DMH1, a Small Molecule Inhibitor of BMP Type I Receptors, Suppresses Growth and Invasion of Lung Cancer Jijun Hao 1 *, Rachel Lee 2 , Andy Chang 2 , Jeffery Fan 2 , Chantelle Labib 3 , Cyrus Parsa 4 , Robert Orlando 4 , Bradley Andresen 2 , Ying Huang 2 * 1 College of Veterinary Medicine, Western University of Health Sciences, Pomona, California, United States of America, 2 College of Pharmacy, Western University of Health Sciences, Pomona, California, United States of America, 3 College of Biomedical Sciences, Western University of Health Sciences, Pomona, California, United States of America, 4 Department of Clinical Sciences, College of Osteopathic Medicine, Western University of Health Sciences, Pomona, California, United States of America Abstract The bone morphogenetic protein (BMP) signaling cascade is aberrantly activated in human non-small cell lung cancer (NSCLC) but not in normal lung epithelial cells, suggesting that blocking BMP signaling may be an effective therapeutic approach for lung cancer. Previous studies demonstrated that some BMP antagonists, which bind to extracellular BMP ligands and prevent their association with BMP receptors, dramatically reduced lung tumor growth. However, clinical application of protein-based BMP antagonists is limited by short half-lives, poor intra-tumor delivery as well as resistance caused by potential gain-of-function mutations in the downstream of the BMP pathway. Small molecule BMP inhibitors which target the intracellular BMP cascades would be ideal for anticancer drug development. In a zebrafish embryo-based structure and activity study, we previously identified a group of highly selective small molecule inhibitors specifically antagonizing the intracellular kinase domain of BMP type I receptors. In the present study, we demonstrated that DMH1, one of such inhibitors, potently reduced lung cell proliferation, promoted cell death, and decreased cell migration and invasion in NSCLC cells by blocking BMP signaling, as indicated by suppression of Smad 1/5/8 phosphorylation and gene expression of Id1, Id2 and Id3. Additionally, DMH1 treatment significantly reduced the tumor growth in human lung cancer xenograft model. In conclusion, our study indicates that small molecule inhibitors of BMP type I receptors may offer a promising novel strategy for lung cancer treatment. Citation: Hao J, Lee R, Chang A, Fan J, Labib C, et al. (2014) DMH1, a Small Molecule Inhibitor of BMP Type I Receptors, Suppresses Growth and Invasion of Lung Cancer. PLoS ONE 9(3): e90748. doi:10.1371/journal.pone.0090748 Editor: Carl G. Maki, Rush University Medical Center, United States of America Received December 12, 2013; Accepted February 5, 2014; Published March 6, 2014 Copyright: ß 2014 Hao et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by the seed fund of College of Veterinary Medicine at Western University of Health Sciences (J.H), and Western University of Health Sciences Faculty Development Fund (Y.H). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: jhao@westernu.edu (JH); yhuang@westernu.edu (YH) Introduction Lung cancer is one of the most common types of cancer and the leading cause of cancer deaths. About 228,190 cases of lung cancer are expected to be newly diagnosed in 2013, accounting for ,27% of all cancer deaths annually in the US [1]. The major type of lung cancer, non-small cell lung cancer (NSCLC), comprises approx- imately 85% of all diagnosed lung cancers. Despite improvements in the diagnosis and chemotherapy, 5-year survival rate for patients with NSCLC is still very low. Recently, great progresses have been made in the understanding of the molecular mecha- nisms driving lung cancer development, which resulted in a few targeted therapies [2]. However, the patients who respond initially invariably relapse. There is a need to identify novel targets for NSCLC. Bone morphogenetic proteins (BMPs) are members of the TGF- b superfamily and their biological activity is mediated through the formation of heterodimeric complexes of the BMP type I and type II serine/threonine kinases receptors. After the ligand binding, the BMP type I receptors are phosphorylated by the constitutively active type II receptors, leading to phosphorylation of the intracellular Smad 1/5/8 proteins, which then form a complex with Smad4 and translocate into the nucleus to regulate transcriptional response [3,4]. Over 20 BMP ligands have been identified to date [5]. Overexpression of BMP-2 has been associated with ,98% of NSCLC and other types of malignancy [6,7]. In addition, forced expression of BMP-2 in NSCLC cell lines significantly enhanced tumor growth in a mouse model of lung cancer following tail intravenous injection of tumor cells [8]. Conversely, the BMP antagonist Noggin and the extracellular pseudoreceptor spp24 (secreted phosphoprotein 24 kD) dramati- cally reduced lung tumor growth in subcutaneous xenograft mouse models [9,10], suggesting that inhibition of the BMP signaling may be an effective therapy for lung cancer. However, the protein- based BMP antagonists or pseudoreceptor spp24 mainly interfere the binding of extracellular BMP ligands to their receptors. Their clinical application could be limited by potential gain-of-function mutations in the downstream members of the BMP signaling cascade or short half-lives and poor delivery to tumors which are common problems associated with protein-based therapy. PLOS ONE | www.plosone.org 1 March 2014 | Volume 9 | Issue 3 | e90748