title: Methylation of SFRP5 is related to multidrug resistance in leukemia cells.
abstract: Methylation of secreted frizzle-related protein (SFRP) genes activates Wnt/ß-catenin signaling and promotes tumor development. This study investigated whether SFRP5 gene methylation causes multidrug resistance (MDR) in leukemia through the Wnt/ß-catenin signaling, leading to the upregulation of the mdr1 gene and its product, P-glycoprotein (P-gp). Methylation-specific PCR identified SFRP5 gene methylation in cultured bone mononuclear cells from 7/12 patients with acute leukemia and in four human leukemia cell lines (HL-60, Raji, U937 and KG1a). Western blotting revealed absent SFRP5 protein expression in cells from 5/7 patients with SFRP5 gene methylation and in all cell lines. Treatment with a demethylation agent (DAC) rescued SFRP5 expression. mdr1 mRNA and P-gp protein were detected in cells from 3/5 patients with absent SFRP5, and in the KG1a cell line; these cells also had the highest levels of activated ß-catenin. In cells from these three patients, DAC rescued SFRP5 expression and downregulated mdr1 and P-gp. SFRP5 protein expression was rescued in transgenic KG1a/SFRP5 cells, compared with KG1a/eGFP or untransfected KG1a cells. mdr1 and P-gp in KG1a/SFRP5 cells were downregulated. Doxorubicin IC50 values were significantly lower in KG1a/SFRP5 (0.573±0.131 μM) than in KG1a (0.963±0.115) or KG1a/eGFP (0.917±0.138) cells (P<0.05). We conclude that SFRP5 gene methylation in leukemia cells activates Wnt/ß-catenin signaling to upregulate mdr1/P-gp expression and cause MDR. Recovery of SFRP5 expression reversed MDR in the KG1a leukemia cell line. Our results suggest that modulating SFRP5 methylation could decrease MDR in leukemia patients.
authors.affiliation: Department of Hematology, Shengjing Hospital affiliated to China Medical University, Shenyang, China.
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Urology, Shengjing Hospital affiliated to China Medical University, Shenyang, China.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Hematology, Shengjing Hospital affiliated to China Medical University, Shenyang, China.
authors.forename: R
authors.initials: R
authors.lastname: Hu
authors.affiliation: Department of Hematology, Shengjing Hospital affiliated to China Medical University, Shenyang, China.
authors.forename: W
authors.initials: W
authors.lastname: Yang
authors.affiliation: Department of Hematology, Shengjing Hospital affiliated to China Medical University, Shenyang, China.
authors.forename: A
authors.initials: A
authors.lastname: Liao
authors.affiliation: Department of Pathophysiology, China Medical University, Shenyang, China.
authors.forename: C
authors.initials: C
authors.lastname: Zhao
authors.affiliation: Department of Hematology, Shengjing Hospital affiliated to China Medical University, Shenyang, China.
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Hematology, Shengjing Hospital affiliated to China Medical University, Shenyang, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000704:Analysis of Variance; D015153:Blotting, Western; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000235:genetics*; D004317:Doxorubicin; D018432:Drug Resistance, Multiple / Q000235:genetics*; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D006801:Humans; D020128:Inhibitory Concentration 50; D007938:Leukemia / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013778:Tetrazolium Salts; D013844:Thiazoles; D060449:Wnt Signaling Pathway / Q000502:physiology*; D051176:beta Catenin / Q000378:metabolism; D000094742:Secreted Frizzled-Related Proteins
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D048868:Adaptor Proteins, Signal Transducing; D004317:Doxorubicin; D005136:Eye Proteins; D008565:Membrane Proteins; D013778:Tetrazolium Salts; D013844:Thiazoles; D051176:beta Catenin; C513055:ABCB1 protein, human; C118511:SFRP5 protein, human; D000094742:Secreted Frizzled-Related Proteins; C022616:thiazolyl blue