ABSTRACT
Overexpression of P-glycoprotein, the product of the multidrug resistance-1 (MDR1) gene, is associated with treatment failure in some hematopoietic tumors. Although expression of P-glycoprotein in normal hematopoietic cells is tightly regulated during hematopoietic differentiation, its aberrant overexpression in hematopoietic malignancies occurs at the transcriptional level. We have demonstrated that 12-O-tetradecanoylphorbol-13-acetate (TPA) increases transcription of the MDR1 gene and activates the MDR1 promoter, and that promoter activation by TPA requires binding of the zinc finger transcription factor EGR1 to specific MDR1 promoter sequences (C. McCoy and M. M. Cornwell, Mol. Cell. Biol., 15: 6100-6108, 1995). We demonstrate here that the Wilms' tumor (WT) suppressor, WT1, a member of the EGR family, inhibits the response of the MDR1 promoter to TPA in K562 cells. Inhibition is likely a direct effect of WT1 binding to the MDR1 promoter because: (a) WT1 expression does not inhibit the increase in EGR1 after TPA treatment; (b) inhibition by WT1 requires the zinc finger domain; (c) WT1 binds to MDR1 promoter sequences that bind EGR1 and are responsive to TPA; and (d) there is an inverse correlation between WT1 protein expression and MDR1 expression and promoter activity. These results suggest that the MDR1 gene is a target for regulation by WT1 and suggest mechanisms by which MDR1 may be regulated by WT1 and EGR1 during normal and aberrant hematopoiesis.
Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics , DNA-Binding Proteins/metabolism , Gene Expression Regulation, Neoplastic , Genes, Wilms Tumor , Immediate-Early Proteins , Promoter Regions, Genetic , Transcription Factors/metabolism , Wilms Tumor/genetics , Zinc Fingers , DNA-Binding Proteins/biosynthesis , DNA-Binding Proteins/genetics , Early Growth Response Protein 1 , Gene Expression Regulation, Neoplastic/drug effects , Humans , K562 Cells , Tetradecanoylphorbol Acetate/antagonists & inhibitors , Tetradecanoylphorbol Acetate/pharmacology , Transcription Factors/biosynthesis , Transcription Factors/genetics , WT1 ProteinsABSTRACT
Expression of the human multidrug resistance 1 gene (MDR1), which encodes the P-glycoprotein transmembrane efflux pump, has been associated with treatment failure of some leukemias, primarily acute myeloid leukemia (AML). To elucidate the epigenetic events associated with overexpression of MDR1 in AML, we analyzed the methylation status of a 2000 bp region within the MDR1 locus using a bisulphite genomic sequencing technique. A CpG-rich domain, approximately 1 kb in size, encompasses the promoter region, exon I, and intron I. This domain was found to be relatively unmethylated in five out of six primary and cultured human hematopoietic cells, as well as five out of six AML patient samples, independent of the MDR1 phenotype. The data suggest that the methylation status of the CpG-rich domain does not act as a 'switch' to regulate expression of the MDR1 gene. In addition, we found an upstream Alu repeat sequence to be unmethylated in three out of five cultured hematopoietic cell lines, both MDR1 expressing and non-expressing. However, analysis of primary CD8-positive T cells and AML patient samples revealed dense methylation of this region which is consistent with methylation of Alu repeat sequences observed in somatic tissues.
Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics , DNA Methylation , Leukemia, Myeloid/genetics , Acute Disease , Adult , Alu Elements/genetics , CD8-Positive T-Lymphocytes/physiology , CpG Islands/genetics , Drug Resistance, Multiple , Drug Resistance, Neoplasm , Flow Cytometry , Humans , Leukemia, Myeloid/pathology , Reverse Transcriptase Polymerase Chain Reaction , Tumor Cells, CulturedABSTRACT
The authors examined the effect of hospitalization on cognitive and behavioral symptoms in delirious elderly patients with and without dementia. Forty-four (13%) of the patients admitted to a Veterans Affairs Medical Center geropsychiatric unit were diagnosed with delirium and were administered the Mini-Mental State Examination, the Hamilton Depression Rating Scale, the Brief Psychiatric Rating Scale (BPRS), the Rating Scale for Side Effects, and the Cohen-Mansfield Agitation Inventory. The total sample significantly improved on all measures. When patients with delirium were divided into subgroups with and without dementia, both subgroups improved similarly. Patients discharged to more restrictive environments improved significantly on the BPRS only.
