CASP6

Gene Summary

Gene:CASP6; caspase 6
Aliases: MCH2
Location:4q25
Summary:This gene encodes a member of the cysteine-aspartic acid protease (caspase) family of enzymes. Sequential activation of caspases plays a central role in the execution-phase of cell apoptosis. Caspases exist as inactive proenzymes which undergo proteolytic processing at conserved aspartic acid residues to produce two subunits, large and small, that dimerize to form the active enzyme. This protein is processed by caspases 7, 8 and 10, and is thought to function as a downstream enzyme in the caspase activation cascade. Alternative splicing of this gene results in multiple transcript variants that encode different isoforms. [provided by RefSeq, Oct 2015]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:caspase-6
Source:NCBIAccessed: 16 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 16 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.

Tag cloud generated 16 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (5)

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: CASP6 (cancer-related)

Patel N, Garikapati KR, Ramaiah MJ, et al.
miR-15a/miR-16 induces mitochondrial dependent apoptosis in breast cancer cells by suppressing oncogene BMI1.
Life Sci. 2016; 164:60-70 [PubMed] Related Publications
AIMS: miRNAs are small non-coding RNA molecules that regulate post-transcriptional gene expression. Here we have made an endeavor to search whether any miRNAs are involved in the regulation of BMI1 in breast cancer that leads to mitochondrial dependent apoptotic cell death.
MAIN METHODS: Renilla luciferase reporter assay was performed to detect the ectopically expressed miRNAs that regulate the expression of 3' UTR of BMI1. MTT assay was performed to check the cytotoxicity level. Western blotting and qRT-PCR were performed to check the expression of BMI1, pro-apoptotic, anti-apoptotic proteins and mRNA expression levels respectively. JC-1 staining, Caspase-3, Caspase-6/9 assay and mitochondrial cytosolic fractionation were performed to monitor mitochondrial dependent apoptosis. Wound healing assay was performed to investigate migration. All experiments were performed upon miR-15a and miR-16 overexpression in MCF-7, MDAMB-231 breast cancer cells.
KEY FINDINGS: In MCF-7, MDAMB-231 breast cancer cells luciferase reporter assay confirmed the significant reduction of reporter activity upon co-transfection of 3' UTR of BMI1 along with miR-15a and miR-16. miR-15a and miR-16 significantly down-regulated BMI1 protein and mRNA expression levels as well as anti-apoptotic protein BCL2 and up-regulated pro-apoptotic proteins. Ectopic expression of miR-15a, miR-16, increased mitochondrial ROS resulting in impaired mitochondrial membrane potential, followed by cytochrome-C release into the cytosol that activated Caspase-3 and Caspase-6/9 leading to intrinsic apoptosis. Additionally, it also inhibits migration.
SIGNIFICANCE: Our results suggest that overexpression of miR-15a and miR-16 mediates down-regulation of BMI1, and leads to mitochondrial mediated apoptosis.

Zhang L, Ren J, Zhang H, et al.
HER2-targeted recombinant protein immuno-caspase-6 effectively induces apoptosis in HER2-overexpressing GBM cells in vitro and in vivo.
Oncol Rep. 2016; 36(5):2689-2696 [PubMed] Related Publications
Glioblastoma multiforme (GBM), which is associated with a high rate of morbidity and mortality, is among the most malignant and treatment-refractory neoplasms in human adults. As GBM is highly resistant to conventional therapies, immunotherapies are a promising treatment candidate. HER2 is an attractive target for GBM immunotherapy, as its expression is highly associated with various types of GBM. We previously reported that a novel HER2-targeted recombinant protein e23sFv-Fdt-casp6 has an antitumor effect on HER2-positive gastric cancer cells. In this study, we established a genetically modified Chinese hamster ovary cell line, which produced and secreted e23sFv-Fdt-casp6 proteins. Following specific binding to and internalization into HER2-overexpressing tumor cells, the e23sFv-Fdt-casp6 protein induced tumor cell apoptosis and inhibited the proliferation of HER2-overexpressing A172 and U251MG cells in vitro, but not in U87MG cells with undetectable HER2. The e23sFv-Fdt-casp6 gene was introduced into severe combined immunodeficient mice bearing human glioblastoma xenografts by using intramuscular injections of a liposome-encapsulated vector. The recombinant protein e23sFv-Fdt-casp6 specifically targeted tumor cells and induced apoptosis, thereby leading to potent inhibition of tumor growth and prolonged the survival time of tumor-bearing mice. We concluded that e23sFv‑Fdt‑casp6 represents a promising HER2-targeted treatment option for human gliomas.

Kim SH, Ho JN, Jin H, et al.
Upregulated expression of BCL2, MCM7, and CCNE1 indicate cisplatin-resistance in the set of two human bladder cancer cell lines: T24 cisplatin sensitive and T24R2 cisplatin resistant bladder cancer cell lines.
Investig Clin Urol. 2016; 57(1):63-72 [PubMed] Free Access to Full Article Related Publications
PURPOSE: The mechanism of resistance to cisplatin during treatment of bladder cancer (BC) has been a subject of intense investigation in clinical research. This study aims to identify candidate genes associated with resistance to cisplatin, in order to understand the resistance mechanism of BC cells to the drug, by combining the use of microarray profiling, quantitative reverse transcription-polymerase chain reaction (RT-PCR), and Western blot analyses.
MATERIALS AND METHODS: The cisplatin sensitive human BC cell line (T24) and the cisplatin resistant BC cell line, T24R2, were used for microarray analysis to determine the differential expression of genes that are significant in cisplatin resistance. Candidate upregulated genes belonging to three well-known cancer-related KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways (p53 tumor suppressor, apoptosis, and cell cycle) were selected from the microarray data. These candidate genes, differentially expressed in T24 and T24R2, were then confirmed by quantitative RT-PCR and western blot. A fold change ≥2 with a p-value <0.05 was considered significant.
RESULTS: A total of 18 significantly upregulated genes were detected in the three selected cancer-related pathways in both microarray and RT-PCR analyses. These genes were PRKAR2A, PRKAR2B, CYCS, BCL2, BIRC3, DFFB, CASP6, CDK6, CCNE1, STEAP3, MCM7, ORC2, ORC5, ANAPC1, and ANAPC7, CDC7, CDC27, and SKP1. Western blot analyses also confirmed the upregulation of BCL2, MCM7, and CCNE1 at the protein level, indicating their crucial association with cisplatin resistance.
CONCLUSIONS: The BCL2, MCM7, and CCNE1 genes might play distinctive roles in cisplatin resistance in BC.

Song S, Wang Y, Xu P, et al.
The inhibition of histone deacetylase 8 suppresses proliferation and inhibits apoptosis in gastric adenocarcinoma.
Int J Oncol. 2015; 47(5):1819-28 [PubMed] Related Publications
Histone deacetylase 8 (HDAC8), a unique member of class I HDACs, shows remarkable correlation with advanced disease stage. The depletion of HDAC8 leads to inhibition of proliferation, apoptosis and cell cycle arrest in multiple malignant tumors. However, little is known about the contribution of HDAC8 to the tumorigenesis of gastric cancer (GC). The present study investigated expression of HDAC8 in GC cell lines and tissues, and the roles of HDAC8 inhibition in the proliferation, cell cycle and apoptosis of gastric cancer cells and explored the potential mechanisms. In the present study, quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), western blotting, and immunohistochemistry were used to examine the mRNA and protein expression of HDAC8 in GC cell lines and tissues. Then, the correlation between the clinicopathological parameters and the expression of HDAC8 was assessed. Finally, siRNA transfection and HDAC8 plasmid was performed to explore the functions of HDAC8 in GC progression in vitro. We found that the expression of HDAC8 was significantly upregulated both in GC cell lines and tumor tissues compared to human normal gastric epithelial cell, GES-1 and matched non-tumor tissues. Furthermore, depletion of HDAC8 remarkably inhibited GC cell proliferation, increased the apoptosis rate and G0/G1 phase percentage in vitro. Western blotting showed that the expression of protein promoting apoptosis such as, Bmf, activated caspase-3, caspase-6 were elevated following HDAC8 depletion. Our data exhibited an important role of HDAC8 in promoting gastric cancer tumorigenesis and identify this HDAC8 as a potential therapeutic target for the treatment of gastric cancer.

Zhang Y, Yu J, Liu H, et al.
Novel Epigenetic CREB-miR-630 Signaling Axis Regulates Radiosensitivity in Colorectal Cancer.
PLoS One. 2015; 10(8):e0133870 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: miR-630 has been reported to be a modulator of several cancers, but the mechanism by which is it influences radioresistance remains unknown. We aimed to identify the molecular function of miR-630 and its regulatory mechanism in colorectal cancer (CRC) cell lines.
METHODOLOGY: Overexpression and loss-of-function analyses of miR-630 were performed in CRC cell lines by measuring their levels of growth and apoptosis after ionic radiation (IR). Target genes were detected via a dual-luciferase assay and Western blot. Chromatin immunoprecipitation assay was carried out to identify the transcription factor regulating miR-630, and a demethylation experiment was also conducted.
RESULTS: miR-630 expression was found to be positively correlated with radiosensitivity in CRC cell lines (p<0.05). After IR treatment, miR-630 induced apoptosis in cells; however, the opposite was observed when miR-630 was downregulated (p<0.05). BCL2L2 and TP53RK were identified as the target genes of miR-630, and the function of miR-630 was found to depend on these two genes (p<0.05). In addition, evidence showed that CREB regulates the level of miR-630, and demethylation can elevate miR-630 levels (p<0.05).
CONCLUSION: CREB-miR-630-BCL2L2 and TP53RK comprise a novel signaling cascade regulating radiosensitivity in CRC cell lines by inducing cell apoptosis and death.

Petchsak P, Sripanidkulchai B
Momordica cochinchinensis Aril Extract Induced Apoptosis in Human MCF-7 Breast Cancer Cells.
Asian Pac J Cancer Prev. 2015; 16(13):5507-13 [PubMed] Related Publications
Momordica cochinchinensis Spreng (MC) has been used in traditional medicine due to its high carotenoid content. The objective of this study was to investigate mechanisms underlying apoptotic effects of MC on human MCF-7 breast cancer cells. A lycopene-enriched aril extract of MC (AE) showed cytotoxicity and antiestrogenicity to MCF-7 cells. On DAPI staining, AE induced cell shrinkage and chromatin condensation were evident. With flow cytometric analysis, AE increased the percentage of cells in an early apoptosis stage when compared with the control group. RT-PCR analysis showed AE to significantly increase the expression of the proapoptotic bax gene without effect on expression of the anti-apoptotic bcl-2 gene. Moreover, AE enhanced caspase 6, 8 and 9 activity. Taken together, we conclude that AE of MC fruit has anticancer effects on human MCF-7 breast cancer cells by induction of cell apoptosis via both intrinsic and extrinsic pathways of signaling.

Zheng N, Zhang P, Huang H, et al.
ERα down-regulation plays a key role in silibinin-induced autophagy and apoptosis in human breast cancer MCF-7 cells.
J Pharmacol Sci. 2015; 128(3):97-107 [PubMed] Related Publications
The estrogen receptor alpha (ERα) has been proven to be one of the most important therapeutic targets in breast cancer over the last 30 years. Previous studies pointed out that a natural flavonoid, silibinin, induced apoptosis in human breast cancer MCF-7 cells. In the present study we report that exposure of MCF-7 cells to silibinin led to cell death through the down-regulation of ERα expression. Silibinin-induced apoptosis of MCF-7 cells through up-regulation of caspase 6 due to ERα signalling repression was further boosted by ERα antagonist. Moreover, up-regulation of autophagy induced by silibinin accounted for apoptotic exacerbation, being further enhanced by ERα inhibition. Upon ERα activation, series of downstream signalling pathways can be activated. We found that silibinin reduced the expressions of Akt/mTOR and extracellular-signal-related kinase (ERK), which respectively accounted for the induction of autophagy and apoptosis. These effects were further augmented by co-treatment with ERα inhibitor. We conclude that the treatment with silibinin of ERα-positive MCF-7 cells down-regulates the expression of ERα, and subsequently mTOR and ERK signaling pathways, ERα downstream, finally resulting in induction of autophagy and apoptosis.

Guzzo MF, Carvalho LR, Bronstein MD
Ketoconazole Treatment Decreases the Viability of Immortalized Pituitary Cell Lines Associated with an Increased Expression of Apoptosis-Related Genes and Cell Cycle Inhibitors.
J Neuroendocrinol. 2015; 27(7):616-23 [PubMed] Related Publications
Ketoconazole, which was initially developed as an antifungal agent, is a potent inhibitor of adrenal steroidogenesis and has therefore been used in the management of Cushing's disease. Surprisingly, the reduction of cortisol levels during ketoconazole treatment is not accompanied by the expected elevation in plasma adrenocorticotrophic hormone (ACTH) at the loss of negative cortisol feedback from corticotrophic cells, suggesting a direct effect of ketoconazole on these cells. To characterize the direct effects of ketoconazole, we evaluated its in vitro effect on cell viability using the pituitary tumoural cell lines AtT-20 (which secretes ACTH), GH3 (which secretes growth hormone and prolactin) and αT3.1 (which secretes α-subunit) and we also determined the expression levels of genes involved in apoptosis and DNA replication by the quantitative reverse transcription polymerase chain reaction (qRT-PCR). We also evaluated ACTH levels in AtT-20 cells during ketoconazole treatment. We observed a ketoconazole concentration-dependent decrease in pituitary cell viability and reduced ACTH levels in AtT-20 cells after removal of the drug. We also observed increased expression of cell death receptors (e.g. Fas, tumour necrosis factor receptor) and caspases (e.g., caspase-6, caspase-7, caspase-9), suggesting activation of the apoptosis pathway. In addition, we observed increased gene expression of the cell cycle inhibitors p21 and p27 in GH3 cells and increased expression of p21 in αT3.1 cells. In conclusion, our findings suggest that ketoconazole significantly reduces cell viability in a concentration-dependent manner in pituitary tumour cell lines and is associated with an increase in apoptosis- and cell cycle regulation-related gene expression.

Picco R, Tomasella A, Fogolari F, Brancolini C
Transcriptomic analysis unveils correlations between regulative apoptotic caspases and genes of cholesterol homeostasis in human brain.
PLoS One. 2014; 9(10):e110610 [PubMed] Free Access to Full Article Related Publications
Regulative circuits controlling expression of genes involved in the same biological processes are frequently interconnected. These circuits operate to coordinate the expression of multiple genes and also to compensate dysfunctions in specific elements of the network. Caspases are cysteine-proteases with key roles in the execution phase of apoptosis. Silencing of caspase-2 expression in cultured glioblastoma cells allows the up-regulation of a limited number of genes, among which some are related to cholesterol homeostasis. Lysosomal Acid Lipase A (LIPA) was up-regulated in two different cell lines in response to caspase-2 down-regulation and cells silenced for caspase-2 exhibit reduced cholesterol staining in the lipid droplets. We expanded this observation by large-scale analysis of mRNA expression. All caspases were analyzed in terms of co-expression in comparison with 166 genes involved in cholesterol homeostasis. In the brain, hierarchical clustering has revealed that the expression of regulative apoptotic caspases (CASP2, CASP8 CASP9, CASP10) and of the inflammatory CASP1 is linked to several genes involved in cholesterol homeostasis. These correlations resulted in altered GBM (Glioblastoma Multiforme), in particular for CASP1. We have also demonstrated that these correlations are tissue specific being reduced (CASP9 and CASP10) or different (CASP2) in the liver. For some caspases (CASP1, CASP6 and CASP7) these correlations could be related to brain aging.

Yi S, Wen L, He J, et al.
Deguelin, a selective silencer of the NPM1 mutant, potentiates apoptosis and induces differentiation in AML cells carrying the NPM1 mutation.
Ann Hematol. 2015; 94(2):201-10 [PubMed] Related Publications
Nucleophosmin (NPM1) is a multifunctional protein that functions as a molecular chaperone, shuttling between the nucleolus and the cytoplasm. In up to one third of patients with acute myeloid leukemia, mutation of NPM1 results in the aberrant cytoplasmic accumulation of mutant protein and is thought to be responsible for leukemogenesis. Deguelin, a rotenoid isolated from several plant species, has been shown to be a strong anti-tumor agent. Human leukemia cell lines were used for in vitro studies. Drug efficacy was evaluated by apoptosis and differentiation assays, and associated molecular events were assessed by Western blot. Gene silencing was performed using small interfering RNA (siRNA). Deguelin exhibited strong cytotoxic activity in the cell line of OCI-AML3 and selectively down-regulated the NPM1 mutant protein, which was accompanied by up-regulation of the activity of caspase-6 and caspase-8 in high concentrations. Deguelin induced differentiation of OCI-AML3 cells at a nontoxic concentration which was associated with a decrease in expression of activated caspase-8, p53, p21, and the 30-kD form of CCAAT/enhancer binding protein α (C/EBPα), whereas no effects were found in OCIM2 cells expressing NPM-wt. Moreover, treatment with siRNA in the NPM mutant cell line OCI-AML3 decreased expression of p53, p21, pro-caspase-8, and the 30-kD form of C/EBPα, and it inhibited proliferation and induced differentiation of the OCI-AML3 cells. In conclusion, deguelin is a potent in vitro inhibitor of the mutant form of NPM1, which provides the molecular basis for its anti-leukemia activities in NPM1 mutant acute myeloid leukemia cells.

Wu W, Tan XF, Tan HT, et al.
Unbiased proteomic and transcript analyses reveal that stathmin-1 silencing inhibits colorectal cancer metastasis and sensitizes to 5-fluorouracil treatment.
Mol Cancer Res. 2014; 12(12):1717-28 [PubMed] Related Publications
UNLABELLED: Colorectal cancer metastasis is a major cause of mortality worldwide, which may only be controlled with novel methods limiting tumor dissemination and chemoresistance. High stathmin-1 (STMN1) expression was previously established as a hallmark of colorectal cancer progression and predictor of poor survival; however, the mechanism of action is less clear. This work demonstrates that STMN1 silencing arrests tumor-disseminative cascades by inhibiting multiple metastatic drivers, and repressing oncogenic and mesenchymal transcription. Using a sensitive iTRAQ labeling proteomic approach that quantified differential abundance of 4562 proteins, targeting STMN1 expression was shown to reinstate the default cellular program of metastatic inhibition, and promote cellular adhesion via amplification of hemidesmosomal junctions and intermediate filament tethering. Silencing STMN1 also significantly improved chemoresponse to the classical colorectal cancer therapeutic agent, 5FU, via a novel caspase-6 (CASP6)-dependent mechanism. Interestingly, the prometastatic function of STMN1 was independent of p53 but required phosphorylations at S25 or S38; abrogating phosphorylative events may constitute an alternative route to achieving metastatic inhibition. These findings establish STMN1 as a potential target in antimetastatic therapy, and demonstrate the power of an approach coupling proteomics and transcript analyses in the global assessment of treatment benefits and potential side-effects.
IMPLICATIONS: Stathmin-1 is a potential candidate in colorectal cancer therapy that targets simultaneously the twin problems of metastatic spread and chemoresistance.

Yang KM, Kim BM, Park JB
ω-Hydroxyundec-9-enoic acid induces apoptosis through ROS-mediated endoplasmic reticulum stress in non-small cell lung cancer cells.
Biochem Biophys Res Commun. 2014; 448(3):267-73 [PubMed] Related Publications
ω-Hydroxyundec-9-enoic acid (ω-HUA), a hydroxyl unsaturated fatty acid derivative, is involved in the antifungal activity of wild rice (Oryza officinalis). Here, we investigated the anti-cancer activity of ω-HUA on a non-small cell lung cancer (NSCLC) cell line. ω-HUA increased apoptosis and induced cleavages of caspase-6, caspase-9, and poly (ADP-ribose) polymerase (PARP). ω-HUA treatment significantly induced endoplasmic reticulum (ER) stress response. Suppression of CHOP expression and inhibiting ER stress by 4-phenylbutyrate (4-PBA) significantly attenuated the ω-HUA treatment-induced activation of caspase-6, caspase-9, and PARP, and subsequent apoptotic cell death, indicating a role for ER stress in ω-HUA-induced apoptosis. In addition, cells subjected to ω-HUA exhibited significantly increased quantity of reactive oxygen species (ROS), and the ROS scavenger N-acetyl-L-cysteine (NAC) inhibited ω-HUA-induced apoptotic cell death and ER stress signals, indicating a role for ROS in ER stress-mediated apoptosis in ω-HUA-treated cells. Taken together, these results suggest that sequential ROS generation and ER stress activation are critical in ω-HUA treatment-induced apoptosis and that ω-HUA represents a promising candidate for NSCLC treatment.

Di Martino MT, Campani V, Misso G, et al.
In vivo activity of miR-34a mimics delivered by stable nucleic acid lipid particles (SNALPs) against multiple myeloma.
PLoS One. 2014; 9(2):e90005 [PubMed] Free Access to Full Article Related Publications
Multiple myeloma (MM) is a disease with an adverse outcome and new therapeutic strategies are urgently awaited. A rising body of evidence supports the notion that microRNAs (miRNAs), master regulators of eukaryotic gene expression, may exert anti-MM activity. Here, we evaluated the activity of synthetic miR-34a in MM cells. We found that transfection of miR-34a mimics in MM cells induces a significant change of gene expression with relevant effects on multiple signal transduction pathways. We detected early inactivation of pro-survival and proliferative kinases Erk-2 and Akt followed at later time points by caspase-6 and -3 activation and apoptosis induction. To improve the in vivo delivery, we encapsulated miR-34a mimics in stable nucleic acid lipid particles (SNALPs). We found that SNALPs miR-34a were highly efficient in vitro in inhibiting growth of MM cells. Then, we investigated the activity of the SNALPs miR-34a against MM xenografts in SCID mice. We observed significant tumor growth inhibition (p<0.05) which translated in mice survival benefits (p=0.0047). Analysis of miR-34a and NOTCH1 expression in tumor retrieved from animal demonstrated efficient delivery and gene modulation induced by SNALPs miR-34a in the absence of systemic toxicity. We here therefore provide evidence that SNALPs miR-34a may represent a promising tool for miRNA-therapeutics in MM.

Chen MH, Hagemann TL, Quinlan RA, et al.
Caspase cleavage of GFAP produces an assembly-compromised proteolytic fragment that promotes filament aggregation.
ASN Neuro. 2013; 5(5):e00125 [PubMed] Free Access to Full Article Related Publications
IF (intermediate filament) proteins can be cleaved by caspases to generate proapoptotic fragments as shown for desmin. These fragments can also cause filament aggregation. The hypothesis is that disease-causing mutations in IF proteins and their subsequent characteristic histopathological aggregates could involve caspases. GFAP (glial fibrillary acidic protein), a closely related IF protein expressed mainly in astrocytes, is also a putative caspase substrate. Mutations in GFAP cause AxD (Alexander disease). The overexpression of wild-type or mutant GFAP promotes cytoplasmic aggregate formation, with caspase activation and GFAP proteolysis. In this study, we report that GFAP is cleaved specifically by caspase 6 at VELD²²⁵ in its L12 linker domain in vitro. Caspase cleavage of GFAP at Asp²²⁵ produces two major cleavage products. While the C-GFAP (C-terminal GFAP) is unable to assemble into filaments, the N-GFAP (N-terminal GFAP) forms filamentous structures that are variable in width and prone to aggregation. The effect of N-GFAP is dominant, thus affecting normal filament assembly in a way that promotes filament aggregation. Transient transfection of N-GFAP into a human astrocytoma cell line induces the formation of cytoplasmic aggregates, which also disrupt the endogenous GFAP networks. In addition, we generated a neo-epitope antibody that recognizes caspase-cleaved but not the intact GFAP. Using this antibody, we demonstrate the presence of the caspase-generated GFAP fragment in transfected cells expressing a disease-causing mutant GFAP and in two mouse models of AxD. These findings suggest that caspase-mediated GFAP proteolysis may be a common event in the context of both the GFAP mutation and excess.

Ryu JS, Lee JT, Lim MU, et al.
Plant-derived mAbs have effective anti-cancer activities by increasing ganglioside expression in colon cancers.
Biotechnol Lett. 2013; 35(12):2031-8 [PubMed] Related Publications
An epithelial cell adhesion molecule (EpCAM) was selectively expressed in human colorectal carcinoma. Treatment with plant-derived anti-EpCAM mAb (mAbP CO17-1A) and RAW264.7 cells inhibited cell growth in the human colorectal cancer cell line SW620. In SW620 treated with mAbP CO17-1A and RAW264.7 cells, expression of p53 and p21 increased, whereas the expression of G1 phase-related proteins, cyclin D1, CDK4, cyclin E, and CDK2, decreased, similar to mammalian-derived mAb (mAbM) CO17-1A. Similar to mAbM CO17-1A, treatment with mAbP CO17-1A and RAW264.7 cell decreased the expression of anti-apoptotic protein, Bcl-2, but the expression of pro-apoptotic proteins Bax, TNF-α, caspase-3, caspase-6, caspase-8 and caspase-9, increased. Cells treated with mAbP CO17-1A and RAW264.7 cells expressed metastasis-related gangliosides, GM1 and GD1a, similar to mAbM CO17-1A. These results suggest that mAbP CO17-1A is as effective on anti-cancer activity as mAbM CO17-1A.

Zheng Z, Yang J, Zhao D, et al.
Downregulated adaptor protein p66(Shc) mitigates autophagy process by low nutrient and enhances apoptotic resistance in human lung adenocarcinoma A549 cells.
FEBS J. 2013; 280(18):4522-30 [PubMed] Related Publications
Macroautophagy or autophagy is a lysosome-dependent process in which enzymatic degradation and recycling of cytosolic components occur in stressful contexts. The mechanisms underlying the signaling from starvation to the regulation of autophagy are not fully understood. We previously showed that the Src family member p66(Shc) (focal adhesion-associated 66 kDa isoform of the Src homology and collagen) promotes anoikis and suppresses tumor metastasis via k-Ras-dependent control of proliferation and survival. However, the role of p66(Shc) in low-nutrient-induced autophagy-related pathways remains elusive. In this work, human lung adenocarcinoma A549 cells were used to further investigate the biological effects of p66(Shc) on autophagy and apoptotic resistance. Here, we show that deficiency of p66(Shc) mitigates the low-nutrient-induced autophagy process in the levels of microtubule-associated protein 1A light chain protein 3B (LC3B) conversion, in the number of autophagic vacuoles and in p62/sequestosome 1 protein degradation. However, autophagy-related protein Beclin 1 was not significantly changed during low-nutrient treatment. Furthermore, we found that prolonged phosphorylation of extracellular signaling-regulated kinase (Erk)1/2, but not phosphorylation of Akt is significantly sustained when p66(Shc) expression is inhibited by shRNA. In addition, cleavage of caspase 7 and poly(ADP-ribose) polymerase, but not caspase 6 and 9 are retarded with this effect compared to the shRNA control cells. Together, these findings suggest the possibility that p66(Shc) plays a pivotal role in coordinately regulating autophagy process and apoptotic resistance in A549 cells under nutrient-limited conditions.

Guan X, Liu Z, Liu H, et al.
A functional variant at the miR-885-5p binding site of CASP3 confers risk of both index and second primary malignancies in patients with head and neck cancer.
FASEB J. 2013; 27(4):1404-12 [PubMed] Free Access to Full Article Related Publications
Caspases are important regulators and executioners in the apoptosis pathways and play crucial roles in carcinogenesis. We tested the hypothesis that functional variants of CASP genes are associated with risk of squamous cell carcinoma of the head and neck (SCCHN) and second primary malignancy (SPM). We genotyped 7 selected, potentially functional single nucleotide polymorphisms (SNPs) located in the microRNA binding sites of the 3' untranslational region (UTR; 2 in CASP3, 1 in CASP6, and 4 in CASP7) and evaluated their associations first with risk of SCCHN in 1066 patients with SCCHN and 1074 cancer-free control subjects and then with SPM in 846 patients in the same non-Hispanic white study population. We found that compared with the CASP3 TT genotype of rs1049253, the variant TC/CC genotypes were associated with significantly increased risk of SCCHN (adjusted odds ratio=1.29 and 95% confidence interval=1.07-1.56) and SPM (adjusted hazard ratio=1.79 and 95% CI=1.02-3.16) and worse SPM-free survival (log-rank P = 0.020), but no associations were found for the other 6 SNPs. We then performed additional experiments to seek functional relevance of the rs1049253 SNP. First, the luciferase activity and miR-885-5p mimic transfection tests suggested that CASP3 was the target of miR-885-5p and that rs1049253T>C resulted in altered regulation of the CASP3 expression. Second, the rs1049253 CC genotype was associated with reduced levels of CASP3 mRNA in peripheral blood mononuclear cells from 118 SCCHN patients and 103 cancer-free control subjects and lower levels of CASP3 protein expression in 11 head and neck cancer cell lines, compared with the TT genotype. Taken together, our data suggest that the miR-885-5p binding site rs1049253T>C SNP in the 3'-UTR of CASP3 modulates CASP3 expression at both mRNA and protein levels and thus contributes to SCCHN susceptibility.

Wong FY, Liem N, Xie C, et al.
Combination therapy with gossypol reveals synergism against gemcitabine resistance in cancer cells with high BCL-2 expression.
PLoS One. 2012; 7(12):e50786 [PubMed] Free Access to Full Article Related Publications
Although gemcitabine is highly active in several cancer types, intrinsic and acquired drug resistance remains a major challenge. Overexpression of Bcl-2 has been associated with gemcitabine resistance. The aim of this study is to determine whether gossypol can overcome gemcitabine resistance in cell lines with high level of Bcl-2 expression in combination drug therapy. Our study demonstrated that in 10 cell lines derived from different cancers, high Bcl-2 baseline expression was observed in cell lines that were resistant to gemcitabine (GEM-R). Furthermore, synergistic effect of combination therapy was observed in gemcitabine-resistant (GEM-R) cell lines with high Bcl-2 expression, but not in a gemcitabine-sensitive (GEM-S) cell lines regardless of Bcl-2 expression. Gossypol treatment resulted in the decrease of anti-apoptotic genes such as Bcl-2 and Bcl-xl and an upregulation of the pro-apoptotic gene, Noxa. Furthermore, the addition of gossypol to gemcitabine resulted in lower expressions of anti-apoptotic genes compared to gemcitabine alone. Gene expression profiling in GEM-R and GEM-S cell lines suggest that anti-apoptotic genes such as pAkt and PI3KR2 may play important role in gemcitabine resistance, while pro-apoptotic Bcl-2 related genes (Bad, Caspase-6 and Calpain-1) may regulate synergistic interaction in combination therapy.

Zhou BG, Liu MY, Qiu XC, et al.
A novel recombinant immunocasp-6 fusion gene specifically and efficiently suppresses HER2-overexpressing osteosarcoma.
Oncol Rep. 2013; 29(1):276-82 [PubMed] Related Publications
Osteosarcoma is the most common primary malignant tumor of bone for adolescent or children. The poor prognosis of patients, due to its remote metastasis, has led to the exploration of more effective and less toxic treatments. Immunotherapy is a promising strategy for the treatment of human epidermal growth factor receptor 2 (HER2)-overexpressing tumors. Herein, we describe experiments conducted with a fusion gene, immunocasp-6, which was generated by fusing a HER2-specific single-chain Ab, a single-chain Pseudomonas exotoxin A and an active caspase-6 which can directly cleave lamin A leading to nucleus damage inducing programmed cell death. We demonstrated that immunocasp-6 can specifically and efficiently recognize and induce apoptosis in HER2-overexpressing osteosarcoma cells in vitro. The immunocasp-6 was transferred into BALB/c athymic mice bearing human osteosarcoma by i.m. injection of liposome-encapsulated pCMV-immunocap-6. Expression of immunocasp-6 not only strongly inhibited tumor growth and significantly prolonged animal survival, but also greatly prevented tumor metastasis. Our data showed that the immuno-casp-6 can specifically recognize HER2-overexpressing osteosarcoma cells, can also promptly attack their nucleus and induce apoptotic death, suggesting the potential of this strategy for the treatment of human HER2-overexpressing tumors.

Ptak A, Kolaczkowska E, Gregoraszczuk EL
Leptin stimulation of cell cycle and inhibition of apoptosis gene and protein expression in OVCAR-3 ovarian cancer cells.
Endocrine. 2013; 43(2):394-403 [PubMed] Free Access to Full Article Related Publications
The OVCAR-3 cell line expressing the long (ObRb) and short (ObRt) isoforms of leptin receptor mRNA was used to analyze the effect of leptin on the expression of selected genes and proteins involved in the cell cycle and apoptosis. OVCAR-3 cells were exposed to 2, 20, 40, and 100 ng/ml of leptin. Cell proliferation was determined using the alamarBlue cell viability test and flow cytometry. Apoptosis was measured using a cellular DNA fragmentation ELISA kit. The expression of selected cell cycle and apoptosis genes was evaluated by real-time PCR and confirmed by western blot. The stimulatory action of leptin on cell proliferation was observed as an increase in cells in the S and G2/M phases. Up-regulation of genes responsible for inducing cell proliferation and suppression of genes responsible for inhibition of proliferation were noted. Western blots revealed increased expression of cyclins D and A and inhibition of p21WAF1/CIP1 protein expression by leptin. Inhibition of DNA fragmentation was observed under all leptin doses. Suppression of genes involved in the extrinsic and intrinsic apoptotic pathway was observed. Western blots illustrated decreased Bad, TNFR1, and caspase 6 protein expression in response to leptin treatment. Leptin promotes ovarian cancer cell line growth by up-regulating genes and proteins responsible for inducing cell proliferation as well as down-regulating pro-apoptotic genes and proteins in apoptotic pathways. Results of this study warrant examining the relationship between the risk of ovarian cancer and elevated leptin levels in obese women.

Jin X, Wu XX, Jin C, et al.
Delineation of apoptotic genes for synergistic apoptosis of lexatumumab and anthracyclines in human renal cell carcinoma cells by polymerase chain reaction array.
Anticancer Drugs. 2012; 23(4):445-54 [PubMed] Related Publications
Lexatumumab, a human agonistic monoclonal antibody against tumor necrosis factor (TNF)-related apoptosis-inducing ligand receptor-2 (TRAIL-R2), is a promising molecular-targeted therapeutic agent. Our past study indicated that low concentrations of doxorubicin sensitized renal cell carcinoma (RCC) cells to lexatumumab-mediated apoptosis. The present study was designed to examine the cellular and molecular effects of lexatumumab and anthracyclines in RCC cells. The treatment of human RCC cells with lexatumumab in combination with anthracyclines, epirubicin, and pirarubicin had a synergistic cytotoxicity. A marked synergistic apoptosis was induced by lexatumumab in combination with epirubicin or pirarubicin. Epirubicin and pirarubicin significantly increased the TRAIL-R2 expression at both the mRNA and the protein levels. The combination-induced cytotoxicity was significantly suppressed by the human recombinant DR5:Fc chimeric protein. To further explore the molecular mechanisms in this synergistic cytotoxicity with lexatumumab and anthracyclines, the changes in 84 apoptosis-related genes were evaluated by a quantitative polymerase chain reaction (PCR) array. Among these genes, 18 (CD40LG, FASLG, LTA, TNSF7, FAS, BAG3, BAK1, BAX, BID, BIK, BCL10, caspase-1, caspase-5, caspase-6, caspase-10, TNF receptor-associated factor 1, PYCARD, and CIDEA) were significantly upregulated and eight (TNF receptor-associated factor 4, TNFRSF11B, TNF, BCL2, BCL2L1, BNIP3L, caspase-9, and DAPK1) were downregulated at mRNA levels in RCC cells cotreated with lexatumumab and epirubicin. Furthermore, the upregulation of mRNA levels of PYCARD and CIDEA was confirmed using real-time reverse transcriptase-PCR analysis. The present study demonstrates that anthracylines sensitize RCC cells to lexatumumab-mediated apoptosis by inducing TRAIL-R2 expression, and the utility of PCR array to elucidate the mechanism of synergistic apoptosis.

Yashiro M, Qiu H, Hasegawa T, et al.
An EGFR inhibitor enhances the efficacy of SN38, an active metabolite of irinotecan, in SN38-refractory gastric carcinoma cells.
Br J Cancer. 2011; 105(10):1522-32 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Acquired drug resistance to irinotecan is one of the significant obstacles in the treatment of advanced gastric cancer. This study was performed to clarify the effect of epidermal growth factor receptor (EGFR) inhibitors in combination with SN38, an active metabolite of irinotecan, on the proliferation of irinotecan-refractory gastric cancer.
METHODS: Two irinotecan-resistant gastric cancer cell lines, OCUM-2M/SN38 and OCUM-8/SN38 were, respectively, established by stepwise exposure to SN38 from the parent gastric cancer cell lines OCUM-2M and OCUM-8. The combination effects of two EGFR inhibitors, gefitinib and lapatinib, with SN38 on proliferation, apoptosis, and cell cycle on gastric cancer cells were examined.
RESULTS: Gefitinib or lapatinib showed synergistic anti-tumour effects against OCUM-2M/SN38 and OCUM-8/SN38 cells when used in combination with SN38, but not against OCUM-2M or OCUM-8 cells. SN38 increased the expression of EGFR and HER2 in OCUM-2M/SN38 and OCUM-8/SN38 cells. The combination of an EGFR inhibitor and SN38 significantly increased the levels of apoptosis-related molecules, caspase-6, p53, and DAPK-2, and resulted in the induction of apoptosis of irinotecan-resistant cells. The EGFR inhibitors increased the S-phase and decreased the UGT1A1 and ABCG expression in irinotecan-resistant cells. The SN38 plus Lapatinib group more effectively suppressed in vivo tumour growth by OCUM-2M/SN38 cells than either alone group.
CONCLUSION: The combination treatment with an EGFR inhibitor and irinotecan might produce synergistic anti-tumour effects for irinotecan-refractory gastric cancer cells. The regulation of SN38 metabolism-related genes and cell cycle by EGFR inhibitors might be responsible for the synergism.

Brown J, Bothma H, Veale R, Willem P
Genomic imbalances in esophageal carcinoma cell lines involve Wnt pathway genes.
World J Gastroenterol. 2011; 17(24):2909-23 [PubMed] Free Access to Full Article Related Publications
AIM: To identify molecular markers shared across South African esophageal squamous cell carcinoma (ESCC) cell lines using cytogenetics, fluorescence in situ hybridization (FISH) and single nucleotide polymorphism (SNP) array copy number analysis.
METHODS: We used conventional cytogenetics, FISH, and multicolor FISH to characterize the chromosomal rearrangements of five ESCC cell lines established in South Africa. The whole genome copy number profile was established from 250K SNP arrays, and data was analyzed with the CNAT 4.0 and GISTIC software.
RESULTS: We detected common translocation breakpoints involving chromosomes 1p11-12 and 3p11.2, the latter correlated with the deletion, or interruption of the EPHA3 gene. The most significant amplifications involved the following chromosomal regions and genes: 11q13.3 (CCND1, FGF3, FGF4, FGF19, MYEOV), 8q24.21(C-MYC, FAM84B), 11q22.1-q22.3 (BIRC2, BIRC3), 5p15.2 (CTNND2), 3q11.2-q12.2 (MINA) and 18p11.32 (TYMS, YES1). The significant deletions included 1p31.2-p31.1 (CTH, GADD45α, DIRAS3), 2q22.1 (LRP1B), 3p12.1-p14.2 (FHIT), 4q22.1-q32.1 (CASP6, SMAD1), 8p23.2-q11.1 (BNIP3L) and 18q21.1-q21.2 (SMAD4, DCC). The 3p11.2 translocation breakpoint was shared across four cell lines, supporting a role for genes involved at this site, in particular, the EPHA3 gene which has previously been reported to be deleted in ESCC.
CONCLUSION: The finding that a significant number of genes that were amplified (FGF3, FGF4, FGF19, CCND1 and C-MYC) or deleted (SFRP2 gene) are involved in the Wnt and fibroblast growth factor signaling pathways, suggests that these pathways may be activated in these cell lines.

Seo HW, Rengaraj D, Choi JW, et al.
The expression profile of apoptosis-related genes in the chicken as a human epithelial ovarian cancer model.
Oncol Rep. 2011; 25(1):49-56 [PubMed] Related Publications
The purpose of our study was to examine the expression pattern of apoptosis-related genes in normal and cancerous ovaries of the hen. Localization of apoptosis-related gene mRNA was investigated in cancerous ovaries using in situ hybridization. The expression patterns of apoptosis-related genes were confirmed with RT-PCR in normal and cancerous ovaries. Differences of expression level between normal ovaries and ovarian cancers were analyzed using quantitative RT-PCR. In both normal and cancerous chicken ovaries, the expression of CASP1, CASP2, CASP3, CASP6, CASP8 and CASP9 were detected through RT-PCR analysis. The expression of BCL2, BCL2L1 and BID were confirmed in normal and cancerous ovaries of the hen. Quantitative RT-PCR showed that CASP1 expression was significantly increased in cancerous ovaries compared with normal ovaries, whereas BID expression was decreased. Our results showed a resistance to removal of abnormal cells via apoptosis in cancerous ovaries of the hen. Collectively, this phenomenon is closely associated with the dysregulation of CASP1 and BID expression in chicken ovarian cancer.

Klein A, Capitanio JS, Maria DA, Ruiz IR
Gene expression in SK-Mel-28 human melanoma cells treated with the snake venom jararhagin.
Toxicon. 2011; 57(1):1-8 [PubMed] Related Publications
Alternative approaches to improve the treatment of advanced melanomas are highly needed. The disintegrin domain of metalloproteinases binds integrin receptors on tumor cells, blocking migration, invasion, and metastatization. Previous studies showed that jararhagin, from the Bothrops jararaca snake venom, induces changes in the morphology and viability of SK-Mel-28 human melanoma cells, and decreases the number of metastases in mice injected with pre-treated cells. The purpose of this study was to evaluate the molecular effects of jararhagin on SK-Mel-28 cells and fibroblasts, concerning the expression of integrins, cadherins, caspases, and TP53 genes. Sub-toxic doses of jararhagin were administered to confluent cells. RT-PCR was performed following extraction of total RNA. Jararhagin treatments induced similar morphological alterations in both normal and tumor cells, with higher IC50 values for fibroblasts. Integrin genes were downregulated in untreated cells, except for ITGA6a,b, ITGAv, and ITGB3 which were highly expressed in SK-Mel-28. The integrin expression profiles were not affected by the toxin. However, jararhagin 30ng/μl upregulated genes TP53, CDKN1A, CDKN2A, CASP3, CASP5, CASP6, CASP8, and E-CDH in SK-Mel-28, and genes ITGB6, ITGB7, CASP3, TP53, and CDKN1B in fibroblasts. Appropriate jararhagin concentration can have apoptotic and suppressant effects on SK-Mel-28 cells, rather than on fibroblasts, and can be used to develop potential anti-cancer drugs.

Marcos CÁ, Alonso-Guervós M, Prado NR, et al.
Genetic model of transformation and neoplastic progression in laryngeal epithelium.
Head Neck. 2011; 33(2):216-24 [PubMed] Related Publications
BACKGROUND: The aim of this study was to analyze genetic alterations in the transformation-progression model of laryngeal tumors.
METHODS: Copy number changes of 37 genes were analyzed by multiple ligation-dependent probe amplification (MLPA) in 94 tissue samples.
RESULTS: In the smoker normal mucosa group TP53 loss was predominant, whereas in the precursor lesions CDKN2A loss and CDKN2D gain were most frequent. Precursor lesions with progression presented CTNNB1 loss. In the carcinoma group the most common changes were CDKN2A, MLH1, CTNNB1, and CASP6 losses and RECQL4, CCND1, and EMS1 gains. Positive lymph node primary tumors were related to TP53, IL1A, and RB1 losses and STK11 gain. The lymph node metastases differed from their corresponding primary tumor in LMNA, RECQL4, and IGF1R losses, and N33 and CDKN2D gains.
CONCLUSIONS: Genetic changes and new key genes were found to be associated with specific steps. We included new steps, not presented in the classic models: normal mucosa tobacco exposed, positive lymph node primary tumor, and corresponding lymph node metastases.

Yoo NJ, Kim MS, Park SW, et al.
Expression analysis of caspase-6, caspase-9 and BNIP3 in prostate cancer.
Tumori. 2010 Jan-Feb; 96(1):138-42 [PubMed] Related Publications
AIMS: Altered regulation of cell death is a feature of human cancer. The aim of this study was to explore whether the expression of the proapoptotic proteins caspase-6, caspase-9, and Bcl-2/adenovirus E1B-19kDa-interacting protein3 (BNIP3) is altered in prostate cancers.
METHODS: We analyzed the expression of caspase-6, caspase-9, and BNIP3 in 107 prostate adenocarcinoma tissues by immunohistochemistry using a tissue microarray (TMA) method.
RESULTS: Normal glandular cells expressed caspase-6 and BNIP3 proteins in 10 (9.3%) and 9 (8.4%) prostate tissues, respectively. By contrast, the prostate cancers expressed caspase-6 and BNIP3 in 65 (60.7%) and 69 (64.5%) cases, respectively. Prostate intraepithelial neoplasia (PIN) showed caspase-6 and BNIP3 expression in 65% and 65% of cases, respectively. We observed caspase-9 expression in 40 (37.4%) normal, 8 (40%) PIN, and 45 (42.1%) cancer tissues. None of the expression of caspase-6, caspase-9 or BNIP3 was associated with pathological characteristics such as tumor size, patient age, Gleason score, or tumor stage.
CONCLUSION: Our data showed that prostate cancer and PIN cells display higher expression of the proapoptotic proteins caspase-6 and BNIP3 than normal cells. Neo-expression of these proteins from the PIN stage suggests that apoptosis deregulation might occur in the early stage of prostate carcinogenesis, and that altered expression of proapoptotic proteins may be a feature of prostate cancer.

Carter BZ, Mak DH, Schober WD, et al.
Simultaneous activation of p53 and inhibition of XIAP enhance the activation of apoptosis signaling pathways in AML.
Blood. 2010; 115(2):306-14 [PubMed] Free Access to Full Article Related Publications
Activation of p53 by murine double minute (MDM2) antagonist nutlin-3a or inhibition of X-linked inhibitor of apoptosis (XIAP) induces apoptosis in acute myeloid leukemia (AML) cells. We demonstrate that concomitant inhibition of MDM2 by nutlin-3a and of XIAP by small molecule antagonists synergistically induced apoptosis in p53 wild-type OCI-AML3 and Molm13 cells. Knockdown of p53 by shRNA blunted the synergy, and down-regulation of XIAP by antisense oligonucleotide (ASO) enhanced nutlin-3a-induced apoptosis, suggesting that the synergy was mediated by p53 activation and XIAP inhibition. This is supported by data showing that inhibition of both MDM2 and XIAP by their respective ASOs induced significantly more cell death than either ASO alone. Importantly, p53 activation and XIAP inhibition enhanced apoptosis in blasts from patients with primary AML, even when the cells were protected by stromal cells. Mechanistic studies demonstrated that XIAP inhibition potentiates p53-induced apoptosis by decreasing p53-induced p21 and that p53 activation enhances XIAP inhibition-induced cell death by promoting mitochondrial release of second mitochondria-derived activator of caspases (SMAC) and by inducing the expression of caspase-6. Because both XIAP and p53 are presently being targeted in ongoing clinical trials in leukemia, the combination strategy holds promise for expedited translation into the clinic.

Day TW, Wu CH, Safa AR
Etoposide induces protein kinase Cdelta- and caspase-3-dependent apoptosis in neuroblastoma cancer cells.
Mol Pharmacol. 2009; 76(3):632-40 [PubMed] Free Access to Full Article Related Publications
In this report, we reveal that etoposide inhibits the proliferation of SK-N-AS neuroblastoma cancer cells and promotes protein kinase Cdelta (PKCdelta)- and caspase-dependent apoptosis. Etoposide induces the caspase-3-dependent cleavage of PKCdelta to its active p40 fragment, and active PKCdelta triggers the processing of caspase-3 by a positive-feedback mechanism. Treatment of cells with the caspase-3-specific inhibitor N-benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethyl ketone or caspase-3-specific small interacting RNA (siRNA) prevented the etoposide-induced activation of caspase-8 and inhibited apoptosis. The silencing of the caspase-2 or caspase-8 genes using siRNAs did not affect the etoposide-induced processing of caspase-3, indicating that these caspases lie downstream of caspase-3 in this signaling pathway. Furthermore, the etoposide-induced processing of caspase-2 required the expression of caspase-8, and the etoposide-mediated processing of caspase-8 required the expression of caspase-2, indicating that these two caspases activate each other after etoposide treatment. We also observed that etoposide-mediated apoptosis was decreased by treating the cells with the caspase-6-specific inhibitor benzyloxycarbonyl-Val-Glu(OMe)-Ile-Asp-(OMe)-fluoromethyl ketone and that caspase-6 was activated by a caspase-8-dependent mechanism. Finally, we show that rottlerin blocks etoposide-induced apoptosis by inhibiting the PKCdelta-mediated activation of caspase-3 and by degrading caspase-2, which prevents caspase-8 activation. Our results add important insights into how etoposide mediates apoptotic signaling and how targeting these pathways may lead to the development of novel therapeutics for the treatment of neuroblastomas.

Min W, Wen-li M, Zhao-hui S, et al.
Microarray analysis identifies differentially expressed genes induced by human papillomavirus type 18 E6 silencing RNA.
Int J Gynecol Cancer. 2009; 19(4):547-63 [PubMed] Related Publications
The oncoprotein E6 of high-risk human papillomavirus (HPV) types promotes cell proliferation and contributes to carcinogenesis of HPV-positive cervical cancer cells. In this study, we used small interfering RNA (siRNA) technology to silence the E6 gene in HPV-18-transformed human cervical cell line HeLa and determined the effects of E6 gene knockdown on the cell by using microarray-based gene expression profiling coupled with gene functional classification with bioinformatics methods. Silencing RNA prepared by siRNA expression cassettes against HPV-18 E6 gene could significantly inhibit E6 gene expression and induce HeLa cells to apoptosis. The microarray analysis identified 359 differentially expressed genes containing 307 up-regulated and 52 down-regulated genes. We analyzed the gene functions and cellular pathways in detail, including cell cycle-related genes, CCNG1 and p21; apoptosis-related genes, CASP4, CASP6, IGFBP3, and DFFA; ubiquitin proteolysis pathway-related genes, UBE3A and UBE2C; keratinocyte differentiation-related genes, KRT4, KRT6E, and KRT18; and antioncogenes, RECK and VEL. In addition, it can be concluded that cellular apoptosis induced by HPV-18 E6 siRNA mainly depends on the P53 and ubiquitin proteolysis pathway to regulate gene expression, consequently inhibiting cell proliferation and promoting cell apoptosis. Meanwhile, activation of antioncogene and upper regulation of immunization-related genes signified the degression of the malignant extent of tumor cells after E6 inhibition. Our approach, which combines the use of siRNA-mediated gene silencing, microarray screening, and functional classification of differential genes, can be used in functional genomics study to elucidate the role of E6 oncogene in the carcinogenesis of HPV-18 and provide some possible targets for clinical treatment and drug development of cervical cancer.

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