Extract of <em>Pleurotus pulmonarius</em> Suppresses Liver Cancer Development and Progression through Inhibition of VEGF-Induced PI3K/AKT Signaling Pathway

Liver cancer or hepatocellular carcinoma is one of the leading causes of cancer-related deaths. Conventional chemotherapies are limited by the development of drug resistance and various side effects. Because of its non-toxicity and potent biopharmacological activity, metabolites derived from mushrooms have received more attention in cancer therapy. Our previous studies have demonstrated the anticancer effects of polysaccharide-protein complexes derived from the Pleurotus mushrooms. The aim of this study was to investigate the underlying molecular mechanism of the anticancer activity of a hot water extract containing a polysaccharide-protein complex isolated from Pleurotus pulmonarius (PP) in liver cancer cells. Our results indicated that exposure of liver cancer cells to PP not only significantly reduced the in vitro cancer cell proliferation and invasion but also enhanced the drug-sensitivity to the chemotherapeutic drug Cisplatin. Both oral administration and intraperitoneal injection of PP significantly inhibited the tumor growth in xenograft BALB/c nude mice. PP triggered a marked suppression of the PI3K/AKT signaling pathway in liver cancer cells in vitro and in vivo, and overexpression of the constitutively active form of AKT, Myr-AKT, abrogated this effect and the inhibited proliferation and invasion by PP. Both western blot and ELISA results showed that PP-treated liver cancer cells had reduced expression and secretion of vascular endothelial growth factor (VEGF). Addition of recombinant human VEGF attenuated the inhibitory effects of PP on PI3K/AKT pathway and the cancer phenotypes. Our results demonstrated that PP suppressed the proliferation, invasion, and drug-resistance of liver cancer cells in vitro and in vivo, mediated by the inhibition of autocrine VEGF-induced PI3K/AKT signaling pathway. This study suggests the potential therapeutic implication of PP in the treatment of human liver cancer.肝癌即肝细胞癌（hepatocellular carcinoma）是癌症相关死亡的主要诱因之一。传统化疗受限于耐药性的产生与多种不良反应。由于蘑菇来源的代谢物无毒且具备强效生物药理活性，其在癌症治疗领域受到了越来越多的关注。我们此前的研究已证实侧耳属（Pleurotus）蘑菇来源的多糖-蛋白复合物具有抗癌作用。本研究旨在探究从肺形侧耳（Pleurotus pulmonarius，简称PP）中分离得到的、含多糖-蛋白复合物的热水提取物针对肝癌细胞的抗癌活性背后的潜在分子机制。研究结果显示，将肝癌细胞暴露于PP环境中，不仅可显著降低体外癌细胞的增殖与侵袭能力，还能增强其对化疗药物顺铂（Cisplatin）的药物敏感性。无论是口服给药还是腹腔注射PP，均可显著抑制异种移植BALB/c裸小鼠体内的肿瘤生长。PP可在体外及体内的肝癌细胞中显著抑制PI3K/AKT信号通路（PI3K/AKT signaling pathway）的激活；而过表达组成型激活形式的AKT（即Myr-AKT）则可抵消这一效应，同时解除PP对癌细胞增殖与侵袭的抑制作用。蛋白质免疫印迹（western blot）与酶联免疫吸附实验（ELISA）结果均表明，经PP处理的肝癌细胞中，血管内皮生长因子（vascular endothelial growth factor，VEGF）的表达与分泌水平均有所下调。添加重组人VEGF可减弱PP对PI3K/AKT通路及癌症表型的抑制作用。本研究结果证实，PP可通过抑制自分泌VEGF介导的PI3K/AKT信号通路，在体外及体内抑制肝癌细胞的增殖、侵袭与耐药性。本研究提示，PP在人类肝癌的治疗中具备潜在的临床应用价值。