YM155 induces apoptosis through downregulation of specificity protein 1 and myeloid cell leukemia-1 in human oral cancer cell lines Khadka Sachita 1, *, Hyun-Ju Yu 1, *, Jun-Won Yun 2 , Jeong-Sang Lee 3 , Sung-Dae Cho 1 1 Department of Oral Pathology, School of Dentistry, Institute of Biodegradable Material, Institute of Oral Bioscience, Chonbuk National University, Jeonju, Korea; 2 Department of Experimental Animal Research, Biomedical Research Institute, Seoul National University Hospital, Seoul, Korea; 3 Department of Health and Functional Food, College of Medical Science, Jeonju University, Jeonju, Korea BACKGROUND: YM155 is a small-molecule pro- apoptotic agent which has shown to inhibit survivin expression and induce apoptosis in various cancer cells. In this study, we investigated the function and molecular mechanism of YM155 in human oral cancer cells. METHODS: The apoptotic effects and related signaling pathways of YM155 were evaluated using trypan blue exclusion assay, 4 0 -6-diamidino-2-phenylindole staining, Western blotting, RT-PCR, and siRNA. RESULTS: YM155 inhibited the growth and caused cas- pase-dependent apoptosis in MC3 and HN22 cells. YM155 significantly suppressed the level of survivin protein expression through proteasome-dependent protein deg- radation to confirm its survivin-inhibiting function. YM155 reduced myeloid cell leukemia-1 (Mcl-1) protein, but it did not alter Mcl-1 mRNA. It was associated with the facilitation of lysosome-dependent protein degrada- tion. The modifications of Mcl-1 and survivin by YM155 were caspase-independent manner. Treatment of MC-3 and HN22 cells with YM155 inhibited specificity protein 1 (Sp1) and the knockdown of Sp1 by siRNA demonstrated that Mcl-1 was regulated by Sp1 protein. CONCLUSIONS: We demonstrated the novel mecha- nism that YM155 causes apoptosis of human oral cancer cell lines through downregulation of Sp1 and Mcl-1. Therefore, it may be a potential anticancer drug candi- date for the treatment of oral cancer. J Oral Pathol Med (2014) Keywords: apoptosis; myeloid cell leukemia-1; oral cancer; specificity protein 1; YM155 Introduction Various prevention and treatment modalities are reestab- lished for cancer treatment; however, the number of new cases is still increasing annually. Oral cancer is one of the most frequent cancers worldwide, the sixth most common, and incidence rates are higher in men than women (1, 2). Recently, early detection and screening programs have decreased the mortality rates, and it can be potentiated by chemotherapy. Thus, discovering new treatment to control oral cancer has been pursued by many researchers. YM155, also called as a sepantronium bromide, is an imidazolium derivative that represses survivin expression and induces apoptosis in a variety of other tumor cell lines such as prostate, colon, and lung cancer (3, 4). Although survivin is a smallest member of inhibitor of apoptosis (IAP) gene family, it is expressed during embryonic development and is truant in most normal tissues. In a context for decreasing cancer cells selectively while normal cells are not disturbing, survivin becomes an ideal target for cancer therapy. An attention has been growing due to its overex- pression in human tumors universally, its prominent role in networks of cellular division, intracellular signaling, and anti-apoptosis. (5–7). Specificity protein 1 (Sp1) is a zinc finger-type DNA- binding domain that binds to guanine–cytosine (GC)-rich motifs and is involved in many cellular processes such as tumor cell growth, survival, angiogenesis, and apoptosis (8– 11). Also, the expression of Sp1 is highly dominated in many tumor and cancer cell lines. Previously, our group had identified that decreasing Sp1 level regulates the expression of anti-apoptotic proteins, such as survivin and myeloid cell leukemia-1 (Mcl-1) in prostate cancer cell lines (12). It has been recommended that targeting Sp1 and its downstream target protein may have a potential for oral cancer therapy. Correspondence: Jeong-Sang Lee, PhD, Director of Food Industry Research Institute, Health Science Research Institute, Department of Health and Functional Food, College of Medical Science, Jeonju University, Jeonju 560-759, Korea. Tel: 82-63-220-2054, Fax: 82-63-270-4027, E-mail: jslee11@jj.ac.kr and Sung-Dae Cho, DVM, PhD, Departments of Oral Pathology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 561-756, Korea. Tel: 82-63-270-4025, Fax: 82-63-270-4027, E-mail: efiwdsc@chonbuk.ac.kr *These authors contributed equally to this work. Accepted for publication November 3, 2014 doi: 10.1111/jop.12299 J Oral Pathol Med © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd wileyonlinelibrary.com/journal/jop