UV radiation facilitates methotrexate resistance and amplification of the dihydrofolate reductase gene in cultured 3T6 mouse cells

1984 ◽  
Vol 4 (6) ◽  
pp. 1050-1056
Author(s):  
T D Tlsty ◽  
P C Brown ◽  
R T Schimke
Keyword(s):  
Gene Amplification ◽  
Uv Radiation ◽  
Dihydrofolate Reductase ◽  
Copy Number ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Methotrexate Resistance ◽  
Reductase Gene ◽  
Mouse Cells

Pretreatment of 3T6 murine cells with the carcinogen UV radiation or N-acetoxy-N-acetylaminofluorene increased the number of methotrexate-resistant colonies. This carcinogen-induced enhancement was seen only at low toxicities. The enhancement was transient and was observed at its maximum when cells were subjected to methotrexate selection 12 to 24 h after treatment. The addition of a tumor-promoting agent, 12-O-tetradecanoylphorbol-13-acetate, during or after carcinogen treatment further enhanced this effect. A large proportion of the resistant colonies had an increase in the dihydrofolate reductase gene copy number and the relative proportions of colonies with amplified genes were similar, regardless of whether selected cells were untreated, treated with carcinogen, or treated with carcinogen plus promoter. We discuss some of the variables which both enhance the generation and improve the detection of methotrexate-resistant colonies, as well as certain implications of our results for the generation and mechanism of gene amplification.

scholarly journals UV radiation facilitates methotrexate resistance and amplification of the dihydrofolate reductase gene in cultured 3T6 mouse cells.

1984 ◽  
Vol 4 (6) ◽  
pp. 1050-1056 ◽  
Author(s):  
T D Tlsty ◽  
P C Brown ◽  
R T Schimke
Keyword(s):  
Gene Amplification ◽  
Uv Radiation ◽  
Dihydrofolate Reductase ◽  
Copy Number ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Methotrexate Resistance ◽  
Reductase Gene ◽  
Mouse Cells

Pretreatment of 3T6 murine cells with the carcinogen UV radiation or N-acetoxy-N-acetylaminofluorene increased the number of methotrexate-resistant colonies. This carcinogen-induced enhancement was seen only at low toxicities. The enhancement was transient and was observed at its maximum when cells were subjected to methotrexate selection 12 to 24 h after treatment. The addition of a tumor-promoting agent, 12-O-tetradecanoylphorbol-13-acetate, during or after carcinogen treatment further enhanced this effect. A large proportion of the resistant colonies had an increase in the dihydrofolate reductase gene copy number and the relative proportions of colonies with amplified genes were similar, regardless of whether selected cells were untreated, treated with carcinogen, or treated with carcinogen plus promoter. We discuss some of the variables which both enhance the generation and improve the detection of methotrexate-resistant colonies, as well as certain implications of our results for the generation and mechanism of gene amplification.

Mathematical models of gene amplification with applications to cellular drug resistance and tumorigenicity.

Genetics ◽  
1990 ◽  
Vol 125 (3) ◽  
pp. 633-644
Author(s):  
M Kimmel ◽  
D E Axelrod
Keyword(s):  
Mathematical Models ◽  
Cell Lines ◽  
Gene Amplification ◽  
Dihydrofolate Reductase ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Published Data ◽  
Reductase Gene ◽  
Double Minute ◽  
Double Minute Chromosomes

Abstract An increased number of copies of specific genes may offer an advantage to cells when they grow in restrictive conditions such as in the presence of toxic drugs, or in a tumor. Three mathematical models of gene amplification and deamplification are proposed to describe the kinetics of unstable phenotypes of cells with amplified genes. The models differ in details but all assume probabilistic mechanisms of increase and decrease in gene copy number per cell (gene amplification/deamplification). Analysis of the models indicates that a stable distribution of numbers of copies of genes per cell, observed experimentally, exists only if the probability of deamplification exceeds the probability of amplification. The models are fitted to published data on the loss of methotrexate resistance in cultured cell lines, due to the loss of amplified dihydrofolate reductase gene. For two mouse cell lines unstably resistant to methotrexate the probabilities of amplification and deamplification of the dihydrofolate reductase gene on double minute chromosomes are estimated to be approximately 2% and 10%, respectively. These probabilities are much higher than widely presumed. The models explain the gradual disappearance of the resistant phenotype when selective pressure is withdrawn, by postulating that the rate of deamplification exceeds the rate of amplification. Thus it is not necessary to invoke a growth advantage of nonresistant cells which has been the standard explanation. For another analogous process, the loss of double minute chromosomes containing the myc oncogene from SEWA tumor cells, the growth advantage model does seem to be superior to the amplification and deamplification model. In a more theoretical section of the paper, it is demonstrated that gene amplification/deamplification can result in reduction to homozygosity, such as is observed in some tumors. Other applications are discussed.

MET Gene High Copy Number (Amplification/Polysomy) Identified in Melanoma for Potential Targeted Therapy

2021 ◽  
Author(s):  
Nisha S Ramani ◽  
Ajaykumar C Morani ◽  
Shengle Zhang
Keyword(s):  
Targeted Therapy ◽  
Gene Amplification ◽  
Copy Number ◽  
Kinase Inhibitors ◽  
Gene Copy Number ◽  
Tissue Microarrays ◽  
High Copy Number ◽  
Gene Copy ◽  
Aberrant Expression ◽  
Mesenchymal Epithelial Transition Factor

Abstract Objectives Aberrant expression of the mesenchymal epithelial transition factor (MET) gene has been observed in several malignancies, and drugs targeting the MET gene have been implicated in clinical trials with promising results. Hence, MET is a potentially targetable oncogenic driver. We explored the frequency of MET gene high copy number in melanomas and carcinomas. Methods The study group included 135 patients. Tissue microarrays were constructed with 19 melanomas and 116 carcinomas diagnosed from 2010 to 2012. We screened MET gene copy number by fluorescence in situ hybridization analysis using probes for MET gene and CEP7 as control. Results We found MET gene amplification in 2 (11%) of 19 melanoma cases, whereas 5 (26%) of 19 melanoma cases showed polysomy. For carcinomas, there was no MET gene amplification identified. However, 8 (7%) of 116 cases showed polysomy. Conclusions In our study, MET gene amplification was identified in 11% of melanomas and is relatively concordant with few reported studies. However, about 26% of the additional melanoma cases showed MET gene polysomy, which has not been reported as per our knowledge. If these results are validated with further orthogonal studies, more of the melanoma cases could potentially benefit from targeted therapy with MET tyrosine kinase inhibitors.

Resistance to methotrexate due to gene amplification in a patient with acute leukemia.

1984 ◽  
Vol 2 (1) ◽  
pp. 16-20 ◽  
Author(s):  
M D Carman ◽  
J H Schornagel ◽  
R S Rivest ◽  
S Srimatkandada ◽  
C S Portlock ◽  
...  
Keyword(s):  
Gene Amplification ◽  
Copy Number ◽  
Cdna Probe ◽  
Leukemia Cell ◽  
Gene Copy Number ◽  
Leukemia Cell Line ◽  
Gene Copy ◽  
Acute Myelocytic Leukemia ◽  
Human Leukemia ◽  
Dot Blot

A patient is described with acute myelocytic leukemia refractory to conventional therapy, who also became highly resistant to methotrexate (MTX) after repeated courses of this drug. Leukemia cells from this patient were found to contain an elevated level of dihydrofolate reductase (DHFR) activity, with no change in the affinity of the enzyme for MTX. A sensitive "dot blot" assay revealed a fourfold increase in the gene copy number of DHFR. Southern blot analysis with a human DHFR cDNA probe confirmed this increase in the gene copy number, and demonstrated a similar restriction pattern with Eco R1, Hind III, and Pst 1 as seen with a highly amplified human leukemia cell line, K562. Additional DHFR fragments were detected, not seen in the K562 blot, suggesting the presence of pseudogenes, or a result of gene rearrangements occurring as part of the amplification process. Resistance to MTX in this patient was therefore ascribed to gene amplification and overproduction of DHFR.

Gene copy number of epidermal growth factor receptor (EGFR) by fluorescent in situ hybridization (FISH) in head and neck squamous cell carcinomas (HNSCC) is closely correlated with EGFR protein levels assessed by automated quantitative protein analysis (AQUA)

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 6023-6023
Author(s):  
P. Weinberger ◽  
A. Psyrri ◽  
P. Kountourakis ◽  
T. Rampias ◽  
C. Sasaki ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Protein Expression ◽  
Protein Content ◽  
Gene Amplification ◽  
Copy Number ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Egfr Gene ◽  
Protein Levels

6023 Background: EGFR overexpression correlates with recurrence and with treatment resistance in HNSCC. The mechanisms of EGFR protein overexpression are poorly understood. Nonetheless, previous investigators have not demonstrated a correlation between EGFR gene copy number and protein content, using conventional immunohistochemistry (IHC). The aim of this study was to evaluate the relationship of EGFR gene copy number and protein expression utilizing fluorescence in situ hybridization (FISH) and AQUA, a novel, immunohistochemical method of automated quantitative in situ proteomic analysis which permits subcellular localization. Methods: A tissue microarray composed of 137 HNSCC treated with (chemo)radiation was constructed and analyzed for EGFR copy number by FISH (Vysis/Abbot) and EGFR protein expression (DAKO antibody) using AQUA analysis of EGFR staining scored on a scale of 0–255 and by conventional IHC. Agreement was assessed using kappa. Results: Sixteen (15%) of one-hundred six tumors with FISH results demonstrated EGFR high polysomy and/or gene amplification (FISH+). AQUA demonstrated a range of 3.6–102.2; protein levels assessed by AQUA in the FISH amplified cases were significantly higher (p =0.008) than in the FISH non- amplified ones. Using the EGFR 75th percentile as a cut-off, AQUA and FISH showed significant agreement (percentage of overall agreement 82%, kappa=0.458, p=0.003). To the contrary there was no concordance between FISH and conventional IHC results in this series. Conclusions: The discrepancy between EGFR gene amplification rate and protein expression by IHC reported previously may be due to the limitations and nonquantitative nature of conventional IHC. EGFR protein content correlates with gene copy number if protein content is quantitated and automatically analyzed, as with AQUA. No significant financial relationships to disclose.

Level of HER2 Gene Amplification Predicts Response and Overall Survival in HER2-Positive Advanced Gastric Cancer Treated With Trastuzumab

2013 ◽  
Vol 31 (35) ◽  
pp. 4445-4452 ◽  
Author(s):  
Carlos Gomez-Martin ◽  
Jose Carlos Plaza ◽  
Roberto Pazo-Cid ◽  
Antonieta Salud ◽  
Francesc Pons ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Overall Survival ◽  
Advanced Gastric Cancer ◽  
Gene Amplification ◽  
Copy Number ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Her2 Gene ◽  
Optimal Cutoff ◽  
Her2 Gene Amplification

Purpose Previous studies have highlighted the importance of an appropriate human epidermal growth factor receptor 2 (HER2) evaluation for the proper identification of patients eligible for treatment with anti-HER2 targeted therapies. Today, the relationship remains unclear between the level of HER2 amplification and the outcome of HER2-positive gastric cancer treated with first-line chemotherapy with trastuzumab. The aim of this study was to determine whether the level of HER2 gene amplification determined by the HER2/CEP17 ratio and HER2 gene copy number could significantly predict some benefit in overall survival and response to therapy in advanced gastric cancer treated with trastuzumab-based chemotherapy. Patients and Methods Ninety patients with metastatic gastric cancer treated with first-line trastuzumab-based chemotherapy were studied. The optimal cutoff values for HER2/CEP17 ratio and HER2 gene copy number (GCN) for discriminating positive results in terms of response and prolonged survival were determined using receiver operating characteristic curves analyses. Results In this study, a median HER2/CEP17 ratio of 6.11 (95% CI, 2.27 to 21.90) and a median HER2 gene copy number of 11.90 (95% CI, 3.30 to 43.80) were found. A mean HER2/CEP17 ratio of 4.7 was identified as the optimal cutoff value discriminating sensitive and refractory patients (P = .005). Similarly, the optimal cutoff for predicting survival longer than 12 months was 4.45 (P = .005), and for survival longer than 16 months was 5.15 (P = .004). For HER2 GCN, the optimal cutoff values were 9.4, 10.0, and 9.5, respectively (P = .02). Conclusion The level of HER2 gene amplification significantly predicts sensitivity to therapy and overall survival in advanced gastric cancer treated with trastuzumab-based chemotherapy.

scholarly journals Enhancement of methotrexate resistance and dihydrofolate reductase gene amplification by treatment of mouse 3T6 cells with hydroxyurea.

1983 ◽  
Vol 3 (6) ◽  
pp. 1097-1107 ◽  
Author(s):  
P C Brown ◽  
T D Tlsty ◽  
R T Schimke
Keyword(s):  
Dna Synthesis ◽  
Gene Amplification ◽  
Dihydrofolate Reductase ◽  
Time Interval ◽  
Frequency Of Occurrence ◽  
Methotrexate Resistance ◽  
Reductase Gene ◽  
Initial Selection ◽  
Selection Of

We investigated various parameters associated with the initial selection of mouse 3T6 cells for resistance to single concentrations of methotrexate and characterized resistant colonies for the presence of additional (amplified) copies of the dihydrofolate reductase gene. Our results indicate that the frequency of occurrence of dihydrofolate reductase gene amplification varies with the selecting concentration of methotrexate and is highly variable between clonally derived sublines of mouse 3T6 cells. Second, we increased the frequency of occurrence of cells with amplified dihydrofolate reductase genes by transiently inhibiting DNA synthesis with hydroxyurea before the selection of cells in single concentrations of methotrexate. This effect was dependent on the concentration of hydroxyurea, the time of exposure to the drug, and the time interval between the removal of hydroxyurea and the selection of cells in methotrexate.

Phenotypic and genotypic characteristics of epidermal growth factor receptor (EGFR) in colorectal cancer patients

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 4110-4110
Author(s):  
G. A. Milano ◽  
M. C. Etienne-Grimaldi ◽  
M. Francoual ◽  
D. Benchimol ◽  
M. Chazal ◽  
...  
Keyword(s):  
Gene Amplification ◽  
Copy Number ◽  
Binding Assay ◽  
Gene Copy Number ◽  
Normal Mucosa ◽  
Gene Copy ◽  
Colorectal Tumors ◽  
Egfr Gene ◽  
Egfr Expression ◽  
The Mean

4110 Background: Colorectal tumors express EGFR and are responsive to anti-EGFR therapies. However, there is no tumoral predictive factor for anti-EGFR therapy in colorectal cancer and EGFR gene copy number is currently a good candidate. The aim of this study was to examine relationships between EGFR germinal polymorphisms, EGFR gene copy number and EGFR expression. Methods: Eighty primary colorectal tumors were analyzed along with 39 normal mucosas. Tumor staging was : 4 stage 0, 13 stage I, 22 stage II, 23 stage III and 18 stage IV. EGFR -216G>T and -191C>A genotypes were analyzed by PCR-RFLP, CA-repeats polymorphism in intron 1 by fluorescent genotyping and gene copy number was measured by PCR amplification. EGFR expression was quantified with the reference Scatchard binding assay giving high- and low-affinity sites along with Kd values (Francoual M et al. Ann Oncol 17, 2006). Results: The number of CA- repeats varied from 14 to 21. Considered genotypes were superimposable between tumoral and normal tissues. A linkage disequilibrium was noted between -216G>T and -191C>A genotypes (p = 0.011). CA-repeats polymorphism and -216G>T genotype were not independent (p = 0.002). No relationship was observed between any of the analyzed EGFR genotypes and EGFR expression. EGFR expression was not related to gene amplification. EGFR gene amplification in tumor and normal tissue varied over a 4.7- and 2.9-fold range, respectively, and were not correlated. The mean value of the tumor/normal mucosa amplification ratio was 1.16 (range 0.55–2.68) and 14% of patients exhibited lower amplification in the tumor relative to the normal mucosa (ratio < 0.75). The mean ratio of high-affinity sites between tumor and normal mucosa was 1.20 (range 0.03–13.33). Conclusions: In colorectal tumors, neither EGFR gene amplification nor EGFR germinal gene polymorphisms influenced EGFR expression quantified with a specific ligand-binding assay. No significant financial relationships to disclose.

SOX2 and FGFR1 gene copy number in surgically resected non-small cell lung cancer (NSCLC).

2012 ◽  
Vol 30 (15_suppl) ◽  
pp. 7061-7061
Author(s):  
Luca Toschi ◽  
Giovanna Finocchiaro ◽  
Teresa T. Nguyen ◽  
Margaret Skokan ◽  
Laura Giordano ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Gene Amplification ◽  
Squamous Cell ◽  
Cell Lung Cancer ◽  
Copy Number ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Prognostic Impact ◽  
Prognostic Relevance ◽  
Fgfr1 Gene

7061 Background: SOX2 is a member of the SRY-related HMG-box family of transcription factors and has been shown to be frequently amplified and overexpressed in squamous cell lung cancer, with conflicting results regarding its prognostic relevance. Similarly, FGFR1, a transmembrane tyrosine kinase receptor belonging to the fibroblast growth factor receptor family, has been recently reported to be amplified in squamous cell lung carcinomas, suggesting a potential role for FGFR1 as a therapeutic target in NSCLC. Aim of the present study is to evaluate SOX2 and FGFR1 gene copy number in surgically resected NSCLCs, to investigate their prognostic relevance and their association with clinico-pathological characteristics. Methods: SOX2 and FGFR1 gene copy number was assessed by fluorescence in situ hybridization (FISH) in tissue microarray cores from 447 surgically resected NSCLCs. Each patient was given a score ranging from 1 to 6 according to increasing mean copy number per cell of each gene, with 6 indicating true gene amplification. Results: SOX2 and FGFR1 FISH was successfully performed in 445 patients (pts), which were grouped as + (score 5-6) and - (score 1-4). Using this scoring system 105 (23.6%) pts tested SOX2+, while 74 (16.6%) pts resulted FGFR1+. True gene amplification for SOX2 and FGFR1 was observed in 19 (4.3%) and 37 (8.3%) cases, respectively. SOX2+ and FGFR1+ status was significantly associated with squamous histology (p<.001). Additionally, SOX2+ pts had a significantly higher chance of being former/current smokers, male and FGFR1+. FGFR1 gene status had no prognostic impact in the whole population and in the squamous cell carcinoma subgroup. Conversely, SOX2+ pts had significantly longer overall survival compared with SOX2- pts (HR 0.68, p=.020). When restricting survival analysis to squamous cell histology, stage I-II SOX2+ pts had a significant survival advantage compared with SOX2- group (HR 0.38, p=.006), while no difference was observed in stage III-IV pts. Conclusions: Increased SOX2 and FGFR1 gene copy number is a common event in lung cancer pts with squamous cell histology. SOX2 gene gain is a favorable prognostic factor in surgically resected pts, particularly in early stage squamous cell cancers.

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