BIK

Gene Summary

Gene:BIK; BCL2 interacting killer
Aliases: BP4, NBK, BIP1
Location:22q13.2
Summary:The protein encoded by this gene shares a critical BH3 domain with other death-promoting proteins, such as BID, BAK, BAD and BAX, that is required for its pro-apoptotic activity, and for interaction with anti-apoptotic members of the BCL2 family, and viral survival-promoting proteins. Since the activity of this protein is suppressed in the presence of survival-promoting proteins, it is suggested as a likely target for anti-apoptotic proteins. [provided by RefSeq, Sep 2011]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:bcl-2-interacting killer
Source:NCBIAccessed: 13 March, 2017

Ontology:

What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 13 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Biomarkers, Tumor
  • Membrane Proteins
  • Serine Endopeptidases
  • Breast Cancer
  • Polymerase Chain Reaction
  • DNA Methylation
  • Mice, Inbred BALB C
  • Cell Proliferation
  • siRNA
  • RTPCR
  • Antineoplastic Agents
  • Genetic Vectors
  • Cancer DNA
  • Chromosome 22
  • Drug Resistance
  • Messenger RNA
  • p53 Protein
  • Genetic Therapy
  • BIK
  • BCL2 protein
  • bcl-X Protein
  • Cell Survival
  • Proto-Oncogene Proteins
  • Promoter Regions
  • Tissue Distribution
  • Translocation
  • Proteins
  • Cancer Gene Expression Regulation
  • Gene Expression Profiling
  • Ribonucleases
  • Apoptosis Regulatory Proteins
  • Oligonucleotide Array Sequence Analysis
  • Western Blotting
  • Apoptosis
  • Vidarabine Phosphate
  • Urinary System Cancers
  • BCL2
  • Transfection
  • Mutation
  • Recurrence
  • Leukemic Gene Expression Regulation
Tag cloud generated 13 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (2)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: BIK (cancer-related)

Dai L, Wang G, Pan W
Andrographolide Inhibits Proliferation and Metastasis of SGC7901 Gastric Cancer Cells.
Biomed Res Int. 2017; 2017:6242103 [PubMed] Free Access to Full Article Related Publications
To explore the mechanisms by which andrographolide inhibits gastric cancer cell proliferation and metastasis, we employed the gastric cell line SGC7901 to investigate the anticancer effects of andrographolide. The cell survival ratio, cell migration and invasion, cell cycle, apoptosis, and matrix metalloproteinase activity were assessed. Moreover, western blotting and real-time PCR were used to examine the protein expression levels and the mRNA expression levels, respectively. The survival ratio of cells decreased with an increasing concentration of andrographolide in a dose-dependent manner. Consistent results were also obtained using an apoptosis assay, as detected by flow cytometry. The cell cycle was blocked at the G2/M2 phase by andrographolide treatment, and the proportion of cells arrested at G1/M was enhanced as the dose increased. Similarly, wound healing and Transwell assays showed reduced migration and invasion of the gastric cancer cells at various concentrations of andrographolide. Andrographolide can inhibit cell proliferation, invasion, and migration, block the cell cycle, and promote apoptosis in SGC7901 cells. The mechanisms may include upregulated expression of Timp-1/2, cyclin B1, p-Cdc2, Bax, and Bik and downregulated expression of MMP-2/9 and antiapoptosis protein Bcl-2.

Wang CY, Guo ST, Wang JY, et al.
Inhibition of HSP90 by AUY922 Preferentially Kills Mutant KRAS Colon Cancer Cells by Activating Bim through ER Stress.
Mol Cancer Ther. 2016; 15(3):448-59 [PubMed] Related Publications
Oncogenic mutations of KRAS pose a great challenge in the treatment of colorectal cancer. Here we report that mutant KRAS colon cancer cells are nevertheless more susceptible to apoptosis induced by the HSP90 inhibitor AUY922 than those carrying wild-type KRAS. Although AUY922 inhibited HSP90 activity with comparable potency in colon cancer cells irrespective of their KRAS mutational statuses, those with mutant KRAS were markedly more sensitive to AUY922-induced apoptosis. This was associated with upregulation of the BH3-only proteins Bim, Bik, and PUMA. However, only Bim appeared essential, in that knockdown of Bim abolished, whereas knockdown of Bik or PUMA only moderately attenuated apoptosis induced by AUY922. Mechanistic investigations revealed that endoplasmic reticulum (ER) stress was responsible for AUY922-induced upregulation of Bim, which was inhibited by a chemical chaperone or overexpression of GRP78. Conversely, siRNA knockdown of GRP78 or XBP-1 enhanced AUY922-induced apoptosis. Remarkably, AUY922 inhibited the growth of mutant KRAS colon cancer xenografts through activation of Bim that was similarly associated with ER stress. Taken together, these results suggest that AUY922 is a promising drug in the treatment of mutant KRAS colon cancers, and the agents that enhance the apoptosis-inducing potential of Bim may be useful to improve the therapeutic efficacy.

Ju W, Zhang M, Wilson KM, et al.
Augmented efficacy of brentuximab vedotin combined with ruxolitinib and/or Navitoclax in a murine model of human Hodgkin's lymphoma.
Proc Natl Acad Sci U S A. 2016; 113(6):1624-9 [PubMed] Free Access to Full Article Related Publications
Despite relative success of therapy for Hodgkin's lymphoma (HL), novel therapeutic agents are needed for patients with refractory or relapsed disease. Recently, anti-PD1 immunotherapy or treatment with the anti-CD30 toxin conjugate brentuximab vedotin (BV) have been associated with remissions; however, the median responses of complete responses (CRs) with the latter were only 6.7 mo. To obtain curative therapy, other effective agents, based on HL biology, would have to be given in combination with BV. Hodgkin's Reed-Sternberg (HRS) cells secrete cytokines including IL-6 and -13, leading to constitutive activation of JAK/STAT signaling. In the present study the JAK1/2 inhibitor ruxolitinib reduced phosphorylation of STAT3 and STAT6 and expression of c-Myc in the HL cell line HDLM-2. These changes were enhanced when, on the basis of a matrix screen of drug combinations, ruxolitinib was combined with the Bcl-2/Bcl-xL inhibitor Navitoclax. The combination augmented expression of Bik, Puma, and Bax, and attenuated Bcl-xL expression and the phosphorylation of Bad. The use of the two-agent combination of either ruxolitinib or Navitoclax with BV or the three-agent combination strongly activated Bax and increased activities of cytochrome c and caspase-9 and -3 that, in turn, led to cleavage of poly(ADP ribose) polymerase and Mcl-1. Either ruxolitinib combined with Navitoclax or BV alone prolonged survival but did not cure HDLM-2 tumor-bearing mice, whereas BV combined with ruxolitinib and/or with Navitoclax resulted in a sustained, complete elimination of the HDLM-2 HL. These studies provide scientific support for a clinical trial to evaluate BV combined with ruxolitinib in select patients with HL.

Hopkins TG, Mura M, Al-Ashtal HA, et al.
The RNA-binding protein LARP1 is a post-transcriptional regulator of survival and tumorigenesis in ovarian cancer.
Nucleic Acids Res. 2016; 44(3):1227-46 [PubMed] Free Access to Full Article Related Publications
RNA-binding proteins (RBPs) are increasingly identified as post-transcriptional drivers of cancer progression. The RBP LARP1 is an mRNA stability regulator, and elevated expression of the protein in hepatocellular and lung cancers is correlated with adverse prognosis. LARP1 associates with an mRNA interactome that is enriched for oncogenic transcripts. Here we explore the role of LARP1 in epithelial ovarian cancer, a disease characterized by the rapid acquisition of resistance to chemotherapy through the induction of pro-survival signalling. We show, using ovarian cell lines and xenografts, that LARP1 is required for cancer cell survival and chemotherapy resistance. LARP1 promotes tumour formation in vivo and maintains cancer stem cell-like populations. Using transcriptomic analysis following LARP1 knockdown, cross-referenced against the LARP1 interactome, we identify BCL2 and BIK as LARP1 mRNA targets. We demonstrate that, through an interaction with the 3' untranslated regions (3' UTRs) of BCL2 and BIK, LARP1 stabilizes BCL2 but destabilizes BIK with the net effect of resisting apoptosis. Together, our data indicate that by differentially regulating the stability of a selection of mRNAs, LARP1 promotes ovarian cancer progression and chemotherapy resistance.

Ruiz Esparza-Garrido R, Torres-Márquez ME, Viedma-Rodríguez R, et al.
Breast cancer cell line MDA-MB-231 miRNA profile expression after BIK interference: BIK involvement in autophagy.
Tumour Biol. 2016; 37(5):6749-59 [PubMed] Related Publications
B-cell lymphoma 2 (BCL2)-interacting killer (apoptosis inducing) (BIK) has been proposed as a tumor suppressor in diverse types of cancers. However, BIK's overexpression in breast cancer (BC) and in non-small lung cancer cells (NSCLCs), associated with a poor prognosis, suggests its participation in tumor progression. In this study, we evaluated the global expression pattern of microRNAs (miRNAs), messenger RNA (mRNA) expression changes in autophagy, and autophagic flux after BIK interference. BIK gene expression was silenced by small interfering RNA (siRNA) in BC cell MDA-MB-231, and BIK interference efficiency was tested by real-time PCR and by Western blotting. BIK expression levels decreased by 75 ± 18 % in the presence of 600 nM siRNA, resulting in the abolishment of BIK expression by 94 ± 30 %. BIK interference resulted in the overexpression of 17 miRNAs that, according to the DIANA-miRPath v3.0 database, are mainly implied in the control of cell signaling, gene expression, and autophagy. The autophagy array revealed downregulation of transcripts which participate in autophagy, and their interactome revealed a complex network, where hepatocyte growth factor-regulated tyrosine kinase substrate (HGS), α-synuclein (SNCA), unc-51-like autophagy activating kinase 1/2 (ULK1/2), and mitogen-activated protein kinase 3 (MAPK3) were shown to be signaling hubs. LC3-II expression-an autophagy marker-was increased by 169 ± 25 % after BIK interference, which indicates the involvement of BIK in autophagy. Altogether, our results indicate-for the first time-that BIK controls the expression of miRNAs, as well as the autophagic flux in MDA-MB-231 cells.

Wu J, Chen Z, Liu Q, et al.
Silencing of Kv1.5 Gene Inhibits Proliferation and Induces Apoptosis of Osteosarcoma Cells.
Int J Mol Sci. 2015; 16(11):26914-26 [PubMed] Free Access to Full Article Related Publications
Kv1.5 (also known as KCNA5) is a protein encoded by the KCNA5 gene, which belongs to the voltage-gated potassium channel, shaker-related subfamily. Recently, a number of studies have suggested that Kv1.5 is overexpressed in numerous cancers and plays crucial roles in cancer development. However, until now, the expression and functions of Kv1.5 in osteosarcoma are still unclear. To characterize the potential biological functions of Kv1.5 in osteosarcoma, herein, we examined the expression levels of Kv1.5 in osteosarcoma cells and tissues using quantitative real-time polymerase chain reaction (qRT-PCR), western blot, and immunohistochemistry assays. Four short hairpin RNAs (shRNAs) targeting Kv1.5 were designed and homologous recombination technology was used to construct pGeneSil-Kv1.5 vectors. In addition, the vectors were transfected into osteosarcoma MG63 cells and Kv1.5 mRNA level was measured by qRT-PCR and the Kv1.5 protein level was examined by western blot. We also examined the effects of Kv1.5 silencing on proliferation, cell cycle and apoptosis of the osteosarcoma cells using CCK-8, colony formation, flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays. Our results showed that Kv1.5 was aberrantly expressed in osteosarcoma and that the synthesized shRNA targeting Kv1.5 reduced Kv1.5 mRNA and protein expression effectively. Silencing Kv1.5 expression in the osteosarcoma cells significantly inhibited the proliferation of osteosarcoma cells, induced cell cycle arrest at G0/G1 phase, and induced cell apoptosis through up-regulation of p21, p27, Bax, Bcl-XL and caspase-3 and down-regulation of cyclins A, cyclins D1, cyclins E, Bcl-2 and Bik. In summary, our results indicate that Kv1.5 silencing could suppress osteosarcoma progression through multiple signaling pathways and suggest that Kv1.5 may be a novel target for osteosarcoma therapeutics.

Maxfield KE, Taus PJ, Corcoran K, et al.
Comprehensive functional characterization of cancer-testis antigens defines obligate participation in multiple hallmarks of cancer.
Nat Commun. 2015; 6:8840 [PubMed] Free Access to Full Article Related Publications
Tumours frequently activate genes whose expression is otherwise biased to the testis, collectively known as cancer-testis antigens (CTAs). The extent to which CTA expression represents epiphenomena or confers tumorigenic traits is unknown. In this study, to address this, we implemented a multidimensional functional genomics approach that incorporates 7 different phenotypic assays in 11 distinct disease settings. We identify 26 CTAs that are essential for tumor cell viability and/or are pathological drivers of HIF, WNT or TGFβ signalling. In particular, we discover that Foetal and Adult Testis Expressed 1 (FATE1) is a key survival factor in multiple oncogenic backgrounds. FATE1 prevents the accumulation of the stress-sensing BH3-only protein, BCL-2-Interacting Killer (BIK), thereby permitting viability in the presence of toxic stimuli. Furthermore, ZNF165 promotes TGFβ signalling by directly suppressing the expression of negative feedback regulatory pathways. This action is essential for the survival of triple negative breast cancer cells in vitro and in vivo. Thus, CTAs make significant direct contributions to tumour biology.

Waye S, Naeem A, Choudhry MU, et al.
The p53 tumor suppressor protein protects against chemotherapeutic stress and apoptosis in human medulloblastoma cells.
Aging (Albany NY). 2015; 7(10):854-68 [PubMed] Free Access to Full Article Related Publications
Medulloblastoma (MB), a primitive neuroectodermal tumor, is the most common malignant childhood brain tumor and remains incurable in about a third of patients. Currently, survivors carry a significant burden of late treatment effects. The p53 tumor suppressor protein plays a crucial role in influencing cell survival in response to cellular stress and while the p53 pathway is considered a key determinant of anti-tumor responses in many tumors, its role in cell survival in MB is much less well defined. Herein, we report that the experimental drug VMY-1-103 acts through induction of a partial DNA damage-like response as well induction of non-survival autophagy. Surprisingly, the genetic or chemical silencing of p53 significantly enhanced the cytotoxic effects of both VMY and the DNA damaging drug, doxorubicin. The inhibition of p53 in the presence of VMY revealed increased late stage apoptosis, increased DNA fragmentation and increased expression of genes involved in apoptosis, including CAPN12 and TRPM8, p63, p73, BIK, EndoG, CIDEB, P27Kip1 and P21cip1. These data provide the groundwork for additional studies on VMY as a therapeutic drug and support further investigations into the intriguing possibility that targeting p53 function may be an effective means of enhancing clinical outcomes in MB.

Choi YC, Yoon S, Byun Y, et al.
MicroRNA library screening identifies growth-suppressive microRNAs that regulate genes involved in cell cycle progression and apoptosis.
Exp Cell Res. 2015; 339(2):320-32 [PubMed] Related Publications
Micro(mi)RNAs play important and varied roles in tumorigenesis; however, the full repertoire of miRNAs that affect cancer cell growth is not known. In this study, an miRNA library was screened to identify those that affect the growth of A549 tumor cells. Among 300 miRNAs, miR-28-5p, -323-5p, -510-5p, -552-3p, and -608 were the most effective in inhibiting cell growth. More specifically, overexpressing miR-28-5p, -323-5p, and -510-5p induced G1 arrest, as determined by flow cytometry, whereas that of miR-608 induced cell death in a caspase-dependent manner. Moreover, several genes involved in apoptosis and cell cycle progression were downregulated upon overexpression of each of the five miRNAs, with the functional targets of miR-552-3p and miR-608 confirmed by microarray, quantitative real-time PCR, and luciferase reporter assay. In miR-608-transfected cells, B cell lymphoma 2-like 1 (BCL2L1), D-type cyclin 1 (CCND1), CCND3, cytochrome b5 reductase 3 (CYB5R3), phosphoinositide 3-kinase regulatory subunit 2 (PIK3R2), specificity protein 1 (SP1), and phosphorylated Akt were all downregulated, while Bcl-2-interacting killer (BIK) was upregulated. Moreover, miR-608 was determined to have a suppressive function on tumor growth in an NCI-H460 xenograft model. These findings provide insights into the roles of five miRNAs in growth inhibition and their potential function as cancer therapeutics.

Huang J, Wang L, Jiang M, et al.
Low BIK outside-inside-out interactive inflammation immune-induced transcription-dependent apoptosis through FUT3-PMM2-SQSTM1-SFN-ZNF384.
Immunol Res. 2016; 64(2):461-9 [PubMed] Related Publications
Eighteen different Pearson mutual-positive-correlation BIK-activatory molecular feedback upstream and downstream networks were constructed from 79 overlapping of 376 GRNInfer and 98 Pearson under BIK CC ≥ 0.25 in low normal adjacent tissues of Taiwan compared with high lung adenocarcinoma. Our identified BIK interactive total feedback molecular network showed FUT3 [fucosyltransferase 3 (galactoside 3(4)-L-fucosyltransferase Lewis blood group)], PMM2 (phosphomannomutase 2), SQSTM1 (sequestosome 1), SFN_2 [REX2 RNA exonuclease 2 homolog (S. cerevisiae)] and ZNF384 (zinc finger protein 384) in low normal adjacent tissues of lung adenocarcinoma. BIK interactive total feedback terms included mitochondrial envelope, endomembrane system, integral to membrane, Golgi apparatus, cytoplasm, nucleus, cytosol, intracellular signaling cascade, mitochondrion, extracellular space, inflammation, immune response, apoptosis, cell differentiation, cell cycle, regulation of cell cycle, cell proliferation, estrogen-responsive protein Efp controls cell cycle and breast tumors growth, induction or regulation of apoptosis based on integrative GO, KEGG, GenMAPP, BioCarta and disease databases in low normal adjacent tissues of lung adenocarcinoma. Therefore, we propose low BIK outside-inside-out interactive inflammation immune-induced transcription-dependent apoptosis through FUT3-PMM2-SQSTM1-SFN-ZNF384 in normal adjacent tissues of lung adenocarcinoma.

Dai HY, Chen HY, Lai WC, et al.
Targeted expression of BikDD combined with metronomic doxorubicin induces synergistic antitumor effect through Bax activation in hepatocellular carcinoma.
Oncotarget. 2015; 6(27):23807-19 [PubMed] Free Access to Full Article Related Publications
Conventional chemotherapy is commonly used to treat advanced non-resectable hepatocellular carcinoma (HCC) but this treatment modality has not demonstrated convincing survival benefit in HCC patients. Our previous studies indicated that targeted expression of therapeutic BikDD driven by a liver cancer-specific α-fetoprotein promoter/enhancer (eAFP) in the VISA backbone (eAFP-VISA-BikDD) significantly and specifically kills HCC cells in multiple orthotopic animal models. To enhance its therapeutic efficacy, we combined eAFP-VISA-BikDD with chemotherapeutic agents and found that eAFP-VISA-BikDD plus doxorubicin (Dox) or 5-fluorouracil (5-FU) demonstrated synergistic cytotoxicity in HCC cells. Specifically, the combination of eAFP-VISA-BikDD plus Dox markedly induced apoptosis via increased Bax mitochondrial translocation and cytoplasmic cytochrome c release. Compared with either agent alone, a low dose of Dox combined with eAFP-VISA-BikDD induced better antitumor effect and prolonged longer survival of mice in two orthotopic liver cancer xenograft models. Our findings provide strong preclinical support for evaluating the combined therapy of eAFP-VISA-BikDD and Dox in a clinical setting as a treatment option for HCC.

Oral AY, Cevatemre B, Sarimahmut M, et al.
Anti-growth effect of a novel trans-dichloridobis[2-(2-hydroxyethyl)pyridine]platinum (II) complex via induction of apoptosis on breast cancer cell lines.
Bioorg Med Chem. 2015; 23(15):4303-10 [PubMed] Related Publications
Breast cancer still continues to be the leading cause of cancer-related mortality in women worldwide. Although advances have been made in the treatment of this disease during the past decade, new approaches and novel compounds are urgently needed. The aim of this study was to evaluate the cytotoxic activity of trans-[PtCl2(2-hepy)2] [2-hepy=2-(2-hydroxyethyl) pyridine] on breast cancer cell lines, MCF-7 and MDA-MB-231. The platinum (II) complex was synthesized and characterized by our laboratory working group. Anti-growth effect was assayed by the MTT and ATP viability assays and also monitored real-time using xCELLigence system. The mode of cell death was evaluated by using the fluorescence microscopy (Hoechst 33342+Calcein-AM+Propidium iodide staining), Western blotting (cleaved PARP and caspase 3, total caspase 8), flow cytometry (quantitative analysis of live, early/late apoptotic, dead cells and caspase 3/7 activity) and the RT-PCR (the genes analyzed were BCL-2L10, BIK, BAX, BCL-2, FASLG, HRK, TNFRSF10B, and TNFRSF10A). The platinum (II) complex had anti-growth effect in a dose dependent manner in vitro. Cells were killed by apoptosis as evidenced by the pyknotic nuclei, cleavage of poly-(ADP-ribose) polymerase (PARP) and induction of active caspase-3. These results suggest that the complex might represent a potentially active novel drug for the breast cancer treatment and warrants further studies due to its promising cytotoxic activity.

Trejo-Vargas A, Hernández-Mercado E, Ordóñez-Razo RM, et al.
Bik subcellular localization in response to oxidative stress induced by chemotherapy, in Two different breast cancer cell lines and a Non-tumorigenic epithelial cell line.
J Appl Toxicol. 2015; 35(11):1262-70 [PubMed] Related Publications
Cancer chemotherapy remains one of the preferred therapeutic modalities against malignancies despite its damaging side effects. An expected outcome while utilizing chemotherapy is apoptosis induction. This is mainly regulated by a group of proteins known as the Bcl-2 family, usually found within the endoplasmic reticulum or the mitochondria. Recently, these proteins have been located in other sites and non-canonic functions have been unraveled. Bik is a pro-apoptotic protein, which becomes deregulated in cancer, and as apoptosis is associated with oxidative stress generation, our objective was to determine the subcellular localization of Bik either after a direct oxidative insult due to H2 O2 , or indirectly by cisplatin, an antineoplastic agent. Experiments were performed in two human transformed mammary gland cell lines MDA-MB-231 and MCF-7, and one non-tumorigenic epithelial cell line MCF-10A. Our results showed that in MCF-7, Bik is localized within the cytosol and that after oxidative stress treatment it translocates into the nucleus. However, in MDA-MB-231, Bik localizes in the nucleus and translocates to the cytosol. In MCF10A Bik did not change its cellular site after either treatment. Interestingly, MCF10A were more resistant to cisplatin than transformed cell lines. This is the first report showing that Bik is located in different cellular compartments depending on the cancer stage, and it has the ability to change its subcellular localization in response to oxidative stress. This is associated with increased sensitivity when exposed to toxic agents, thus rendering novel opportunities to study new therapeutic targets allowing the development of more active and less harmful agents.

Viedma-Rodríguez R, Ruiz Esparza-Garrido R, Baiza-Gutman LA, et al.
Involvement of multiple cellular pathways in regulating resistance to tamoxifen in BIK-suppressed MCF-7 cells.
Tumour Biol. 2015; 36(9):6991-7005 [PubMed] Related Publications
Majority of women with estrogen receptor (ER)-positive breast cancers initially respond to hormone therapies such as tamoxifen (TAM; antagonist of estrogen). However, many tumors eventually become resistant to TAM. Therefore, understanding the various cellular components involved in causing resistance to TAM is of paramount importance in designing novel entities for efficacious hormone therapy. Previously, we found that suppression of BIK gene expression induced TAM resistance in MCF-7 breast cancer cells. In order to understand the response of these cells to TAM and its association with resistance, a microarray analysis of gene expression was performed in the BIK-suppressed MCF-7 cells and compared it to the TAM-only-treated cells (controls). Several genes participating in various cellular pathways were identified. Molecules identified in the drug resistance pathway were 14-3-3z or YWHAZ, WEE1, PRKACA, NADK, and HSP90AA 1. Further, genes involved in cell cycle control, apoptosis, and cell proliferation were also found differentially expressed in these cells. Transcriptional and translational analysis of key molecules such as STAT2, AKT 3, and 14-3-3z revealed similar changes at the messenger RNA (mRNA) as well as at the protein level. Importantly, there was no cytotoxic effect of TAM on BIK-suppressed MCF-7 cells. Further, these cells were not arrested at the G0-G1 phase of the cell cycle although 30 % of BIK-suppressed cells were arrested at the G2 phase of the cycle on TAM treatment. Furthermore, we found a relevant interaction between 14-3-3z and WEE1, suggesting that the cytotoxic effect of TAM was prevented in BIK-suppressed cells because this interaction leads to transitory arrest in the G2 phase leading to the repair of damaged DNA and allowing the cells to proliferate.

Wang Y, Luo Z, Pan Y, et al.
Targeting protein neddylation with an NEDD8-activating enzyme inhibitor MLN4924 induced apoptosis or senescence in human lymphoma cells.
Cancer Biol Ther. 2015; 16(3):420-9 [PubMed] Free Access to Full Article Related Publications
Recent studies indicate that post-translational protein neddylation is required for the maintenance of cell viability in several lymphoma cell lines, while inhibition of the neddylation pathway with an NEDD8-activating enzyme (NAE) inhibitor MLN4924 induces apoptosis in lymphoma cells. However, the mechanism by which neddylation inhibition induces apoptosis in lymphoma cells has not been fully elucidated. Moreover, it is unknown whether neddylation inhibition triggers non-apoptotic cell-killing responses, such as cell senescence, in lymphoma cells. Here, we report that MLN4924 specifically inhibited protein neddylation, inactivated cullin-RING E3 ligase (CRL), the best-known neddylation substrate, and induced the accumulation of tumor-suppressive CRL substrates in lymphoma cells. Moreover, MLN4924 potently suppressed the growth of lymphoma cells by inducing G2 cell-cycle arrest, followed by apoptosis or senescence in a cell line-dependent manner. MLN4924-induced apoptosis was mediated by intrinsic apoptotic signaling with substantial up-regulation of pro-apoptotic Bik and Noxa as well as down-regulation of anti-apoptotic XIAP, c-IAP1 and c-IAP2, while senescence induction upon neddylation inhibition seemed dependent on the expression of tumor suppressor p21/p27. Together, these findings expand our understanding on how lymphoma cells respond to neddylation inhibition and support the development of neddylation inhibitors (e.g. MLN4924) for the treatment of lymphoma.

Assent D, Bourgot I, Hennuy B, et al.
A membrane-type-1 matrix metalloproteinase (MT1-MMP)-discoidin domain receptor 1 axis regulates collagen-induced apoptosis in breast cancer cells.
PLoS One. 2015; 10(3):e0116006 [PubMed] Free Access to Full Article Related Publications
During tumour dissemination, invading breast carcinoma cells become confronted with a reactive stroma, a type I collagen-rich environment endowed with anti-proliferative and pro-apoptotic properties. To develop metastatic capabilities, tumour cells must acquire the capacity to cope with this novel microenvironment. How cells interact with and respond to their microenvironment during cancer dissemination remains poorly understood. To address the impact of type I collagen on the fate of tumour cells, human breast carcinoma MCF-7 cells were cultured within three-dimensional type I collagen gels (3D COL1). Using this experimental model, we have previously demonstrated that membrane type-1 matrix metalloproteinase (MT1-MMP), a proteinase overexpressed in many aggressive tumours, promotes tumour progression by circumventing the collagen-induced up-regulation of BIK, a pro-apoptotic tumour suppressor, and hence apoptosis. Here we performed a transcriptomic analysis to decipher the molecular mechanisms regulating 3D COL1-induced apoptosis in human breast cancer cells. Control and MT1-MMP expressing MCF-7 cells were cultured on two-dimensional plastic plates or within 3D COL1 and a global transcriptional time-course analysis was performed. Shifting the cells from plastic plates to 3D COL1 activated a complex reprogramming of genes implicated in various biological processes. Bioinformatic analysis revealed a 3D COL1-mediated alteration of key cellular functions including apoptosis, cell proliferation, RNA processing and cytoskeleton remodelling. By using a panel of pharmacological inhibitors, we identified discoidin domain receptor 1 (DDR1), a receptor tyrosine kinase specifically activated by collagen, as the initiator of 3D COL1-induced apoptosis. Our data support the concept that MT1-MMP contributes to the inactivation of the DDR1-BIK signalling axis through the cleavage of collagen fibres and/or the alteration of DDR1 receptor signalling unit, without triggering a drastic remodelling of the transcriptome of MCF-7 cells.

Ferreira AF, de Oliveira GL, Tognon R, et al.
Apoptosis-related gene expression profile in chronic myeloid leukemia patients after imatinib mesylate and dasatinib therapy.
Acta Haematol. 2015; 133(4):354-64 [PubMed] Related Publications
BACKGROUND/AIMS: We investigated the effects of tyrosine kinase inhibitors (TKIs) on the expression of apoptosis-related genes (BCL-2 and death receptor family members) in chronic myeloid leukemia (CML) patients.
METHODS: Peripheral blood mononuclear cells from 32 healthy subjects and 26 CML patients were evaluated before and after treatment with imatinib mesylate (IM) and dasatinib (DAS) by quantitative PCR.
RESULTS: Anti-apoptotic genes (c-FLIP and MCL-1) were overexpressed and the pro-apoptotic BIK was reduced in CML patients. Expression of BMF, A1, c-FLIP, MCL-1, CIAP-2 and CIAP-1 was modulated by DAS. In IM-resistant patients, expression of A1, c-FLIP, CIAP-1 and MCL-1 was upregulated, and BCL-2, CIAP-2, BAK, BAX, BIK and FASL expression was downregulated.
CONCLUSION: Taken together, our results point out that, in CML, DAS interferes with the apoptotic machinery regulation. In addition, the data suggest that apoptosis-related gene expression profiles are associated with primary resistance to IM.

Okamoto K, Zaanan A, Kawakami H, et al.
Reversal of Mutant KRAS-Mediated Apoptosis Resistance by Concurrent Noxa/Bik Induction and Bcl-2/Bcl-xL Antagonism in Colon Cancer Cells.
Mol Cancer Res. 2015; 13(4):659-69 [PubMed] Free Access to Full Article Related Publications
UNLABELLED: KRAS mutations are frequently detected in human colorectal cancer and contribute to de novo apoptosis resistance and ultimately therapeutic failure. To overcome KRAS-mediated apoptosis resistance, the irreversible proteasome inhibitor, carfilzomib, was evaluated and found to potently induce Noxa, which was dependent upon c-Myc, and Bik. Isogenic mutant versus wild-type KRAS carcinoma cells showed elevated Bcl-xL, confirmed by KRAS siRNA or ectopic expression. Upregulated Bcl-xL by mutant KRAS was mediated by ERK as indicated by ERK knockdown. Bcl-xL expression was regulated at the level of mRNA and protein as shown using actinomycin D and cyclohexamide, respectively. Suppression of Bcl-xL by shRNA sensitized mutant KRAS cells to carfilzomib. Concurrent Bcl-xL antagonism by the BH3 mimetic ABT-263 combined with carfilzomib synergistically enhanced apoptosis that was dependent on Bax or p53, and was attenuated by Noxa or Bik shRNA. In support of this strategy, ectopically expressed Noxa enhanced apoptosis by ABT-263. Carfilzomib-induced Noxa and Bik sequestered Mcl-1 and ABT-263 released Bik and Bak from Bcl-xL, suggesting a mechanism for drug synergy. These preclinical findings establish mutant KRAS-mediated Bcl-xL upregulation as a key mechanism of apoptosis resistance in KRAS-mutant colorectal cancer. Furthermore, antagonizing Bcl-xL enabled carfilzomib-induced Noxa and Bik to induce synergistic apoptosis that reversed KRAS-mediated resistance.
IMPLICATIONS: This novel study reveals a promising treatment strategy to overcome apoptosis resistance in KRAS-mutant colorectal cancer by concurrent upregulation of Noxa/Bik and antagonism of Bcl-xL.

Stankiewicz TR, Gray JJ, Winter AN, Linseman DA
C-terminal binding proteins: central players in development and disease.
Biomol Concepts. 2014; 5(6):489-511 [PubMed] Related Publications
C-terminal binding proteins (CtBPs) were initially identified as binding partners for the E1A-transforming proteins. Although the invertebrate genome encodes one CtBP protein, two CtBPs (CtBP1 and CtBP2) are encoded by the vertebrate genome and perform both unique and duplicative functions. CtBP1 and CtBP2 are closely related and act as transcriptional corepressors when activated by nicotinamide adenine dinucleotide binding to their dehydrogenase domains. CtBPs exert transcriptional repression primarily via recruitment of a corepressor complex to DNA that consists of histone deacetylases (HDACs) and histone methyltransferases, although CtBPs can also repress transcription through HDAC-independent mechanisms. More recent studies have demonstrated a critical function for CtBPs in the transcriptional repression of pro-apoptotic genes such as Bax, Puma, Bik, and Noxa. Nonetheless, although recent efforts have characterized the essential involvement of CtBPs in promoting cellular survival, the dysregulation of CtBPs in both neurodegenerative disease and cancers remains to be fully elucidated.

van Keimpema M, Grüneberg LJ, Mokry M, et al.
FOXP1 directly represses transcription of proapoptotic genes and cooperates with NF-κB to promote survival of human B cells.
Blood. 2014; 124(23):3431-40 [PubMed] Free Access to Full Article Related Publications
The forkhead transcription factor FOXP1 is involved in B-cell development and function and is generally regarded as an oncogene in activated B-cell-like subtype of diffuse large B-cell lymphoma (DLBCL) and mucosa-associated lymphoid tissue lymphoma, lymphomas relying on constitutive nuclear factor κB (NF-κB) activity for survival. However, the mechanism underlying its putative oncogenic activity has not been established. By gene expression microarray, upon overexpression or silencing of FOXP1 in primary human B cells and DLBCL cell lines, combined with chromatin immunoprecipitation followed by next-generation sequencing, we established that FOXP1 directly represses a set of 7 proapoptotic genes. Low expression of these genes, encoding the BH3-only proteins BIK and Harakiri, the p53-regulatory proteins TP63, RASSF6, and TP53INP1, and AIM2 and EAF2, is associated with poor survival in DLBCL patients. In line with these findings, we demonstrated that FOXP1 promotes the expansion of primary mature human B cells by inhibiting caspase-dependent apoptosis, without affecting B-cell proliferation. Furthermore, FOXP1 is dependent upon, and cooperates with, NF-κB signaling to promote B-cell expansion and survival. Taken together, our data indicate that, through direct repression of proapoptotic genes, (aberrant) expression of FOXP1 complements (constitutive) NF-κB activity to promote B-cell survival and can thereby contribute to B-cell homeostasis and lymphomagenesis.

Xie X, Kong Y, Tang H, et al.
Targeted BikDD expression kills androgen-dependent and castration-resistant prostate cancer cells.
Mol Cancer Ther. 2014; 13(7):1813-25 [PubMed] Free Access to Full Article Related Publications
Targeted gene therapy is a promising approach for treating prostate cancer after the discovery of prostate cancer-specific promoters such as prostate-specific antigen, rat probasin, and human glandular kallikrein. However, these promoters are androgen dependent, and after castration or androgen ablation therapy, they become much less active or sometimes inactive. Importantly, the disease will inevitably progress from androgen-dependent (ADPC) to castration-resistant prostate cancer (CRPC), at which treatments fail and high mortality ensues. Therefore, it is critical to develop a targeted gene therapy strategy that is effective in both ADPC and CRPC to eradicate recurrent prostate tumors. The human telomerase reverse transcriptase-VP16-Gal4-WPRE integrated systemic amplifier composite (T-VISA) vector we previously developed, which targets transgene expression in ovarian and breast cancer, is also active in prostate cancer. To further improve its effectiveness based on androgen response in ADPC progression, the ARR2 element (two copies of androgen response region from rat probasin promoter) was incorporated into T-VISA to produce AT-VISA. Under androgen analog (R1881) stimulation, the activity of AT-VISA was increased to a level greater than or comparable to the cytomegalovirus promoter in ADPC and CRPC cells, respectively. Importantly, AT-VISA demonstrated little or no expression in normal cells. Systemic administration of AT-VISA-BikDD encapsulated in liposomes repressed prostate tumor growth and prolonged mouse survival in orthotopic animal models as well as in the transgenic adenocarcinoma mouse prostate model, indicating that AT-VISA-BikDD has therapeutic potential to treat ADPC and CRPC safely and effectively in preclinical setting.

Jiao S, Wu M, Ye F, et al.
BikDDA, a mutant of Bik with longer half-life expression protein, can be a novel therapeutic gene for triple-negative breast cancer.
PLoS One. 2014; 9(3):e92172 [PubMed] Free Access to Full Article Related Publications
Our previous studies showed that BikDD, a constitutively active mutant form of Bik, exhibited powerful antitumor effects in preclinical pancreatic, lung and breast cancer models. Howerver, the antitumor activity of BikDD in triple-negative breast cancer (TNBC) is unknown. Here we show that aberrant expression of p-ERK1/2 was a meaningful molecular phenotype in TNBC patients, and can be an obstacle for treatment because of the converse correlation with Bik. A novel mutant, BikDDA, in which Ser124 was changed to Alanine to block BikDD phosphorylation by p-ERK1/2 prevented subsequent ubiquitin-proteasome degradation. BikDDA showed a prolonged half-life and enhanced pro-apoptotic ability in TNBC cells compared with BikDD. Moreover, aberrant expression of p-ERK1/2 was associated with 5-fluorouracil resistance in breast cancer patients and BikDDA enhanced the therapeutic effects of 5-fluorouracil in vitro.

Guo S, Chan JK, Iqbal J, et al.
EZH2 mutations in follicular lymphoma from different ethnic groups and associated gene expression alterations.
Clin Cancer Res. 2014; 20(12):3078-86 [PubMed] Related Publications
PURPOSE: Gain-of-function mutations of enhancer of Zeste homolog 2 (EZH2) occur frequently in diffuse large B-cell lymphomas and in follicular lymphomas. However, the frequency of EZH2 mutation in Chinese follicular lymphomas and the potential targets affected by this mutation are unknown.
EXPERIMENTAL DESIGN: We determined EZH2 codon 641 mutations in Chinese follicular lymphomas (n = 124) and compared them with Western follicular lymphomas (n = 70) using a sensitive pyrosequencing assay. Gene expression profiling (GEP) was performed to determine differential gene expression between the mutated versus unmutated subgroups, and selected genes were validated using immunohistochemistry.
RESULTS: Our results showed similar frequencies of EZH2 codon 641 mutations in Chinese and Western follicular lymphoma cohorts (16.9% vs. 18.6%, χ(2) test, P = 0.773), including all five reported mutation variants. We observed significant association of EZH2 mutation with low morphologic grade follicular lymphomas (grade 1-2, 23.6% vs. grade 3, 7.7%, χ(2) test, P = 0.02). EZH2 mutations also showed significant association with BCL2 rearrangement in the Chinese cohort (26.8% vs. 8.8%, χ(2) test, P = 0.008) and combined cohorts (26.3% vs. 9.1%, χ(2) test, P = 0.002). GEP analysis identified several genes, including TCF4, FOXP1, TCL1A, BIK, and RASSF6P, with significantly lower mRNA expression (P < 0.01) in mutated cases, and the potential target TCL1A showed consistent results at the protein level.
CONCLUSION: Similar prevalence of EZH2 mutation in two ethnic groups suggests shared pathogenetic mechanisms. The much lower frequency of EZH2 mutation in cases without BCL2 translocation suggests a different pattern of evolution of this subtype of follicular lymphoma. GEP studies showed a set of differentially expressed genes and suggested that EZH2 mutation may help to lock the tumor cells at the germinal center stage of differentiation.

Sale MJ, Cook SJ
The increase in BIK expression following ERK1/2 pathway inhibition is a consequence of G₁ cell-cycle arrest and not a direct effect on BIK protein stability.
Biochem J. 2014; 459(3):513-24 [PubMed] Related Publications
BIK (BCL2-interacting killer) is a pro-apoptotic BH3 (BCL2 homology domain 3)-only protein and a member of the BCL2 protein family. It was proposed recently that BIK abundance is controlled by ERK1/2 (extracellular-signal-regulated kinase 1/2)-catalysed phosphorylation, which targets the protein for proteasome-dependent destruction. In the present study, we examined ERK1/2-dependent regulation of BIK, drawing comparisons with BIM(EL) (BCL2-interacting mediator of cell death; extra long), a well-known target of ERK1/2. In many ERK1/2-dependent tumour cell lines, inhibition of BRAF(V600E) (v-raf murine sarcoma viral oncogene homologue B1, V600E mutation) or MEK1/2 (mitogen-activated protein kinase/ERK kinase 1/2) had very little effect on BIK expression, whereas BIM(EL) was strongly up-regulated. In some cell lines we observed a modest increase in BIK expression; however, this was not apparent until ~16 h or later, whereas BIM(EL) expression increased rapidly within a few hours. Although BIK was degraded by the proteasome, we found no evidence that this was regulated by ERK1/2 signalling. Rather, the delayed increase in BIK expression was prevented by actinomycin D, and was accompanied by increases in BIK mRNA. Finally, the delayed increase in BIK expression following ERK1/2 inhibition was phenocopied by a highly selective CDK4/6 (cyclin-dependent kinases 4 and 6) inhibitor, which caused a strong G₁ cell-cycle arrest without inhibiting ERK1/2 signalling. In contrast, BIM(EL) expression was induced by ERK1/2 inhibition, but not by CDK4/6 inhibition. We conclude that BIK expression is not subject to direct regulation by the ERK1/2 pathway; rather, we propose that BIK expression is cell-cycle-dependent and increases as a consequence of the G₁ cell-cycle arrest which results from inhibition of ERK1/2 signalling.

Viedma-Rodriguez R, Baiza-Gutman LA, García-Carrancá A, et al.
Suppression of the death gene BIK is a critical factor for resistance to tamoxifen in MCF-7 breast cancer cells.
Int J Oncol. 2013; 43(6):1777-86 [PubMed] Free Access to Full Article Related Publications
Apoptosis is controlled by the BCL-2 family of proteins, which can be divided into three different subclasses based on the conservation of BCL-2 homology domains. BIK is a founding member of the BH3-only pro-apoptotic protein family. BIK is predominantly localized in the endoplasmic reticulum (ER) and induces apoptosis through the mitochondrial pathway by mobilizing calcium from the ER to the mitochondria. In this study, we determined that suppression of the death gene Bik promotes resistance to tamoxifen (TAM) in MCF-7 breast cancer cells. We utilized small interfering (siRNA) to specifically knockdown BIK in MCF-7 cells and studied their response to tamoxifen. The levels of cell apoptosis, the potential mitochondrial membrane (∆Ψ(m)), and the activation of total caspases were analyzed. Western blot analysis was used to determine the expression of some BCL-2 family proteins. Flow cytometry studies revealed an increase in apoptosis level in MCF-7 cells and a 2-fold increase in relative BIK messenger RNA (mRNA) expression at a concentration of 6.0 μM of TAM. BIK silencing, with a specific RNAi, blocked TAM-induced apoptosis in 45 ± 6.78% of cells. Moreover, it decreased mitochondrial membrane potential (Ψm) and total caspase activity, and exhibited low expression of pro-apoptotic proteins BAX, BAK, PUMA and a high expression of BCl-2 and MCL-1. The above suggests resistance to TAM, regulating the intrinsic pathway and indicate that BIK comprises an important factor in the process of apoptosis, which may exert an influence the ER pathway, which regulates mitochondrial integrity. Collectively, our results show that BIK is a central component of the programmed cell death of TAM-induced MCF-7 breast cancer cells. The silencing of BIK gene will be useful for future studies to establish the mechanisms of regulation of resistance to TAM.

Wei X, Lv T, Chen D, Guan J
Lentiviral vector mediated delivery of RHBDD1 shRNA down regulated the proliferation of human glioblastoma cells.
Technol Cancer Res Treat. 2014; 13(1):87-93 [PubMed] Related Publications
Rhomboid domain containing 1 (RHBDD1) gene, a new member of rhomboid family of proteins is highly responsible for the regulation of apoptosis by cleaving pro-apoptotic Bcl-2 family protein BIK. Therefore, the higher expression levels of RHBDD1 in cancer tissues may have a direct influence on cancer progression by arresting apoptosis. With this background this study was focused to find out the effect of RHBDD1 silencing on the progression of human brain glioblastoma cells, U251 and U87MG. The results indicated that both cell lines show a higher expression level of RHBDD1 and RNA interference (RNA) mediated gene silencing successfully down regulated the RHBDD1 gene expression. As a result of RHBDD1 silencing the proliferation of both cell types was reduced by over 50%, 5 days after silencing. Moreover the colony formation was completely inhibited and there were no cells present following two week RHBDD1 gene silencing. The cell proliferation was inhibited as a result of cell cycle arrest due to RHBDD1 absence. Therefore, these results clearly indicate that, RHBDD1 is essential for the progression of glioblastoma cells and silencing of it is resulting in significant inhibition of cell cycle progression and cell proliferation. Collectively, this study shows that RHBDD1 gene engineering could be used as an effective tool in malignant brain tumor therapy.

van Boxtel R, Gomez-Puerto C, Mokry M, et al.
FOXP1 acts through a negative feedback loop to suppress FOXO-induced apoptosis.
Cell Death Differ. 2013; 20(9):1219-29 [PubMed] Free Access to Full Article Related Publications
Transcriptional activity of Forkhead box transcription factor class O (FOXO) proteins can result in a variety of cellular outcomes depending on cell type and activating stimulus. These transcription factors are negatively regulated by the phosphoinositol 3-kinase (PI3K)-protein kinase B (PKB) signaling pathway, which is thought to have a pivotal role in regulating survival of tumor cells in a variety of cancers. Recently, it has become clear that FOXO proteins can promote resistance to anti-cancer therapeutics, designed to inhibit PI3K-PKB activity, by inducing the expression of proteins that provide feedback at different levels of this pathway. We questioned whether such a feedback mechanism may also exist directly at the level of FOXO-induced transcription. To identify critical modulators of FOXO transcriptional output, we performed gene expression analyses after conditional activation of key components of the PI3K-PKB-FOXO signaling pathway and identified FOXP1 as a direct FOXO transcriptional target. Using chromatin immunoprecipitation followed by next-generation sequencing, we show that FOXP1 binds enhancers that are pre-occupied by FOXO3. By sequencing the transcriptomes of cells in which FOXO is specifically activated in the absence of FOXP1, we demonstrate that FOXP1 can modulate the expression of a specific subset of FOXO target genes, including inhibiting expression of the pro-apoptotic gene BIK. FOXO activation in FOXP1-knockdown cells resulted in increased cell death, demonstrating that FOXP1 prevents FOXO-induced apoptosis. We therefore propose that FOXP1 represents an important modulator of FOXO-induced transcription, promoting cellular survival.

Pang CY, Chiu SC, Harn HJ, et al.
Proteomic-based identification of multiple pathways underlying n-butylidenephthalide-induced apoptosis in LNCaP human prostate cancer cells.
Food Chem Toxicol. 2013; 59:281-8 [PubMed] Related Publications
Although numerous studies have shown the cancer-preventive properties of butylidenephthalide (BP), there is little report of BP affecting human prostate cancer cells. In the present study, proteomic-based approaches were used to elucidate the anticancer mechanism of BP in LNCaP human prostate cancer cells. BP treatment decreased the viability of LNCaP human prostate cancer cells in a concentration- and time-dependent manner, which was correlated with G0/G1 phase cell cycle arrest. Increased cell cycle arrest was associated with a decrease in the level of CCND1, CDK2, and PCNA proteins and an increase in the level of CDKN2A, CDKN1A, and SFN proteins. Proteomic studies revealed that among 48 differentially expressed proteins, 25 proteins were down-regulated and 23 proteins were up-regulated and these proteins fall into one large protein protein interaction network. Among these proteins, FAS, AIFM1, BIK, CYCS, SFN, PPP2R1A, CALR, HSPA5, DDIT3, and ERN1 are apoptosis and endoplasmic reticulum (ER) stress associated proteins. Proteomic data suggested that multiple signaling pathways including FAS-dependent pathway, mitochondrial pathway, and ER stress pathway are involved in the apoptosis induced by BP.

Rubis B, Holysz H, Gladych M, et al.
Telomerase downregulation induces proapoptotic genes expression and initializes breast cancer cells apoptosis followed by DNA fragmentation in a cell type dependent manner.
Mol Biol Rep. 2013; 40(8):4995-5004 [PubMed] Free Access to Full Article Related Publications
The aim of the study was to analyze the consequence of silencing genes coding for the key subunits of the telomerase complex, i.e. TERT, TERC and TP1 in human breast cancer MCF7 and MDA-MB-231cells. The transfection was performed using Lipofectamine2000 and pooled siRNAs. The cytotoxic and/or antiproliferative effect of siRNA was measured by the SRB assay, the cell cycle was analysed by flow cytometry and DNA fragmentation by TUNEL analysis. Telomerase activity was assessed by TRAP, followed by PAGE and ELISA assays. Telomerase downregulation was also assessed using qPCR in order to estimate the changes in the expression profile of genes engaged in apoptosis. It was revealed that treatment of breast cancer cells with different siRNAs (100 nM) resulted in a cell type and time-dependent effects. The downregulation of telomerase subunits was followed by reduction of telomerase activity down to almost 60% compared to control cells. However, a significant effect was only observed when the TERT subunit was downregulated. Its silencing resulted in a significant (p<0.05) increase of apoptosis (over 10% in MCF7 and about 5% in MDA-MB-231 cells, corresponding to the Annexin V assay) and DNA fragmentation (almost 30% in MCF7 and over 25% in MDA-MB-231 cells). Interestingly, also several proapoptotic genes were induced after the downregulation of the key telomerase subunit, including Bax, Bik or caspase-1 and caspase-14, as well as NGFR and TNFSF10 which were upregulated twice and more.

Vasilatos SN, Katz TA, Oesterreich S, et al.
Crosstalk between lysine-specific demethylase 1 (LSD1) and histone deacetylases mediates antineoplastic efficacy of HDAC inhibitors in human breast cancer cells.
Carcinogenesis. 2013; 34(6):1196-207 [PubMed] Free Access to Full Article Related Publications
Our previous studies demonstrated that lysine-specific demethylase 1 (LSD1) and histone deacetylases (HDACs) closely interact in controlling growth of breast cancer cells. However, the underlying mechanisms are largely unknown. In this study, we showed that knockdown of LSD1 expression (LSD1-KD) by RNAi decreased mRNA levels of HDAC isozymes in triple-negative breast cancer (TNBC) cells. Small interfering RNA (siRNA)-mediated depletion of HDAC5 expression induced the most significant accumulation of H3K4me2, a specific substrate of LSD1. Combined treatment with LSD1 inhibitor, pargyline, and HDAC inhibitor, SAHA (Vorinostat), led to superior growth inhibition and apoptotic death in TNBC cells, but exhibited additive or antagonistic effect on growth inhibition in non-TNBC counterparts or non-tumorigenic breast cells. Additionally, LSD1-KD enhanced SAHA-induced reexpression of a subset of aberrantly silenced genes, such as NR4A1, PCDH1, RGS16, BIK, and E-cadherin whose reexpression may be tumor suppressive. Genome-wide microarray study in MDA-MB-231 cells identified a group of tumor suppressor genes whose expression was induced by SAHA and significantly enhanced by LSD1-KD. We also showed that concurrent depletion of RGS16 by siRNA reduced overall cytotoxicity of SAHA and blocked the reexpression of E-cadherin, CDKN1C and ING1 in LSD1-deficient MDA-MB-231 cells. Furthermore, cotreatment with RGS16 siRNA reversed the downregulation of nuclear factor-kappaB expression induced by combined inhibition of LSD1 and HDACs, suggesting a crucial role of RGS16 in controlling key pathways of cell death in response to combination therapy. Taken together, these results provide novel mechanistic insight into the breast cancer subtype-dependent role of LSD1 in mediating HDAC activity and therapeutic efficacy of HDAC inhibitor.

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