title: The increased expression of integrin α6 (ITGA6) enhances drug resistance in EVI1(high) leukemia.
abstract: Ecotropic viral integration site-1 (EVI1) is one of the candidate oncogenes for human acute myeloid leukemia (AML) with chromosomal alterations at 3q26. High EVI1 expression (EVI1(high)) is a risk factor for AML with poor outcome. Using DNA microarray analysis, we previously identified that integrin α6 (ITGA6) was upregulated over 10-fold in EVI1(high) leukemia cells. In this study, we determined whether the increased expression of ITGA6 is associated with drug-resistance and increased cell adhesion, resulting in poor prognosis. To this end, we first confirmed the expression pattern of a series of integrin genes using semi-quantitative PCR and fluorescence-activated cell sorter (FACS) analysis and determined the cell adhesion ability in EVI1(high) leukemia cells. We found that the adhesion ability of EVI1(high) leukemia cells to laminin increased with the increased expression of ITGA6 and integrin β4 (ITGB4). The introduction of small-hairpin RNA against EVI1 (shEVI1) into EVI1(high) leukemia cells reduced the cell adhesion ability and downregulated the expression of ITGA6 and ITGB4. In addition, the overexpression of EVI1 in EVI1(low) leukemia cells enhanced their cell adhesion ability and increased the expression of ITGA6 and ITGB4. In a subsequent experiment, the introduction of shRNA against ITGA6 or ITGB4 into EVI1(high) AML cells downregulated their cell adhesion ability; however, the EVI1(high) AML cells transfected with shRNA against ITGA6 could not be maintained in culture. Moreover, treating EVI1(high) leukemia cells with neutralizing antibodies against ITGA6 or ITGB4 resulted in an enhanced responsiveness to anti-cancer drugs and a reduction of their cell adhesion ability. The expression of ITGA6 is significantly elevated in cells from relapsed and EVI1(high) AML cases; therefore, ITGA6 might represent an important therapeutic target for both refractory and EVI1(high) AML.
authors.affiliation: Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, Faculty of Medicine, University of Miyazaki, Miyazaki, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Yamakawa
authors.forename: Kazuko
authors.initials: K
authors.lastname: Kaneda
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Saito
authors.forename: Emi
authors.initials: E
authors.lastname: Ichihara
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Morishita
mesh_terms: D016475:3T3 Cells; D000818:Animals; D057134:Antibodies, Neutralizing / Q000276:immunology; D002417:Cattle; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002453:Cell Cycle; D045744:Cell Line, Tumor; D003094:Collagen / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation; D004338:Drug Combinations; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D039503:Integrin alpha6 / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D039663:Integrin beta4 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007797:Laminin / Q000378:metabolism; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000473:pathology*; D000074008:MDS1 and EVI1 Complex Locus Protein; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D011509:Proteoglycans / Q000378:metabolism; D011519:Proto-Oncogenes; D034741:RNA, Small Interfering / Q000235:genetics; D012008:Recurrence; D014157:Transcription Factors / Q000378:metabolism*; D000097794:Kalinin
chemical_list: D057134:Antibodies, Neutralizing; D015815:Cell Adhesion Molecules; D003094:Collagen; D004268:DNA-Binding Proteins; D004338:Drug Combinations; D039503:Integrin alpha6; D039663:Integrin beta4; D007797:Laminin; D000074008:MDS1 and EVI1 Complex Locus Protein; D011509:Proteoglycans; D034741:RNA, Small Interfering; D014157:Transcription Factors; D000097794:Kalinin; C059834:ITGB4 protein, human; C063575:MECOM protein, human; C059485:matrigel