title: Osteopontin is involved in the development of acquired chemo-resistance of cisplatin in small cell lung cancer.
abstract: Osteopontin (OPN) is a multi-functional cytokine involved in cell survival, migration and adhesion which is associated with tumorigenesis, progression and metastasis. However, the role of OPN in chemo-sensitivity of human lung cancer has not yet been elucidated. The purpose of this study is to investigate the role of OPN in chemo-sensitivity of lung cancer cells. We developed a stable OPN transfectant (SBC-3/OPN) and a control transfectant (SBC-3/NEO) from human small cell lung cancer cell line, SBC-3. SBC-3/OPN cells were more resistant to cisplatin than SBC-3/NEO cells. Multi-drug resistance-associated protein (MRP) does not appear to be involved in the development of acquired chemo-resistance, since MRP inhibitor did not alter chemo-sensitivity. After exposure to cisplatin, the apoptotic SBC-3/OPN cells were reduced in number compared to SBC-3/NEO cells. Treatment with cisplatin revealed that the expression of anti-apoptotic protein, bcl-2, was down-regulated in SBC-3/NEO cells, while that of SBC-3/OPN cells was not altered. In contrast, pro-apoptotic protein, bax, was not altered in both SBC-3/OPN and SBC-3/NEO cells, thus bcl-2/bax ratio was decreased in SBC-3/NEO but not altered in SBC-3/OPN cells. Activation of caspase-3 and caspase-9 was increased in SBC-3/NEO cells, but not in SBC-3/OPN cells. Our results suggest that OPN enhances chemo-resistance of cisplatin in SBC-3 cells by suppressing bcl-2 protein down-regulation, thereby blocking the caspase-9- and caspase-3-dependent cell apoptosis.
authors.affiliation: Department of Respiratory Medicine and Research Institute for Diseases of Old Ages, Juntendo University, School of Medicine, 2-1-1 Hongo, Bunkyo-Ku, Tokyo 113-8421, Japan.
authors.forename: Tao
authors.initials: T
authors.lastname: Gu
authors.forename: Rina
authors.initials: R
authors.lastname: Ohashi
authors.forename: Ri
authors.initials: R
authors.lastname: Cui
authors.forename: Ken
authors.initials: K
authors.lastname: Tajima
authors.forename: Masakata
authors.initials: M
authors.lastname: Yoshioka
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Iwakami
authors.forename: Shinichi
authors.initials: S
authors.lastname: Sasaki
authors.forename: Atsuko
authors.initials: A
authors.lastname: Shinohara
authors.forename: Takehisa
authors.initials: T
authors.lastname: Matsukawa
authors.forename: Jun
authors.initials: J
authors.lastname: Kobayashi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Inaba
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000627:therapeutic use*; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D053495:Osteopontin / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D055752:Small Cell Lung Carcinoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D053495:Osteopontin; D053148:Caspase 3; D053453:Caspase 9; D002945:Cisplatin