Monitoring drug induced apoptosis and treatment sensitivity in non-small cell lung carcinoma using dielectrophoresis

Non-invasive real time methods for characterizing biomolecular events that contribute towards apoptotic kinetics would be of significant importance in the field of cancer biology. Effective drug-induced apoptosis is an important factor for establishing the relationship between cancer genetics and treatment sensitivity. The objective of this study was to develop a non-invasive technique to characterize cancer cells that are undergoing drug-induced apoptosis. We used dielectrophoresis to determine apoptotic cells as early as 2 h post drug treatment as compared to 24 h with standard flow cytometry method using non-small cell lung cancer (NSCLC) adenocarcinoma cell line (HCC1833) as a study model. Our studies have shown significant differences in apoptotic cells by chromatin condensation, formation of apoptotic bodies and exposure of phosphatidylserine (PS) on the extracellular surface when the cells where treated with a potent Bcl-2 family inhibitor drug (ABT-263). Time lapse dielectrophoretic studies were performed over 24 h period after exposure to ABT-263 at clinically relevant concentrations. The dielectrophoretic studies were compared to Annexin-V FITC flow assay for the detection of PS in mid-stage apoptosis using flow cytometry. As a result of physical and biochemical changes, inherent dielectric properties of cells undergoing varying stages of apoptosis showed amplified changes in their cytoplasmic and membrane capacitance. In addition, zeta potential of these fixed isolated cells was measured to obtain direct correlation to biomolecular events.     

Bcl-2/Bcl-xL inhibitor ABT-263 overcomes hypoxia-driven radioresistence and improves radiotherapy

Hypoxia, a characteristic of most human solid tumors, is a major obstacle to successful radiotherapy. While moderate acute hypoxia increases cell survival, chronic cycling hypoxia triggers adaptation processes, leading to the clonal selection of hypoxia-tolerant, apoptosis-resistant cancer cells. Our results demonstrate that exposure to acute and adaptation to chronic cycling hypoxia alters the balance of Bcl-2 family proteins in favor of anti-apoptotic family members, thereby elevating the apoptotic threshold and attenuating the success of radiotherapy. Of note, inhibition of Bcl-2 and Bcl-xL by BH3-mimetic ABT-263 enhanced the sensitivity of HCT116 colon cancer and NCI-H460 lung cancer cells to the cytotoxic action of ionizing radiation. Importantly, we observed this effect not only in normoxia, but also in severe hypoxia to a similar or even higher extent. ABT-263 furthermore enhanced the response of xenograft tumors of control and hypoxia-selected NCI-H460 cells to radiotherapy, thereby confirming the beneficial effect of combined treatment in vivo. Targeting the Bcl-2 rheostat with ABT-263, therefore, is a particularly promising approach to overcome radioresistance of cancer cells exposed to acute or chronic hypoxia with intermittent reoxygenation. Moreover, we found intrinsic as well as ABT-263- and irradiation-induced regulation of Bcl-2 family members to determine therapy sensitivity. In this context, we identified Mcl-1 as a resistance factor that interfered with apoptosis induction by ABT-263, ionizing radiation, and combinatorial treatment. Collectively, our findings provide novel insights into the molecular determinants of hypoxia-mediated resistance to apoptosis and radiotherapy and a rationale for future therapies of hypoxic and hypoxia-selected tumor cell fractions.Subject terms: Cancer microenvironment, Radiotherapy, Cell biology     

Combining Paclitaxel with ABT-263 Has a Synergistic Effect on Paclitaxel Resistant Prostate Cancer Cells

We assessed the capability of paclitaxel, one of the taxanes, to induce death in two prostate cancer lines, LNCaP and PC3. Paclitaxel drove an apoptotic pathway in LNCaP, but not in PC3 cells, in response to G2/M arrest. An examination of the levels of anti-apoptotic proteins revealed that Bcl-xl was much higher in PC3 cells than in LNCaP cells and Bcl2 could be detected only in PC3 cells, not in LNCaP cells. Knocking down Bcl-xl enhanced paclitaxel-induced apoptosis in LNCaP cells, while we were unable to knock down Bcl-xl efficiently in PC3 cells. Significantly, a comparison of ABT-263, a specific inhibitor of Bcl2 and Bcl-xl, with ABT-199, a Bcl2 selective inhibitor, disclosed that only ABT-263, not ABT-199, could induce apoptosis in LNCaP and PC3 cells. The results indicate that Bcl-xl has a protective role against paclitaxel-induced apoptosis in LNCaP and PC3 cells, and its overexpression causes the paclitaxel resistance seen in PC3 cells. Interestingly, combined paclitaxel with ABT-263 to treat LNCaP and PC3 cells demonstrated synergistic apoptosis activation, indicating that ABT-263 could enhance paclitaxel-induced apoptosis in LNCaP cells and overcome Bcl-xl overexpression to trigger paclitaxel-induced apoptosis in PC3 cells. We also observed that the activation of apoptosis in LNCaP cells was more efficient than in PC3 cells in response to paclitaxel plus ABT-263 or to ABT-263 alone, suggesting that the apoptosis pathway in PC3 cells might have further differences from that in LNCaP cells even after Bcl-xl overexpression is accounted for.     

HCC cells with high levels of Bcl-2 are resistant to ABT-737 via activation of the ROS–JNK–autophagy pathway

The Bcl-2 inhibitor ABT-737 has shown promising antitumor efficacy in vivo and in vitro. However, some reports have demonstrated that HCC cells are resistant to ABT-737, and the corresponding molecular mechanisms of this resistance are not well known. In this study, we found that HCC cells with high levels of Bcl-2 were markedly resistant to ABT-737 compared to HCC cells with low levels of Bcl-2. In HCC cells with high levels of Bcl-2 (such as HepG2 cells), ABT-737 induced protective autophagy via the sequential triggering of reactive oxygen species (ROS) accumulation, short-term activation of JNK, enhanced phosphorylation of Bcl-2, and dissociation of Beclin 1 from the Bcl-2/Beclin 1 complex. Moreover, autophagy suppressed the overactivation of the ROS–JNK pathway and protected against apoptosis. In HCC cells with low levels of Bcl-2 (i.e., Huh7 cells), ABT-737 induced apoptosis via the sequential stimulation of ROS, sustained activation of JNK, enhanced translocation of Bax from the cytosol to the mitochondria, and release of cytochrome c. In sum, this study indicated that the activation of the ROS–JNK–autophagy pathway may be an important mechanism by which HCC cells with high levels of Bcl-2 are resistant to ABT-737.     

Novel combination of Celecoxib and proteasome inhibitor MG132 provides synergistic antiproliferative and proapoptotic effects in human liver tumor cells

Molecular targeted therapy has shown promise as a treatment for advanced hepatocellular carcinoma (HCC). Celecoxib (Celebrex®) exhibits antitumor effects in human HCC cells, and its mechanism of action is mediated either by its ability to inhibit cyclooxygenase 2 (COX-2) or by a number of various other COX-2 independent effects. Proteasome inhibitors (PIs) can exert cell growth inhibitory and apoptotic effects in different tumor cell types, including HCC cells. The present study examined the interaction between celecoxib and the PI MG132 in two human liver tumor cell lines HepG2 and HA22T/VGH. Our data showed that each inhibitor reduced proliferation and induced apoptosis in a dose-dependent manner in both cell lines. Moreover, the combination of celecoxib with MG132 synergistically inhibited cell viability and increased apoptosis, as documented by caspase 3 and 7 activation, PARP cleavage, and down-regulation of Bcl-2. Celecoxib and MG132, both alone and synergistically in combination, induced expression of the endoplasmic reticulum (ER) stress genes ATF4, CHOP, TRB3 and promoted the splicing of XBP1 mRNA. Knockdown of TRB3 mRNA expression by small interference RNA significantly decreased combination-induced cell death in HA22T/VGH cells, whereas it increased combination-induced cell death in HepG2 cells, suggesting that activation of the ER stress response might have either a detrimental or a protective role in liver tumor cell survival. In conclusion, our data indicate that combination treatment with celecoxib and MG132 resulted in synergistic antiproliferative and proapoptotic effects against liver cancer cells, providing a rational basis for the clinical use of this combination in the treatment of liver cancer.     

Anticancer compound ABT-263 accelerates apoptosis in virus-infected cells and imbalances cytokine production and lowers survival rates of infected mice

ABT-263 and its structural analogues ABT-199 and ABT-737 inhibit B-cell lymphoma 2 (Bcl-2), BCL2L1 long isoform (Bcl-xL) and BCL2L2 (Bcl-w) proteins and promote cancer cell death. Here, we show that at non-cytotoxic concentrations, these small molecules accelerate the deaths of non-cancerous cells infected with influenza A virus (IAV) or other viruses. In particular, we demonstrate that ABT-263 altered Bcl-xL interactions with Bcl-2 antagonist of cell death (Bad), Bcl-2-associated X protein (Bax), uveal autoantigen with coiled-coil domains and ankyrin repeats protein (UACA). ABT-263 thereby activated the caspase-9-mediated mitochondria-initiated apoptosis pathway, which, together with the IAV-initiated caspase-8-mediated apoptosis pathway, triggered the deaths of IAV-infected cells. Our results also indicate that Bcl-xL, Bcl-2 and Bcl-w interact with pattern recognition receptors (PRRs) that sense virus constituents to regulate cellular apoptosis. Importantly, premature killing of IAV-infected cells by ABT-263 attenuated the production of key pro-inflammatory and antiviral cytokines. The imbalance in cytokine production was also observed in ABT-263-treated IAV-infected mice, which resulted in an inability of the immune system to clear the virus and eventually lowered the survival rates of infected animals. Thus, the results suggest that the chemical inhibition of Bcl-xL, Bcl-2 and Bcl-w could potentially be hazardous for cancer patients with viral infections.     

Resistance to butyrate impairs bile acid-induced apoptosis in human colon adenocarcinoma cells via up-regulation of Bcl-2 and inactivation of Bax

A critical risk factor in colorectal carcinogenesis and tumor therapy is the resistance to the apoptotic effects of different compounds from the intestinal lumen, among them butyrate (main regulator of colonic epithelium homeostasis). Insensitivity to butyrate-induced apoptosis yields resistance to other agents, as bile acids or chemotherapy drugs, allowing the selective growth of malignant cell subpopulations. Here we analyze bile acid-induced apoptosis in a butyrate-resistant human colon adenocarcinoma cell line (BCS-TC2.BR2) to determine the mechanisms that underlay the resistance to these agents in comparison with their parental butyrate-sensitive BCS-TC2 cells. This study demonstrates that DCA and CDCA still induce apoptosis in butyrate-resistant cells through increased ROS production by activation of membrane-associated enzymes and subsequent triggering of the intrinsic mitochondrial apoptotic pathway. Although this mechanism is similar to that described in butyrate-sensitive cells, cell viability is significantly higher in resistant cells. Moreover, butyrate-resistant cells show higher Bcl-2 levels that confer resistance to bile acid-induced apoptosis sequestering Bax and avoiding Bax-dependent pore formation in the mitochondria. We have confirmed that this resistance is reverted using the Bcl-2 inhibitor ABT-263, thus demonstrating that the lower sensitivity of butyrate-resistant cells to the apoptotic effects of bile acids is mainly due to increased Bcl-2 levels.     

Salirasib sensitizes hepatocarcinoma cells to TRAIL-induced apoptosis through DR5 and survivin-dependent mechanisms

Ras activation is a frequent event in human hepatocarcinoma that may contribute to resistance towards apoptosis. Salirasib is a ras and mTOR inhibitor that induces a pro-apoptotic phenotype in human hepatocarcinoma cell lines. In this work, we evaluate whether salirasib sensitizes those cells to TRAIL-induced apoptosis. Cell viability, cell death and apoptosis were evaluated in vitro in HepG2, Hep3B and Huh7 cells treated with DMSO, salirasib and YM155 (a survivin inhibitor), alone or in combination with recombinant TRAIL. Our results show that pretreatment with salirasib sensitized human hepatocarcinoma cell lines, but not normal human hepatocytes, to TRAIL-induced apoptosis. Indeed, FACS analysis showed that 25 (Huh7) to 50 (HepG2 and Hep3B) percent of the cells treated with both drugs were apoptotic. This occurred through activation of the extrinsic and the intrinsic pathways, as evidenced by a marked increase in caspase 3/7 (five to ninefold), caspase 8 (four to sevenfold) and caspase 9 (eight to 12-fold) activities in cells treated with salirasib and TRAIL compared with control. Survivin inhibition had an important role in this process and was sufficient to sensitize hepatocarcinoma cells to apoptosis. Furthermore, TRAIL-induced apoptosis in HCC cells pretreated with salirasib was dependent on activation of death receptor (DR) 5. In conclusion, salirasib sensitizes hepatocarcinoma cells to TRAIL-induced apoptosis by a mechanism involving the DR5 receptor and survivin inhibition. These results in human hepatocarcinoma cell lines and primary hepatocytes provide a rationale for testing the combination of salirasib and TRAIL agonists in human hepatocarcinoma.     

Efficient elimination of cancer cells by deoxyglucose-ABT-263/737 combination therapy

As single agents, ABT-263 and ABT-737 (ABT), molecular antagonists of the Bcl-2 family, bind tightly to Bcl-2, Bcl-xL and Bcl-w, but not to Mcl-1, and induce apoptosis only in limited cell types. The compound 2-deoxyglucose (2DG), in contrast, partially blocks glycolysis, slowing cell growth but rarely causing cell death. Injected into an animal, 2DG accumulates predominantly in tumors but does not harm other tissues. However, when cells that were highly resistant to ABT were pre-treated with 2DG for 3 hours, ABT became a potent inducer of apoptosis, rapidly releasing cytochrome c from the mitochondria and activating caspases at submicromolar concentrations in a Bak/Bax-dependent manner. Bak is normally sequestered in complexes with Mcl-1 and Bcl-xL. 2DG primes cells by interfering with Bak-Mcl-1 association, making it easier for ABT to dissociate Bak from Bcl-xL, freeing Bak to induce apoptosis. A highly active glucose transporter and Bid, as an agent of the mitochondrial apoptotic signal amplification loop, are necessary for efficient apoptosis induction in this system. This combination treatment of cancer-bearing mice was very effective against tumor xenograft from hormone-independent highly metastasized chemo-resistant human prostate cancer cells, suggesting that the combination treatment may provide a safe and effective alternative to genotoxin-based cancer therapies.     

Human Pluripotent Stem Cells and Derived Neuroprogenitors Display Differential Degrees of Susceptibility to BH3 Mimetics ABT-263, WEHI-539 and ABT-199

Human embryonic stem cells (hESCs) are hypersensitive to genotoxic stress and display lower survival ability relative to their differentiated progeny. Herein, we attempted to investigate the source of this difference by comparing the DNA damage responses triggered by the topoisomerase I inhibitor camptothecin, in hESCs, human induced pluripotent stem cells (hiPSCs) and hESCs-derived neuroprogenitors (NP). We observed that upon camptothecin exposure pluripotent stem cells underwent apoptosis more swiftly and at a higher rate than differentiated cells. However, the cellular response encompassing ataxia-telangiectasia mutated kinase activation and p53 phosphorylation both on serine 15 as well as on serine 46 resulted very similar among the aforementioned cell types. Importantly, we observed that hESCs and hiPSCs express lower levels of the anti-apoptotic protein Bcl-2 than NP. To assess whether Bcl-2 abundance could account for this differential response we treated cells with ABT-263, WEHI-539 and ABT-199, small molecules that preferentially target the BH3-binding pocket of Bcl-xL and/or Bcl-2 and reduce their ability to sequester pro-apoptotic factors. We found that in the absence of stress stimuli, NP exhibited a higher sensitivity to ABT- 263 and WEHI-539 than hESCs and hiPSCs. Conversely, all tested cell types appeared to be highly resistant to the Bcl-2 specific inhibitor, ABT-199. However, in all cases we determined that ABT-263 or WEHI-539 treatment exacerbated camptothecin-induced apoptosis. Importantly, similar responses were observed after siRNA-mediated down-regulation of Bcl-xL or Bcl-2. Taken together, our results suggest that Bcl-xL contrary to Bcl-2 contributes to ensure cell survival and also functions as a primary suppressor of DNA double-strand brake induced apoptosis both in pluripotent and derived NP cells. The emerging knowledge of the relative dependence of pluripotent and progenitor cells on Bcl-2 and Bcl-xL activities may help to predict cellular responses and potentially manipulate these cells for therapeutic purposes in the near future.     

Characterization and phytochemical constituents of Periploca hydaspidis Falc crude extract and its anticancer activities

The current study aims to investigate the anticancer potential of Periploca hydaspidis extracts against HCCLM3 and MDA-MB 231 cell lines with invasive properties and to identify molecular targets underlying its action mechanism. Cytotoxic screening of plant extracts was done via MTT assay against liver and breast cancer cell lines and GC/MS of the best cytotoxic fraction was performed to identify its chemical composition. Flow cytometry detected apoptosis and cell-cycle changes after drug treatment. The specified cells were studied for migration and invasion potential along with performing western blot analysis of proteins involved in apoptosis, cell-cycle, metastasis, and MAPK (Mitogen-activated protein kinase) cell-signaling pathway. The results revealed the crude methanol (PHM) fraction of P. hydaspidis shown dose and time dependent cell-proliferative inhibition response. GC/MS analysis detected 54 compounds of which fatty acids (29.8%), benzenoids (15.7%), and esters (14.3%) constituted the bulk. The inhibitory effect against cancer cells was linked with cell-cycle arrest at G0/G1 phase, induction of apoptosis, reduced migration and invasion capabilities post treatment. PHM induced apoptosis via downregulation of anti-apoptotic (survivin, B-cell lymphoma Extra-large; BCL-XL, X-linked inhibitor of apoptosis protein; XIAP, Myelocytomatosis; C-myc), metastatic (Matrix metallopeptidases 9/2; MMP9/2), and cell-cycle regulatory (cyclin D1 and E) proteins, whereas upregulation of pro-apoptotic proteins (Bcl-2 homologous antagonist/killer; BAK, Bcl-2-Associate X protein; BAX, cleaved caspases; 3,7,8,9, and PARP) and activation of MAPK (Jun amino-terminal kinase; JNK and P38) pathway. P38 was needed for PHM-induced apoptosis, where the inhibition of P38 by pharmacological inhibitor (SB239063) diminished the apoptotic effects. Overall, our results conclude that PHM can inhibit cell-proliferation and induce apoptotic effects by activation of P38 MAPK cell-signaling pathway. This suggests the methanol fraction of P. hydaspidis (PHM) to have anticancer compounds, potentially useful for treating liver and breast cancer. In future, one-step advance studies of PHM regarding its role in metastatic inhibition, immune response modulation for reducing tumor, and inducing apoptosis in suitable animal models would be an interesting and promising research area.     

Upregulating Noxa by ER Stress,Celastrol Exerts Synergistic Anti-Cancer Activity in Combination with ABT-737 in Human Hepatocellular Carcinoma Cells

The human hepatocellular carcinoma (HCC) represents biologically aggressive and chemo-resistant cancers. Owing to the low affinity with the apoptotic factor Mcl-1, the BH3 mimetic drug ABT-737 failed to exert potent cancer-killing activities in variety of cancer models including HCC. The current study demonstrated that combining ABT-737 and Celastrol synergistically suppressed HCC cell proliferation, and induced apoptosis which was accompanied with the activation of caspase cascade and release of cytochrome c from mitochondria. Further study revealed that the enhanced Noxa caused by Celastrol was the key factor for the synergy, since small interfering RNA-mediated knockdown of Noxa expression in HCC cells resulted in decreased apoptosis and attenuated anti-proliferative effects of the combination. In addition, our study unraveled that, upon Celastrol exposure, the activation of endoplasmic reticulum (ER) stress, specifically, the eIF2α-ATF4 pathway played indispensable roles in the activation of Noxa, which was validated by the observation that depletion of ATF4 significantly abrogated the Noxa elevation by Celastrol. Our findings highlight a novel signaling pathway through which Celastrol increase Noxa expression, and suggest the potential use of ATF4-mediated regulation of Noxa as a promising strategy to improve the anti-cancer activities of ABT-737.     

The Stress Protein BAG3 Stabilizes Mcl-1 Protein and Promotes Survival of Cancer Cells and Resistance to Antagonist ABT-737

Members of the Bcl-2 family of proteins are important inhibitors of apoptosis in human cancer and are targets for novel anticancer agents such as the Bcl-2 antagonists, ABT-263 (Navitoclax), and its analog ABT-737. Unlike Bcl-2, Mcl-1 is not antagonized by ABT-263 or ABT-737 and is considered to be a major factor in resistance. Also, Mcl-1 exhibits differential regulation when compared with other Bcl-2 family members and is a target for anticancer drug discovery. Here, we demonstrate that BAG3, an Hsp70 co-chaperone, protects Mcl-1 from proteasomal degradation, thereby promoting its antiapoptotic activity. Using neuroblastoma cell lines, with a defined Bcl-2 family dependence, we found that BAG3 expression correlated with Mcl-1 dependence and ABT-737 resistance. RNA silencing of BAG3 led to a marked reduction in Mcl-1 protein levels and overcame ABT-737 resistance in Mcl-1-dependent cells. In ABT-737-resistant cells, Mcl-1 co-immunoprecipitated with BAG3, and loss of Mcl-1 after BAG3 silencing was prevented by proteasome inhibition. BAG3 and Mcl-1 were co-expressed in a panel of diverse cancer cell lines resistant to ABT-737. Silencing BAG3 reduced Mcl-1 protein levels and overcame ABT-737 resistance in several of the cell lines, including triple-negative breast cancer (MDA-MB231) and androgen receptor-negative prostate cancer (PC3) cells. These studies identify BAG3-mediated Mcl-1 stabilization as a potential target for cancer drug discovery.     

YM155 sensitizes non-small cell lung cancer cells to EGFR-tyrosine kinase inhibitors through the mechanism of autophagy induction

Resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs), such as erlotinib and gefitinib, is a major clinical problem in the treatment of patients with non-small cell lung cancer (NSCLC). YM155 is a survivin small molecule inhibitor and has been demonstrated to induce cancer cell apoptosis and autophagy. EGFR-TKIs have been known to induce cancer cell autophagy. In this study, we showed that YM155 markedly enhanced the sensitivity of erlotinib to EGFR-TKI resistant NSCLC cell lines H1650 (EGFR exon 19 deletion and PTEN loss) and A549 (EGFR wild type and KRAS mutation) through inducing autophagy-dependent apoptosis and autophagic cell death. The effects of YM155 combined with erlotinib on apoptosis and autophagy inductions were more obvious than those of YM155 in combination with survivin knockdown by siRNA transfection, suggesting that YM155 induced autophagy and apoptosis in the NSCLC cells partially depend on survivin downregulation. Meanwhile, we found that the AKT/mTOR pathway is involved in modulation of survivin downregulation and autophagy induction caused by YM155. In addition, YM155 can induce DNA damage in H1650 and A549 cell lines. Moreover, combining erlotinib further augmented DNA damage by YM155, which were retarded by autophagy inhibitor 3MA, or knockdown of autophagy-related protein Beclin 1, revealing that YM155 induced DNA damage is autophagy-dependent. Similar results were also observed in vivo xenograft experiments. Therefore, combination of YM155 and erlotinib offers a promising therapeutic strategy in NSCLC with EGFR-TKI resistant phenotype.     

Effect of simvastatin on the resistance to EGFR tyrosine kinase inhibitors in a non-small cell lung cancer with the T790M mutation of EGFR

Although non-small cell lung cancer (NSCLC) tumors with activating mutations in the epidermal growth factor receptor (EGFR) are highly responsive to EGFR tyrosine kinase inhibitors (TKIs) including gefitinib and erlotinib, development of acquired resistance is almost inevitable. Statins show antitumor activity, but it is unknown whether they can reverse EGFR-TKIs resistance in NSCLC with the T790M mutation of EGFR. This study investigated overcoming resistance to EGFR-TKI using simvastatin. We demonstrated that addition of simvastatin to gefitinib enhanced caspase-dependent apoptosis in T790M mutant NSCLC cells. Simvastatin also strongly inhibited AKT activation, leading to suppression of β-catenin activity and the expression of its targets, survivin and cyclin D1. Both insulin treatment and AKT overexpression markedly increased p-β-catenin and survivin levels, even in the presence of gefitinib and simvastatin. However, inhibition of AKT by siRNA or LY294002 treatment decreased p-β-catenin and survivin levels. To determine the role of survivin in simvastatin-induced apoptosis of gefitinib-resistant NSCLC, we showed that the proportion of apoptotic cells following treatment with survivin siRNA and the gefitinib–simvastatin combination was greater than the theoretical additive effects, whereas survivin up-regulation could confer protection against gefitinib and simvastatin-induced apoptosis. Similar results were obtained in erlotinib and simvastatin-treated HCC827/ER cells. These findings suggest that survivin is a key molecule that renders T790M mutant NSCLC cells resistant to apoptosis induced by EGFR-TKIs and simvastatin. Overall, these data indicate that simvastatin may overcome EGFR-TKI resistance in T790M mutant NSCLCs via an AKT/β-catenin signaling-dependent down-regulation of survivin and apoptosis induction.     

Histone deacetylase inhibitors facilitate dihydroartemisinin-induced apoptosis in liver cancer in vitro and in vivo

Liver cancer ranks in prevalence and mortality among top five cancers worldwide. Accumulating interests have been focused in developing new strategies for liver cancer treatment. We have previously showed that dihydroartemisinin (DHA) exhibited antitumor activity towards liver cancer. In this study, we demonstrated that histone deacetylase inhibitors (HDACi) significantly augmented the antineoplastic effect of DHA via increasing apoptosis in vitro and in vivo. Inhibition of ERK phosphorylation contributed to DHA-induced apoptosis, due to the fact that inhibitor of ERK phosphorylation (PD98059) increased DHA-induced apoptosis. Compared with DHA alone, the combined treatment with DHA and HDACi reduced mitochondria membrane potential, released cytochrome c into cytoplasm, increased p53 and Bak, decreased Mcl-1 and p-ERK, activated caspase 3 and PARP, and induced apoptotic cells. Furthermore, we showed that HDACi pretreatment facilitated DHA-induced apoptosis. In Hep G2-xenograft carrying nude mice, the intraperitoneal injection of DHA and SAHA resulted in significant inhibition of xenograft tumors. Results of TUNEL and H&E staining showed more apoptosis induced by combined treatment. Immunohistochemistry data revealed the activation of PARP, and the decrease of Ki-67, p-ERK and Mcl-1. Taken together, our data suggest that the combination of HDACi and DHA offers an antitumor effect on liver cancer, and this combination treatment should be considered as a promising strategy for chemotherapy.     

甘氨鹅脱氧胆酸钠通过MAPK/ERK1/2介导Bcl-2在Ser70位点的磷酸化引起人肝细胞癌的抗药

B细胞淋巴瘤-2（Bcl-2）是一种重要的抗凋亡蛋白质,在多种人类肿瘤中普遍过表达。甘氨鹅脱氧胆酸钠（GCDA）与消化道肿瘤的发生发展密切相关,并能介导肝癌细胞对化疗药物的抵抗。本文旨在探讨在GCDA介导的人肝细胞癌（HCC）耐药性中Bcl-2的作用及其机制。本研究以肝癌细胞系为研究对象,Western印迹结果显示,Bcl-2在多种肝癌细胞系中均有表达。设计靶向Bcl-2的siRNA沉默HCC细胞系内源性Bcl-2的表达,发现Bcl-2沉默之后促进了化疗药物5-FU介导的HCC细胞凋亡。机制上,GCDA可介导Bcl-2在Ser70位点的磷酸化,而Ser70位点的磷酸化能够被PD98059（MAPK/ERK1/2抑制剂）所抑制。构建huBcl2-WT和huBcl2-S70A真核表达载体,脂质体转染HCC细胞系。用Annexin V-FITC/PI流式细胞术检测凋亡细胞。结果显示,huBcl2-WT过表达能抑制5 FU介导的凋亡,S70位点失活突变成A后,Bcl-2的过表达不能抑制5-FU介导的凋亡。本研究提示,GCDA通过MAPK/ERK1/2通路介导的Bcl-2 Ser70位点的磷酸化,在肝癌细胞的存活和抗药中发挥重要作用。抑制Bcl-2能够促进化疗药物5-FU介导的HCC细胞凋亡,该结果为治疗GCDA介导的耐药性肝癌提供新的思路。     

甘氨鹅脱氧胆酸钠通过MAPK/ERK1/2介导Bcl-2在Ser70位点的磷酸化引起人肝细胞癌的抗药

B细胞淋巴瘤-2（Bcl-2）是一种重要的抗凋亡蛋白质,在多种人类肿瘤中普遍过表达。甘氨鹅脱氧胆酸钠（GCDA）与消化道肿瘤的发生发展密切相关,并能介导肝癌细胞对化疗药物的抵抗。本文旨在探讨在GCDA介导的人肝细胞癌（HCC）耐药性中Bcl-2的作用及其机制。本研究以肝癌细胞系为研究对象,Western印迹结果显示,Bcl-2在多种肝癌细胞系中均有表达。设计靶向Bcl-2的siRNA沉默HCC细胞系内源性Bcl-2的表达,发现Bcl-2沉默之后促进了化疗药物5-FU介导的HCC细胞凋亡。机制上,GCDA可介导Bcl-2在Ser70位点的磷酸化,而Ser70位点的磷酸化能够被PD98059（MAPK/ERK1/2抑制剂）所抑制。构建huBcl2-WT和huBcl2-S70A真核表达载体,脂质体转染HCC细胞系。用Annexin V-FITC/PI流式细胞术检测凋亡细胞。结果显示,huBcl2-WT过表达能抑制5 FU介导的凋亡,S70位点失活突变成A后,Bcl-2的过表达不能抑制5-FU介导的凋亡。本研究提示,GCDA通过MAPK/ERK1/2通路介导的Bcl-2 Ser70位点的磷酸化,在肝癌细胞的存活和抗药中发挥重要作用。抑制Bcl-2能够促进化疗药物5-FU介导的HCC细胞凋亡,该结果为治疗GCDA介导的耐药性肝癌提供新的思路。