Midkine promotes hepatocellular carcinoma metastasis by elevating anoikis resistance of circulating tumor cells

// Bin Sun 1, * , Congli Hu 1, * , Zhibin Yang 2, * , Xiaofeng Zhang 1, * , Linlin Zhao 1, * , Junye Xiong 1 , Junyong Ma 1 , Lei Chen 1 , Haihua Qian 1 , Xiangji Luo 1 , Lehua Shi 1 , Jun Li 1 , Xianshuo Cheng 2 , Zhengfeng Yin 1 1 Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai, China 2 Colorectal Cancer Clinical Research Center, Third Affiliated Hospital, Kunming Medical University, Kunming, China * These authors contributed equally to this work Correspondence to: Zhengfeng Yin, email: yinzfk@aliyun.com Keywords: midkine, hepatocellular carcinoma, circulating tumor cells, anoikis resistance Received: November 30, 2016      Accepted: February 15, 2017      Published: March 01, 2017 ABSTRACT Midkine is overexpressed in hepatocellular carcinoma (HCC) and plays a role in tumor progression, but less is known about its role in resistance of circulating tumor cells (CTCs) to anoikis which leading to recurrence and metastasis. The aim of the present study was to analyze whether midkine was associated with HCC progression with anoikis resistance. We found that cultured HCC cells were more resistant to anoikis, which paralleled midkine expression, and midkine treatment significantly inhibited anoikis in a dose-dependent manner. Furthermore, in in vitro and in vivo assays, knockdown of midkine resulted in significant sensitivity to anoikis, decreased cell survival and significantly decreased tumor occurrence rate. Patients with midkine-elevated HCC had higher CTC counts and less apoptotic CTCs, as well as significantly higher recurrence rate and shorter recurrence-free interval. To understand the molecular mechanism underlying the midkine with HCC progression, we performed in vitro and in vivo studies. We found that midkine plays an important role in enhancement of HCC cell resistance to anoikis, thereby promoting subsequent metastasis. Activation of PI3K/Akt/NF-κB/TrkB signaling by midkine-activated anaplastic lymphomakinase (ALK) is responsible for anoikis resistance.