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Fang B. RAS signaling and anti-RAS therapy: lessons learned from genetically engineered mouse models, human cancer cells, and patient-related studies. Acta Biochim Biophys Sin (Shanghai) 2016; 48:27-38. [PMID: 26350096 DOI: 10.1093/abbs/gmv090] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 07/09/2015] [Indexed: 12/13/2022] Open
Abstract
Activating mutations of oncogenic RAS genes are frequently detected in human cancers. The studies in genetically engineered mouse models (GEMMs) reveal that Kras-activating mutations predispose mice to early onset tumors in the lung, pancreas, and gastrointestinal tract. Nevertheless, most of these tumors do not have metastatic phenotypes. Metastasis occurs when tumors acquire additional genetic changes in other cancer driver genes. Studies on clinical specimens also demonstrated that KRAS mutations are present in premalignant tissues and that most of KRAS mutant human cancers have co-mutations in other cancer driver genes, including TP53, STK11, CDKN2A, and KMT2C in lung cancer; APC, TP53, and PIK3CA in colon cancer; and TP53, CDKN2A, SMAD4, and MED12 in pancreatic cancer. Extensive efforts have been devoted to develop therapeutic agents that target enzymes involved in RAS posttranslational modifications, that inhibit downstream effectors of RAS signaling pathways, and that kill RAS mutant cancer cells through synthetic lethality. Recent clinical studies have revealed that sorafenib, a pan-RAF and VEGFR inhibitor, has impressive benefits for KRAS mutant lung cancer patients. Combination therapy of MEK inhibitors with either docetaxel, AKT inhibitors, or PI3K inhibitors also led to improved clinical responses in some KRAS mutant cancer patients. This review discusses knowledge gained from GEMMs, human cancer cells, and patient-related studies on RAS-mediated tumorigenesis and anti-RAS therapy. Emerging evidence demonstrates that RAS mutant cancers are heterogeneous because of the presence of different mutant alleles and/or co-mutations in other cancer driver genes. Effective subclassifications of RAS mutant cancers may be necessary to improve patients' outcomes through personalized precision medicine.
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Affiliation(s)
- Bingliang Fang
- Department of Thoracic and Cardiovascular Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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Fang B, Mehran RJ, Heymach JV, Swisher SG. Predictive biomarkers in precision medicine and drug development against lung cancer. CHINESE JOURNAL OF CANCER 2015; 34:295-309. [PMID: 26134262 PMCID: PMC4593363 DOI: 10.1186/s40880-015-0028-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 06/04/2015] [Indexed: 02/06/2023]
Abstract
The molecular characterization of various cancers has shown that cancers with the same origins, histopathologic diagnoses, and clinical stages can be highly heterogeneous in their genetic and epigenetic alterations that cause tumorigenesis. A number of cancer driver genes with functional abnormalities that trigger malignant transformation and that are required for the survival of cancer cells have been identified. Therapeutic agents targeting some of these cancer drivers have been successfully developed, resulting in substantial improvements in clinical symptom amelioration and outcomes in a subset of cancer patients. However, because such therapeutic drugs often benefit only a limited number of patients, the successes of clinical development and applications rely on the ability to identify those patients who are sensitive to the targeted therapies. Thus, biomarkers that can predict treatment responses are critical for the success of precision therapy for cancer patients and of anticancer drug development. This review discusses the molecular heterogeneity of lung cancer pathogenesis; predictive biomarkers for precision medicine in lung cancer therapy with drugs targeting epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), c-ros oncogene 1 receptor tyrosine kinase (ROS1), and immune checkpoints; biomarkers associated with resistance to these therapeutics; and approaches to identify predictive biomarkers in anticancer drug development. The identification of predictive biomarkers during anticancer drug development is expected to greatly facilitate such development because it will increase the chance of success or reduce the attrition rate. Additionally, such identification will accelerate the drug approval process by providing effective patient stratification strategies in clinical trials to reduce the sample size required to demonstrate clinical benefits.
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Affiliation(s)
- Bingliang Fang
- Department of Thoracic and Cardiovascular Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
| | - Reza J Mehran
- Department of Thoracic and Cardiovascular Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
| | - John V Heymach
- Department of Thoracic and Head/Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
| | - Stephen G Swisher
- Department of Thoracic and Cardiovascular Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
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Abstract
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The
concept of synthetic lethality (the creation of a lethal phenotype
from the combined effects of mutations in two or more genes) has recently
been exploited in various efforts to develop new genotype-selective
anticancer therapeutics. These efforts include screening for novel
anticancer agents, identifying novel therapeutic targets, characterizing
mechanisms of resistance to targeted therapy, and improving efficacies
through the rational design of combination therapy. This review discusses
recent developments in synthetic lethality anticancer therapeutics,
including poly ADP-ribose polymerase inhibitors for BRCA1- and BRCA2-mutant cancers, checkpoint inhibitors
for p53 mutant cancers, and small molecule agents targeting RAS gene mutant cancers. Because cancers are caused by mutations
in multiple genes and abnormalities in multiple signaling pathways,
synthetic lethality for a specific tumor suppressor gene or oncogene
is likely cell context-dependent. Delineation of the mechanisms underlying
synthetic lethality and identification of treatment response biomarkers
will be critical for the success of synthetic lethality anticancer
therapy.
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Affiliation(s)
- Bingliang Fang
- Department of Thoracic and Cardiovascular Surgery, Unit 1489, The University of Texas MD Anderson Cancer Center , 1515 Holcombe Boulevard, Houston, Texas 77030, United States
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4
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Genetic Interactions of STAT3 and Anticancer Drug Development. Cancers (Basel) 2014; 6:494-525. [PMID: 24662938 PMCID: PMC3980611 DOI: 10.3390/cancers6010494] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 02/18/2014] [Accepted: 02/20/2014] [Indexed: 12/18/2022] Open
Abstract
Signal transducer and activator of transcription 3 (STAT3) plays critical roles in tumorigenesis and malignant evolution and has been intensively studied as a therapeutic target for cancer. A number of STAT3 inhibitors have been evaluated for their antitumor activity in vitro and in vivo in experimental tumor models and several approved therapeutic agents have been reported to function as STAT3 inhibitors. Nevertheless, most STAT3 inhibitors have yet to be translated to clinical evaluation for cancer treatment, presumably because of pharmacokinetic, efficacy, and safety issues. In fact, a major cause of failure of anticancer drug development is lack of efficacy. Genetic interactions among various cancer-related pathways often provide redundant input from parallel and/or cooperative pathways that drives and maintains survival environments for cancer cells, leading to low efficacy of single-target agents. Exploiting genetic interactions of STAT3 with other cancer-related pathways may provide molecular insight into mechanisms of cancer resistance to pathway-targeted therapies and strategies for development of more effective anticancer agents and treatment regimens. This review focuses on functional regulation of STAT3 activity; possible interactions of the STAT3, RAS, epidermal growth factor receptor, and reduction-oxidation pathways; and molecular mechanisms that modulate therapeutic efficacies of STAT3 inhibitors.
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Parfett CL, Healy C. Tandemly repeated DNA sequence instabilities induced by two promoters of morphological transformation in vitro: a short-term response to non-mutagenic agents in C3H/10T1/2 cells. Mutat Res 2006; 604:42-52. [PMID: 16459133 DOI: 10.1016/j.mrgentox.2005.12.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Revised: 12/12/2005] [Accepted: 12/20/2005] [Indexed: 11/23/2022]
Abstract
The ability of tumour promoters to alter DNA stability within regions that contain tandemly repeated sequences (TRSs), was studied in a cell culture model of multi-stage carcinogenesis. Non-cytotoxic concentrations of TPA (12-O-tetradecanoyl-phorbol-13-acetate) and xanthine oxidase with xanthine substrate, sufficient to promote morphological transformation in C3H/10T1/2 cultures, were tested for their effects on mutation frequencies in TRSs by a DNA fingerprinting approach. Specifically, restriction digests of genomic DNA samples from randomly selected, non-transformed clones, isolated from cultures after several days exposure to promoters, were visualized by Southern hybridizations with the multi-locus pentamer repeat sequence probe, Ms6-Hm (Pc-1). Basal and promoter-induced frequencies of sub-clone TRS fingerprint polymorphisms were estimated in five cell populations: an uncloned stock culture, three populations established from normal-appearing sub-clones, and one clonal population established from a 3-methylcholanthrene (MCA)-transformed focus. Basal variant fingerprint frequencies spanned a range from 0.0 to 0.43% mutants/band among cells from the four untransformed populations. Both TPA and xanthine oxidase treatments significantly increased recorded mutation frequencies, 2.3- and 2.7-fold, respectively, using combined data from the progenitor population and three untransformed clones. The untreated MCA-transformed clonal population appeared to contain a single, pre-existing mutant restriction fragment, but additional mutations were induced thereafter, in response to the promoting treatments. Taken together, the measured increases in mutations were highly significant and suggest that promoters of cell transformation in the C3H/10T1/2 cell line might induce a genome-wide instability targeted to regions containing Ms6-Hm sequence motifs.
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Affiliation(s)
- Craig L Parfett
- Mutagenesis Section, Healthy Environments and Consumer Safety Branch, Health Canada, Environmental Health Centre 0803A, Tunney's Pasture, Ottawa, Ont., Canada K1A 0L2.
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Friday BB, Adjei AA. K-ras as a target for cancer therapy. Biochim Biophys Acta Rev Cancer 2005; 1756:127-44. [PMID: 16139957 DOI: 10.1016/j.bbcan.2005.08.001] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2005] [Revised: 07/29/2005] [Accepted: 08/01/2005] [Indexed: 11/30/2022]
Abstract
The central role K-, H- and N-Ras play in regulating diverse cellular pathways important for cell growth, differentiation and survival is well established. Dysregulation of Ras proteins by activating mutations, overexpression or upstream activation is common in human tumors. Of the Ras proteins, K-ras is the most frequently mutated and is therefore an attractive target for cancer therapy. The complexity of K-ras signaling presents many opportunities for therapeutic targeting. A number of different approaches aimed at abrogating K-ras activity have been explored in clinical trials. Several of the therapeutic agents tested have demonstrated clinical activity, supporting ongoing development of K-ras targeted therapies. However, many of the agents currently being evaluated have multiple targets and their antitumor effects may not be due to K-Ras inhibition. To date, no selective, specific inhibitor of K-ras is available for routine clinical use. In this review, we will summarize the structure and function of K-ras with attention to its role in tumorigenesis and discuss the successes and failures of the various strategies designed to therapeutically target this important oncogene.
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Affiliation(s)
- Bret B Friday
- Division of Medical Oncology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
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Charles MW, Mill AJ, Darley PJ. Carcinogenic risk of hot-particle exposures. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2003; 23:5-28. [PMID: 12729416 DOI: 10.1088/0952-4746/23/1/301] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
It has been suggested that spatially non-uniform radiation exposures, such as those from small radioactive particles ('hot particles'), may be very much more carcinogenic than when the same amount of energy is deposited uniformly throughout a tissue volume. This review provides a brief summary of in vivo and in vitro experimental findings, and human epidemiology data, which can be used to evaluate the veracity of this suggestion. Overall, this supports the contrary view and indicates that average dose, as advocated by the ICRP, is likely to provide a reasonable estimate of carcinogenic risk (within a factor of approximately +/- 3). There are few human data with which to address this issue. The limited data on lung cancer mortality following occupational inhalation of plutonium aerosols, and the incidence of liver cancer and leukaemia due to thorotrast administration for clinical diagnosis, do not appear to support a significant enhancement factor. Very few animal studies, including mainly lung and skin exposures, provide any indication of a hot-particle enhancement for carcinogenicity. Some recent in vitro malignant transformation experiments provide evidence foran enhanced cell transformation for hot-particle exposures but, properly interpreted, the effect is modest. Few studies extend below absorbed doses of approximately 0.1 Gy.
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Affiliation(s)
- M W Charles
- Radiation Biophysics Group, School of Physics and Astronomy, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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Roelofs H, Mostert MC, Pompe K, Zafarana G, van Oorschot M, van Gurp RJ, Gillis AJ, Stoop H, Beverloo B, Oosterhuis JW, Bokemeyer C, Looijenga LH. Restricted 12p amplification and RAS mutation in human germ cell tumors of the adult testis. THE AMERICAN JOURNAL OF PATHOLOGY 2000; 157:1155-66. [PMID: 11021820 PMCID: PMC1850173 DOI: 10.1016/s0002-9440(10)64631-7] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Human testicular germ-cell tumors of young adults (TGCTs), both seminomas and nonseminomas, are characterized by 12p overrepresentation, mostly as isochromosomes, of which the biological and clinical significance is still unclear. A limited number of TGCTs has been identified with an additional high-level amplification of a restricted region of 12p including the K-RAS proto-oncogene. Here we show that the incidence of these restricted 12p amplifications is approximately 8% in primary TGCTs. Within a single cell formation of i(12p) and restricted 12p amplification is mutually exclusive. The borders of the amplicons cluster in short regions, and the amplicon was never found in the adjacent carcinoma in situ cells. Seminomas with the restricted 12p amplification virtually lacked apoptosis and the tumor cells showed prolonged in vitro survival like seminoma cells with a mutated RAS gene. However, no differences in proliferation index between these different groups of seminomas were found. Although patients with a seminoma containing a homogeneous restricted 12p amplification presented at a significantly younger age than those lacking it, the presence of a restricted 12p amplification/RAS mutation did not predict the stage of the disease at clinical presentation and the treatment response of primary seminomas. In 55 primary and metastatic tumors from 44 different patients who failed cisplatinum-based chemotherapy, the restricted 12p amplification and RAS mutations had the same incidence as in the consecutive series of responding patients. These data support the model that gain of 12p in TGCTs is related to invasive growth. It allows tumor cells, in particular those showing characteristics of early germ cells (ie, the seminoma cells), to survive outside their specific microenvironment. Overexpression of certain genes on 12p probably inhibits apoptosis in these tumor cells. However, the copy numbers of the restricted amplification of 12p and K-RAS mutations do not predict response to therapy and survival of the patients.
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Affiliation(s)
- H Roelofs
- Pathology/Laboratory for Experimental Patho-Oncology, University Hospital Rotterdam/Daniel, Josephine Nefkens Institute, Rotterdam, The Netherlands
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9
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Shao J, Sheng H, DuBois RN, Beauchamp RD. Oncogenic Ras-mediated cell growth arrest and apoptosis are associated with increased ubiquitin-dependent cyclin D1 degradation. J Biol Chem 2000; 275:22916-24. [PMID: 10781597 DOI: 10.1074/jbc.m002235200] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cellular responses to activated Ras vary depending on cell type. Normal cells are often induced into pathways that lead to cell growth arrest, senescence, and/or apoptosis in response to activated Ras expression. These are important protective anti-tumorigenic responses that restrict the propagation of cells bearing activated oncogenes. Here we show that induction of Ha-Ras(Val-12) in Rat-1 fibroblasts resulted in G(1) growth arrest and apoptosis with loss of viable cells that is accompanied by a marked decrease in cyclin D1 levels via increased ubiquitin-proteasome-dependent cyclin D1 turnover. This is in contrast with a rat intestinal epithelial cell line in which induction of Ha-Ras(Val-12) results in transformation associated with sustained proliferation and increased levels of cyclin D1, that is not accompanied by anoikis or apoptosis. Expression of the cyclin D1 mutant (T286A) that contains an alanine for threonine 286 substitution and is resistant to ubiquitin-proteasome degradation in the Ha-Ras(Val-12) expressing Rat-1 cells resulted in a sustained transformed phenotype with no accumulation of cells in G(1). Inhibition of mitogen-activated protein kinase (MEK1/2) pathway partially reversed the Ras-mediated decrease in cyclin D1. Induction of Ha-Ras(Val-12) resulted in activation of Akt kinase and inactivation of glycogen-synthase-3beta kinase that are associated with reduction of cyclin D1 protein. These results suggest that Ras-mediated cyclin D1 degradation in Rat-1 cells appears to be partially dependent on activation of mitogen-activated protein kinase pathway and independent of glycogen-synthase-3beta kinase pathway.
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Affiliation(s)
- J Shao
- Department of Medicine, The Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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Sheng H, Williams CS, Shao J, Liang P, DuBois RN, Beauchamp RD. Induction of cyclooxygenase-2 by activated Ha-ras oncogene in Rat-1 fibroblasts and the role of mitogen-activated protein kinase pathway. J Biol Chem 1998; 273:22120-7. [PMID: 9705357 DOI: 10.1074/jbc.273.34.22120] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Elevated cyclooxygenase-2 (COX-2) expression and activity have been observed in several different transformed cell types that express mutated ras genes. To investigate the mechanism of increased COX-2 expression following Ras-mediated transformation, Rat-1:iRas cell line was transfected with an Ha-RasVal-12 cDNA expression vector that is under the transcriptional control of the lac operon and is inducible with isopropyl-1-thio-beta-D-galactopyranoside (IPTG). IPTG treatment caused parallel increases in the levels of Ha-Ras and COX-2 proteins in Rat-1:iRas cells. The increased expression of COX-2 was accompanied by increased prostaglandin E2 production. Selective inhibition of COX-2 activity suppressed the production of prostaglandin E2 by >90% but did not alter the progress of the morphological transformation. The level of COX-2 mRNA was up-regulated by activated Ha-Ras. Induction of Ras increased the transcription of COX-2 by 44.3 +/- 10.1% and increased the half-life of COX-2 mRNA by approximately 3.5-fold. A specific mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) inhibitor (PD 98059) caused a delay in both the activation of ERK1/2 and the induction of COX-2 in IPTG-induced Rat-1:iRas cells. Inhibition of ERK activity by PD 98059 also suppressed the induction of COX-2 by epidermal growth factor in intestinal epithelial cells and significantly reduced the expression of COX-2 in Ha-Ras-transformed rat intestinal epithelial cells. ERK activity appears to be required for induction of COX-2 by Ras.
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Affiliation(s)
- H Sheng
- Department of Surgery,the Vanderbilt Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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Affiliation(s)
- N E Crompton
- Life Sciences Department, Paul Scherrer Institute, Villigen, Switzerland.
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12
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Kim K, Kuo T, Cai J, Shuja S, Murnane MJ. N-ras protein: frequent quantitative and qualitative changes occur in human colorectal carcinomas. Int J Cancer 1997; 71:767-75. [PMID: 9180144 DOI: 10.1002/(sici)1097-0215(19970529)71:5<767::aid-ijc13>3.0.co;2-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Point mutation and overexpression are recognized mechanisms for ras activation in malignancy. However, little information is available on overexpression of N-ras protein compared with H- or K-ras proteins, as N-ras-specific antibodies have only recently become available. For comparative analyses of ras protein levels, we have probed Western blots of extracts from 9 normal human tissues and 55 pairs of colorectal carcinoma and matched control mucosa, using monoclonal antibodies (MAbs) specific for H-, K- or N-ras proteins. On multi-tissue blots, N-ras protein was more highly expressed in colon than in the other human tissues analyzed, suggesting a role for N-ras in colorectal function. N-ras protein levels in multiple independent extracts of normal colon mucosa were consistently higher than either K-ras protein or H-ras protein levels. In 69% of colon carcinomas, N-ras protein levels were increased an average of 4.8-fold over normal mucosa. Overexpression of K-ras protein was also observed in colon cancers but less frequently (13% of cases) than N-ras protein. H-ras protein levels were too low for comparative studies. Alterations in N-ras protein mobility, possibly reflecting increased post-translational processing, were also detected in 42% of colon carcinomas. N-ras protein, typically present as a single 23 kDa band in normal mucosa, was expressed in some cancers as a 22 kDa band or as multiple bands of 20-23 kDa. Sequencing of N-ras DNA from 6 carcinomas with these variations in protein mobility did not reveal mutations in codons 12, 13, 59 or 61. Thus, frequent quantitative and qualitative changes in N-ras protein expression, which do not appear to correlate with the presence of typical N-ras point mutations, result in abnormal N-ras protein patterns in human colorectal carcinomas.
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Affiliation(s)
- K Kim
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, MA 02118, USA
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13
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Volpe JP, Conti CJ, Slaga TJ. Characterization of mutant HA-ras gene expression in transformed murine keratinocyte lines grown under in vitro and in vivo conditions. Mol Carcinog 1996; 17:202-6. [PMID: 8989913 DOI: 10.1002/(sici)1098-2744(199612)17:4<202::aid-mc3>3.0.co;2-f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We investigated the Ha-ras and Ki-ras gene status, tumorigenicity, pathology, line derivation, and intercellular communication of 7,12-dimethylbenz[a]anthracene-initiated papilloma-, carcinoma-, and hyperplastic skin-producing cell lines to further characterize them. Six of nine tumor cell lines grown in vitro expressed both mutant and normal Ha-ras proteins, and three lines expressed only normal Ha-ras. However, when grown subcutaneously in nude mice, seven of the nine lines expressed both mutant and normal Ha-ras, one line expressed normal Ha-ras, and one line did not grow subcutaneously. One papilloma line, P2/15, appeared to have an inducible mutant Ha-ras gene, as it was expressed only in vivo. These findings suggest that mutant Ha-ras genes may be lost in only a minor population of tumor lines during growth in culture. Finally, we found that mutant Ha-ras gene expression was strongly correlated with tumorigenicity in nude mice and that intercellular communication was strongly correlated with the derivation of the lines.
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Affiliation(s)
- J P Volpe
- University of Texas M. D. Anderson Cancer Center, Science Park-Research Division, Smithville, USA
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Weller M, Fontana A. The failure of current immunotherapy for malignant glioma. Tumor-derived TGF-beta, T-cell apoptosis, and the immune privilege of the brain. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1995; 21:128-51. [PMID: 8866671 DOI: 10.1016/0165-0173(95)00010-0] [Citation(s) in RCA: 172] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Human malignant gliomas are rather resistant to all current therapeutic approaches including surgery, radiotherapy and chemotherapy as well as antibody-guided or cellular immunotherapy. The immunotherapy of malignant glioma has attracted interest because of the immunosuppressed state of malignant glioma patients which resides mainly in the T-cell compartment. This T-cell suppression has been attributed to the release by the glioma cells of immunosuppressive factors like transforming growth factor-beta (TGF-beta) and prostaglandins. TGF-beta has multiple effects in the immune system, most of which are inhibitory. TGF-beta appears to control downstream elements of various cellular activation cascades and regulates the expression of genes that are essential for cell cycle progression and mitosis. Since TGF-beta-mediated growth arrest of T-cell lines results in their apoptosis in vitro, glioma-derived TGF-beta may prevent immune-mediated glioma cell elimination by inducing apoptosis of tumor-infiltrating lymphocytes in vivo. T-cell apoptosis in the brain may be augmented by the absence of professional antigen-presenting cells and of appropriate costimulating signals. Numerous in vitro studies predict that tumor-derived TGF-beta will incapacitate in vitro-expanded and locally administered lymphokine-activated killer cells (LAK-cells) or tumor-infiltrating lymphocytes. Thus, TGF-beta may be partly responsible for the failure of current adoptive cellular immunotherapy of malignant glioma. Recent experimental in vivo studies on non-glial tumors have corroborated that neutralization of tumor-derived TGF-beta activity may facilitate immune-mediated tumor rejection. Current efforts to improve the efficacy of immunotherapy for malignant glioma include various strategies to enhance the immunogenicity of glioma cells and the cytotoxic activity of immune effector cells, e.g., by cytokine gene transfer. Future strategies of cellular immunotherapy for malignant glioma will have to focus on rendering glioma cell-targeting immune cells resistent to local inactivation and apoptosis which may be induced by TGF-beta and other immunosuppressive molecules at the site of neoplastic growth. Cytotoxic effectors targeting Fas/APO-1, the receptor protein for perforin-independent cytotoxic T-cell killing, might be promising, since Fas/APO-1 is expressed by glioma cells but not by untransformed brain cells, and since Fas/APO-1-mediated killing in vitro is not inhibited by TGF-beta.
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Affiliation(s)
- M Weller
- Neurologische Klinik der Universität Tübingen, Germany
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Kiaris H, Spandidos DA, Jones AS, Vaughan ED, Field JK. Mutations, expression and genomic instability of the H-ras proto-oncogene in squamous cell carcinomas of the head and neck. Br J Cancer 1995; 72:123-8. [PMID: 7599040 PMCID: PMC2034114 DOI: 10.1038/bjc.1995.287] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Mutation and overexpression are the main activating mechanisms for the ras family of genes in human cancer and the variable tandem repeat (VTR) located at the 3' end of H-ras has been associated with this risk. In the present study, we have analysed the relative levels of expression of H-ras mRNA in 26 samples of squamous cell carcinomas of the head and neck (SCCHN) by competitive reverse transcription-polymerase chain reaction (competitive RT-PCR) and also investigated whether there is an association between ras expression and alterations in the 3'-VTR region. In addition, we have studied the incidence of point mutations in codon 12 of H-ras, codons 12 and 13 of K-ras and codon 61 of N-ras in 120 SCCHN samples. Our results indicate that only two samples carry mutations, both of which are located in codon 12 of K-ras, but that overexpression of the H-ras proto-oncogene is a frequent event in SCCHN [54% (14/26)] and is associated with a favourable prognosis: 3 of 14 patients with H-ras overexpression have died, whereas 9 of 12 patients with low levels of H-ras expression have died. We have also undertaken an analysis of these results together with our previous investigations on microsatellite instability and loss of heterozygosity in SCCHN, but no associations were found. We therefore conclude that ras mutations are an infrequent event in the progression of the SCCHN in the Western world, whereas overexpression of the H-ras proto-oncogene is a common event.
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Affiliation(s)
- H Kiaris
- Department of Clinical Dental Sciences, University of Liverpool, School of Dentistry, UK
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