Proteasome inhibitor-resistant cells cause EMT-induction via suppression of E-cadherin by miR-200 and ZEB1.
Downregulation of E-cadherin (gene: CDH1) plays an important role in epithelial-mesenchymal transition (EMT), which is critical for normal development and disease states. As a result of long-term treatment of endometrial carcinoma Ishikawa cells with epoxomicin (EXM), the cells exhibited the phenotype for EXM-resistance (Ish/EXM cells). Moreover, CDH1 mRNA and its protein were suppressed and EMT was induced in Ish/EXM cells. Ish/EXM cells exhibited drug-resistance to other proteasome inhibitors, MG-132, PSI and PS-341 (Bortezomib). The proteasome inhibitor-resistant cells acquired invasiveness as a result of the chemotherapy. In Ish/EXM cells, E-cadherin was suppressed by upregulation of its transcriptional repressor ZEB1. Furthermore, expression of the miR-200 family (miR-200a, miR-200b, miR-200c and miR-141) found in Ishikawa cells was suppressed in Ish/EXM cells. Overexpression of the miR-200 family in Ish/EXM cells caused by transfection with the pre-miR-200 family induced downregulation of ZEB1 and enhanced expression of E-cadherin. Conversely, suppression of miR-200 expression in the Ishikawa cells by transfection with anti-miR-200 elevated the expression of ZEB1 and suppressed the expression of E-cadherin. These results suggest that acquirement of EXM-resistance in Ish/EXM cells induces up regulation of ZEB1 via suppression of the miR-200 family following suppression of E-cadherin. Since suppression of ZEB1 in Ish/EXM cells by treatment with its siRNA did not restore the miR-200 family expression, miR-200 family was placed upstream of ZEB1 to regulate the expression.
Department of Biochemistry, Jikei University School of Medicine, Tokyo 105-8461, Japan.
Tadashi
T
Asakura
Department of Biochemistry, Jikei University School of Medicine, Tokyo 105-8461, Japan.
Noriko
N
Yamaguchi
Department of Biochemistry, Jikei University School of Medicine, Tokyo 105-8461, Japan.
Kiyoshi
K
Ohkawa
Department of Biochemistry, Jikei University School of Medicine, Tokyo 105-8461, Japan.
Kiyotsugu
K
Yoshida
D015153:Blotting, Western; D015820:Cadherins / Q000096:biosynthesis*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D016889:Endometrial Neoplasms / Q000235:genetics*; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics*; D000071799:Zinc Finger E-box-Binding Homeobox 1
D015820:Cadherins; D018398:Homeodomain Proteins; C533896:MIRN200 microRNA, human; D035683:MicroRNAs; D061988:Proteasome Inhibitors; D014157:Transcription Factors; C486307:ZEB1 protein, human; D000071799:Zinc Finger E-box-Binding Homeobox 1