Pro-apoptotic Activity of BH3-only Proteins and BH3 Mimetics: from Theory to Potential Cancer Therapy

The evasion of cancer cells from the induction of cell death pathways results in the resistance of tumor to current treatment modalities. Therefore, the resistance to cell death, one of the hallmarks of cancer, is a major target in the development of new approaches to selectively affect cancer cells. The complex interplay between individual members of Bcl-2 family regulates both cell survival and the mitochondrial pathway of apoptosis by maintaining mitochondrial membrane integrity (anti-apoptotic Bcl-2 subfamily) and by triggering its disruption in response to stress stimuli (Bax-like subfamily). BH3-only proteins, another Bcl-2 subfamily, act either by direct stimulation of pro-apoptotic proteins of the Bax subfamily or by interfering with anti-apoptotic proteins of the Bcl-2 subfamily. Thus, pro-apoptotic BH3 mimetics, thought to function as BH3-only proteins, are expected to improve the effectiveness of cancer treatment. BH3 mimetics could be either natural or synthetic, peptidic or only based on a helical peptide-like scaffold. Experimental and clinical evidence indicates that BH3 mimetics may not be sufficient to cure cancer patients when used as a single agent. BH3 profiling of cancer cells was introduced to better predict the in vivo responsiveness of tumor to BH3 mimetics combined with conventional therapies. In summary, targeting the Bcl-2 proteins is a promising tool with potential to generate new treatment modalities and to complement existing anti-cancer therapies. This review presents the current knowledge on BH3-only proteins and the spectrum of strategies employing BH3 mimetics in preclinical and clinical studies that aim at tumor targeting.     

Different contribution of BH3-only proteins and caspases to doxorubicin-induced apoptosis in p53-deficient leukemia cells

Bcl-2 family proteins are key regulators of the intrinsic apoptotic pathway, either facilitating (Bax, Bak, BH3-only) or inhibiting (Bcl-2, Bcl-x_L, Mcl-1, A1) mitochondrial release of apoptogenic factors. The role of caspases in this process is a matter of controversy. We have analyzed the relative contribution of caspases and Bcl-2 family of proteins in the induction phase of apoptosis triggered by doxorubicin in two p53-deficient leukemia cell lines, Jurkat and U937. First, we have found that caspases are dispensable for the induction phase of doxorubicin-induced apoptosis in both cell lines but they are needed to speed up the execution phase in Jurkat cells, not expressing Bax. Thus, down-regulation of Bak expression by siRNA significantly prevented doxorubicin-induced apoptosis in Jurkat but not in U937 cells. Reduction of Mcl-1 protein levels with siRNA increased sensitivity to apoptosis in both cell lines. Moreover, our results indicate that the contribution of BH3-only proteins to apoptosis is cell line specific. In Jurkat cells simultaneous silencing of Bim and PUMA was necessary to reduce doxorubicin-induced apoptosis. In U937 cells silencing of Bim or Noxa reduced sensitivity to doxorubicin. Immunoprecipitation experiments discarded an interaction between Mcl-1 and Bak in both cell lines and underscored the role of Bim and PUMA as mediators of Bax/Bak activation.     

Research of BH3 domain protein inducing cell apoptosis

Objective BH3 domain protein plays an important role in control mechanism of cell apoptosis.The article mainly discusses its mechanism of promoting cell apoptosis and control.Methods The article analyzed and evaluated the mechanism of BH3 domain protein promoting cell apoptosis by internal and overseas literature.Results Activation of BH3 domain protein could promote the increase of mitochondrial membrane permeability,then it would start mitochondrial apoptosis pathway,and at the last the cell apoptosis.Conclusions BH3 domain protein is the necessary condition of starting cell apoptosis.Its activation can cause cell apoptosis.     

Intracellular Delivery of Bak BH3 Peptide by Microbubble-Enhanced Ultrasound

Purpose. To investigate the possibility of intracellular delivery of Bak BH3 peptide using sonoporation effect by microbubble-enhanced ultrasound.Methods. HeLa and BJAB cells were exposed to 1.696-Mhz focused ultrasound with 2% microbubble contrast agents (OPTISON®). Cell-impermeable calcein was used as an indicator for successful sonoporation, and propidium iodide staining was used for cell viability assessment. Peptides were also exposed to ultrasound with OPTISON® and analyzed with mass spectrometry for evaluation of stability under ultrasound exposure. The effect of transduced Bak BH3 peptide was evaluated by the cell viability of successfully sonoporated cells.Results. Bak BH3 peptides did not undergo mechanical degradation with microbubble-enhanced ultrasound exposure. With the increase of acoustic energy exposure, the sonoporation efficiency saturated both in BJAB and HeLa cells, while direct cell death rate by ultrasound exposure tended to increase. When BJAB cells were treated with 100 M Bak BH3 peptides, and ultrasound exposure with ultrasound contrast agents (OPTISON®), an increased 35% cell death was confirmed. On the other hand, although HeLa cells had a similar trend, they failed to exhibit statistical significance.Conclusions. Our results suggest that microbubble-enhanced focused ultrasound peptide transduction is possible. Further optimization of ultrasound exposure conditions may be necessary.     

BH3 mimetics to improve cancer therapy; mechanisms and examples

Tumor cell survival is highly dependent on the expression of certain pro-survival Bcl-2 family proteins. An attractive therapeutic approach is to inhibit these proteins using agents that mimic the Bcl-2 homology 3 (BH3) domains of the proapoptotic Bcl-2 family members, which neutralize these proteins by binding to their surface hydrophobic grooves. A number of BH3 mimetic peptides and small molecules have been described, a few of which have advanced into clinical trials. Recent studies have highlighted ABT-737, a bona fide BH3 mimetic and potent inhibitor of antiapoptotic Bcl-2 family members, as a promising anticancer agent. This review summarizes recent advances in understanding the mechanisms of action of BH3 domains and several classes of BH3 mimetics, as well as the prospects of using these agents to improve cancer therapy.     

Nicotine increases survival in human colon cancer cells treated with chemotherapeutic drugs

Cigarette smoking is implicated in the development of colon cancer. Furthermore, nicotine increases cell proliferation and inhibits apoptosis through α₇-nicotinic acetylcholine receptor (α₇-nAChR) activation in human colon carcinoma cells. An open issue is whether nicotine interfere with colorectal cancer pharmacological treatment, by inhibiting drug-mediated apoptosis. To assess this hypothesis, we evaluated nicotine effect on Caco-2 and HCT-8 colon cancer cells, treated with 5-Fluorouracil (5-FU) and Camptothecin (CPT), chemotherapeutics commonly utilized as adjuvant treatment of colon cancer. Nicotine decreased anti-proliferative and pro-apoptotic effects exerted by chemotherapeutics on both cell lines. These effects partially reverted by exposure to α-bungarotoxin (α-BTX), an inhibitor of α₇-nAChR. Nicotine addition to Caco-2 and HCT-8, treated with 5-FU or CPT, decreased the cleavage of substrate of caspase 3 and 7, poly-ADP-ribose polymerase (PARP). Moreover, P-ERK/ERK ratio was modified by nicotine addition to 5-FU and CPT treated cells in an opposite manner. However, when co-administrating PD98059, an ERK phosphorylation inhibitor, an increased apoptosis was observed. In Caco-2 and HCT-8 nicotine reverted 5-FU and CPT apoptotic effects through AKT phosphorylation, as demonstrated by apoptotic increase in presence of LY294002, an AKT phosphorylation inhibitor. Nicotine interfered with colorectal cancer pharmacological treatment in vitro by inhibiting apoptosis induced by chemotherapeutic drugs. Nicotine anti-apoptotic effects were exerted through ERK and AKT pathway activation.     

Involvement of nitric oxide and biopterin in proinflammatory cytokine-induced apoptotic cell death in mouse osteoblastic cell line MC3T3-E1.

We previously demonstrated that the addition of proinflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta, and interferon-gamma) caused induction of mRNAs for inducible nitric oxide (NO) synthase and GTP cyclohydrolase I, a rate-limiting enzyme for 5,6,7,8-tetrahydrobiopterin (BH4) biosynthesis, and produced their end-products, NO and BH4, in osteoblastic cells. In the present study, we examined whether NO and BH4, biologically active substances produced in response to proinflammatory cytokines, are involved in the effect of these cytokines on cell viability and apoptotic cell death involving DNA fragmentation. Cytokines as well as S-nitroso-N-acetyl-d,l-penicillamine, an NO generator, decreased cell viability, whereas sepiapterin, which was converted intracellularly to BH4, increased it. The examination of cytotoxicity measured in terms of lactate dehydrogenase release and apoptotic cell death assessed by flow cytometric analysis showed that cytokine-induced reduction of cell viability may be based upon cell death by apoptosis, but not lytic death as in necrosis. In the presence of sepiapterin, cytokine treatment resulted in a statistically pronounced reduction in the amount of DNA fragmentation. Furthermore, this fragmentation could be blocked by 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazole-1-oxyl 3-oxide, an NO scavenger. These results suggest that cytokine-induced apoptotic cell death is attributed to NO and is protected by BH4, and that osteoblastic cells in response to proinflammatory cytokines operate both a stimulatory process resulting in NO production and an inhibitory one resulting in BH4 production for apoptotic cell death. Cytokine-induced apoptotic cell death may be a consequence of the predominance of the stimulatory process over the inhibitory process.     

Expression of 14-3-3delta, cdc2 and cyclin B proteins related to exotoxin A-induced apoptosis in HeLa S3 cells

After reports on regression of cancer in humans and animals infected with microbial pathogens date back more than 100 years, much effort has been spent over the years in developing wild type or attenuated bacterial and purified bacterial proteins for the treatment of cancer. Pseudomonas aeruginosa exotoxin A (ETA) is known to inhibit cell growth and trigger significant cell death in various cancer cells. Although ETA induces apoptosis of cancer cells, its exact mechanism of action is not yet known. Four different assays were performed in this study: morphological assessment of apoptotic cells, cell cytotoxicity, cell cycle analysis and Western blot analysis. The proliferation and survival in the cells treated with ETA was decreased. In addition, percentages of apoptotic HeLa S(3) cells treated with ETA were increased. ETA-induced apoptosis rates were confirmed to have increased in a dose-dependent manner through annexin V binding assay. Flow cytometric analysis was examined to ascertain whether ETA could regulate cell cycle in HeLa S(3) cells. ETA treatment demonstrated that the expression of 14-3-3delta proteins was increased, while expression of cdc and cyclin B proteins was decreased, suggesting that ETA induces cell cycle arrest and then progresses to apoptosis. Therefore, these results suggest that P. aeruginosa ETA induced apoptosis in HeLa S(3) cells.     

The modulation of PI3K/Akt pathway by 3β hydroxylup-12-en-28-oic acid isolated from Thymus linearis induces cell death in HCT-116 cells

The presence of intricate carbon skeletons in natural compounds enhances their bioactivity spectrum with unique modes of action at several targets in various dreadful diseases like cancer. The present study was designed to purify the molecules from Thymus linearis and elucidate their antiproliferative activity. The compounds were isolated from the active methanolic extract of Thymus linearis through column chromatography and characterized by various spectroscopic techniques. Antiproliferative activity of isolated compounds was evaluated using MTT assay on cancer and normal cell lines. Mechanism of cell death was elucidated using flow cytometric, microscopic, and Western blot analysis. Four compounds, Sitosterol, Chrysin, 3β-hydroxylup-12-en-28-oic acid (3BH), and β-Sitosterol glycoside, were isolated. Among these, 3BH was most potent antiproliferative agent across all cell lines under study, HCT-116 being the most affected one. 3BH was demonstrated to downregulate PI3Ksubunits (p110α and p85α), downstream pAktSer⁴⁷³ and prompted G₁ phase cell cycle arrest. The cell cycle CDK inhibitor p27 and p21 were upregulated with simultaneous downregulation of cyclin D1 and cyclin E in HCT-116 cells. This was accompanied by apoptosis, as depicted by decrease in Bcl-2/Bax ratio, with increase in active caspases-3 and caspase-9, cleavage of PARP-1, the generation of reactive oxygen species (ROS), and the loss of mitochondrial membrane potential. The findings established that 3BH induced cell death in HCT-116 cells by modulating PI3K/Akt signaling axis, impeding cell cycle, and instigating apoptosis.     

TFAR19蛋白协同米非司酮对前列腺癌PC-3M细胞凋亡的影响

目的初步探讨TFAR19协同米非司酮(MIF)对前列腺癌PC-3M细胞凋亡的影响。方法构建TFAR19真核表达载体,用脂质体介导的方法转染PC-3M细胞。MTT法检测5、10、20、50和100μmol·L-1MIF作用于前列腺癌PC-3M细胞24~96h的吸光度(A)值。在转染TFAR19的细胞中加入20mol·L-1MIF培养24、48h,MTT比色法检测细胞增殖,原位末端标记(TUNEL)法检测细胞凋亡率,透射电镜进一步观察细胞超微结构的改变。结果构建了PCI-neo-TFAR19真核表达载体并在转染的PC-3M细胞中得到了瞬时表达。MTT实验表明,与对照组相比,5、10μmol·L-1MIF组的A值差异无统计学意义(P>0.05),20、50和100μmol·L-1MIF组的A值差异有统计学意义(P<0.01),MIF对前列腺癌PC-3M细胞的抑制作用呈时间、剂量依赖性;转染PCI-neo-TFAR19并加入20 mol·L-1MIF后,与对照组及单独应用MIF组相比,细胞生长明显受到抑制(P<0.01),细胞凋亡率明显增加(P<0.01),透射电镜观察到典型的细胞凋亡特征(细胞体积缩小,核皱缩、碎裂,染色质呈块状边集等)。结论TFAR19蛋白能够协同米非司酮促进前列腺癌PC-3M细胞凋亡,有望成为前列腺癌的辅助治疗药物。     

Apoptosis induction by Bcl-2 proteins independent of the BH3 domain

Bcl-2 proteins, characterized by up to four Bcl-2 homology domains (BH1-BH4), are critical regulators of the mitochondrial proapoptotic pathway. Three major subgroups have been described, namely antiapoptotic proteins, proapoptotic multidomain and BH3-only proteins. These are basic for present models explaining the regulation of the mitochondrial outer membrane permeability. However, several Bcl-2 proteins have been described that do not fit into these models, due to their atypical domain structure or due to their ability to induce apoptosis independently of BH3. These proteins are indicators for new mechanisms in apoptosis control by Bcl-2 proteins, which may supply additional targets for novel therapeutic approaches.     

Involvement of BH3-only proapoptotic proteins in mitochondrial-dependent Phenoxodiol-induced apoptosis of human melanoma cells

Phenoxodiol is a chemically modified analogue of the plant hormone isoflavone with antitumour activities. In the present study, we have examined its ability to induce apoptosis in human melanoma cells and the mechanisms involved. Apoptosis was observed in Phenoxodiol-treated cells by using annexin V/propidium iodide staining and determining mitochondrial membrane potential. To determine which caspase pathways were involved in Phenoxodiol-induced apoptosis, studies were performed using specific caspase inhibitors. Western studies were performed to ascertain which proteins of the apoptosis cascade were affected to cause Phenoxodiol-induced apoptosis. We found that induction of apoptosis by Phenoxodiol was maximal at 48 h with a range of apoptosis of 12+/-4 to 48+/-5% in different melanoma lines. This apoptosis was mainly dependent on activation of caspase-3 and caspase-9. Apoptosis was associated with induction of changes in mitochondrial membrane potential and was inhibited by over-expression of Bcl-2. Variation in sensitivity to Phenoxodiol appeared related to events upstream of the mitochondria and the degree of conformational change in Bax. The p53-regulated BH3-only proteins (Bad, PUMA and Noxa) were increased in the sensitive, but not in the resistant lines, whereas Bim was increased in all the lines tested. Bim appeared, however, to be partially involved because reduction of Bim by RNA interference resulted in decreased levels of apoptosis. Together, these studies suggest that Phenoxodiol induces apoptosis of melanoma cells by induction of p53-dependent BH3 proteins (Bad, PUMA and Noxa) and the p53-independent Bim protein, resulting in activation of Bax and its downstream events.     

Zeylenone抑制人前列腺癌PC-3细胞增殖及诱导凋亡作用研究

目的研究(4R,5S,6S)-4-苯甲酰氧基-6-[(苯甲酰氧基)甲基]-5,6-二羟基-2-环己烯-1-酮Zeylenone(Zey)对人前列腺癌PC-3细胞的生长抑制和诱导凋亡作用。方法采用MTT法观察Zey对PC-3细胞和正常前列腺基质细胞WPMY-1的增殖抑制作用,应用平板克隆形成实验观察Zey对PC-3细胞克隆形成的作用,AO/EB荧光染色观察细胞形态、JC-1染色观察Zey对细胞内线粒体膜电位的影响,An-nexin V-FITC/PI双染检测凋亡细胞比率,Western blot检测凋亡相关蛋白Caspase-9、Caspase-8、Caspase-3、Caspase-7和PARP的激活及Bcl-2、Bax、Bid、Bcl-xL蛋白的表达。结果Zey可以明显抑制人前列腺癌PC-3细胞的增殖并诱导其凋亡,而对正常前列腺基质细胞WPMY-1的抑制作用显著低于PC-3细胞。Zey抑制PC-3细胞克隆形成并明显诱导其凋亡。线粒体膜电位检测结果显示Zey导致细胞内线粒体膜电位的明显降低,Western blot检测结果表明Caspase-8、Caspase-9、Caspase-7、Caspase-3被激活,PARP和Bid被剪切活化,Bcl-2、Bcl-xL表达下降,而Bax表达上调。结论 Zey可选择性抑制人非激素依赖性前列腺癌PC-3细胞的增殖并诱导其凋亡,作用机制与其对Bcl-2和Caspase家族蛋白的影响,从而诱导PC-3细胞发生内源性和外源性凋亡相关。Zey有望成为治疗前列腺癌的候选药物。     

Discovery of small-molecule inhibitors of Bcl-2 through structure-based computer screening.

Bcl-2 belongs to a growing family of proteins which regulates programmed cell death (apoptosis). Overexpression of Bcl-2 has been observed in 70% of breast cancer, 30-60% of prostate cancer, 80% of B-cell lymphomas, 90% of colorectal adenocarcinomas, and many other forms of cancer. Thereby, Bcl-2 is an attractive new anti-cancer target. Herein, we describe the discovery of novel classes of small-molecule inhibitors targeted at the BH3 binding pocket in Bcl-2. The three-dimensional (3D) structure of Bcl-2 has been modeled on the basis of a high-resolution NMR solution structure of Bcl-X(L), which shares a high sequence homology with Bcl-2. A structure-based computer screening approach has been employed to search the National Cancer Institute 3D database of 206 876 organic compounds to identify potential Bcl-2 small-molecule inhibitors that bind to the BH3 binding site of Bcl-2. These potential Bcl-2 small-molecule inhibitors were first tested in an in vitro binding assay for their potency in inhibition of the binding of a Bak BH3 peptide to Bcl-2. Thirty-five potential inhibitors were tested in this binding assay, and seven of them were found to have a binding affinity (IC(50) value) from 1.6 to 14.0 microM. The anti-proliferative activity of these seven active compounds has been tested using a human myeloid leukemia cell line, HL-60, which expresses the highest level of Bcl-2 protein among all the cancer cell lines examined. Compound 6 was the most potent compound and had an IC(50) value of 4 microM in inhibition of cell growth using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Five other compounds had moderate activity in inhibition of cell growth. Compound 6 was further evaluated for its ability to induce apoptosis in cancer cells. It was found that 6 induces apoptosis in cancer cells with high Bcl-2 expression and its potency correlates with the Bcl-2 expression level in cancer cells. Furthermore, using NMR methods, we conclusively demonstrated that 6 binds to the BH3 binding site in Bcl-X(L). Our results showed that small-molecule inhibitors of Bcl-2 such as 6 modulate the biological function of Bcl-2, and induce apoptosis in cancer cells with high Bcl-2 expression, while they have little effect on cancer cells with low or undetectable levels of Bcl-2 expression. Therefore, compound 6 can be used as a valuable pharmacological tool to elucidate the function of Bcl-2 and also serves as a novel lead compound for further design and optimization. Our results suggest that the structure-based computer screening strategy employed in the study is effective for identifying novel, structurally diverse, nonpeptide small-molecule inhibitors that target the BH3 binding site of Bcl-2.     

Antibody Against N‐terminal Domain of Phospholipid Scramblase 1 Induces Apoptosis in Colorectal Cancer Cells Through the Intrinsic Apoptotic Pathway

Phospholipid scramblase 1 involve in biological processes including phospholipid movement, proliferation, and apoptosis. Treatment with an antiphospholipid scramblase 1 antibody (NP1) has been demonstrated to inhibit cell proliferation in colorectal cancer. This study aimed to explore the role of NP1 treatment in the apoptosis of colorectal cancer cells. Results showed that NP1 treatment significantly increases the apoptosis of colorectal cancer cells via the activation of caspase 8, caspase 9, and caspase 3. Moreover, pretreatment with a caspase 8 inhibitor did not fully prevent the apoptotic effects of NP1. Taken together, these data indicate NP1 induces cell apoptosis primary through the intrinsic apoptotic pathway. NP1 may serve as a potential therapeutic agent.     

PDCD4对DAP5表达及大肠癌细胞凋亡的影响

【摘要】目的 探讨程序性死亡基因4(PDCD4)对死亡相关蛋白5（DAP5) 的表达及对人大肠癌细胞系LOVO凋亡的影响。方法 构建重组真核表达载体pFLAG/PDCD4,转染人大肠癌细胞LOVO,G418（500 mg/L）筛选获得稳定表达PDCD4的细胞系。RT-PCR及Western blotting检测LOVO细胞中PDCD4的mRNA及蛋白表达,流式细胞仪检测LOVO细胞凋亡情况,Western blotting检测LOVO细胞DAP5表达的变化。结果 成功建立稳定表达PDCD4的大肠癌 细胞LOVO-pFLAG/PDCD4。转染PDCD4 的LOVO-pFLAG/PDCD4 组与空白对照LOVO 组、转染空载质粒的LOVO-pFLAG组相比,PDCD4蛋白表达和mRNA水平明显升高（P < 0.01）;细胞凋亡率明显增加（P < 0.01）;同时伴有DAP5蛋白表达明显升高（P < 0.01）。结论PDCD4能够诱导大肠癌细胞LOVO的凋亡,其机制可能与上调DAP5的表达有关。     

Role of Bcl‐2 in tumour cell survival and implications for pharmacotherapy

Objectives Bcl‐2 is a protein that inhibits apoptosis, leading to cell survival. The Bcl‐2 family has six different anti‐apoptotic proteins, three pro‐apoptotic proteins that are similar in structure, and other integrating proteins that function as promotors or inhibitors in the progression of apoptosis. In this discussion paper, we provide an overview of apoptosis, the role of Bcl‐2 in normal cellular and molecular processes, and the role of Bcl‐2 in tumour cell survival. It focuses primarily on anti‐apoptotic Bcl‐2, its activation in cancer, the manner in which it regulates the intrinsic and extrinsic mechanisms of apoptosis, and its broad molecular interactions with other critical proteins in the cell. Certain cancer treatments are reviewed and related directions for the future are presented. Key findings Apoptosis is common to all organisms – for eukaryotes it is a normal process of development and regeneration. The rate at which apoptosis occurs is critical to the survival of the organism, as too much can lead to the onset of degenerative diseases such as dementia, and too little may lead to cancer. FKBP‐38 is a binding protein that has been discovered to be upregulated in highly aggressive cancers and binds to Bcl‐2 rather than the pro‐apoptotics to induce a state of hyper‐mitosis. A short binding protein (Nur‐77) provides new insights into Bcl‐2 ‘masking’. Nurr‐77 binds to Bcl‐2 and exposes the BH3 domain, transforming it from a cancer promoter to an unorthodox cancer inhibitor. This presents in itself an interesting and exciting opportunity – increasing the rate of apoptosis in neoplastic cells that are usually protected by Bcl‐2 activity at the mitochondria. Summary Development of drugs in the form of BH3‐only and BH123 mimetic drugs provide a interesting avenue for cancer therapy for the future. Drugs that can either promote, or mimic anti‐IAP activity such as Smac/Diablo would certainly be productive, thereby inducing apoptosis. Medicinal usage which can effectively suppress FKBP38 in Bcl‐2‐dependent cancers would provide further arsenal to combat apoptotic irregularities, particularly a treatment that is more dominant than kinetin riboside. WAVE‐1 inhibitors may effectively suppress the phosphorylation of Bcl‐2, thereby potentially reducing hyper‐mitosis and increasing apoptosis. Recent findings shed molecular light on PDT, namely ER stress, and potential for anti‐cancer therapy via either apoptosis or autophagy. A drug that can effectively upregulate Nurr‐77, thereby masking the anti‐apoptotic properties of Bcl‐2, would indeed be life‐saving for cancer patients.     

Impact of lymphoma‐linked Asn11Tyr point mutation on the interaction between Bcl‐2 and a BH3 mimetic: Insights from molecular dynamics simulation

Frequent mutations in the Bcl‐2 anti‐apoptotic protein are often implicated in diffuse large B‐cell lymphoma (DLBCL), a disease profoundly resistant to drugs. Bcl‐2‐competitive inhibitors, “BH3 mimetics,” activate apoptosis by interfering with the interactions between pro‐apoptotic BH3 domains and the hydrophobic groove of Bcl‐2. The aim of our research is to determine the potential of DLBCL‐linked N11Y mutation to facilitate resistance against a “BH3 mimetic” using molecular dynamics simulation. Binding free energy calculations suggest a significant decrease in the binding affinity in the mutant model. In‐depth analysis of the models using residue interaction network, dynamic cross‐correlation, and free energy landscape approaches reveal that the mutation modifies the conformations of key residues, thereby altering the shape of the hydrophobic groove. This subsequently changes the ligand orientation and counteracts the phenomenon of LB region unwinding, a crucial event observed in the wild‐type model. Lowest frequency motions captured by principal component analysis reflect the stretching of the groove for efficient ligand accommodation in the wild‐type complex but not in the mutant model. This is the first in silico study that unravels the mechanism of drug resistance induced by a Bcl‐2 mutation, which could be of great relevance while designing and tailoring therapeutics.     

Induction of apoptosis by cinobufacini preparation through mitochondria- and Fas-mediated caspase-dependent pathways in human hepatocellular carcinoma cells

Cinobufacini (Huachansu), an aqueous extract from the skins of Bufo bufo gargarizans Cantor, is a well-known traditional Chinese medicine widely used in clinical cancer therapy in China. However, the precise mechanisms induced by cinobufacini in human hepatocellular carcinoma (HCC) cells are still not very clear. The aim of present study was to investigate possible apoptotic mechanisms induced by cinobufacini in HCC cell lines HepG(2) and Bel-7402. We found that cinobufacini treatment resulted in a significant decrease in cell proliferation and induced apoptotic cell death with the increase of treatment time. It indicated that cinobufacini-induced apoptosis was associated with mitochondria-mediated pathway including the loss of mitochondrial membrane potential (Δψm), the increase of Bax/Bcl-2 ratio, cytochrome c release, caspase-9 and caspase-3 activation, and poly(ADP-ribose) polymerase (PARP) degradation. Additionally, cinobufacini also activated Fas-mediated apoptosis pathway obviously as evident by an increase in Fas expression, and caspase-8 and caspase-10 activation. Moreover, the BH3-only protein Bid was cleaved into a truncated Bid (tBid) after cinobufacini treatment. Taken together, these data suggested cinobufacini could induce apoptosis of HCC cells through mitochondria- and Fas-mediated caspase-dependent pathways with the increase of treatment time, which might provide an experimental evidence for cinobufacini treatment of HCC.