey-ras-transformed cells compared to mock-infected cells, whereas human cytomegalovirus infection had no considerable effect on the proliferation of the non-transformed cells. Higher susceptibility to apoptosis was also detected in the human cytomegalovirus-infected ras-transformed cells, which in combination with the higher progeny virus reveals a mode by which human cytomegalovirus achieves efficient spread of infection in the cells expressing the oncogenic Harvey-ras (12V) gene. Collectively, our data suggest that human cytomegalovirus employs the host-cell Ras signaling pathway to ensue viral expression and ultimately successful propagation. Transformed cells with an activated Ras signaling pathway are therefore particularly susceptible to human cytomegalovirus infection.
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Naguib A, Wilson CH, Adams DJ, Arends MJ. Activation of K-RAS by co-mutation of codons 19 and 20 is transforming. J Mol Signal 2011; 6:2. [PMID: 21371307 PMCID: PMC3056876 DOI: 10.1186/1750-2187-6-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Accepted: 03/03/2011] [Indexed: 12/30/2022] Open
Abstract
The K-RAS oncogene is widely mutated in human cancers. Activating mutations in K-RAS give rise to constitutive signalling through the MAPK/ERK and PI3K/AKT pathways promoting increased cell division, reduced apoptosis and transformation. The majority of activating mutations in K-RAS are located in codons 12 and 13. In a human colorectal cancer we identified a novel K-RAS co-mutation that altered codons 19 and 20 resulting in transitions at both codons (L19F/T20A) in the same allele. Using focus forming transformation assays in vitro , we showed that co-mutation of L19F/T20A in K-RAS demonstrated intermediate transforming ability that was greater than that of individual L19F and T20A mutants, but less than that of G12D and G12V K-RAS mutants. This demonstrated the synergistic effects of co-mutation of codons 19 and 20 and illustrated that co-mutation of these codons is functionally significant.
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Affiliation(s)
- Adam Naguib
- Department of Pathology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK, CB2 0QQ, UK.
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Luo F, Poulogiannis G, Ye H, Hamoudi R, Zhang W, Dong G, Arends MJ. Mutant K-ras promotes carcinogen-induced murine colorectal tumourigenesis, but does not alter tumour chromosome stability. J Pathol 2010; 223:390-9. [PMID: 21171084 DOI: 10.1002/path.2790] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 09/08/2010] [Accepted: 09/16/2010] [Indexed: 12/29/2022]
Abstract
K-ras (KRAS) mutations are observed in around 40% of human colorectal adenomas and carcinomas. Previously, we developed and characterized a strain of transgenic mice with inducible intestinal epithelial expression of K-ras{Val12} via a Cre/LoxP system. To evaluate the influence of mutant K-ras on carcinogen-induced colorectal tumourigenesis, we induced neoplastic alterations in the large intestines of wild-type and K-ras{Val12} mice using the colon-selective carcinogen 1,2-dimethylhydrazine (DMH), which has been widely used to induce colorectal tumours that are histopathologically similar to those observed in humans. K-ras{Val12} expression significantly promoted DMH-induced colorectal tumourigenesis: the average lifespan of the mice decreased from 38.52 ± 1.97 weeks for 40 control mice to 32.42 ± 2.17 weeks for 26 K-ras{Val12} mice (mean ± SEM, p < 0.05) and the abundance of large intestinal tumours increased from 2.27 ± 0.15 per control mouse to 3.85 ± 0.20 in K-ras{Val12} mice (mean ± SEM, p < 0.01). Adenomas from DMH-treated K-ras{Val12} mice showed significantly higher proportions of Ki-67-positive proliferating cells (10.9 ± 0.69%) compared with those from DMH-treated wild-type mice (7.77 ± 0.47%) (mean ± SEM, p < 0.01) and a mild increase in apoptotic nuclei staining for cleaved caspase-3 (1.94 ± 0.21% compared with 1.15 ± 0.14%, mean ± SEM, p < 0.01). In the adenomas from DMH-treated K-ras{Val12} mice, K-ras{Val12} transgene recombination and expression were confirmed, with immunohistochemical evidence of strong Erk/MapK and mild PI3K/Akt pathway activation compared with adenomas from DMH-treated wild-type mice. Microarray hybridization and clustering analysis demonstrated different expression profiles in adenomas from DMH-treated wild-type and DMH-treated K-ras{Val12} mice, indicating involvement of different molecular mechanisms including Erk/MapK and PI3K/Akt signalling in K-ras{Val12}-expressing adenomas. Array-comparative genomic hybridization analysis showed chromosome stability in both cohorts, with only a very few tiny alterations observed in one adenoma from a DMH-treated K-ras{Val12} mouse. Taken together, these data show that mutant K-ras significantly promotes DMH-induced colorectal tumourigenesis, resulting in distinct changes in cell signalling and proliferation, but does not alter chromosome stability in the tumours.
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Affiliation(s)
- Feijun Luo
- Department of Pathology, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK
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14
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Luo F, Ye H, Hamoudi R, Dong G, Zhang W, Patek CE, Poulogiannis G, Arends MJ. K-ras exon 4A has a tumour suppressor effect on carcinogen-induced murine colonic adenoma formation. J Pathol 2010; 220:542-50. [PMID: 20087880 DOI: 10.1002/path.2672] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
K-ras encodes two isoforms, K-ras 4A and 4B, that are jointly affected by K-ras activating mutations, which are prevalent in colorectal cancer (CRC). CRC shows alterations in the expressed K-ras 4A : 4B isoform ratio in favour of K-ras 4B, in tumours both with and without K-ras mutations. The present study evaluated whether K-ras 4A expression can suppress colonic adenoma development in the absence of its oncogenic allele. Mice with homozygous targeted deletions of K-ras exon 4A (K-ras(tmDelta4A/tmDelta4A)) that can express the K-ras 4B isoform only, along with heterozygous K-ras(tmDelta4A/+) and wild-type mice, were given ten weekly 1,2-dimethylhydrazine (DMH) treatments to induce colonic adenomas. There was a significant increase in both the number and the size of colonic adenomas in DMH-treated K-ras(tmDelta4A/tmDelta4A) mice, with reduced survival, compared with heterozygous and wild-type mice. No K-ras mutations were found in any of the 30 tumours tested from the three groups. Lack of expression of K-ras 4A transcripts was confirmed, whereas the relative expression levels of K-ras 4B transcripts were significantly increased in the adenomas of K-ras(tmDelta4A/tmDelta4A) mice compared with K-ras(tmDelta4A/+) and wild-type mice. Immunohistochemical studies showed that adenomas of K-ras(tmDelta4A/tmDelta4A) mice had significantly increased cell proliferation and significantly decreased apoptosis with evidence of activation of MapKinase and Akt pathways, with increased phospho-Erk1/2 and both phospho-Akt-Thr308 and phospho-Akt-Ser473 immunostaining, compared with adenomas from K-ras(tmDelta4A/+) and wild-type mice. In conclusion, following DMH treatment, K-ras exon 4A deletion promoted increased number and size of colonic adenomas showing increased K-ras 4B expression, increased proliferation, decreased apoptosis, and activation of MapKinase and Akt pathways, in the absence of K-ras mutations. Therefore, K-ras 4A expression had a tumour suppressor effect on carcinogen-induced murine colonic adenoma formation, explaining the selective advantage of the altered K-ras 4A : 4B isoform ratio found in human colorectal cancer.
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Affiliation(s)
- Feijun Luo
- Department of Pathology, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 2QQ, UK
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Abubaker J, Bavi P, Al-Haqawi W, Sultana M, Al-Harbi S, Al-Sanea N, Abduljabbar A, Ashari LH, Alhomoud S, Al-Dayel F, Uddin S, Al-Kuraya KS. Prognostic significance of alterations in KRAS isoforms KRAS-4A/4B and KRAS mutations in colorectal carcinoma. J Pathol 2010; 219:435-45. [PMID: 19824059 DOI: 10.1002/path.2625] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Somatic KRAS mutation is an early well-known event in colorectal carcinogenesis but a complete understanding of RAS function and dysfunction in colorectal cancer is still to come. Our aim was to study the incidence of KRAS mutation; KRAS splice variants: KRAS4A and KRAS4B; and their relationships with various clinico-pathological characteristics in colorectal cancer (CRC).In this study, 285 CRC cases were analysed for KRAS mutation by direct DNA sequencing followed by immunohistochemical analysis after validation with real-time PCR assay, to study the protein expression of KRAS4A and -4B isoforms. KRAS gene mutations were seen in 80/285 CRCs (28.1%) and of the mutated cases, the majority of the mutations were seen in codon 12 (81.2%) as opposed to codon 13 (18.8%). CRCs with KRAS mutations were associated with a poor overall survival (p = 0.0009). Furthermore, KRAS mutations at codon 12 were associated with a poor overall survival of 64.4% at 5 years compared with a 5-year overall survival of 75.8% and 78.2% with codon 13 mutation and absence of KRAS mutations, respectively (p = 0.0025). KRAS4A protein expression was predominantly seen in the cytoplasm, while KRAS4B protein was nuclear. KRAS4A overexpression was significantly associated with left colon, histology subtype of adenocarcinoma, p27kip1, and cleaved caspase3 expression. Interestingly, KRAS4A overexpression was associated with a better overall survival (p = 0.0053). On the other hand, KRAS4B overexpression (33.2%) was significantly associated with larger tumour size (p = 0.0234) and inversely correlated with p27kip1 protein (p = 0.0159). Both KRAS mutation and KRAS4A were independent prognostic markers in a multivariate analysis with age, gender, stage, differentiation, and MSI status. Our results highlight the differential role of KRAS isoforms in CRC, their utility as a prognostic biomarker, and underline the importance of KRAS alterations as a potential therapeutic target for CRC.
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Affiliation(s)
- Jehad Abubaker
- Human Cancer Genomic Research, Research Center, King Faisal Specialist Hospital and Research Centre, Riyadh 11211, Saudi Arabia
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Luo F, Brooks DG, Ye H, Hamoudi R, Poulogiannis G, Patek CE, Winton DJ, Arends MJ. Mutated K-ras(Asp12) promotes tumourigenesis in Apc(Min) mice more in the large than the small intestines, with synergistic effects between K-ras and Wnt pathways. Int J Exp Pathol 2009; 90:558-74. [PMID: 19765110 DOI: 10.1111/j.1365-2613.2009.00667.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Summary K-ras mutations are found in 40-50% of human colorectal adenomas and carcinomas, but their functional contribution remains incompletely understood. Here, we show that a conditional mutant K-ras mouse model (K-ras(Asp12)/Cre), with transient intestinal Cre activation by beta-Naphthoflavone (beta-NF) treatment, displayed transgene recombination and K-ras(Asp12) expression in the murine intestines, but developed few intestinal adenomas over 2 years. However, when crossed with Apc(Min/+) mice, the K-ras(Asp12)/Cre/Apc(Min/+) offspring showed acceleration of intestinal tumourigenesis with significantly changed average lifespan (P < 0.05) decreased to 18.4 +/- 5.4 weeks from 20.9 +/- 4.7 weeks (control Apc(Min/+) mice). The numbers of adenomas in the small intestine and large intestine were significantly (P < 0.01) increased by 1.5-fold and 5.7-fold, respectively, in K-ras(Asp12)/Cre/Apc(Min/+) mice compared with Apc(Min/+) mice, with the more marked increase in adenoma prevalence in the large intestine. To explore possible mechanisms for K-ras(Asp12) and Apc(Min) co-operation, the Mitogen-activated protein kinase (Mapk), Akt and Wnt signalling pathways, including selected target gene expression levels, were evaluated in normal large intestine and large intestinal tumours. K-ras(Asp12) increased activation of Mapk and Akt signalling pathway targets phospho-extracellular signal-regulated kinase (pErk) and pAkt, and increased relative expression levels of Wnt pathway targets vascular endothelial growth factor (VEGF), gastrin, cyclo-oxygenase 2 (Cox2) and T-cell lymphoma invasion and metastasis 1 (Tiam1) in K-ras(Asp12)/Cre/Apc(Min/+) adenomas compared with that of Apc(Min/+) adenomas, although other Wnt signalling pathway target genes such as Peroxisome proliferator-activated receptor delta (PPARd), matrix metalloproteinase 7 (MMP7), protein phosphatase 1 alpha (PP1A) and c-myc remained unchanged. In conclusion, intestinal expression of K-ras(Asp12) promotes mutant Apc-initiated intestinal adenoma formation in vivo more in the large intestine than the small intestine, with evidence of synergistic co-operation between mutant K-ras and Apc involving increased expression of some Wnt-pathway target genes.
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Affiliation(s)
- Feijun Luo
- Department of Pathology, Addenbrooke's Hospital, University of Cambridge, UK
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17
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Bmi1 is critical for lung tumorigenesis and bronchioalveolar stem cell expansion. Proc Natl Acad Sci U S A 2008; 105:11857-62. [PMID: 18697930 DOI: 10.1073/pnas.0803574105] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Understanding the pathways that control epithelial carcinogenesis is vital to the development of effective treatments. The Polycomb group family member Bmi1 is overexpressed in numerous epithelial tumors, but its role in their development has not been established. We now show a key role for Bmi1 in lung adenocarcinoma. Whereas lung development occurs normally in Bmi1-deficient mice, loss of Bmi1 decreases the number and progression of lung tumors at a very early point in an oncogenic K-ras-initiated mouse model of lung cancer. This correlates with a defect in the ability of Bmi1-deficient putative bronchiolalveolar stem cells (BASCs) to proliferate in response to the oncogenic stimulus. Notably, in the absence of oncogenic K-ras, Bmi1-deficient BASCs show impaired proliferation and self-renewal capacity in culture and after lung injury in vivo. Abrogated lung cancer development and BASC self-renewal occur partially in a p19(ARF)-dependent manner. Our data suggest that Bmi1 deficiency suppresses tumor development by limiting the expansion potential of BASCs, the apparent lung cancer cells of origin. Because Bmi1 is elevated in additional tumor types, this suggests that Bmi1 plays a key role in regulating proliferation of both stem cells and tumor cells in diverse adult epithelial tissues.
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18
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Patek CE, Arends MJ, Rose L, Luo F, Walker M, Devenney PS, Berry RL, Lawrence NJ, Ridgway RA, Sansom OJ, Hooper ML. The pro-apoptotic K-Ras 4A proto-oncoprotein does not affect tumorigenesis in the ApcMin/+ mouse small intestine. BMC Gastroenterol 2008; 8:24. [PMID: 18554389 PMCID: PMC2442095 DOI: 10.1186/1471-230x-8-24] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Accepted: 06/13/2008] [Indexed: 12/21/2022] Open
Abstract
Background Alterations in gene splicing occur in human sporadic colorectal cancer (CRC) and may contribute to tumour progression. The K-ras proto-oncogene encodes two splice variants, K-ras 4A and 4B, and K-ras activating mutations which jointly affect both isoforms are prevalent in CRC. Past studies have established that splicing of both the K-ras oncogene and proto-oncogene is altered in CRC in favour of K-ras 4B. The present study addressed whether the K-Ras 4A proto-oncoprotein can suppress tumour development in the absence of its oncogenic allele, utilising the ApcMin/+ (Min) mouse that spontaneously develops intestinal tumours that do not harbour K-ras activating mutations, and the K-rastmΔ4A/tmΔ4A mouse that can express the K-ras 4B splice variant only. By this means tumorigenesis in the small intestine was compared between ApcMin/+, K-ras+/+ and ApcMin/+, K-rastmΔ4A/tmΔ4A mice that can, and cannot, express the K-ras 4A proto-oncoprotein respectively. Methods The relative levels of expression of the K-ras splice variants in normal small intestine and small intestinal tumours were quantified by real-time RT-qPCR analysis. Inbred (C57BL/6) ApcMin/+, K-ras+/+ and ApcMin/+, K-rastmΔ4A/tmΔ4A mice were generated and the genotypes confirmed by PCR analysis. Survival of stocks was compared by the Mantel-Haenszel test, and tumour number and area compared by Student's t-test in outwardly healthy mice at approximately 106 and 152 days of age. DNA sequencing of codons 12, 13 and 61 was performed to confirm the intestinal tumours did not harbour a K-ras activating mutation. Results The K-ras 4A transcript accounted for about 50% of K-ras expressed in the small intestine of both wild-type and Min mice. Tumours in the small intestine of Min mice showed increased levels of K-ras 4B transcript expression, but no appreciable change in K-ras 4A transcript levels. No K-ras activating mutations were detected in 27 intestinal tumours derived from Min and compound mutant Min mice. K-Ras 4A deficiency did not affect mouse survival, or tumour number, size or histopathology. Conclusion The K-Ras 4A proto-oncoprotein does not exhibit tumour suppressor activity in the small intestine, even though the K-ras 4A/4B ratio is reduced in adenomas lacking K-ras activating mutations.
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Affiliation(s)
- Charles E Patek
- Sir Alastair Currie Cancer Research UK Laboratories, Molecular Medicine Centre, The University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU, UK.
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19
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Lee MK, Sabapathy K. The R246S hot-spot p53 mutant exerts dominant-negative effects in embryonic stem cells in vitro and in vivo. J Cell Sci 2008; 121:1899-906. [DOI: 10.1242/jcs.022822] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
p53 is the most frequently mutated tumour-suppressor gene in human cancers. Mutant p53 is thought to contribute to carcinogenesis by the acquisition of gain-of-function properties or through the exertion of dominant-negative (DN) effects over the remaining wild-type protein. However, the context in which the DN effects are observed is not well understood. We have therefore generated `knock-in' mouse embryonic stem (ES) cells to investigate the effects of expressing a commonly found hot-spot p53 mutant, R246S – the mouse equivalent of human R249S, which is associated with hepatocellular carcinomas. We demonstrate here that R246S mutant p53 exhibits DN effects with respect to target gene expression, cell survival and cell cycle arrest both in cells that are in the undifferentiated state and upon differentiation. The knock-in cells contain higher levels of p53 that localizes to the nucleus even in the absence of genotoxic stress and yet remains non-functional, reminiscent of mutant p53 found in human tumours. In a model based on carbon-tetrachloride-induced liver injury, these cells were consistently highly tumorigenic in vivo, similar to p53–/– cells and in contrast to both p53+/+ and p53+/– ES cells. These data therefore indicate that the DN effects of mutant p53 are evident in the stem-cell context, in which its expression is relatively high compared with terminally differentiated cells.
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Affiliation(s)
- Ming Kei Lee
- Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre, 11 Hospital Drive, Singapore 169610, Singapore
| | - Kanaga Sabapathy
- Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre, 11 Hospital Drive, Singapore 169610, Singapore
- Department of Biochemistry, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore
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20
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Luo F, Brooks DG, Ye H, Hamoudi R, Poulogiannis G, Patek CE, Winton DJ, Arends MJ. Conditional expression of mutated K-ras accelerates intestinal tumorigenesis in Msh2-deficient mice. Oncogene 2007; 26:4415-27. [PMID: 17297472 DOI: 10.1038/sj.onc.1210231] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
K-ras mutation occurs in 40-50% of human colorectal adenomas and carcinomas, but its contribution to intestinal tumorigenesis in vivo is unclear. We developed K-ras(V12) transgenic mice that were crossed with Ah-Cre mice to generate K-ras(V12)/Cre mice, which showed beta-naphthoflavone-induction of Cre-mediated LoxP recombination that activated intestinal expression of K-ras(V12) 4A and 4B transcripts and proteins. Only very occasional intestinal adenomas were observed in beta-naphthoflavone-treated K-ras(V12)/Cre mice aged up to 2 years, suggesting that mutated K-ras expression alone does not significantly initiate intestinal tumourigenesis. To investigate the effects of mutated K-ras on DNA mismatch repair (MMR)-deficient intestinal tumour formation, these mice were crossed with Msh2(-/-) mice to generate K-ras(V12)/Cre/Msh2(-/-) offspring. After beta-naphthoflavone treatment, K-ras(V12)/Cre/Msh2(-/-) mice showed reduced average lifespan of 17.3+/-5.0 weeks from 26.9+/-6.8 (control Msh2(-/-) mice) (P<0.01). They demonstrated increased adenomas in the small intestine from 1.41 (Msh2(-/-) controls) to 7.75 per mouse (increased fivefold, P<0.01). In the large intestine, very few adenomas were found in Msh2(-/-) mice (0.13 per mouse) whereas K-ras(V12)/Cre/Msh2(-/-) mice produced 2.70 adenomas per mouse (increased 20-fold, P<0.01). Over 80% adenomas from K-ras(V12)/Cre/Msh2(-/-) mice showed transgene recombination with expression of K-ras(V12) 4A and 4B transcripts and proteins. Sequencing of endogenous murine K-ras showed mutations in two out of 10 tumours examined from Msh2(-/-) mice, but no mutations in 17 tumours from K-ras(V12)/Cre/Msh2(-/-) mice. Expression of K-ras(V12) in tumours caused activation of the mitogen-activated protein kinase and Akt/protein kinase B signaling pathways, demonstrated by phosphorylation of p44MAPK, Akt and GSK3beta, as well as transcriptional upregulation of Pem, Tcl-1 and Trap1a genes (known targets of K-ras(V12) expression in stem cells). Thus, mutated K-ras cooperates synergistically with MMR deficiency to accelerate intestinal tumorigenesis, particularly in the large intestine.
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Affiliation(s)
- F Luo
- Department of Pathology, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK
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21
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Luo F, Hamoudi R, Brooks DG, Patek CE, Arends MJ. Stem cell gene expression changes induced specifically by mutated K-ras. Gene Expr 2007; 14:101-15. [PMID: 18257393 PMCID: PMC6042043 DOI: 10.3727/105221607783417583] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
K-Ras proteins transduce signals from membrane-bound receptors via multiple downstream effector pathways and thereby regulate fundamental stem cell processes that affect neoplasia, including proliferation, apoptosis, and differentiation, but their contribution to tumourigenesis is unclear. Because cancers develop from stem cells, we set out to determine the characteristic changes in gene expression brought about by mutated K-ras (without interference from normal K-ras) in otherwise normal stem cells. cDNA microarrays were used to analyze gene expression profiles comparing wild-type murine embryonic stem (ES) cells with K-ras(Val12) expressing ES cells (previously made null for both endogenous K-ras alleles and transfected with K-ras(Val12), with valine for glycine at codon 12). K-ras(Val12) was expressed at 1.2-fold normal K-ras levels and produced transcripts for both activated K-Ras4A and 4B isoforms. The array expression data were confirmed by real-time quantitative PCR analysis of selected genes expressed both in the K-ras(Val12) expressing ES cells (R = 0.91 with array data) and in the normal intestinal tissues of K-ras(Val12) transgenic mice (R = 0.91 with array data). Changes in gene expression were correlated with the effects of K-ras(Val12) expression on ES cells of enhancing self-renewal in an undifferentiated state, increasing susceptibility to DNA damage-induced apoptosis, and increased proliferation. These expression data may explain, at least in part, some neoplasia-related aspects of the phenotypic changes brought about in this ES cell line by mutated K-ras, in that upregulation of cell growth-related proteins and DNA-associated proteins is consistent with increased proliferation; upregulation of certain apoptosis-related proteins is consistent with a greater susceptibility to DNA damage-induced apoptosis; and downregulation of structural proteins, extracellular matrix components, secretory proteins and receptors is consistent with a less differentiated phenotype.
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Affiliation(s)
- Feijun Luo
- *Department of Pathology, Addenbrooke’s Hospital, Hills Road, University of Cambridge, Cambridge, CB2 2QQ, UK
| | - Rifat Hamoudi
- *Department of Pathology, Addenbrooke’s Hospital, Hills Road, University of Cambridge, Cambridge, CB2 2QQ, UK
| | - David G. Brooks
- *Department of Pathology, Addenbrooke’s Hospital, Hills Road, University of Cambridge, Cambridge, CB2 2QQ, UK
| | - Charles E. Patek
- †Sir Alastair Currie Cancer Research UK Laboratories, Molecular Medicine Centre, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU, UK
| | - Mark J. Arends
- *Department of Pathology, Addenbrooke’s Hospital, Hills Road, University of Cambridge, Cambridge, CB2 2QQ, UK
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Teraishi F, Guo W, Zhang L, Dong F, Davis JJ, Sasazuki T, Shirasawa S, Liu J, Fang B. Activation of sterile20-like kinase 1 in proteasome inhibitor bortezomib-induced apoptosis in oncogenic K-ras-transformed cells. Cancer Res 2006; 66:6072-9. [PMID: 16778179 PMCID: PMC1482805 DOI: 10.1158/0008-5472.can-06-0125] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Bortezomib (PS-341), a specific proteasome inhibitor, exhibits antitumor activity against a wide range of malignancies. However, the molecular mechanisms by which bortezomib causes apoptosis selectively in cancer cells still remain unclear. Ras signaling is involved in multiple cellular processes, including cell cycle progression, differentiation, and apoptosis, and can either promote or inhibit apoptosis depending on the type of apoptotic stimuli and the cell model. Here, we investigated the role of K-ras signaling in bortezomib-induced apoptosis. We found that K-ras-transformed cells were more susceptible to bortezomib-induced apoptosis than were nontransformed cells and that bortezomib-induced apoptosis was mainly caspase dependent in K-ras-transformed cells. We also found that mammalian sterile20-like kinase 1 (MST1) was activated by bortezomib in K-ras-transformed cells and K-ras-mutated cancer cells. Treatment of K-ras-transformed cells with bortezomib resulted in translocation of MST1 from cytoplasm into the nucleus and an increase of phosphorylated histone H2B and histone H2AX. Moreover, pretreatment with leptomycin B, an inhibitor of the nuclear export signal receptor, dramatically enhanced bortezomib-mediated MST1 activation, phosphorylation of histones H2B and H2AX, and apoptosis induction in K-ras-transformed cells. Knockdown of MST1 expression by small interfering RNA diminished bortezomib-induced apoptosis or caspase-3 activation. Our data suggested that bortezomib may be useful for treatment of K-ras-mutated cancer cells, and MST1 is one of the mediators for bortezomib-induced apoptosis in K-ras-transformed cells.
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Affiliation(s)
| | - Wei Guo
- Department of Thoracic and Cardiovascular Surgery, and
| | - Lidong Zhang
- Department of Thoracic and Cardiovascular Surgery, and
| | - Fengqing Dong
- Department of Thoracic and Cardiovascular Surgery, and
| | - John J. Davis
- Department of Thoracic and Cardiovascular Surgery, and
| | - Takehiko Sasazuki
- Research Institute, International Medical Center of Japan, Tokyo, Japan
| | - Senji Shirasawa
- Research Institute, International Medical Center of Japan, Tokyo, Japan
| | - Jinsong Liu
- Department of Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas
| | - Bingliang Fang
- Department of Thoracic and Cardiovascular Surgery, and
- Requests for reprints: Bingliang Fang, Department of Thoracic and Cardiovascular Surgery, Unit 445, M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030. Phone: 713-563-9147; Fax: 713-794-4901; E-mail:
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23
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Choi D, Lee HJ, Jee S, Jin S, Koo SK, Paik SS, Jung SC, Hwang SY, Lee KS, Oh B. In vitro differentiation of mouse embryonic stem cells: enrichment of endodermal cells in the embryoid body. Stem Cells 2005; 23:817-27. [PMID: 15917477 DOI: 10.1634/stemcells.2004-0262] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Embryonic stem (ES) cells have the potential to differentiate into all three germ layers, providing new perspectives not only for embryonic development but also for the application in cell replacement therapies. Even though the formation of an embryoid body (EB) in a suspension culture has been the most popular method to differentiate ES cells into a wide range of cells, not much is known about the characteristics of EB cells. To this end, we investigated the process of EB formation in the suspension culture of ES cells at weekly intervals for up to 6 weeks. We observed that the central apoptotic area is most active in the first week of EB formation and that the cell adhesion molecules, except beta-catenin, are highly expressed throughout the examination period. The sequential expression of endodermal genes in EBs during the 6-week culture correlated closely with that of normal embryo development. The outer surface of EBs stained positive for alpha-fetoprotein and GATA-4. When isolated from the 2-week-old EB by trypsin treatment, these endodermal lineage cells matured in vitro into hepatocytes upon stimulation with various hepatotrophic factors. In conclusion, our results demonstrate that endodermal cells can be retrieved from EBs and matured into specific cell types, opening new therapeutic usage of these in vitro differentiated cells in the cell replacement therapy of various diseases.
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Affiliation(s)
- Dongho Choi
- Department of Surgery, Stem Cell Therapy Center, Soonchunhyang University Hospital, Seoul, Korea
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24
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Klampfer L, Huang J, Sasazuki T, Shirasawa S, Augenlicht L. Oncogenic Ras Promotes Butyrate-induced Apoptosis through Inhibition of Gelsolin Expression. J Biol Chem 2004; 279:36680-8. [PMID: 15213223 DOI: 10.1074/jbc.m405197200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of Ras promotes oncogenesis by altering a multiple of cellular processes, such as cell cycle progression, differentiation, and apoptosis. Oncogenic Ras can either promote or inhibit apoptosis, depending on the cell type and the nature of the apoptotic stimuli. The response of normal and transformed colonic epithelial cells to the short chain fatty acid butyrate, a physiological regulator of epithelial cell maturation, is also divergent: normal epithelial cells proliferate, and transformed cells undergo apoptosis in response to butyrate. To investigate the role of k-ras mutations in butyrate-induced apoptosis, we utilized HCT116 cells, which harbor an oncogenic k-ras mutation and two isogenic clones with targeted inactivation of the mutant k-ras allele, Hkh2, and Hke-3. We demonstrated that the targeted deletion of the mutant k-ras allele is sufficient to protect epithelial cells from butyrate-induced apoptosis. Consistent with this, we showed that apigenin, a dietary flavonoid that has been shown to inhibit Ras signaling and to reverse transformation of cancer cell lines, prevented butyrate-induced apoptosis in HCT116 cells. To investigate the mechanism whereby activated k-ras sensitizes colonic cells to butyrate, we performed a genome-wide analysis of Ras target genes in the isogenic cell lines HCT116, Hkh2, and Hke-3. The gene exhibiting the greatest down-regulation by the activating k-ras mutation was gelsolin, an actin-binding protein whose expression is frequently reduced or absent in colorectal cancer cell lines and primary tumors. We demonstrated that silencing of gelsolin expression by small interfering RNA sensitized cells to butyrate-induced apoptosis through amplification of the activation of caspase-9 and caspase-7. These data therefore demonstrate that gelsolin protects cells from butyrate-induced apoptosis and suggest that Ras promotes apoptosis, at least in part, through its ability to down-regulate the expression of gelsolin.
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Affiliation(s)
- Lidija Klampfer
- Department of Oncology, Albert Einstein Cancer Center, Montefiore Medical Center, 111 E. 210th Street, Bronx, NY 10467, USA.
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25
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Rabizadeh S, Xavier RJ, Ishiguro K, Bernabeortiz J, Lopez-Ilasaca M, Khokhlatchev A, Mollahan P, Pfeifer GP, Avruch J, Seed B. The scaffold protein CNK1 interacts with the tumor suppressor RASSF1A and augments RASSF1A-induced cell death. J Biol Chem 2004; 279:29247-54. [PMID: 15075335 DOI: 10.1074/jbc.m401699200] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The connector enhancer of KSR (CNK) is a multidomain scaffold protein discovered in Drosophila, where it is necessary for Ras activation of the Raf kinase. Recent studies have shown that CNK1 also interacts with RalA and Rho and participates in some aspects of signaling by these GTPases. Herein we demonstrate a novel aspect of CNK1 function, i.e. reexpression of CNK1 suppresses tumor cell growth and promotes apoptosis. As shown previously for apoptosis induced by Ki-Ras(G12V), CNK1-induced apoptosis is suppressed by a dominant inhibitor of the mammalian sterile 20 kinases 1 and (MST1/MST2). Immunoprecipitates of MST1 endogenous to LoVo colon cancer cells contain endogenous CNK1; however, no association of these two polypeptides can be detected in a yeast two-hybrid assay. CNK1 does, however, bind directly to the RASSF1A and RASSF1C polypeptides, constitutive binding partners of the MST1/2 kinases. Deletion of the MST1 carboxyl-terminal segment that mediates its binding to RASSF1A/C eliminates the association of MST1 with CNK1. Coexpression of CNK1 with the tumor suppressive isoform, RASSF1A, greatly augments CNK1-induced apoptosis, whereas the nonsuppressive RASSF1C isoform is without effect on CNK1-induced apoptosis. Overexpression of CNK1-(1-282), a fragment that binds RASSF1A but is not proapoptotic, blocks the apoptosis induced by CNK1 and by Ki-Ras(G12V). Thus, in addition to its positive role in the proliferative outputs of active Ras, the CNK1 scaffold protein, through its binding of a RASSF1A.MST complex, also participates in the proapoptotic signaling initiated by active Ras.
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Affiliation(s)
- Shahrooz Rabizadeh
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
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26
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Choi JA, Park MT, Kang CM, Um HD, Bae S, Lee KH, Kim TH, Kim JH, Cho CK, Lee YS, Chung HY, Lee SJ. Opposite effects of Ha-Ras and Ki-Ras on radiation-induced apoptosis via differential activation of PI3K/Akt and Rac/p38 mitogen-activated protein kinase signaling pathways. Oncogene 2004; 23:9-20. [PMID: 14712206 DOI: 10.1038/sj.onc.1206982] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
It has been well known that Ras signaling is involved in various cellular processes, including proliferation, differentiation, and apoptosis. However, distinct cellular functions of Ras isozymes are not fully understood. Here we show the opposing roles of Ha-Ras and Ki-Ras genes in the modulation of cell sensitivity to ionizing radiation. Overexpression of active isoform of Ha-Ras (12V-Ha-Ras) in Rat2 cells increases resistance to the ionizing radiation. Constitutive activation of phosphoinositide-3-kinase (PI3K) and Akt is detected specifically in 12V-Ha-Ras-overexpressing cells. The specific PI3K inhibitor LY294002 inhibits PI3K/Akt signaling and potentiates the radiation-induced apoptosis, suggesting that activation of the PI3K/Akt signaling pathway is involved in the increased radio-resistance in cells overexpressing 12V-Ha-Ras. Overexpression of activated Ki-Ras (12V-Ki-Ras), on the other hand, markedly increases radiation sensitivity. The p38 mitogen-activated protein kinase (MAPK) activity is selectively enhanced by ionizing radiation in cells overexpressing 12V-Ki-Ras. The specific p38 MAPK inhibitor, PD169316, or dominant-negative p38 MAPK decreases radiation-induced cell death. We further show that the mechanism that underlies potentiation of cell death in cells overexpressing 12V-Ki-Ras involves Bax translocation to the mitochondrial membrane. Elevated Bax translocation following ionizing irradiation in 12V-Ki-Ras-overexpressing cells is completely inhibited by PD169316 or dominant-negative p38 MAPK. In addition, introduction of cells with RacN17, a dominant-negative mutant of Rac, resulted in a marked inhibition of radiation-induced Bax translocation and apoptotic cell death as well as p38 MAPK activation. Taken together, these findings explain the opposite effects of Ha-Ras and Ki-Ras on modulation of radiosensitivity, and suggest that differential activation of PI3K/Akt and Rac/p38 MAPK signaling by Ha-Ras and Ki-Ras may account for the opposing response to the ionizing radiation. These data provide an explanation for the diverse biological functions of Ras isozymes, and partly accounts for the differential response of transformed cells to anticancer treatments.
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Affiliation(s)
- Jung-A Choi
- Laboratory of Radiation Effect, Korea Institute of Radiological & Medical Sciences, Seoul 139-706, Korea
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Plowman SJ, Williamson DJ, O'Sullivan MJ, Doig J, Ritchie AM, Harrison DJ, Melton DW, Arends MJ, Hooper ML, Patek CE. While K-ras is essential for mouse development, expression of the K-ras 4A splice variant is dispensable. Mol Cell Biol 2004; 23:9245-50. [PMID: 14645534 PMCID: PMC309700 DOI: 10.1128/mcb.23.24.9245-9250.2003] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In mammals, the three classical ras genes encode four highly homologous proteins, N-Ras, H-Ras, and the isoforms K-Ras 4A and 4B. Previous studies have shown that K-ras is essential for mouse development and that while K-ras 4A and 4B are expressed during development, K-ras 4A expression is regulated temporally and spatially and occurs in adult kidney, intestine, stomach, and liver. In the present study, the pattern of K-ras 4A expression was examined in a wide range of wild-type adult mouse tissues, and gene targeting was used to generate K-ras 4A-deficient mice to examine its role in development. It was found that K-ras 4A is also expressed in uterus, lung, pancreas, salivary glands, seminal vesicles, bone marrow cells, and cecum, where it was the major K-Ras isoform expressed. Mating between K-ras(tmDelta4A/+) mice produced viable K-ras(tmDelta4A/tmDelta4A) offspring with the expected Mendelian ratios of inheritance, and these mice expressed the K-ras 4B splice variant only. K-ras(tmDelta4A/tmDelta4A) mice were fertile and showed no histopathological abnormalities on inbred (129/Ola) or crossbred (129/Ola x C57BL/6) genetic backgrounds. The results demonstrate that K-Ras 4A, like H- and N-Ras, is dispensable for normal mouse development, at least in the presence of functional K-Ras 4B.
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Affiliation(s)
- Sarah J Plowman
- Sir Alastair Currie Cancer Research UK Laboratories, Molecular Medicine Centre, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, Scotland, U.K
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Liou JS, Chen JS, Faller DV. Characterization of p21Ras-mediated apoptosis induced by protein kinase C inhibition and application to human tumor cell lines. J Cell Physiol 2003; 198:277-94. [PMID: 14603530 DOI: 10.1002/jcp.10409] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Suppression of PKC activity can selectively induce apoptosis in cells expressing a constitutively activated p21Ras protein. We demonstrate that continued expression of p21Ras activity is required in PKC-mediated apoptosis because farnesyltransferase inhibitors abrogated the loss of viability in p21Ras-transformed cells occurring following PKC inhibition. Studies utilizing gene transfer or viral vectors demonstrate that transient expression of oncogenic p21Ras activity is sufficient for induction of apoptosis by PKC inhibition, whereas physiologic activation of p21Ras by growth factor is not sufficient to induce apoptosis. Mechanistically, the p21Ras-mediated apoptosis induced by PKC inhibition is dependent upon mitochondrial dysregulation, with a concurrent loss of mitochondrial membrane potential (psim). Cyclosporine A, which prevented the loss of psim, also inhibited HMG-induced DNA fragmentation in cells expressing an activated p21Ras. Induction of apoptosis by PKC inhibition in human tumors with oncogenic p21Ras mutations was demonstrated. Inhibition of PKC caused increased apoptosis in MIA-PaCa-2, a human pancreatic tumor line containing a mutated Ki-ras allele, when compared to HS766T, a human pancreatic tumor line with normal Ki-ras alleles. Furthermore, PKC inhibition induced apoptosis in HCT116, a human colorectal tumor line containing an oncogenic Ki-ras allele but not in a subline (Hke3) in which the mutated Ki-ras allele had been disrupted. The PKC inhibitor 1-O-hexadecyl-2-O-methyl-rac-glycerol (HMG), significantly reduced p21Ras-mediated tumor growth in vivo in a nude mouse MIA-PaCa-2 xenograft model. Collectively these studies suggest the therapeutic feasibility of targeting PKC activity in tumors expressing an activated p21Ras oncoprotein.
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Affiliation(s)
- James S Liou
- Boston University School of Medicine, Cancer Research Center, Boston, Massachusetts 02118, USA
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