Adenovirus 5 E1A enhances histone deacetylase inhibitors-induced apoptosis through Egr-1-mediated Bim upregulation

MRCK as a Potential Target for Claudin-Low Subtype of Breast Cancer

To find new molecular targets for triple negative breast cancer (TNBC), we analyzed a large-scale drug screening dataset based on breast cancer subtypes. We discovered that BDP-9066, a specific MRCK inhibitor (MRCKi), may be an effective drug against TNBC. After confirming the efficacy and specificity of BDP-9066 against TNBC in vitro and in vivo, we further analyzed the underlying mechanism of specific activity of BDP-9066 against TNBC. Comparing the transcriptome of BDP-9066-sensitive and -resistant cells, the activation of the focal adhesion and YAP/TAZ pathway were found to play an important role in the sensitive cells. Furthermore, YAP/TAZ is indeed repressed by BDP-9066 in the sensitive cells, and active form of YAP suppresses the effects of BDP-9066. YAP/TAZ expression and activity are high in TNBC, especially the Claudin-low subtype, consistent with the expression of focal adhesion-related genes. Interestingly, NF-κB functions downstream of YAP/TAZ in TNBC cells and is suppressed by BDP-9066. Furthermore, the PI3 kinase pathway adversely affected the effects of BDP-9066 and that alpelisib, a PI3 kinase inhibitor, synergistically increased the effects of BDP-9066, in PIK3CA mutant TNBC cells. Taken together, we have shown for the first time that MRCKi can be new drugs against TNBC, particularly the Claudin-low subtype.

Early Growth Response-1: Friend or Foe in the Heart?

Cardiovascular disease is a major cause of mortality and morbidity worldwide. Early growth response-1 (Egr-1) plays a critical regulatory role in a range of experimental models of cardiovascular diseases. Egr-1 is an immediate-early gene and is upregulated by various stimuli including shear stress, oxygen deprivation, oxidative stress and nutrient deprivation. However, recent research suggests a new, underexplored cardioprotective side of Egr-1. The main purpose of this review is to explore and summarise the dual nature of Egr-1 in cardiovascular pathobiology.

Ras Participates in the Regulation of the Stability of Adenoviral Protein E1A via MAP-kinase ERK

The E1A adenoviral protein required for the initiation of the viral life cycle is being actively studied as a sensitizing agent in the combination therapy of cancer, and tumors with activated Ras in particular. We investigated the role played by the Ras signaling pathway in the regulation of E1A protein stability and showed that overexpression of activated Ras increases the basal level of E1A, but enhances the degradation of the E1A protein under treatment with histone deacetylase inhibitors (HDIs). It has been found that the MAP kinase ERK is the key factor in E1A stabilization, and ERK inactivation upon HDI treatment reduces the E1A protein level. Our results indicate that the combination treatment of tumors with activated Ras using adenoviral E1A and HDI has limitations attributed to intense HDI-dependent degradation of E1A. Nevertheless, the established contribution of ERK kinase to the regulation of E1A stability can be used to search for new effective drug combinations based on the adenoviral E1A protein.

Expression of Adenoviral E1A in Transformed Cells as an Additional Factor of HDACi-Dependent FoxO Regulation

The adenoviral early region 1A (E1A) protein has proapoptotic and angiogenic activity, along with its chemosensitizing effect, making it the focus of increased interest in the context of cancer therapy. It was previously shown that E1A-induced chemosensitization to different drugs, including histone deacetylases inhibitors (HDACi), appears to be mediated by Forkhead box O (FoxO) transcription factors. In this study, we explore the relationship between E1A expression and the modulation of FoxO activity with HDACi sodium butyrate (NaBut). We show here that the basal FoxO level is elevated in E1A-expressing cells. Prolonged NaBut treatment leads to the inhibition of the FoxO expression and activity in E1A-expressing cells. However, in E1A-negative cells, NaBut promotes the transactivation ability of FoxO over time. A more detailed investigation revealed that the NaBut-induced decrease of FoxO activity in E1A-expressing cells is due to the NaBut-dependent decrease in E1A expression. Therefore, NaBut-induced inhibition of FoxO in E1A-positive cells can be overcome under unregulated overexpression of E1A. Remarkably, the CBP/p300-binding domain of E1Aad5 is responsible for stabilization of the FoxO protein. Collectively, these data show that the expression of E1A increases the FoxO stability but makes the FoxO level more sensitive to HDACi treatment.

Egr-1 is involved in coronary microembolization-induced myocardial injury via Bim/Beclin-1 pathway-mediated autophagy inhibition and apoptosis activation

Coronary microembolization (CME) substantially reduces the clinical benefits of myocardial reperfusion therapy. Autophagy and apoptosis participate in the pathophysiological processes of almost all cardiovascular diseases, including CME-induced myocardial injury, but the precise underlying mechanisms remain unclear. In the present study, we observed that Egr-1 expression was substantially increased after CME modeling. Inhibition of Egr-1 expression through the targeted delivery of rAAV9-Egr-1-shRNA improved cardiac function and reduced myocardial injury. The microinfarct size was also significantly smaller in the Egr-1 inhibitor group than in the CME group. These benefits were partially reversed by the autophagy inhibitor 3-MA. As shown in our previous study, autophagy in the myocardium was impaired after CME. Inhibition of Egr-1 expression in vivo restored the autophagy flux and reduced myocardial apoptosis, at least partially, by inhibiting the Egr-1/Bim/Beclin-1 pathway, as evidenced by the results of the western blot, RT-qPCR, and TUNEL staining. At the same time, TEM showed a dramatic increase in the number of typical autophagic vacuoles in the Egr-1 inhibitor group compared to the CME group. Based on these findings, the Egr-1/Bim/Beclin-1 pathway may be involved in CME-induced myocardial injury by regulating myocardial autophagy and apoptosis, and this pathway represents a potential therapeutic target in CME.

The potential role of YAP in Axl-mediated resistance to EGFR tyrosine kinase inhibitors

Yes-associated protein (YAP) is a transcription co-regulator downstream of the Hippo pathway, and plays a critical role in cancer. Although YAP regulation in the canonical Hippo pathway is well established, the Hippo-independent regulation of YAP is not well explored. Here, we showed the possible new mechanism of YAP regulation by the receptor tyrosine kinase Axl. Co-immunoprecipitation and Western blot analysis demonstrated the interaction between YAP and Axl, which was enhanced by Axl ligand Growth Arrest Specific 6 (GAS6) stimulation. Furthermore, we found that YAP is phosphorylated at tyrosine residues by GAS6 stimulation in vivo and Axl directly phosphorylates YAP in vitro. Axl overexpression or GAS6 stimulation increased YAP-mediated transcriptional activity, and YAP-mediated colony forming activity in soft agar was enhanced by co-expression of Axl. In EGFR tyrosine kinase inhibitor (TKI)-sensitive lung cancer cells, YAP protein was downregulated in response to TKI treatment, while overexpression of YAP attenuated TKI sensitivity, suggesting that YAP is a key determinant of TKI response. Moreover Axl overexpression reversed TKI-induced YAP downregulation and induced TKI-resistance, which was reversed by YAP knockdown, further supporting the notion that YAP functions downstream of Axl. Together, these findings suggest a novel role of YAP in Axl-mediated TKI resistance.

Overexpression of Adenoviral E1A Sensitizes E1A+Ras-Transformed Cells to the Action of Histone Deacetylase Inhibitors

The adenoviral E1A protein induces cell proliferation, transformation, and tumor formation in rodents, on the one hand. On the other hand, E1A expression increases cell sensitivity to a number of cytotoxic agents. Therefore, E1A is a candidate for use as a component of combination therapy for malignant tumors. The highest augmentation in the cytotoxic effect was achieved by a combined use of E1A expression and histone deacetylases (HDAC) inhibitors. However, HDAC inhibitors do not induce apoptosis in cells transformed with E1A and cHa-ras oncogenes. In this study, it was shown that HDAC inhibitors reduce the expression of adenoviral E1A. However, under unregulated E1A overexpression, these cells undergo apoptosis in the presence of HDAC inhibitors. Treatment with a HDAC inhibitor, sodium butyrate (NaBut), was shown to activate the anti-apoptotic factor NF-kB in control cells. However, NaBut was unable to modulate the NF-kB activity in E1A overexpressed cells. Therefore, it is fair to postulate that cells transformed with E1A and cHa-ras oncogenes avoid the apoptosis induced by HDAC inhibitors thanks to a NaBut-dependent decrease in E1A expression.

Histone deacetylase inhibitor trichostatin A sensitises cisplatin-resistant ovarian cancer cells to oncolytic adenovirus

Ovarian cancer is often termed a silent killer due to the late onset of symptoms. Whilst patients initially respond to chemotherapy, they rapidly develop chemo-resistance. Oncolytic adenoviruses (OAds) are promising anti-cancer agents engineered to "hijack" the unique molecular machinery of cancer cells enabling tumour-selective viral replication. This allows spread to adjacent cells and amplification of oncolysis within the tumour. OAds represent an excellent opportunity for ovarian cancer therapy via intra-peritoneal delivery, however the efficacy of OAds thus far is limited. Here, we evaluate chromatin (histone) modification in chemo-resistant cells and its relationship to Ad efficacy (wild-type or oncolytic Ad). In contrast to cisplatin-sensitive A2780 cells that show an efficient reduction of cell viability by Ad in the presence of cisplatin, cisplatin-resistant A2780/cp70 cells show diminishing Ad-mediated reduction of cell viability with escalating doses of cisplatin. Histone deacetylase (HDAC)-2 and to a lesser extent HDAC1 were up-regulated in cisplatin-resistant but not cisplatin-sensitive cells. Cisplatin-resistant cells treated with a pan-HDAC inhibitor trichostatin A (TsA) significantly enhanced Ad-mediated reduction of cell viability in the presence of cisplatin. Cells treated with TsA alone did not reduce cell viability suggesting these findings are Ad-dependent. Thus, we identify HDAC inhibition as a potential means to sensitise cisplatin-resistant ovarian cancer cells to virotherapies, an observation that may offer improved outcomes for patients with late stage, chemotherapy-resistant ovarian cancer.

MKP1 mediates chemosensitizer effects of E1a in response to cisplatin in non-small cell lung carcinoma cells

The adenoviral gene E1a is known to enhance the antitumor effect of cisplatin, one of the cornerstones of the current cancer chemotherapy. Here we study the molecular basis of E1a mediated sensitivity to cisplatin in an experimental model of Non-small cell lung cancer. Our data show how E1a blocks the induction of autophagy triggered by cisplatin and promotes the apoptotic response in resistant cells. Interestingly, at the molecular level, we present evidences showing how the phosphatase MKP1 is a major determinant of cisplatin sensitivity and its upregulation is strictly required for the induction of chemosensitivity mediated by E1a. Indeed, E1a is almost unable to promote sensitivity in H460, in which the high expression of MKP1 remains unaffected by E1a. However, in resistant cell as H1299, H23 or H661, which display low levels of MKP1, E1a expression promotes a dramatic increase in the amount of MKP1 correlating with cisplatin sensitivity. Furthermore, effective knock down of MKP1 in H1299 E1a expressing cells restores resistance to a similar extent than parental cells.

In summary, the present work reinforce the critical role of MKP1 in the cellular response to cisplatin highlighting the importance of this phosphatase in future gene therapy approach based on E1a gene.

Shikonin induces apoptosis of lung cancer cells via activation of FOXO3a/EGR1/SIRT1 signaling antagonized by p300

Shikonin derivatives exert powerful cytotoxic effects including induction of apoptosis. Here, we demonstrate the cytotoxic efficacy of shikonin in vivo in xenograft models, which did not affect body weight as well as its reduction of cell viability in vitro using several non-small cell lung cancer (NSCLC) cell lines. We found that inhibition of AKT by shikonin activated the forkhead box (FOX)O3a/early growth response protein (EGR)1 signaling cascade and enhanced the expression of the target gene Bim, leading to apoptosis in lung cancer cells. Overexpression of wild-type or a constitutively active mutant of FOXO3a enhanced shikonin-induced Bim expression. The NAD⁺-dependent histone deacetylase sirtuin (SIRT)1 amplified the pro-apoptotic effect by deacetylating FOXO3a, which induced EGR1 binding to the Bim promoter and activated Bim expression. Meanwhile, PI3K/AKT activity was enhanced, whereas that of FOXO3a was reduced and p300 was upregulated by treatment with a sublethal dose of shikonin. FOXO3a acetylation was enhanced by p300 overexpression, while shikonin-induced Bim expression was suppressed by p300 overexpression, which promoted cell survival. FOXO3a acetylation was increased by p300 overexpression and treatment with SIRT1 inhibitor, improving cell survival. In addition, shikonin-induced FOXO3a nuclear localization was blocked by AKT activation and SIRT1 inhibition, which blocked Bim expression and conferred resistance to the cytotoxic effects of shikonin. The EGR1 increase induced by shikonin was restored by pretreatment with SIRT1 inhibitor. These results suggest that shikonin induces apoptosis in some lung cancer cells via activation of FOXO3a/EGR1/SIRT1 signaling, and that AKT and p300 negatively regulate this process via Bim upregulation.

Dicer Elicits Paclitaxel Chemosensitization and Suppresses Cancer Stemness in Breast Cancer by Repressing AXL

Paclitaxel is a standard-of-care chemotherapy for breast cancer, despite the increasing recognition of its poor effectiveness in the treatment of patients with advanced disease. Here, we report that adenovirus-type 5 E1A-mediated elevation of the miRNA-processing enzyme Dicer is sufficient to enhance paclitaxel sensitization and reduce cancer stem-like cell properties in this setting. Elevating Dicer expression increased levels of the AXL kinase targeting miRNA miR-494, thereby repressing AXL expression to increase paclitaxel sensitivity. We found that Dicer expression was regulated at the transcription level by E1A, through activation of an MAPK14/CEBPα pathway. Our findings define a mechanism of E1A-mediated chemosensitization for paclitaxel, which is based upon the suppression of breast cancer stem-like cells, with potential implications for the diagnosis and treatment of breast cancer patients. Cancer Res; 76(13); 3916-28. ©2016 AACR.

AduPARE1A and gemcitabine combined treatment trigger synergistic antitumor effects in pancreatic cancer through NF-κB mediated uPAR activation

BACKGROUND

Combined treatment of oncolytic adenoviruses with chemotherapeutic agents is foreseen as a therapeutic option for cancer. Here we have investigated the potential to use gemcitabine in combination with the oncolytic adenovirus AduPARE1A to treat pancreatic cancer and evaluate the underlying mechanism.

METHODS

We treated pancreatic cancer cell lines BxPC-3 and PANC-1 with AduPARE1A and gemcitabine individually or in combination and analyzed cell viability, combination index, apoptosis and viral production. We also investigated the effects of the combination on tumor growth and mice survival in two xenograft models. Furthermore, we analyzed uPAR promoter activity from different uPAR-controlled adenovirus and studied NF-κB mediated effects.

RESULTS

Synergistic cell killing from the combination AduPARE1A/Gemcitabine was observed in BxPC-3 and PANC-1 cells. Moreover, the combination treatment produced therapeutic benefits over either individual modality in two mouse models bearing orthotopic tumors, showing reduced tumor progression and significant prolonged mouse survival. Mechanistic studies showed that the synergistic cell death was not due to an increase in viral replication but occurred through an enhancement of apoptotic cell death. Gemcitabine stimulation increased the transcription of uPAR-controlled transgenes through the induction of NF-κB acting on the uPAR promoter. Interestingly, NF-κB gemcitabine-mediated induction of AduPAR adenoviruses interfered with the activation of NF-κB regulated genes, probably as a result of an intracellular competition for NF-κB DNA binding. Consequently, AduPARE1A infection sensitized cells to gemcitabine-induced apoptosis in the combined treatment.

CONCLUSIONS

These data highlights the potential of the combination as a treatment modality for pancreatic cancer patients.

The anti-tumor activity of E1A and its implications in cancer therapy

The adenovirus type 5 E1A protein (E1A) plays a critical role in anti-cancer gene therapy and has been tested in clinical trials. The expression of E1A significantly reduces tumorigenesis, promotes cell death, and inhibits cancer cell mobility. Chemosensitization is one of the anti-tumor effects of E1A, increasing in vitro and in vivo sensitization of anti-cancer drugs, including cisplatin, gemcitabine, etoposide, doxorubicin, paclitaxel, and tumor necrosis factor-related apoptosis-inducing ligand and histone deacetylase inhibitors in different types of cancer cells. E1A also demonstrates anti-metastasis activity through various molecular mechanisms such as the repression of protease expression, suppression of HER2/neu and downregulation of microRNA (miR-520h). Moreover, E1A has been reported to reprogram transcription in tumor cells and stabilize tumor suppressors such as PP2A/C, p21 and p53. Because E1A plays a potentially significant role in anti-tumor therapy, there exists an urgent need to study the anti-cancer activities of E1A. This paper presents a review of our current understanding of the tumor-suppressive functions and molecular regulation of E1A, as well as the potential clinical applications of E1A.

Elements in the Development of a Production Process for Modified Vaccinia Virus Ankara

The production of several viral vaccines depends on chicken embryo fibroblasts or embryonated chicken eggs. To replace this logistically demanding substrate, we created continuous anatine suspension cell lines (CR and CR.pIX), developed chemically-defined media, and established production processes for different vaccine viruses. One of the processes investigated in greater detail was developed for modified vaccinia virus Ankara (MVA). MVA is highly attenuated for human recipients and an efficient vector for reactogenic expression of foreign genes. Because direct cell-to-cell spread is one important mechanism for vaccinia virus replication, cultivation of MVA in bioreactors is facilitated if cell aggregates are induced after infection. This dependency may be the mechanism behind our observation that a novel viral genotype (MVA-CR) accumulates with serial passage in suspension cultures. Sequencing of a major part of the genomic DNA of the new strain revealed point mutations in three genes. We hypothesize that these changes confer an advantage because they may allow a greater fraction of MVA-CR viruses to escape the host cells for infection of distant targets. Production and purification of MVA-based vaccines may be simplified by this combination of designed avian cell line, chemically defined media and the novel virus strain.

Tumor-specific cytolysis caused by an E1B55K-attenuated adenovirus in nasopharyngeal carcinoma is augmented by cisplatin

An E1B55K-attenuated adenovirus, dl1520, has been shown to replicate selectively in and lyse tumor cells. In this study, the antitumor activities of dl1520, alone or in combination with the chemotherapeutic agent cisplatin, were investigated in nasopharyngeal carcinoma (NPC) cells. The results demonstrated that dl1520 replicated in and destroyed NPC cells, and induced apoptosis in vitro. In a nude mouse xenograft model, dl1520 significantly inhibited the growth of NPC cell xenografts, and the viral replication was associated with tumor regression. Importantly, the antitumor activity of dl1520 was augmented by the addition of cisplatin both in vitro and in vivo, showing that dl1520 and cisplatin have a synergistic anti-NPC effect. These data suggest that dl1520 exerts an efficient anti-NPC activity through oncolysis and the induction of apoptosis, which is enhanced synergistically by cisplatin. These findings indicate that oncolytic viral therapeutics using the E1B55K-attenuated adenovirus dl1520 could be promising in the comprehensive treatment of NPC, especially in combination with platinum-based chemotherapy.

E1a promotes c-Myc-dependent replicative stress: implications in glioblastoma radiosensitization

The E1a gene from adenovirus is known to be a potent inducer of chemo/radiosensitivity in a wide range of tumors. However, the molecular bases of its radiosensitizer properties are still poorly understood. In an attempt to study this effect, U87MG cells, derived from a radio-resistant tumor as glioblastoma, where infected with lentivirus carrying E1a gene developing an acute sensitivity to ionizing radiation. The induction of radiosensitivity correlated with a marked G 2/M phase accumulation and a potent apoptotic response. Our findings demonstrate that c-Myc plays a pivotal role in E1a-associated radiosensitivity through the induction of a replicative stress situation, as our data support by genetic approaches, based in interference and overexpression in U87MG cells. In fact, we present evidence showing that Chk1 is a novel transcriptional target of E1a gene through the effect exerted by this adenoviral protein onto c-Myc. Moreover, c-Myc upregulation also explains the marked phosphorylation of H2AX associated to E1a expression in the absence of DNA damage. Indeed, all these observations were applicable to other experimental models, such as T98G, LN-405 and A172, rendering the same pattern in terms of radiosensitivity, cell cycle distribution, upregulation of Chk1, c-Myc, and phosphorylation pattern of H2AX. In summary, our data propose a novel mechanism to explain how E1a mediates radiosensitivity through the signaling axis E1a→c-Myc→ replicative stress situation. This novel mechanism of E1a-mediated radiosensitivity could be the key to open new possibilities in the current therapy of glioblastoma.

Heavy metal response of the heat shock protein 70 gene is mediated by duplicated heat shock elements and heat shock factor 1

Heavy metals induce transcription of a number of mammalian genes, but in most cases the mechanism of induction has not been well characterized. The human heat shock protein 70 gene (hsp70) is activated by several heavy metals such as Cd and Zn, and the heat shock element (HSE) has been proposed to mediate metal response by previous studies. However, it was observed that the lack of further upstream sequences rendered the hsp70 promoter unresponsive to metals. A detailed deletion analysis of the promoter revealed that the distal HSE-like sequence (dHSE) is required for heavy metal response. A supershift assay showed that the heat shock factor 1 (HSF1) recognized dHSE, as well as the proximal HSE (pHSE). An hsp70 promoter variant with a dHSE mutation that blocks HSF1 binding completely lost metal response, demonstrating that the HSF1/dHSE interaction is crucial. Another promoter variant with a similar pHSE mutation partially lost metal response, indicating that both HSEs are required for full activity. Knockdown of HSF1 dramatically reduced the metal response of hsp70, demonstrating its essential role. Furthermore, a reporter gene regulated by the human hsp70 promoter, which lacked metal response in HSF1-null mouse cells, acquired the response upon over-expression of a recombinant human HSF1. These results demonstrate that the duplicated HSEs and HSF1 constitute the mechanism for the heavy metal response of hsp70, which is distinct from the known metal regulatory system for the metallothionein genes.

Caspase-independent cell death is involved in the negative effect of EGF receptor inhibitors on cisplatin in non-small cell lung cancer cells

PURPOSE

Results of multiple clinical trials suggest that EGF receptor (EGFR) tyrosine kinase inhibitors (TKI) exhibit negative effects on platinum-based chemotherapy in patients with lung cancer with wild-type (WT) EGFR, but the underlying molecular mechanisms are still uncertain. Studies that identify the mechanism of how TKIs negatively affect patients with WT EGFR are important for future development of effective strategies to target lung cancer. Thus, we returned to in vitro study to investigate and determine a possible explanation for this phenomenon.

EXPERIMENTAL DESIGN

We investigated the effects of TKIs and cisplatin on caspase-independent cell death (CID) and the role of CID in the efficacy of each drug and the combination. Furthermore, we studied the mechanism by which EGFR signaling pathway is involved in CID. Finally, on the basis of the identified mechanism, we tested the combinational effects of cisplatin plus suberoylanilide hydroxamic acid (SAHA) or erastin on CID.

RESULTS

We found that gefitinib inhibited cisplatin-induced CID but not caspase-dependent apoptotic cell death. In WT EGFR cells, gefitinib not only inhibited CID but also failed to induce apoptosis, therefore compromising the efficacy of cisplatin. Inhibition of EGFR-ERK/AKT by gefitinib activates FOXO3a, which in turn reduces reactive oxygen species (ROS) and ROS-mediated CID. To overcome this, we showed that SAHA and erastin, the inducers of ROS-mediated CID, strongly enhanced the effect of cisplatin in WT EGFR cells.

CONCLUSION

TKI-mediated inhibition of CID plays an important role in the efficacy of chemotherapy. Moreover, FOXO3a is a key factor in the negative effects of TKI by eliminating cisplatin-induced ROS.

Early growth response 1 regulates glucose deprivation-induced necrosis

Necrosis is commonly found in the core region of solid tumours due to metabolic stress such as hypoxia and glucose deprivation (GD) resulting from insufficient vascularization. Necrosis promotes tumour growth and development by releasing the tumour-promoting cytokine high mobility group box 1 (HMGB1); however, the molecular mechanism underlying necrotic cell death remains largely unknown. In this study, we show that early growth response 1 (Egr-1) is induced in a reactive oxygen species (ROS)-dependent manner by GD in several cell lines such as A549, MDA-MB-231 and HepG2 cells that exhibit necrosis upon GD. We found that Egr-1 short hairpin RNA (shRNA) prevented GD-induced necrosis and HMGB1 release. Necrosis-inhibiting activity of Egr-1 shRNA was also seen in multicellular tumour spheroids (MTSs), an in vitro tumour model system. In contrast, Egr-1 overexpression appeared to make tumour cells more susceptible to GD-induced necrosis. Finally, Egr-1 shRNA suppressed the growth of MTSs. These findings demonstrate that Egr-1 is implicated in GD-induced necrosis and tumour progression.

SAHA down-regulates the expression of indoleamine 2,3-dioxygenase via inhibition of the JAK/STAT1 signaling pathway in gallbladder carcinoma cells

The aim of the present study was to investigate the role of the JAK/STAT1 signaling pathway in suberoylanilide hydroxamic acid (SAHA)-mediated down-regulation of indoleamine 2,3-dioxygenase (IDO) in gallbladder carcinoma cells. We treated SGC-996 gallbladder carcinoma cells with IFN-γ and SAHA. Western blotting was used to detect the expression of IDO, signal transducer and activator of transcription 1 (STAT1) phosphorylation and interferon regulatory factor genes-1 (IRF-1). Confocal microscopy analysis was used to detect STAT1 translocation. Transient transfection and reporter gene assay was used for detecting the activation of γ-activated sites (GAS) and interferon-stimulated response elements (ISRE). The results revealed that IDO was expressed in SGC-996 cells in a dose- and time-dependent manner when stimulated with IFN-γ and SAHA down-regulated the expression of IDO induced by IFN-γ in a dose-dependent manner. SAHA blocked the expression of IRF-1 induced by IFN-γ and SAHA inhibited IFN-γ-induced STAT1 phosphorylation and nuclear translocation. In addition, SAHA down-regulated IFN-γ-induced activation of GAS and ISRE. In conclusion, SAHA down-regulated IDO expression via inhibition of the activation of members of the JAK/STAT1 signaling pathway. Therefore, regulation of the JAK/STAT1 signaling pathway may provide a new gallbladder carcinoma immunotherapeutic strategy to break tumor immune tolerance.

Migfilin sensitizes cisplatin-induced apoptosis in human glioma cells in vitro

AIM

Filamin binding LIM protein 1, also known as migfilin, is a skeleton organization protein that binds to mitogen-inducible gene 2 at cell-extracellular matrix adhesions. The aim of this study was to investigate the role of migfilin in cisplatin-induced apoptosis in human glioma cells, to determine the functional domains of migfilin, and to elucidate the molecular mechanisms underlying the regulation of cisplatin-related chemosensitivity.

METHODS

The human glioma cell lines Hs683, H4, and U-87 MG were transfected with pEGFP-C2-migfilin to elevate the expression level of migfilin. RNA interference was used to reduce the expression of migfilin. To determine the functional domains of migfilin, U-87 MG cells were transfected with plasmids of migfilin deletion mutants. After treatment with cisplatin (40 μmol/L) for 24 h, the cell viability was assessed using the MTS assay, and the cell apoptotic was examined using the DAPI staining assay and TUNEL analysis. Expression levels of apoptosis-related proteins were detected by Western blot analysis.

RESULTS

Overexpression of migfilin significantly enhanced cisplatin-induced apoptosis in Hs683, H4, and U-87 MG cells, whereas downregulation of migfilin expression inhibited the chemosensitivity of these cell lines. The N-terminal region of migfilin alone was able to enhance the cisplatin-induced apoptosis. However, despite the existence of the N-terminal region, mutants of migfilin with any one of three LIM domains deleted led to a function loss. Furthermore, apoptotic proteins (PARP and caspase-3) and the anti-apoptotic protein Bcl-xL were modulated by the expression level of migfilin in combination with cisplatin.

CONCLUSION

The LIM1-3 domains of migfilin play a key role in sensitizing glioma cells to cisplatin-induced apoptosis through regulation of apoptosis-related proteins.

New players in ovarian cancer

Ovarian cancer is the leading cause of gynecologic cancer mortality worldwide. The aim of this review is to highlight the most recent studies regarding ovarian cancer pathogenesis and the new therapeutic approaches against this insidious disease. We focus on the relevance of some cell cycle genes, transcription factors, and microRNAs in the carcinogenesis of ovarian cancer as well as on a new hypothesis for therapy using histone deacetylase inhibitors. We also report recent studies regarding some mechanisms of chemoresistance, a major obstacle in the treatment of ovarian cancer. Together these studies can improve our knowledge of ovarian cancer tumorigenesis and diagnosis providing new tools to hopefully defeat this deadly disease.

Egr-1 transactivates Bim gene expression to promote neuronal apoptosis

The proapoptotic BH3-only protein Bim is a crucial regulator of neuronal apoptosis. Previous studies have indicated the involvement of the c-Jun, FOXO1/3a, and B/C-Myb transcription factors in the regulation of Bim during neuronal apoptosis. However, the mechanism underlying the transcriptional regulation of Bim in activity deprivation-induced neuronal apoptosis has remained unclear. The present study demonstrates that early growth response 1 (Egr-1), rather than c-Jun, FOXO1/3a, or B/C-Myb, directly transactivates Bim gene expression to mediate apoptosis of rat cerebellar granule neurons. We showed that Egr-1 was sufficient and necessary for neuronal apoptosis. Suppression of Egr-1 activity using dominant-negative mutant or knockdown of Egr-1 using small interfering RNAs led to a decrease in Bim expression, whereas overexpression of Egr-1 resulted in induction of Bim. Deletion and site-directed mutagenesis of the Bim promoter revealed that Bim transcriptional activation depends primarily on a putative Egr-binding sequence between nucleotides -56 and -47 upstream of the start site. We also showed that Egr-1 binding to this sequence increased in response to activity deprivation in vitro and in vivo. Moreover, inhibition of Egr-1 binding to the Bim promoter, by mithramycin A and chromomycin A3, reduced the activity deprivation-induced increases in Bim promoter activity and mRNA and protein levels and protected neurons from apoptosis, further supporting the Egr-1-mediated transactivation of Bim. Additionally, Bim overcame the Egr-1 knockdown-mediated inhibition of apoptosis, whereas Bim knockdown impaired the increase in apoptosis induced by Egr-1. These findings establish Bim as an Egr-1 target gene in neurons, uncovering a novel Egr-1/Bim pathway by which activity deprivation induces neuronal apoptosis.