Leukemia Research 34 (2010) 816–820 Contents lists available at ScienceDirect Leukemia Research journal homepage: www.elsevier.com/locate/leukres OSU-03012 sensitizes TIB-196 myeloma cells to imatinib mesylate via AMP-activated protein kinase and STAT3 pathways Li-Yuan Bai a,b , Jing-Ru Weng c , Chen-Hsun Tsai d , Aaron Sargeant d , Cheng-Wen Lin e , Chang-Fang Chiu a,b,∗ a Graduate Institute of Clinical Medical Science, College of Medicine, China Medical University, Taichung, Taiwan b Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan c Department of Biological Science and Technology, College of Life Sciences, China Medical University, Taichung, Taiwan d Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, OH, USA e Department of Medical Laboratory Science and Biotechnology, College of Health Care, China Medical University, Taichung, Taiwan article info Article history: Received 1 August 2009 Received in revised form 16 November 2009 Accepted 18 November 2009 Available online 14 December 2009 Keywords: Myeloma OSU-03012 Imatinib mesylate AMPK STAT3 abstract Although c-Kit is expressed on the surface of myeloma cells in one-third of myeloma patients, the efficacy of imatinib mesylate for patients with myeloma is still controversial. To investigate the combinatorial effect of OSU-03012 and imatinib mesylate, we treated a c-Kit-expressing myeloma cell line, TIB-196, with DMSO, OSU-03012 alone, imatinib mesylate alone and OSU-03012 plus imatinib mesylate. OSU-03012 sensitized TIB-196 cells to imatinib mesylate cytotoxicity. p-STAT3 (Tyr705), as well as down-stream cyclin D1 and Mcl-1, was down regulated. Additionally, there was markedly increased p-AMPK (Thr172) and down-regulation of p-p70S6K (Thr386) in the combination group. Combined treatments targeting c-Kit, AMPK and STAT3 may be a potential strategy for treating patients with myeloma. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction About one-third of myeloma patients exhibit c-Kit expression on the surface of myeloma cells but not normal plasma cells [1–3]. The biological significance of c-Kit and its ligand, stem cell factor (SCF), has also been demonstrated in myeloma cells [4]. The addition of SCF resulted in a 2.4-fold increase in the number of cell colonies, a higher proportion of cells in S-phase, and enhancement of the proliferation of MT3 and U266 cells mediated by other cytokines. When tested on fresh myeloma samples, SCF significantly increased the number of S-phase plasma cells and enhanced proliferation of myeloma cells responsive to interleukin-6 [4]. Because the down- stream signaling pathways of c-Kit, including mitogen-activated protein (MAP) kinase pathways, phosphatidyl-inositol-3 kinase (PI3-kinase) pathway, phospholipase C- pathway, Src pathway and Janus kinase (JAK)/signal transducers and activators of tran- scription (STAT) pathway, are essential for cellular function and ∗ Corresponding author at: Division of Hematology and Oncology, Department of Internal Medicine, China Medical University Hospital, 2 Yude Road, North District, Taichung 404, Taiwan. Tel.: +886 4 22052121ext 2019; fax: +886 4 22038883. E-mail address: d5686@www.cmuh.org.tw (C.-F. Chiu). survival [5–7], it is rational to treat patients with multiple myeloma by drugs targeting c-Kit. Imatinib mesylate, a tyrosine kinase inhibitor targeting ABL pro- tein, c-Kit protein and platelet-derived growth factor receptor, has been successfully used to treat chronic myeloid leukemia and gas- trointestinal stromal tumor [8–11]. It has been shown to induce apoptosis in cells with BCR-ABL chimeric proteins and gastroin- testinal stromal tumors expressing c-Kit protein. In addition to the already defined targets, recently imatinib mesylate was found to act on other cellular targets as well. Larmonier and his col- leagues found that imatinib mesylate at concentrations achieved clinically impaired CD4 + CD25 + FoxP3 + regulatory T cell function and FoxP3 expression by suppressing the activity of STAT3 and STAT5 [12]. Dewar et al. demonstrated that the macrophage colony- stimulating factor receptor c-fms, which was implicated in ovarian cancer, rheumatoid arthritis and excess osteoclast activity in multi- ple myeloma, was inhibited by imatinib mesylate [13,14]. Although these data suggest value in using imatinib mesylate to treat patients with multiple myeloma, its efficacy is still controversial [1,15]. OSU-03012, a novel celecoxib derivative without cyclooxygenase-2 inhibitory activity, has potent activity against myeloma cell lines and primary myeloma cells [16]. The mech- anisms of OSU-03012-mediated cytotoxicity in myeloma cells include inhibition of PI3-kinase/Akt pathway, down-regulation 0145-2126/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.leukres.2009.11.014