6aR,12aR,12a-羟基紫穗槐苷元上调Bim诱导肝癌细胞SMMC-7721发生凋亡的机制

肝细胞癌(HCC)是一种高度恶性的肿瘤。化疗是临床上一种重要的治疗方法,但由于化疗药物的毒副作用和耐药效应,现有的化疗药物或多或少有一定的局限性。因此,寻找毒副作用小且有效的化疗药物一直是肝癌患者的迫切需求。本研究从紫穗槐种子中分离纯化出一种天然产物6aR,12aR,12a-羟基紫穗槐苷元,采用CCK-8法检测了其对人肝癌SMMC-7721细胞的杀伤作用,应用流式细胞术检测了其对肝癌细胞的凋亡诱导情况,通过免疫印迹法检测了6aR,12aR,12a-羟基紫穗槐苷元上调Bim蛋白表达进而诱导肝癌细胞凋亡的作用机制。结果表明,6aR,12aR,12a-羟基紫穗槐苷元可呈浓度依赖性和时间依赖性抑制人肝癌SMMC-7721细胞的活力,24 h、48 h和72 h的半数抑制浓度(IC50)分别为21.77μmol/L、5.65μmol/L、5.0μmol/L;同时可浓度依赖性地提高细胞凋亡率;可通过下调抑凋亡蛋白Survivin、Mcl-1、Bcl-XL、Bcl-2,上调促凋亡蛋白Bak、Bim、Bax、Bid的表达,进而促进PARP和caspase-3的活化,从而诱导细胞发生凋亡;进一步地研究发现:6aR,12aR,12a-羟基紫穗槐苷元通过延长Bim的半衰期而增加Bim的积累,且具有和MG132类似的生物学功能,能够阻断蛋白的降解途径来抑制Bim降解。上述研究表明,6aR,12aR,12a-羟基紫穗槐苷元可通过抑制蛋白降解从而上调细胞中Bim蛋白的水平,进而诱导肝癌细胞SMMC-7721发生凋亡。     

Toll样受体4通过Akt/FoxO3a/Bim信号通路参与海马神经元凋亡

为了探讨海马神经元中是否有Toll样受体4(Toll-like receptor 4,TLR4)介导的Akt/FoxO3a/Bim信号通路,及该通路在海马神经元凋亡中的作用和机制,本实验运用脂多糖(lipopolysaccharide,LPS)作用于原代培养的大鼠海马神经元,利用不同的工具药,以减弱或加强TLR4/Akt/FoxO3a/Bim通路的作用。应用CCK-8法检测细胞活力,Western blot法检测神经元p-Akt(Ser473)、Akt、p-FoxO3a(Thr32)、FoxO3a、Bim、活化的Caspase-3蛋白的表达变化,real-time PCR法检测海马神经元Bim的mRNA表达变化,免疫荧光法观察FoxO3a核易位情况,流式细胞术检测细胞凋亡率。结果显示:LPS作用于海马神经元不同时间后,各组细胞活力均下降(P0.05),且具有一定的时间依赖性;LPS作用后p-Akt(Ser473)、p-FoxO3a(Thr32)表达减少,FoxO3a易位进入胞核,而促凋亡蛋白Bim及活化的Caspase-3表达增加,且海马神经元的凋亡率也增加(P0.05);PI3K特异性抑制剂LY294002预处理后p-Akt(Ser473)、p-FoxO3a(Thr32)表达较LPS组降低,而促凋亡蛋白Bim及活化的Caspase-3表达升高,细胞凋亡率也明显升高(P0.05);TLR4抗体预处理后p-Akt(Ser473)、p-FoxO3a(Thr32)较LPS组增多,FoxO3a易位进入胞核的活动减弱,而促凋亡蛋白Bim、活化的Caspase-3及细胞的凋亡率均减少(P0.05)。以上结果表明,海马神经元中有TLR4介导的Akt/FoxO3a/Bim通路;神经元可通过该通路引起自身的凋亡。     

沙眼衣原体感染HeLa229细胞Bim表达及抑制凋亡研究

研究沙眼衣原体(D血清型)感染的HeLa229细胞中Bim蛋白质的表达及凋亡诱导剂作用后的凋亡情况。Western-blot检测沙眼衣原体感染和未感染的HeLa229细胞Bim蛋白质的表达水平。凋亡诱导剂etopo- side作用HeLa229细胞后,经Hoechst33258染色用荧光显微镜观察核浓缩和凋亡小体;流式细胞仪检测凋亡率。HeLa229细胞在未感染及感染沙眼衣原体6 h后可检测到Bim的表达;在感染24、48 h后均未检测到Bim的表达。经etoposide作用后,未感染的HeLa229细胞观察到明显的核浓缩和凋亡小体;流式细胞仪检测的凋亡率为90.64%。感染24 h的HeLa229细胞,未观察到核浓缩和凋亡小体;流式细胞仪检测的凋亡率为11.50%,与未感染的HeLa229细胞诱导后的凋亡率比较有统计学意义(P<0.05)。沙眼衣原体感染HeLa229细胞后可降低Bim蛋白质的表达;并能抑制etoposide诱导的细胞凋亡。     

Bcl-2家族蛋白调控线粒体膜通透性和细胞色素C释放的新机制

Bcl-2家族蛋白在调控线粒体功能和细胞色素C释放中起重要作用。最近发现Bcl-2分子通过与其他促凋亡分子相互作用调控线粒体外膜通透性,其具体分子机制尚不完全清楚。本课题组采用化学生物学方法,在研究Bax/Bak非依赖的细胞凋亡途径中,发现了一些小分子化合物能够诱导Bim表达量急剧升高,Bim能转位到线粒体上,与Bcl-2相互作用增强,并直接促进Bcl-2构象变化。有意义的是,Bim可以诱导Bcl-2功能发生转换并能够形成大的复合体通道来介导细胞色素C释放。研究结果提示Bcl-2分子可变成促凋亡分子,参与Bax/Bak非依赖的细胞色素C释放和细胞凋亡。     

FHC和Bim相互作用抵抗细胞凋亡

FHC和Bim参与细胞铁代谢和由ROS引起的细胞凋亡过程.但是其具体的分子机制还未阐明.用pLexA-Bim L作为诱饵,筛选了一个基于pBD42AD的胎脑cDNA文库,发现FHC是一个新的Bim相互作用蛋白.酵母杂交实验发现Bim的相互作用片段为BH3功能域.上述相互作用进一步用免疫共沉淀和荧光共定位得以证实.在HEK293细胞过表达FHC可以减轻由Bim过表达或ROS所引起的细胞凋亡,而用FHC特异性siRNA调低FHC表达,则增加Bim过表达或ROS引起的细胞凋亡.研究首次报道了Bim和FHC的相互作用以及对细胞凋亡和氧化应激的影响,为进一步阐明FHC和Bim参与凋亡和ROS反应提供了新的线索.     

细胞色素c的释放是多巴胺诱导PC12细胞凋亡的重要环节

通过末端脱氧核苷酸转移酶介导dUTP缺口翻译法和DNA凝胶电泳观察多巴胺(DA)对PC12细胞凋亡的诱导作用, 并经蛋白质印迹法检测胞浆细胞色素c、Bcl-2和Bax蛋白以及活化型半胱氨酸蛋白酶3(caspase-3)水平. 结果表明, 在DA诱导PC12细胞凋亡的过程中, 可见PC12细胞中活化型caspase-3蛋白表达, 胞浆中细胞色素c水平明显增高, 同时Bcl-2蛋白水平下降, 而Bax蛋白水平明显增加. 环孢菌素A预处理对细胞色素c释放和caspase-3激活有明显的抑制作用, 而对Bcl-2和Bax蛋白影响不明显. 结果提示, Bcl-2和Bax蛋白、细胞色素c以及caspase-3可能参与DA诱导PC12细胞凋亡, 线粒体细胞色素c向胞浆释放可能是其中的中心环节.     

前凋亡因子与脑血管疾病的关系研究

Bim（bcl—2 interacting mediator of cell death）,又称前凋亡因子（pro-apoptotic Bcl-2 proteins）,是Bcl-2家族中BH3-only亚家族成员,具有促凋亡活性,是重要的凋亡诱导基因,在细胞凋亡过程中有重要作用,而最近研究表明凋亡是脑缺血后神经元死亡的重要形式,故Bim与脑血管疾病关系密切。本文就Bim的分子结构、生物学功能及其调节机制作一简单阐述,并重点讨论了其与脑血管疾病关系方面的研究进展,以望为脑血管疾病的防治提供一新的途径。     

猪流行性腹泻病毒通过病毒蛋白酶激活Caspase-3诱导细胞凋亡

冠状病毒是一大类能够引起呼吸系统疾病,从而威胁人类健康的病毒．目前,对冠状病毒诱导细胞凋亡及其机制研究甚少.本研究以动物冠状病毒 猪流行性腹泻病毒(PEDV) 为模型探讨冠状病毒诱导细胞凋亡效应及其可能作用机制. 通过流式细胞术检测发现感染PEDV病毒后细胞凋亡率明显升高,且PEDV诱导细胞凋亡呈时间和剂量依赖性(P<0.05或P<0.01);进一步研究发现,冠状病毒木瓜样蛋白酶（PLP）在病毒引起凋亡过程中起重要作用.实验发现,转染PEDV-PLP质粒后,caspase-3活化体表达水平明显升高. 提示冠状病毒PLP蛋白酶通过激活caspase-3在病毒诱导细胞凋亡过程中起着关键作用. 以上结果为研究人类冠状病毒PLP蛋白功能及其通过细胞凋亡调节宿主抗病毒天然免疫机制提供重要基础.     

JNK激酶介导mGluR1对细胞凋亡的不同效应

代谢型谷氨酸受体1（mGluR1）可以通过激活多条信号通路促进或抑制细胞凋亡.然而,导致这种生理功能差异的机制尚不明确.本研究选用两种细胞系,即大鼠神经胶质瘤细胞系（C6）和人胚胎肾细胞（HEK293）分别研究内源性和外源转染的mGluR1的激活对细胞凋亡的影响及其调节机制. 结果显示,内源性mGluR1的活化能够激活PI3K/ERK/JNK通路,抑制凋亡试剂STS诱导的细胞凋亡;而外源转染的mGluR1的活化能够分别激活PI3K/ERK和JNK通路,同时促进STS诱导的应激损伤. HEK293细胞中,应用JNK通路抑制剂SP600125,能够部分抑制由mGluR1激活介导的caspase 3的剪切和细胞凋亡;而在C6细胞中阻断JNK通路,则加剧了由mGluR1活化而引起的细胞凋亡. 本文结果提示：mGluR1通过不同信号通路影响细胞凋亡,其中JNK通路可能是调控细胞凋亡的关键途径.本文为受体激活对细胞凋亡能够产生不同的调控作用提供了相应的证据.     

中药有效成分调控NLRP3 炎症小体活化的研究进展

炎症小体是细胞内组装形成的大分子蛋白复合体,可将白介素-1β(IL-1β) 和IL-18 加工成熟,并诱导细胞焦亡性死亡,在协调对抗病原体感染和生理紊乱的过程中发挥重要作用。Nod 样受体蛋白3(Nod-like receptor protein 3, NLRP3) 炎症小体是迄今为止结构和功能研究得最为明确的炎症小体,其活化后参与免疫性疾病、心血管疾病、神经系统疾病等多种疾病发生及发展过程。研究显示,许多中药有效成分可以调节相关疾病靶细胞中NLRP3 炎症小体的活化。从中药有效成分调节相关疾病靶细胞（如神经细胞、肝肾细胞、内皮细胞、肿瘤细胞等）中NLRP3 炎症小体活化的机制出发,综述近4 年国内外对中药有效成分调节NLRP3 炎症小体活化的研究进展,以期阐释相关中药有效成分的作用特点,并为相关疾病的防治提供一定参考。     

CS055 (Chidamide/HBI-8000), a novel histone deacetylase inhibitor, induces G1 arrest, ROS-dependent apoptosis and differentiation in human leukaemia cells

CS055 (Chidamide/HBI-8000) is a novel benzamide-type HDACi (histone deacetylase inhibitor), which has entered Phase I clinical trials in the U.S. and Phase II/III in China. In the present study, we investigated the effects of CS055 on proliferation, differentiation and apoptosis in human leukaemia cell lines and primary myeloid leukaemia cells. The results showed that at low concentrations (<1?μM), CS055 induced G1 arrest. At moderate concentrations (0.5?μM-2?μM), CS055 induced differentiation, as determined by the increased expression of the myeloid differentiation marker CD11b. At relatively high concentrations (2?μM-4?μM), CS055 potently induced caspase-dependent apoptosis. Co-treatment with the ROS (reactive oxygen species) scavengers N-acetyl-L-cysteine or Tiron blocked CS055-induced cell differentiation and apoptosis, suggesting an essential role for ROS in these effects. Cytochrome c release and ROS-mediated mitochondrial dysfunction are involved in CS055-induced apoptosis of leukaemia. In addition to cell lines, CS055 also exhibits therapeutic effects in human primary leukaemia cells. Moreover, daily oral CS055 treatment of nude mice bearing HL60 cell xenografts suppressed tumour growth, induced tumour cell apoptosis and prolonged the survival of tumour-bearing mice. In conclusion, our findings demonstrate that CS055 is a novel HDACi with potential chemotherapeutic value in several haematological malignancies, especially leukaemia.     

Calpain and Reactive Oxygen Species Targets Bax for Mitochondrial Permeabilisation and Caspase Activation in Zerumbone Induced Apoptosis

Fluorescent protein based signaling probes are emerging as valuable tools to study cell signaling because of their ability to provide spatio- temporal information in non invasive live cell mode. Previously, multiple fluorescent protein probes were employed to characterize key events of apoptosis in diverse experimental systems. We have employed a live cell image based approach to visualize the key events of apoptosis signaling induced by zerumbone, the active principle from ginger Zingiber zerumbet, in cancer cells that enabled us to analyze prominent apoptotic changes in a hierarchical manner with temporal resolution. Our studies substantiate that mitochondrial permeabilisation and cytochrome c dependent caspase activation dominate in zerumbone induced cell death. Bax activation, the essential and early event of cell death, is independently activated by reactive oxygen species as well as calpains. Zerumbone failed to induce apoptosis or mitochondrial permeabilisation in Bax knockout cells and over-expression of Bax enhanced cell death induced by zerumbone confirming the essential role of Bax for mitochondrial permeabilsation. Simultaneous inhibition of reactive oxygen species and calpain is required for preventing Bax activation and cell death. However, apoptosis induced by zerumbone was prevented in Bcl 2 and Bcl-XL over-expressing cells, whereas more protection was afforded by Bcl 2 specifically targeted to endoplasmic reticulum. Even though zerumbone treatment down-regulated survival proteins such as XIAP, Survivin and Akt, it failed to affect the pro-apoptotic proteins such as PUMA and BIM. Multiple normal diploid cell lines were employed to address cytotoxic activity of zerumbone and, in general, mammary epithelial cells, endothelial progenitor cells and smooth muscle cells were relatively resistant to zerumbone induced cell death with lesser ROS accumulation than cancer cells.     

Apoptosis induced by the histone deacetylase inhibitor FR901228 in human T-cell leukemia virus type 1-infected T-cell lines and primary adult T-cell leukemia cells

Inhibition of histone deacetylase (HDAC) activity induces growth arrest, differentiation, and, in certain cell types, apoptosis. FR901228, FK228, or depsipeptide, is an HDAC inhibitor effective in T-cell lymphomas. Adult T-cell leukemia (ATL) is caused by human T-cell leukemia virus type 1 (HTLV-1) and remains incurable. We examined whether FR901228 is effective for treatment of ATL by assessing its ability to induce apoptosis of HTLV-1-infected T-cell lines and primary leukemic cells from ATL patients. FR901228 induced apoptosis of Tax-expressing and -unexpressing HTLV-1-infected T-cell lines and selective apoptosis of primary ATL cells, especially those of patients with acute ATL. FR901228 also efficiently reduced the DNA binding of NF-kappaB and AP-1 in HTLV-1-infected T-cell lines and primary ATL cells and down-regulated the expression of Bcl-x(L) and cyclin D2, regulated by NF-kappaB. Although the viral protein Tax is an activator of NF-kappaB and AP-1, FR901228-induced apoptosis was not associated with reduced expression of Tax. In vivo use of FR901228 partly inhibited the growth of tumors of HTLV-1-infected T cells transplanted subcutaneously in SCID mice. Our results indicated that FR901228 could induce apoptosis of these cells and suppress the expression of NF-kappaB and AP-1 and suggest that FR901228 could be therapeutically effective in ATL.     

BIM-mediated AKT phosphorylation is a key modulator of arsenic trioxide-induced apoptosis in cisplatin-sensitive and -resistant ovarian cancer cells

Background

Chemo-resistance to cisplatin-centered cancer therapy is a major obstacle to the effective treatment of human ovarian cancer. Previous reports indicated that arsenic trioxide (ATO) induces cell apoptosis in both drug-sensitive and -resistant ovarian cancer cells.

Principal Findings

In this study, we determined the molecular mechanism of ATO-induced apoptosis in ovarian cancer cells. Our data demonstrated that ATO induced cell apoptosis by decreasing levels of phosphorylated AKT (p-AKT) and activating caspase-3 and caspase-9. Importantly, BIM played a critical role in ATO-induced apoptosis. The inhibition of BIM expression prevented AKT dephosphorylation and inhibited caspase-3 activation during cell apoptosis. However, surprisingly, gene silencing of AKT or FOXO3A had little effect on BIM expression and phosphorylation. Moreover, the activation of caspase-3 by ATO treatment improved AKT dephosphorylation, not only by cleaving the regulatory A subunit of protein phosphatase 2A (PP2A), but also by increasing its activation. Furthermore, our data indicated that the c-Jun N-terminal kinases (JNK) pathway is involved in the regulation of BIM expression.

Conclusions

We demonstrated the roles of BIM in ATO-induced apoptosis and the molecular mechanisms of BIM expression regulated by ATO during ovarian cancer cell apoptosis. Our findings suggest that BIM plays an important role in regulating p-AKT by activating caspase-3 and that BIM mediates the level of AKT phosphorylation to determine the threshold for overcoming cisplatin resistance in ovarian cancer cells.     

Resistance to Apo2 ligand (Apo2L)/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis and constitutive expression of Apo2L/TRAIL in human T-cell leukemia virus type 1-infected T-cell lines

Adult T-cell leukemia (ATL), a CD4+-T-cell malignancy caused by human T-cell leukemia virus type 1 (HTLV-1), is difficult to cure, and novel treatments are urgently needed. Apo2 ligand (Apo2L; also tumor necrosis factor-related apoptosis-inducing ligand [TRAIL]) has been implicated in antitumor therapy. We found that HTLV-1-infected T-cell lines and primary ATL cells were more resistant to Apo2L-induced apoptosis than uninfected cells. Interestingly, HTLV-1-infected T-cell lines and primary ATL cells constitutively expressed Apo2L mRNA. Inducible expression of the viral oncoprotein Tax in a T-cell line up-regulated Apo2L mRNA. Analysis of the Apo2L promoter revealed that this gene is activated by Tax via the activation of NF-kappaB. The sensitivity to Apo2L was not correlated with expression levels of Apo2L receptors, intracellular regulators of apoptosis (FLICE-inhibitory protein and active Akt). NF-kappaB plays a crucial role in the pathogenesis and survival of ATL cells. The resistance to Apo2L-induced apoptosis was reversed by N-acetyl-L-leucinyl-L-leucinyl-lLnorleucinal (LLnL), an NF-kappaB inhibitor. LLnL significantly induced the Apo2L receptors DR4 and DR5. Our results suggest that the constitutive activation of NF-kappaB is essential for Apo2L gene induction and protection against Apo2L-induced apoptosis and that suppression of NF-kappaB may be a useful adjunct in clinical use of Apo2L against ATL.     

BIM mediates EGFR tyrosine kinase inhibitor-induced apoptosis in lung cancers with oncogenic EGFR mutations

Background

Epidermal growth factor receptor (EGFR) mutations are present in the majority of patients with non-small cell lung cancer (NSCLC) responsive to the EGFR tyrosine kinase inhibitors (TKIs) gefitinib or erlotinib. These EGFR-dependent tumors eventually become TKI resistant, and the common secondary T790M mutation accounts for half the tumors with acquired resistance to gefitinib. However, the key proapoptotic proteins involved in TKI-induced cell death and other secondary mutations involved in resistance remain unclear. The objective of this study was to identify the mechanism of EGFR TKI-induced apoptosis and secondary resistant mutations that affect this process.

Methods and Findings

To study TKI-induced cell death and mechanisms of resistance, we used lung cancer cell lines (with or without EGFR mutations), Ba/F3 cells stably transfected with EGFR mutation constructs, and tumor samples from a gefitinib-resistant patient. Here we show that up-regulation of the BH3-only polypeptide BIM (also known as BCL2-like 11) correlated with gefitinib-induced apoptosis in gefitinib-sensitive EGFR-mutant lung cancer cells. The T790M mutation blocked gefitinib-induced up-regulation of BIM and apoptosis. This blockade was overcome by the irreversible TKI CL-387,785. Knockdown of BIM by small interfering RNA was able to attenuate apoptosis induced by EGFR TKIs. Furthermore, from a gefitinib-resistant patient carrying the activating L858R mutation, we identified a novel secondary resistant mutation, L747S in cis to the activating mutation, which attenuated the up-regulation of BIM and reduced apoptosis.

Conclusions

Our results provide evidence that BIM is involved in TKI-induced apoptosis in sensitive EGFR-mutant cells and that both attenuation of the up-regulation of BIM and resistance to gefitinib-induced apoptosis are seen in models that contain the common EGFR T790M and the novel L747S secondary resistance mutations. These findings also suggest that induction of BIM may have a role in the treatment of TKI-resistant tumors.     

Activation of the NLRP3 Inflammasome Complex is Not Required for Stress-Induced Death of Pancreatic Islets

Loss of pancreatic beta cells is a feature of type-2 diabetes. High glucose concentrations induce endoplasmic reticulum (ER) and oxidative stress-mediated apoptosis of islet cells in vitro. ER stress, oxidative stress and high glucose concentrations may also activate the NLRP3 inflammasome leading to interleukin (IL)-1β production and caspase-1 dependent pyroptosis. However, whether IL-1β or intrinsic NLRP3 inflammasome activation contributes to beta cell death is controversial. This possibility was examined in mouse islets. Exposure of islets lacking functional NLRP3 or caspase-1 to H₂O_2, rotenone or thapsigargin induced similar cell death as in wild-type islets. This suggests that oxidative or ER stress do not cause inflammasome-mediated cell death. Similarly, deficiency of NLRP3 inflammasome components did not provide any protection from glucose, ribose or gluco-lipotoxicity. Finally, genetic activation of NLRP3 specifically in beta cells did not increase IL-1β production or cell death, even in response to glucolipotoxicity. Overall, our results show that glucose-, ER stress- or oxidative stress-induced cell death in islet cells is not dependent on intrinsic activation of the NLRP3 inflammasome.     

BECN1 and BIM interactions with MCL-1 determine fludarabine resistance in leukemic B cells

The purine analog fludarabine (Fd) is an essential therapeutic for chronic lymphocytic leukemia (CLL). Innate or acquired resistance to Fd is a significant clinical problem and is largely mediated by increased expression of BCL-2 family members. The antiapoptotic BCL-2 family proteins inhibit both apoptosis and autophagy, therefore, downregulation of antiapoptotic BCL-2 family proteins and enhanced autophagy must coexist in cells dying in response to an apoptosis inducing therapeutic. However, in the drug-resistant cells that have an increased dependence on antiapoptotic proteins, whether autophagy is also inhibited remains unclear. Here, we examined the role of the BCL-2 family in regulating cell death and autophagy in leukemic cell lines and their derivative isogenic Fd-resistant (FdR) cells. MCL-1 degradation following Fd treatment freed the proapoptotic effectors BIM and BECN1, thus leading to cell death-associated autophagy in Fd-sensitive cells. However, in FdR cells, low BIM expression and BECN1 sequestration by MCL-1 prevented cell death. Consistently, in sensitive cells inhibition of apoptosis using siBIM and of both the early-phase autophagy nucleation steps by siBECN1, shATG7 or 3-methyladenine and the late-phase autophagy by shLAMP2, significantly reduced Fd-induced cell death. Paradoxically, FdR cells were addicted to basal autophagy, which was dependent on AMP-activated protein kinase (AMPK) but not BECN1. Moreover, in FdR cells, inhibition of autophagy by shLAMP2, but not siBECN1, enhanced cell death. The BH3-mimetic obatoclax released BIM and BECN1 from MCL-1 in Fd-sensitive and BECN1 from MCL-1 in FdR cells, and was effective at killing both Fd-sensitive and - resistant leukemic cells, including primary CLL cells. Therefore, a differential regulation of autophagy through BECN1 and AMPK signaling in Fd-sensitive and - resistant cells determines the different possible outcomes of autophagy inhibition. These findings suggest effective means to overcome Fd resistance by induction of BIM-dependent apoptosis and activation of BECN1-dependent autophagy.