Adrenomedullin blockade suppresses sunitinib-resistant renal cell carcinoma growth by targeting the ERK/MAPK pathway

// Yongqian Gao 1, * , Jinyi Li 2, * , Na Qiao 3, * , Qingsong Meng 3 , Ming Zhang 3 , Xin Wang 3 , Jianghua Jia 3 , Shuwen Yang 3 , Changbao Qu 3 , Wei Li 3 , Dongbin Wang 3 1 Department of Interventional Radiology, Tangshan Gongren Hospital, Hebei Medical University, Tangshan 063000, P.R. China 2 Department of Urology, Icahn School of Medicine at Mount Sinai, New York, 10029, USA 3 Department of Urologic Surgery, The Second Hospital of Hebei Medical University, Shijiazhuang, 050000, China * These authors contributed equally to this work Correspondence to: Dongbin Wang, email: dongbin.wang@outlook.com Keywords: renal cell carcinoma, adrenomedullin, tyrosine kinase inhibitor, ERK Received: April 29, 2016      Accepted: August 13, 2016      Published: August 22, 2016 ABSTRACT Purpose: To evaluate the mechanisms underlying sunitinib resistance in RCC and to identify targets that may be used to overcome this resistance. Results: Reanalysis of transcriptome microarray datasets (GSE64052 and GSE76068) showed that adrenomedullin expression was increased in sunitinib-resistant tumors. And adrenomedullin expression was increased in sunitinib-resistant tumor xenografts, accompanied by upregulation of phospho-ERK levels. However, blocking adrenomedullin inhibited sunitinib-resistant tumor growth. Treatment of RCC cells with sunitinib and ADM22-52 was superior to monotherapy with either agent. Additionally, adrenomedullin upregulated cAMP and activated the ERK/MAPK pathway, promoting cell proliferation, while knockdown of adrenomedullin inhibited RCC cell growth and invasion in vitro . Materials and methods: We searched the Gene Expression Omnibus (GEO) database to find data regarding sunitinib-resistant RCC. These data were subsequently reanalyzed to identify targets that contribute to sunitinib resistance, and adrenomedullin upregulation was found to mediate sunitinib resistance in RCC. Then, we created an RCC mouse xenograft model. Mice were treated with sunitinib, an adrenomedullin receptor antagonist (ADM22-52), a MEK inhibitor (PD98059) and different combinations of these three drugs to investigate their effects on tumor growth. RCC cells (786-0) were cultured in vitro and treated with an ADM22-52 or PD98059 to determine whether adrenomedullin activates the ERK/MAPK pathway. Adrenomedullin was knocked down in 786-0 cells via siRNA, and the effects of this knockdown on cell were subsequently investigated. Conclusions: Adrenomedullin plays an important role in RCC resistance to sunitinib treatment. The combination of sunitinib and an adrenomedullin receptor antagonist may result in better outcomes in advanced RCC patients.