title: Wnt3/RhoA/ROCK signaling pathway is involved in adhesion-mediated drug resistance of multiple myeloma in an autocrine mechanism.
abstract: Adhesion of myeloma cells to bone marrow stromal cells is now considered to play a critical role in chemoresistance. However, little is known about the molecular mechanism governing cell adhesion-mediated drug resistance (CAM-DR) of myeloma cells. In this study, we focused our interests on the implication of the Wnt signal in CAM-DR. We first screened the expression of Wnt family in myeloma cell lines and found that Wnt3 was overexpressed in all the myeloma cells examined. KMS-5 and ARH77, which highly expressed Wnt3 protein, tightly adhered to human bone marrow stromal cells, and accumulation of beta-catenin and GTP-bounded RhoA was observed in these myeloma cell lines. Conversely, RPMI8226 and MM1S, which modestly expressed Wnt3 protein, rather weakly adhered to human bone marrow stromal. We then examined the relevance of Wnt3 expression to adhesive property to stromal cells and to CAM-DR of myeloma cells. KMS-5 and ARH-77 exhibited apparent CAM-DR against doxorubicin. This CAM-DR was significantly reduced by anti-integrin beta(1) antibody, anti-integrin alpha(6) antibody and a Wnt-receptor competitor, secreted Frizzled-related protein-1, and Rho kinase inhibitor Y27632, but not by the specific inhibitor of canonical signaling (Dickkopf-1), indicating that Wnt-mediated CAM-DR that is dependent on integrin alpha(6)/beta(1) (VLA-6)-mediated attachment to stromal cells is induced by the Wnt/RhoA/Rho kinase pathway signal. This CAM-DR was also significantly reduced by Wnt3 small interfering RNA transfer to KMS-5. These results indicate that Wnt3 contributes to VLA-6-mediated CAM-DR via the Wnt/RhoA/ROCK pathway of myeloma cells in an autocrine manner. Thus, the Wnt3 signaling pathway could be a promising molecular target to overcome CAM-DR of myeloma cells.
authors.affiliation: Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Kobune
authors.forename: Hiroki
authors.initials: H
authors.lastname: Chiba
authors.forename: Junji
authors.initials: J
authors.lastname: Kato
authors.forename: Kazunori
authors.initials: K
authors.lastname: Kato
authors.forename: Kiminori
authors.initials: K
authors.lastname: Nakamura
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kawano
authors.forename: Kohichi
authors.initials: K
authors.lastname: Takada
authors.forename: Rishu
authors.initials: R
authors.lastname: Takimoto
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Takayama
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Hamada
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Niitsu
mesh_terms: D001483:Base Sequence; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D017931:DNA Primers; D019008:Drug Resistance, Neoplasm; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D009101:Multiple Myeloma / Q000378:metabolism / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D016596:Vinculin / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism*; D060508:Wnt3 Protein; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; C555507:WNT3 protein, human; D051153:Wnt Proteins; D060508:Wnt3 Protein; D016596:Vinculin; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein