Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.5.1.3 (dihydrofolate reductase)
 5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Methotrexate (MTX) is one of the most important drugs for osteosarcoma (OS) treatment. To identify genetic aberrations associated with the development of MTX resistance in OS cells, in addition to the previously reported expression changes of dihydrofolate reductase (DHFR) and reduced folate carrier (RFC) genes, comparative genomic hybridization (CGH)-based techniques were used. The direct comparison between MTX-resistant variants of U-2OS or Saos-2 human OS cell lines with their respective parental cell lines by CGH on chromosomes revealed that development of MTX resistance was associated with gain of the chromosomal regions 5q12-q15 and 11q14-qter in U-2OS variants, and with gain of 8q22-qter in Saos-2 variants. Further analyses by CGH on microarrays demonstrated a progressively increasing gain of mixed lineage leukemia (MLL) gene (11q23) in U-2OS MTX-resistant variants, which was also confirmed by fluorescence in situ hybridization (FISH), in addition to gain of FGR (1p36), amplification/overexpression of DHFR, and slight decrease of RFC expression. In Saos-2 MTX-resistant variants, gain of MYC (8q24.12-q24.13) was detected, together with a remarkable decrease of RFC expression. Further analyses of DHFR, MLL, MYC, and RFC gene status in four additional human OS cell lines revealed that only gain of DHFR and MLL were associated with an inherent lower sensitivity to MTX. These data demonstrate that genetic analyses with complementary techniques are helpful for the identification of new candidate genes, which might be considered for an early identification of MTX unresponsive tumors.
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PMID:Genomic imbalances associated with methotrexate resistance in human osteosarcoma cell lines detected by comparative genomic hybridization-based techniques. 1458 36

High-risk types of HPV express the oncoproteins, E6 and E7, that can inactivate TP53 and RB1, respectively, and thus take control of both cell cycle and apoptosis. Herein, the mRNA expression profiles of 24 G1/S checkpoint genes were analysed in cancer and squamous intraepithelial lesions (SIL) of the uterine cervix. In total 35 squamous cervical carcinomas, 26 high-grade SIL (HSIL), 33 low-grade SIL (LSIL) tissues, and 28 normal uterine cervix specimens as controls were assessed by RT-PCR. Five genes were found to be upregulated only in tumours, RBL2, E2F2, CDK6, CCNE1 and MYC; eight in tumours and HSILs, E2F1, E2F3, E2F5, CCND1, CDK2, CDKN1B, PCNA and POLA, and five in tumours, HSILs and LSILs, TP53, E2F4, CDKN1A, CDKN2A and DHFR. MDM2 was found to be upregulated in SIL, while RBL1 was found to be downregulated in all three groups of cases. TP73 exhibited lower levels in carcinomas; however, its exon 13-containing isoforms were increased and exon 2-containing isoforms were reduced in both cancer and HSIL. Three genes, RB1, CDK4 and CDKN2D, did not exhibit any significant alteration in gene expression. Hierarchical clustering revealed that this set of G1/S checkpoint genes was able to discriminate the total 122 samples into groups of disease and non-disease with only 8 exceptions (6.6%). Our data suggest that deregulation of G1/S phase transition in cervical carcinogenesis is a progressive process. Certain clusters of genes are activated very early in pre-cancerous SILs while others are activated later, during malignant transformation. The ability of this array of markers to identify disease status suggests that it could be used for diagnostic purposes.
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PMID:Deregulation of the G1/S phase transition in cancer and squamous intraepithelial lesions of the uterine cervix: a case control study. 1881 14

Gene amplification and copy number changes play a pivotal role in malignant transformation and progression of human tumor cells by mediating the activation of genes and oncogenes, which are involved in many different cellular processes including development of drug resistance. Since doxorubicin (DX) and methotrexate (MTX) are the two most important drugs for high-grade osteosarcoma (OS) treatment, the aim of this study was to identify genes gained or amplified in six DX- and eight MTX-resistant variants of the human OS cell lines U-2OS and Saos-2, and to get insights into the mechanisms underlying the amplification processes. Comparative genomic hybridization techniques identified amplification of MDR1 in all six DX-resistant and of DHFR in three MTX-resistant U-2OS variants. In addition, progressive gain of MLL was detected in the four U-2OS variants with higher resistance levels either to DX or MTX, whereas gain of MYC was found in all Saos-2 MTX-resistant variants and the U-2OS variant with the highest resistance level to DX. Fluorescent in situ hybridization revealed that MDR1 was amplified in U-2OS and Saos-2/DX-resistant variants manifested as homogeneously staining regions and double minutes, respectively. In U-2OS/MTX-resistant variants, DHFR was amplified in homogeneously staining regions, and was coamplified with MLL in relation to the increase of resistance to MTX. Gene amplification was associated with gene overexpression, whereas gene gain resulted in up-regulated gene expression. These results indicate that resistance to DX and MTX in human OS cell lines is a multigenic process involving gene copy number and expression changes.
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PMID:Mechanisms of gene amplification and evidence of coamplification in drug-resistant human osteosarcoma cell lines. 1910 35

Patients with non-muscle invasive bladder cancer (NMIBC) generally have a high risk of relapsing locally after primary tumor resection. The search for new predictive markers of local recurrence thus represents an important goal for the management of this disease. We studied the copy number variations (CNVs) of 24 oncogenes (MDM4, MYCN, ALK, PDGFRA, KIT, KDR, DHFR, EGFR, MET, SMO, FGFR1, MYC, ABL1, RET, CCND1, CCND2, CDK4, MDM2, AURKB, ERBB2, TOP2A, AURKA, AR and BRAF) using multiplex ligation probe amplification technique to verify their role as predictive markers of recurrence. Formalin-fixed paraffin-embedded tissue samples from 43 patients who underwent transurethral resection of the bladder (TURB) were used; 23 patients had relapsed and 20 were disease-free after 5 years. Amplification frequencies were analyzed for all genes and MDM4 was the only gene that showed significantly higher amplification in non recurrent patients than in recurrent ones (0.65 vs. 0.3; Fisher's test p=0.023). Recurrence-free survival analysis confirmed the predictive role of MDM4 (log-rank test p=0.041). Our preliminary results indicate a putative role for the MDM4 gene in predicting local recurrence of bladder cancer. Confirmation of this hypothesis is needed in a larger cohort of NMIBC patients.
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PMID:Copy number analysis of 24 oncogenes: MDM4 identified as a putative marker for low recurrence risk in non muscle invasive bladder cancer. 2502 75

We studied the ability of polypurine reverse Hoogsteen hairpins (PPRHs) to silence a variety of relevant cancer-related genes in several human cell lines. PPRHs are hairpins formed by two antiparallel polypurine strands bound by intramolecular Hoogsteen bonds linked by a pentathymidine loop. These hairpins are able to bind to their target DNA sequence through Watson-Crick bonds producing specific silencing of gene expression. We designed PPRHs against the following genes: BCL2, TOP1, mTOR, MDM2, and MYC and tested them for mRNA levels, cytotoxicity, and apoptosis in prostate, pancreas, colon, and breast cancer cell lines. Even though all PPRHs were effective, the most remarkable results were obtained with those against BCL2 and mammalian target of rapamycin (mTOR) in decreasing cell survival and mRNA levels and increasing apoptosis in prostate, colon, and pancreatic cancer cells. In the case of TOP1, MDM2, and MYC, their corresponding PPRHs produced a strong effect in decreasing cell viability and mRNA levels and increasing apoptosis in breast cancer cells. Thus, we confirm that the PPRH technology is broadly useful to silence the expression of cancer-related genes as demonstrated using target genes involved in metabolism (DHFR), proliferation (mTOR), DNA topology (TOP1), lifespan and senescence (telomerase), apoptosis (survivin, BCL2), transcription factors (MYC), and proto-oncogenes (MDM2).
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PMID:Effect of Polypurine Reverse Hoogsteen Hairpins on Relevant Cancer Target Genes in Different Human Cell Lines. 2604 2

Research on the amplification of oncogenes in thymic malignant tumor is limited. In this study, we aimed to determine the gene amplification status of receptor tyrosine kinases and other cell regulator genes in thymic malignant tumors, with a view toward the future introduction of molecular targeted therapy. In addition, we examined the usefulness of multiplex, ligation-dependent probe amplification (MLPA) in the semi-comprehensive detection of these gene amplifications. The participants of this study were nine patients with thymic carcinoma and one patient with atypical carcinoid who underwent resection at our department from 1999 to 2016. Twenty-four oncogenes (MDM4, MYCN, ALK, PDGFRA, KIT, KDR, DHFR, EGFR, MET, SMO, BRAF, FGFR1, MYC, ABL1, RET, CCND1, CCND2, CDK4, MDM2, AURKB, ERBB2, TOP2A, AURKA, AR) were analyzed for amplification by MLPA. In cases where amplification by MLPA was suspected, confirmation was performed by fluorescence in situ hybridization (FISH). Immunostaining for detected oncoproteins and p53 were performed in cases with confirmed oncogene amplification. MYC (2/10, 20%) and MDM2 (1/10, 10%) amplifications were detected using MLPA and FISH. Immunostaining in both cases was positive. The MDM2-amplified tumor relapsed and spread rapidly after operation despite the use of post-operative chemo-radiotherapy. MYC amplification may be involved in the carcinogenesis of thymic malignant tumors. In addition, MDM2 amplification may be a concern in the increased malignancy.
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PMID:Semi-comprehensive analysis of gene amplification in thymic malignant tumors using multiplex ligation-dependent probe amplification and fluorescence in situ hybridization. 3250 76