Abstract
Multidrug resistance (MDR), an unfavorable factor compromising the treatment efficacy of anticancer drugs, involves the upregulation of ATP binding cassette (ABC) transporters and induction of galectin-3 signaling. Galectin-3 plays an anti-apoptotic role in many cancer cells and regulates various pathways to activate MDR. Thus, the inhibition of galectin-3 has the potential to enhance the efficacy of the anticancer drug epirubicin. In this study, we examined the effects and mechanisms of silencing galectin-3 via RNA interference (RNAi) on the β-catenin/GSK-3β pathway in human colon adenocarcinoma Caco-2 cells. Galectin-3 knockdown increased the intracellular accumulation of epirubicin in Caco-2 cells; suppressed the mRNA expression of galectin-3, β-catenin, cyclin D1, c-myc, P-glycoprotein (P-gp), MDR-associated protein (MRP) 1, and MRP2; and downregulated the protein expression of P-gp, cyclin D1, galectin-3, β-catenin, c-Myc, and Bcl-2. Moreover, galectin-3 RNAi treatment significantly increased the mRNA level of GSK-3β, Bax, caspase-3, and caspase-9; remarkably increased the Bax-to-Bcl-2 ratio; and upregulated the GSK-3β and Bax protein expressions. Apoptosis was induced by galectin-3 RNAi and/or epirubicin as demonstrated by chromatin condensation, a higher sub-G1 phase proportion, and increased caspase-3 and caspase-9 activity, indicating an intrinsic/mitochondrial apoptosis pathway. Epirubicin-mediated resistance was effectively inhibited via galectin-3 RNAi treatment. However, these phenomena could be rescued after galectin-3 overexpression. We show for the first time that the silencing of galectin-3 sensitizes MDR cells to epirubicin by inhibiting ABC transporters and activating the mitochondrial pathway of apoptosis through modulation of the β-catenin/GSK-3β pathway in human colon cancer cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics
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ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism
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ATP-Binding Cassette Transporters / genetics*
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ATP-Binding Cassette Transporters / metabolism
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Apoptosis / drug effects
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Apoptosis / genetics
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Caco-2 Cells
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Caspases / genetics
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Caspases / metabolism
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Cell Cycle / drug effects
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Cell Cycle / genetics
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Cell Line, Tumor
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Colorectal Neoplasms / genetics*
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Colorectal Neoplasms / metabolism*
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Cyclin D1 / genetics
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Cyclin D1 / metabolism
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Epirubicin / pharmacology
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Epirubicin / toxicity
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Galectin 3 / genetics*
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Galectin 3 / metabolism
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Gene Silencing*
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Glycogen Synthase Kinase 3 / genetics
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Glycogen Synthase Kinase 3 / metabolism*
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Glycogen Synthase Kinase 3 beta
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Humans
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Mitochondria / genetics
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Mitochondria / metabolism
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Multidrug Resistance-Associated Protein 2
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Multidrug Resistance-Associated Proteins / genetics
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Multidrug Resistance-Associated Proteins / metabolism
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Proto-Oncogene Proteins c-bcl-2 / genetics
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Proto-Oncogene Proteins c-myc / genetics
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Proto-Oncogene Proteins c-myc / metabolism
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RNA, Messenger / genetics
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Signal Transduction*
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bcl-2-Associated X Protein / genetics
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bcl-2-Associated X Protein / metabolism
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beta Catenin / genetics
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beta Catenin / metabolism*
Substances
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ABCC2 protein, human
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ATP Binding Cassette Transporter, Subfamily B, Member 1
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ATP-Binding Cassette Transporters
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Galectin 3
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Multidrug Resistance-Associated Protein 2
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Multidrug Resistance-Associated Proteins
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Proto-Oncogene Proteins c-bcl-2
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Proto-Oncogene Proteins c-myc
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RNA, Messenger
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RNA, Small Interfering
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bcl-2-Associated X Protein
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beta Catenin
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Cyclin D1
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Epirubicin
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GSK3B protein, human
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Glycogen Synthase Kinase 3 beta
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Glycogen Synthase Kinase 3
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Caspases
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multidrug resistance-associated protein 1
Grants and funding
This study was supported by the grants AB100-318 and AB101-316 from the National University of Tainan, Taiwan and NSC 101-2321-B-006-008, NSC 102-2321-B-006- 006 and NSC 102-2320-B-024-002 from the National Science Council, Taiwan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.