Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Intrinsic and acquired multidrug resistance is an important problem in cancer therapy. Multidrug resistance results from overexpression of the MDR 1 gene, which encodes a drug-efflux pump called P-glycoprotein. We have isolated a 1-kilobase genomic fragment containing the major transcription initiation sites for the human MDR 1 gene. Ribonuclease protection experiments using this fragment indicate that normal human adrenal, colon, and liver cells, the human hepatoma cell line HepG2, and vinblastine-selected human KB multidrug-resistant cells initiate transcription of the MDR 1 gene at the same site within this fragment. The 0.43-kilobase region upstream from the major transcription initiation site linked to the chloramphenicol acetyltransferase gene showed promoter activity in CV-1 monkey kidney cells and in human KB cells. The putative promoter region has a consensus CAAT box and two GC box-like sequences, but no TATA sequence. This identification and isolation of promoter sequences for the MDR 1 gene will permit studies on how expression of this gene is regulated in normal human tissues and cancers.
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PMID:Isolation and sequence of the promoter region of the human multidrug-resistance (P-glycoprotein) gene. 289 92

Among human sarcomas, osteosarcomas usually display high intrinsic mdr1 expression while malignant fibrous histiocytomas (MFH) do not. A comparative polymerase chain reaction (PCR)-based sequence analysis of the mdr1 promoter revealed point mutations in seven out of nine osteosarcomas at nucleotides +103 (2 cases T-->C) and +137 (5 cases G-->T). No changes were seen in eight MFHs. When COS cells transfected with CAT constructs containing the T-->C chloramphenicol acetyltransferase mutant mdr1 promoters were treated with vincristine or doxorubicin, expression of the CAT gene was enhanced to a higher extent than with constructs containing wild-type or G-->T-mutant mdr1 promoters. We suggest that there is a correlation between the type of mdr1 promoter mutation and responsiveness to MDR relevant drugs.
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PMID:Point mutations in the mdr1 promoter of human osteosarcomas are associated with in vitro responsiveness to multidrug resistance relevant drugs. 783 15

To investigate multidrug-resistance gene (MDR1) promoter efficacy and drug inducibility in cells with different multidrug-resistance phenotypes, multidrug-resistant HCT15 and drug-sensitive KM12 human colon carcinoma cell lines were transfected with constructs incorporating the chloramphenicol acetyltransferase (CAT) reporter gene, driven by wild-type and point-mutated MDR1 promoter regions. The basal CAT expression level in HCT15 cells was markedly elevated compared to KM12 cells. CAT induction by vincristine was dose-dependent over a broad concentration range (40-500 ng/ml) in both lines. The induction levels were related to the cells' MDR phenotype, with the multidrug-resistant HCT15 cells showing the greater effect. In both cell types, basal and drug-induced CAT expression were significantly enhanced by the point-mutated promoter regions. The findings support the possible exploitation of the MDR1 promoter for construction of drug-inducible and MDR-cell-targeted expression vectors for use in gene therapy.
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PMID:Vincristine induction of mutant and wild-type human multidrug-resistance promoters is cell-type-specific and dose-dependent. 860 50

Currently, the Category (CAT) II regimen is recommended for patients who have failed the CAT I regimen. We have determined before that prevalence of multidrug-resistant tuberculosis (MDR TB) is relatively high among these patients. On the other hand, the retreatment success rate with CAT II in CAT I treatment failures and defaults is nearly 50%. Therefore, we tried to find another strategy with a higher success rate. From January 2004 to November 2007, 105 patients with pulmonary TB, who failed a prior CAT I regimen or with more than one course of irregular anti-TB treatment, were included in this study, whereas five cases with nontuberculous mycobacteria were excluded. Drug susceptibility testing (DST), for first line anti-TB drugs, and polymerase chain reaction were performed. By the time of availability of DST that took 3 to 4 months, a pilot protocol consisted of isoniazid, rifampin, ethambutol, ofloxacin, cycloserine, and amikacin was started. Then therapeutic regimen was adjusted based on four categories of DST pattern: sensitive, non-MDR pattern, MDR pattern, and culture-negative. Sensitive patients received the standard CAT I regimen, non-MDR patients an individualized regimen based on DST, MDR patients a standard second-line regimen, and culture-negatives a standard CAT I plus a 6-month injectable agent. Treatment outcomes were categorized and analyzed. Forty-eight patients with prior CAT I treatment failure and 52 with more than one irregular treatment courses were included in the analysis. Six percent of subjects had confirmed HIV infection. Seventy-two percent of subjects were assigned to a good outcome and 28% were assigned to a poor outcome group. Seventeen percent were culture-negative. Regarding DST pattern, 13% isolated strains were completely sensitive to first-line drugs. 53% strains were MDR, 10% monodrug-resistant, and 7% polydrug-resistant. There was no significant association between DST pattern and outcome (P = 0.13). The irregular regimen was associated with MDR TB as twice as CAT I regimen failure (69.2% versus 35.4%, P = 0.004). Patients with MDR TB significantly experienced more side effects than non-MDR-TBs (47% versus 27%, P = 0.102). Of 100 patients, 72% were cured, 5% abandoned treatment, 12% died, 6% were classified as treatment failures, 1% relapsed, and 5% were transferred out. Of 53 patients with MDR TB, 33 subjects were cured and seven died. All together, successful outcome was achieved in 62.2%, 76%, and 76% of MDR TB, non-MDR TB, and completely sensitive cases, respectively. A retreatment strategy based on DST and replacing the Category II regimen with an intermediate regimen called revised CAT II may improve clinical outcomes among Category I treatment failures and defaults who found to have active, infectious MDR TB. This strategy significantly reduces delays to MDR TB diagnosis and to the initiation of MDR TB therapy. Success rate of this strategy is 62.2% and 72% in MDR TB and overall CAT I failure cases and defaulters, respectively.
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PMID:Revised Category II regimen as an alternative strategy for retreatment of Category I regimen failure and irregular treatment cases. 2053 8