Ma Lian-Gang, Bian Shi-Bo, Cui Jian-Xin, Xi Hong-Qing, Zhang Ke-Cheng, Qin Hong-Zhen, Zhu Xiao-Ming, Chen Lin
Department of General Surgery, Chinese People's Liberation Army General Hospital, Beijing 100853, P.R. China.
Institute of Basic Medical Sciences, Chinese People's Liberation Army Academy of Military Medical Sciences, Beijing 100850, P.R. China.
Int J Mol Med. 2016 Apr;37(4):1039-48. doi: 10.3892/ijmm.2016.2494. Epub 2016 Feb 19.
Liver kinase B1 (LKB1) is known to suppress the proliferation, energy metabolism and mesenchymal transition of various cancer cells, and is involved in the regulation of Hippo-Yes-associated protein (Yap) and the Wnt/β-catenin signaling pathways. However, the role of LKB1 in gastric cancer (GC) was not fully understood. Thus, in the present study, we studied LKB1 and found that protein expression (0.37±0.061 vs. 0.59±0.108, P=0.006) and the protein ratio of p-Yap/Yap (0.179±0.085 vs. 0.8±0.126, P=0.001) were reduced in 54 gastric adenocarcinoma (GAC) tissues compared with the matched adjacent non-cancerous tissues, using western blotting and RT-qPCR assays. LKB1 expression was also observed decreased in 109 GAC tissues compared with 54 adjacent non-cancerous tissues (χ2=4.678, P=0.0306), and negatively correlated with the nuclear expression of Yap (r=-0.6997) and β-catenin (r=-0.3510), using immunohistochemical analysis. In GC patients, LKB1 expression was negatively associated with tumor size, tumor infiltration, lymph node metastasis and the TNM stage. LKB1 expression was determined to be positively correlated with longer overall survival of GC patients using Kaplan-Meier analysis (P=0.001). Subsequently, LKB1 expression in human GAC AGS cells was enhanced with a full‑length LKB1 transfection. In vitro and in vivo proliferation was inhibited in LKB1-overexpressing GC cells compared with the control cells. Yap and β-catenin expression were assessed by western blotting and RT-qPCR, and were found to be increased in the cytoplasm but decreased in the nucleus in LKB1-overexpressing GC cells compared with the control cells. The increase in cytoplasmic β-catenin was reversed by the silencing of LKB1 or Yap with shRNAs in LKB1-overexpressing GC cells. Moreover, Yap and β-catenin mRNA were barely altered by LKB1 overexpression. Thus, we concluded that LKB1 expression was reduced in GAC tissues but that it correlated positively with better prognosis for GC patients. LKB1 inhibits the proliferation of GC cells by suppressing the nuclear translocation of Yap and β-catenin.
已知肝脏激酶B1（LKB1）可抑制多种癌细胞的增殖、能量代谢和间充质转化，并参与调控Hippo-Yes相关蛋白（Yap）和Wnt/β-连环蛋白信号通路。然而，LKB1在胃癌（GC）中的作用尚未完全明确。因此，在本研究中，我们对LKB1进行了研究，通过蛋白质印迹法和RT-qPCR检测发现，与配对的癌旁非癌组织相比，54例胃腺癌（GAC）组织中的蛋白表达水平降低（0.37±0.061对0.59±0.108，P=0.006），p-Yap/Yap蛋白比例也降低（0.179±0.085对0.8±0.126，P=0.001）。与54例癌旁非癌组织相比，109例GAC组织中LKB1表达也降低（χ2=4.678，P=0.0306），免疫组化分析显示其与Yap（r=-0.6997）和β-连环蛋白（r=-0.3510）的核表达呈负相关。在GC患者中，LKB1表达与肿瘤大小、肿瘤浸润、淋巴结转移及TNM分期呈负相关。采用Kaplan-Meier分析确定LKB1表达与GC患者较长的总生存期呈正相关（P=0.001）。随后，通过转染全长LKB1增强人GAC AGS细胞中的LKB1表达。与对照细胞相比，LKB1过表达的GC细胞在体外和体内的增殖均受到抑制。通过蛋白质印迹法和RT-qPCR评估Yap和β-连环蛋白的表达，发现与对照细胞相比，LKB1过表达的GC细胞中Yap和β-连环蛋白在细胞质中增加而在细胞核中减少。在LKB1过表达的GC细胞中，用shRNA沉默LKB1或Yap可逆转细胞质中β-连环蛋白的增加。此外，LKB1过表达对Yap和β-连环蛋白mRNA几乎没有影响。因此，我们得出结论，GAC组织中LKB1表达降低，但与GC患者较好的预后呈正相关。LKB1通过抑制Yap和β-连环蛋白的核转位来抑制GC细胞的增殖。
