Insulin-like growth factor binding protein 5 (IGFBP5) functions as a tumor suppressor in human melanoma cells

// Junyun Wang 1,2,* , Nan Ding 1,2,* , Yongjun Li 1,* , Hua Cheng 3,* , Dong Wang 4 , Qiong Yang 1,2 , Youhui Deng 1,2 , Yaran Yang 1 , Yanming Li 1 , Xiuyan Ruan 1 , Fang Xie 4 , Hua Zhao 4 and Xiangdong Fang 1 1 CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China 2 University of Chinese Academy of Sciences, Beijing, China 3 Institute of Biology, Hebei Academy of Sciences, Shijiazhuang, China 4 Department of Dermatology, General Hospital of People’s Liberation Army, Beijing, China * These authors have contributed equally to this work Correspondence to: Xiangdong Fang, email: // Hua Zhao, email: // Keywords : IGFBP5; malignant melanoma; tumor suppressor; EMT; ERK-MAPK Received : March 19, 2015 Accepted : April 22, 2015 Published : May 12, 2015 Abstract The insulin-like growth factor binding protein 5 (IGFBP5), which is often dysregulated in human cancers, plays a crucial role in carcinogenesis and cancer development. However, the function and underlying mechanism of IGFBP5 in tumor growth and metastasis has been elusive, particularly in malignant human melanoma. Here, we reported that IGFBP5 acts as an important tumor suppressor in melanoma tumorigenicity and metastasis by a series of experiments including transwell assay, xenograft model, in vivo tumor metastasis experiment, and RNA-Seq. Overexpression of IGFBP5 in A375, a typical human melanoma cell line, inhibited cell malignant behaviors significantly, including in vitro proliferation, anchorage-independent growth, migration and invasion, as well as in vivo tumor growth and pulmonary metastasis. In addition, overexpression of IGFBP5 suppressed epithelial-mesenchymal transition (EMT), and decreased the expression of E-cadherin and the key stem cell markers NANOG, SOX2, OCT4, KLF4, and CD133. Furthermore, IGFBP5 exerts its inhibitory activities by reducing the phosphorylation of IGF1R, ERK1/2, and p38-MAPK kinases and abating the expression of HIF1α and its target genes, VEGF and MMP9. All these findings were confirmed by IGFBP5 knockdown in human melanoma cell line A2058. Taken together, these results shed light on the mechanism of IGFBP5 as a potential tumor-suppressor in melanoma progression, indicating that IGFBP5 might be a novel therapeutic target for human melanoma.