自噬是近年来国内外研究的热点，围绕自噬及其信号进行抗肿瘤药物机制研究成为一种新颖策略。以哇巴因和地高辛为代表的洋地黄类药物作为Na+/K+-ATPase（NKA）抑制剂，临床上广泛用于心力衰竭的治疗。此类药物对肿瘤也具有强效的选择性杀伤活性，且其抗肿瘤效应与NKA抑制作用并不相关。目前有关自噬及相关分子信号通路与洋地黄药物抗肿瘤作用的关系，国内外报道甚少。我们前期工作首次发现此类药物可诱导人肺癌细胞自噬性死亡，并调节自噬相关的AMPK/mTOR以及ERK1/2双重信号通路变化。基于此，本项目拟综合应用多项生物学技术，系统研究自噬及其激酶信号与该类药物抗肿瘤作用的关系，包括研究药物诱导肿瘤细胞自噬的普遍性以及自噬对药物选择性抗肿瘤作用的影响；药物调节自噬相关AMPK等激酶信号的确切分子机制；NKA对自噬及其信号的影响等。本研究属于"老药新用"，将有助于全新阐释靶向NKA的抗肿瘤药物作用机理。

Autophagy and autopahgy-related signaling pathways have been reported to be involved in the mechansims of many anti-cancer agents, thus attracting more and more attentions of oncologists in recent years. Digitalis drugs, represented by digoxin and ouabain, are a diverse family of naturally derived compounds that bind to and inhibit the pumping function of Na+/K+-ATPase (NKA). The class of compounds have been in clinical use for many years to treat heart failure. They are also reported to have selective killing activity in cancer cells and the anti-tumor activity is found to have little correlation with NKA inhibition function. Although multiple anti-cancer mechanisms for the compounds have been revealed, the role of autophagy and related molecular signaling pathways in their anti-cancer activity is not systematically examined. Our preliminary data have shown that autophagic cell death is induced, and may play an important role in digoxin or ouabain-induced toxicity in A549 and H460 cell lines at IC50 level. More importantly and interestingly, AMPK mediated down-regulation of mTOR signaling pathway, as well as activation of ERK1/2 pathway, are both found to be involved in the autophagy regulation. Based on above observations, this project aims to systematically study the correlation between autophagy as well as related signaling pathways and anti-cancer effects of the compounds with the use of multiple cellular and molecular biotechnology. Specifically, we will study whether autophagy is universally induced and its role in the anti-cancer effects of the compounds, and how autophagy-related signaling pathways are mechanistically regulated by the compounds.The role of NKA in the regulation of autophagy and autophagy-related signaling pathways will also be examined. Taken together, the project will help thoroughly understand the molecular action of NKA inhibitors towards cancer.