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Martin EC, Rhodes LV, Elliott S, Krebs AE, Nephew KP, Flemington EK, Collins-Burow BM, Burow ME. microRNA regulation of mammalian target of rapamycin expression and activity controls estrogen receptor function and RAD001 sensitivity. Mol Cancer 2014; 13:229. [PMID: 25283550 PMCID: PMC4203920 DOI: 10.1186/1476-4598-13-229] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 09/24/2014] [Indexed: 01/28/2023] Open
Abstract
Background The AKT/mammalian target of rapamycin (mTOR) signaling pathway is regulated by 17α-estradiol (E2) signaling and mediates E2-induced proliferation and progesterone receptor (PgR) expression in breast cancer. Methods and results Here we use deep sequencing analysis of previously published data from The Cancer Genome Atlas to demonstrate that expression of a key component of mTOR signaling, rapamycin-insensitive companion of mTOR (Rictor), positively correlated with an estrogen receptor-α positive (ERα+) breast tumor signature. Through increased microRNA-155 (miR-155) expression in the ERα+ breast cancer cells we demonstrate repression of Rictor enhanced activation of mTOR complex 1 (mTORC1) signaling with both qPCR and western blot. miR-155-mediated mTOR signaling resulted in deregulated ERα signaling both in cultured cells in vitro and in xenografts in vivo in addition to repressed PgR expression and activity. Furthermore we observed that miR-155 enhanced mTORC1 signaling (observed through western blot for increased phosphorylation on mTOR S2448) and induced inhibition of mTORC2 signaling (evident through repressed Rictor and tuberous sclerosis 1 (TSC1) gene expression). mTORC1 induced deregulation of E2 signaling was confirmed using qPCR and the mTORC1-specific inhibitor RAD001. Co-treatment of MCF7 breast cancer cells stably overexpressing miR-155 with RAD001 and E2 restored E2-induced PgR gene expression. RAD001 treatment of SCID/CB17 mice inhibited E2-induced tumorigenesis of the MCF7 miR-155 overexpressing cell line. Finally we demonstrated a strong positive correlation between Rictor and PgR expression and a negative correlation with Raptor expression in Luminal B breast cancer samples, a breast cancer histological subtype known for having an altered ERα-signaling pathway. Conclusions miRNA mediated alterations in mTOR and ERα signaling establishes a new mechanism for altered estrogen responses independent of growth factor stimulation. Electronic supplementary material The online version of this article (doi:10.1186/1476-4598-13-229) contains supplementary material, which is available to authorized users.
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Rhodes LV, Tate CR, Burks HE, Hoang VT, Gilliam D, Martin EC, Elliott S, Miller DF, Buechlein A, Rusch D, Tang H, Nephew KP, Burow ME, Collins-Burow BM. Abstract 1571: The tumor suppressor Liver Kinase B1 inhibits triple-negative breast cancer cell metastasis via regulation of AP-1 signaling. Cancer Res 2014. [DOI: 10.1158/1538-7445.am2014-1571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
The basal sub-type, which shares features with triple-negative breast cancer (TNBC), is among the most lethal breast cancer subtype, characterized by a highly aggressive and metastatic phenotype. Although pathways that may represent targets for novel therapeutic intervention for basal like breast cancer (BLBC) have begun to be elucidated, the ability to define and selectively target the invasive and metastatic phenotype of basal-type/TNBC remains a major challenge facing the breast cancer field.
Liver kinase B1 (LKB1), also known as serine/threonine kinase 11 (STK11), is a known tumor suppressor in many cancers including breast. Low LKB1expression has been observed in breast cancer patients and we report a significant association between loss of LKB1 expression and poor prognosis specifically in the basal sub-type of breast cancer. Induction of LKB1 expression in BLBC cell lines inhibited invasiveness in vitro as well as lung and brain metastatic burden in an orthotopic xenograft tumor model. Further analysis of BLBC cell lines overexpressing LKB1 by next generation sequencing (RNA-seq) revealed striking regulation of metastasis-associated pathways, including cell adhesion, extra cellular matrix remodeling, and epithelial-to-mesenchymal transition (EMT). We further demonstrated marked inhibition of matrix metalloproteinase 1 (MMP-1) expression and activity via regulation AP-1 family member cJun. Additionally, LKB1 overexpression inhibited EMT-associated genes (CDH2, Vimentin, Twist) and induced the epithelial cell marker CDH1, indicating a reversal of the EMT phenotype in a triple-negative breast cancer cell line MDA-MB-231. We have demonstrated a role for LKB1 expression in the regulation of cell invasion and metastasis in addition to tumorigenesis. Taken together these data support future development of therapeutic agents to induce the LKB1 signaling pathway in BLCB/triple-negative breast cancer.
Citation Format: Lyndsay V. Rhodes, Chandra R. Tate, Hope E. Burks, Van T. Hoang, Diari Gilliam, Elizabeth C. Martin, Steven Elliott, David FB Miller, Aaron Buechlein, Douglas Rusch, Haixu Tang, Kenneth P. Nephew, Matthew E. Burow, Bridgette M. Collins-Burow. The tumor suppressor Liver Kinase B1 inhibits triple-negative breast cancer cell metastasis via regulation of AP-1 signaling. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1571. doi:10.1158/1538-7445.AM2014-1571
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Ozes AR, Miller DF, Liu Y, Nephew KP. Abstract 3551: Non-coding RNA HOTAIR connects DNA damage signaling to NF-κB activation in cisplatin resistant ovarian cancer. Mol Cell Biol 2014. [DOI: 10.1158/1538-7445.am2014-3551] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Wang Y, Cardenas H, Fang F, Condello S, Taverna P, Segar M, Liu Y, Nephew KP, Matei D. Epigenetic targeting of ovarian cancer stem cells. Cancer Res 2014; 74:4922-36. [PMID: 25035395 DOI: 10.1158/0008-5472.can-14-1022] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Emerging results indicate that cancer stem-like cells contribute to chemoresistance and poor clinical outcomes in many cancers, including ovarian cancer. As epigenetic regulators play a major role in the control of normal stem cell differentiation, epigenetics may offer a useful arena to develop strategies to target cancer stem-like cells. Epigenetic aberrations, especially DNA methylation, silence tumor-suppressor and differentiation-associated genes that regulate the survival of ovarian cancer stem-like cells (OCSC). In this study, we tested the hypothesis that DNA-hypomethylating agents may be able to reset OCSC toward a differentiated phenotype by evaluating the effects of the new DNA methytransferase inhibitor SGI-110 on OCSC phenotype, as defined by expression of the cancer stem-like marker aldehyde dehydrogenase (ALDH). We demonstrated that ALDH(+) ovarian cancer cells possess multiple stem cell characteristics, were highly chemoresistant, and were enriched in xenografts residual after platinum therapy. Low-dose SGI-110 reduced the stem-like properties of ALDH(+) cells, including their tumor-initiating capacity, resensitized these OCSCs to platinum, and induced reexpression of differentiation-associated genes. Maintenance treatment with SGI-110 after carboplatin inhibited OCSC growth, causing global tumor hypomethylation and decreased tumor progression. Our work offers preclinical evidence that epigenome-targeting strategies have the potential to delay tumor progression by reprogramming residual cancer stem-like cells. Furthermore, the results suggest that SGI-110 might be administered in combination with platinum to prevent the development of recurrent and chemoresistant ovarian cancer.
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Fang F, Zuo Q, Pilrose J, Wang Y, Shen C, Li M, Wulfridge P, Matei D, Nephew KP. Decitabine reactivated pathways in platinum resistant ovarian cancer. Oncotarget 2014; 5:3579-89. [PMID: 25003579 PMCID: PMC4116504 DOI: 10.18632/oncotarget.1961] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 05/12/2014] [Indexed: 01/08/2023] Open
Abstract
Combination therapy with decitabine, a DNMTi and carboplatin resensitized chemoresistant ovarian cancer (OC) to platinum inducing promising clinical activity. We investigated gene-expression profiles in tumor biopsies to identify decitabine-reactivated pathways associated with clinical response. Gene-expression profiling was performed using RNA from paired tumor biopsies before and 8 days after decitabine from 17 patients with platinum resistant OC. Bioinformatic analysis included unsupervised hierarchical-clustering, pathway and GSEA distinguishing profiles of "responders" (progression-free survival, PFS>6 months) and "non-responders" (PFS< 6 months). Functional validation of selected results was performed in OC cells/tumors. Pre-treatment tumors from responders expressed genes associated with enhanced glycosphingolipid biosynthesis, translational misregulation, decreased ABC transporter expression, TGF-β signaling, and numerous metabolic pathways. Analysis of post-treatment biopsies from responders revealed overexpression of genes associated with reduced Hedgehog pathway signaling, reduced DNA repair/replication, and cancer-associated metabolism. GO and GSEA analyses revealed upregulation of genes associated with glycosaminoglycan binding, cell-matrix adhesion, and cell-substrate adhesion. Computational findings were substantiated by experimental validation of expression of key genes involved in two critical pathways affected by decitabine (TGF-β and Hh). Gene-expression profiling identified specific pathways altered by decitabine and associated with platinum-resensitization and clinical benefit in OC. Our data could influence patient stratification for future studies using epigenetic therapies.
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Ozes AR, Nephew KP. 3D culture adds an extra dimension to targeted epigenetic therapies. Cell Cycle 2014; 12:2173-4. [PMID: 23803725 PMCID: PMC3755066 DOI: 10.4161/cc.25551] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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An J, Kim K, Rhee SM, Chae H, Nephew KP, Kim S. Genome-wide analysis and modeling of DNA methylation susceptibility in 30 breast cancer cell lines by using CpG flanking sequences. J Bioinform Comput Biol 2014; 11:1341003. [PMID: 23796180 DOI: 10.1142/s0219720013410035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
DNA methylation is an epigenetic modification of DNA that adds a methyl group to cytosine. Aberrant DNA methylation in the CpG context is frequently observed in cancer cells and it is known that aberrant DNA methylation silences tumor repressor genes. However, the mechanism of DNA methylation is not well understood. A widely accepted hypothesis is that DNA methylation does not randomly occur and may be controlled by some instructive mechanisms. In this paper, we conducted an extensive study on this important question by using proprietary sequencing data from methyl-binding domain protein (MBD)-Cap ChIP sequencing experiments for 30 breast cancer cell lines. The goal of our study is to investigate difference in nucleotide composition around CpG sites, where high levels of methylation are observed, and use the information for modeling DNA methylation susceptibility. First, we observed that DNA methylation is not uniform in the whole-genome region and also that the character composition of CpG flanking sequences are significantly different between hyper- and hypo-methylated groups. In an in-depth study, we used information theoretic approaches such as entropy and relative entropy to delineate character composition features and found enrichment of A (Adenine) and T (Thymine) in specific positions around hyper-methylated sites. As the methylation level is increased, A, T proportions in specific positions around hypermethylated sites are increased while A, T proportions in other positions around hypermethylated sites are decreased. Second, we built predictive models for methylation susceptibility by using characters flanking CpG sites as features and hyper-/hypo-methylation status as class. Third, we constructed predictive models using a log odds score of two profiles from DNA sequences surrounding CpG sites of hyper- and hypo-methylated groups. This analysis showed that distribution of profile scores of hyper-/hypo-methylated sites sequences is quite distinct. Our genome-wide CpG methylation study shows that nucleotides around CpG sites caries information for cytosine methylation. This is consistent with the seminal work on the instructive evidence of DNA methylation by Keshet et al. (Nature Genetics, 38(2), 149-153 2006). Our study is on the full genome scale and used the sequencing data, thus our study is significantly different in terms of resolution of data and analysis methods used for the study by Keshet et al.
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Wu D, Sunkel B, Chen Z, Liu X, Ye Z, Li Q, Grenade C, Ke J, Zhang C, Chen H, Nephew KP, Huang THM, Liu Z, Jin VX, Wang Q. Three-tiered role of the pioneer factor GATA2 in promoting androgen-dependent gene expression in prostate cancer. Nucleic Acids Res 2014; 42:3607-22. [PMID: 24423874 PMCID: PMC3973339 DOI: 10.1093/nar/gkt1382] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In prostate cancer, androgen receptor (AR) binding and androgen-responsive gene expression are defined by hormone-independent binding patterns of the pioneer factors FoxA1 and GATA2. Insufficient evidence of the mechanisms by which GATA2 contributes to this process precludes complete understanding of a key determinant of tissue-specific AR activity. Our observations suggest that GATA2 facilitates androgen-responsive gene expression by three distinct modes of action. By occupying novel binding sites within the AR gene locus, GATA2 positively regulates AR expression before and after androgen stimulation. Additionally, GATA2 engages AR target gene enhancers prior to hormone stimulation, producing an active and accessible chromatin environment via recruitment of the histone acetyltransferase p300. Finally, GATA2 functions in establishing and/or sustaining basal locus looping by recruiting the Mediator subunit MED1 in the absence of androgen. These mechanisms may contribute to the generally positive role of GATA2 in defining AR genome-wide binding patterns that determine androgen-responsive gene expression profiles. We also find that GATA2 and FoxA1 exhibit both independent and codependent co-occupancy of AR target gene enhancers. Identifying these determinants of AR transcriptional activity may provide a foundation for the development of future prostate cancer therapeutics that target pioneer factor function.
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Garofalo M, Romano G, Di Leva G, Nuovo G, Jeon YJ, Ngankeu A, Sun J, Lovat F, Alder H, Condorelli G, Engelman JA, Ono M, Rho JK, Cascione L, Volinia S, Nephew KP, Croce CM. Correction: Corrigendum: EGFR and MET receptor tyrosine kinase–altered microRNA expression induces tumorigenesis and gefitinib resistance in lung cancers. Nat Med 2014. [DOI: 10.1038/nm0114-103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Liao YP, Chen LY, Huang RL, Su PH, Chan MWY, Chang CC, Yu MH, Wang PH, Yen MS, Nephew KP, Lai HC. Hypomethylation signature of tumor-initiating cells predicts poor prognosis of ovarian cancer patients. Hum Mol Genet 2013; 23:1894-906. [PMID: 24256813 DOI: 10.1093/hmg/ddt583] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
DNA methylation contributes to tumor formation, development and metastasis. Epigenetic dysregulation of stem cells is thought to predispose to malignant development. The clinical significance of DNA methylation in ovarian tumor-initiating cells (OTICs) remains unexplored. We analyzed the methylomic profiles of OTICs (CP70sps) and their derived progeny using a human methylation array. qRT-PCR, quantitative methylation-specific PCR (qMSP) and pyrosequencing were used to verify gene expression and DNA methylation in cancer cell lines. The methylation status of genes was validated quantitatively in cancer tissues and correlated with clinicopathological factors. ATG4A and HIST1H2BN were hypomethylated in OTICs. Methylation analysis of ATG4A and HIST1H2BN by qMSP in 168 tissue samples from patients with ovarian cancer showed that HIST1H2BN methylation was a significant and independent predictor of progression-free survival (PFS) and overall survival (OS). Multivariate Cox regression analysis showed that patients with a low level of HIST1H2BN methylation had poor PFS (hazard ratio (HR), 4.5; 95% confidence interval (CI), 1.4-14.8) and OS (HR, 4.3; 95% CI, 1.3-14.0). Hypomethylation of both ATG4A and HIST1H2BN predicted a poor PFS (HR, 1.8; 95% CI, 1.0-3.6; median, 21 months) and OS (HR, 1.7; 95% CI, 1.0-3.0; median, 40 months). In an independent cohort of ovarian tumors, hypomethylation predicted early disease recurrence (HR, 1.7; 95% CI, 1.1-2.5) and death (HR, 1.4; 95% CI, 1.0-1.9). The demonstration that expression of ATG4A in cells increased their stem properties provided an indication of its biological function. Hypomethylation of ATG4A and HIST1H2BN in OTICs predicts a poor prognosis for ovarian cancer patients.
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Nephew KP, Matei D, Taverna P, Fang F, Tang J, Choy G, Lyons J, Azab M, Pilrose J, Turchi J. Abstract IA17: Targeting the methylome for epigenetic resensitization of ovarian cancer. Clin Cancer Res 2013. [DOI: 10.1158/1078-0432.ovca13-ia17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Women with advanced stage ovarian cancer (OC) have a five-year survival rate of less than 25%. Although most patients respond to platinum-based chemotherapy, relapses are common, leading to platinum-resistant OC, which is uniformly fatal. OC progression is associated with accumulation of epigenetic alterations. In particular, deoxycytosine methylation of CpG islands in promoter regions of tumor suppressor genes (TSGs) plays a prominent role in the development and progression of drug-resistant epithelial OC. We recently demonstrated for the first time in a clinical trial that therapeutic interventions targeting the OC methylome reverse drug resistance and induce meaningful clinical responses. We showed that repetitive low-dose decitabine reactivated silenced genes and restored sensitivity to carboplatin, providing strong clinical and biological support for further study of hypomethylating agents in heavily pre-treated, platinum-resistant ovarian cancer patients. While the FDA-approved demethylating agent decitabine is prone to deamination by cytidine deaminase, SGI-110 (Astex Pharmaceuticals, Inc.), a dinucleotide analogue of decitabine, is more stable, less toxic, and a promising alternative to restoring silenced TSG expression in cancer cells by reversal of DNA methylation. Our preclinical evaluation demonstrated that SGI-110 resensitized platinum-resistant OC cell lines to cisplatin (CDDP) (3-fold reduction in IC50) and reduced the CDDP IC50. SGI-110 treatment induced significant demethylation and subsequent transcriptional derepression of tumor suppressors and differentiation-associated genes in OC cells. SGI-110 alone or in combination with CDDP was well tolerated in non-tumor bearing mice. Significant antitumor activity was observed in mice harboring subcutaneous OC tumors and treated with single SGI-110 and SGI-110 + CDDP treatment in both a biweekly and daily (QD5) regimen. In addition to reducing tumor growth in xenografts, SGI therapy was effective in causing global as well as TSG demethylation and gene reexpression in vivo. Furthermore, the antitumor activity of SGI-110 was associated with reduced chromatin compaction, allowing greater CDDP intercalation into DNA, as assessed by increased DNA platinum adducts in SGI-treated OC cells. The results of our preclinical study support our recently activated clinical trial NCT01696032 using SGI-110 in combination with carboplatin in patients with recurrent, platinum-resistant OC. Clinical specimens (tumor and plasma samples) will be analyzed for epigenetic biomarker changes. We seek to bring forward the new concept of epigenetic targeting in platinum resistant OC by priming the tumors with SGI-110 and set the stage for interventions targeting the OC epigenome, as well as guide and impact the design of future clinical investigations in OC.
Citation Format: Kenneth P. Nephew, Daniela Matei, Pietro Taverna, Fang Fang, Jessica Tang, Gavin Choy, John Lyons, Mohammad Azab, Jay Pilrose, John Turchi. Targeting the methylome for epigenetic resensitization of ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr IA17.
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Lengyel E, Burdette JE, Kenny HA, Matei D, Pilrose J, Haluska P, Nephew KP, Hales DB, Stack MS. Epithelial ovarian cancer experimental models. Oncogene 2013; 33:3619-33. [PMID: 23934194 DOI: 10.1038/onc.2013.321] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Revised: 06/21/2013] [Accepted: 06/21/2013] [Indexed: 12/13/2022]
Abstract
Epithelial ovarian cancer (OvCa) is associated with high mortality and, as the majority (>75%) of women with OvCa have metastatic disease at the time of diagnosis, rates of survival have not changed appreciably over 30 years. A mechanistic understanding of OvCa initiation and progression is hindered by the complexity of genetic and/or environmental initiating events and lack of clarity regarding the cell(s) or tissue(s) of origin. Metastasis of OvCa involves direct extension or exfoliation of cells and cellular aggregates into the peritoneal cavity, survival of matrix-detached cells in a complex ascites fluid phase and subsequent adhesion to the mesothelium lining covering abdominal organs to establish secondary lesions containing host stromal and inflammatory components. Development of experimental models to recapitulate this unique mechanism of metastasis presents a remarkable scientific challenge, and many approaches used to study other solid tumors (for example, lung, colon and breast) are not transferable to OvCa research given the distinct metastasis pattern and unique tumor microenvironment (TME). This review will discuss recent progress in the development and refinement of experimental models to study OvCa. Novel cellular, three-dimensional organotypic, and ex vivo models are considered and the current in vivo models summarized. The review critically evaluates currently available genetic mouse models of OvCa, the emergence of xenopatients and the utility of the hen model to study OvCa prevention, tumorigenesis, metastasis and chemoresistance. As these new approaches more accurately recapitulate the complex TME, it is predicted that new opportunities for enhanced understanding of disease progression, metastasis and therapeutic response will emerge.
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113
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Hsu PY, Hsu HK, Lan X, Juan L, Yan PS, Labanowska J, Heerema N, Hsiao TH, Chiu YC, Chen Y, Liu Y, Li L, Li R, Thompson IM, Nephew KP, Sharp ZD, Kirma NB, Jin VX, Huang THM. Amplification of distant estrogen response elements deregulates target genes associated with tamoxifen resistance in breast cancer. Cancer Cell 2013; 24:197-212. [PMID: 23948299 PMCID: PMC3890247 DOI: 10.1016/j.ccr.2013.07.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 03/12/2013] [Accepted: 07/09/2013] [Indexed: 01/18/2023]
Abstract
A causal role of gene amplification in tumorigenesis is well known, whereas amplification of DNA regulatory elements as an oncogenic driver remains unclear. In this study, we integrated next-generation sequencing approaches to map distant estrogen response elements (DEREs) that remotely control the transcription of target genes through chromatin proximity. Two densely mapped DERE regions located on chromosomes 17q23 and 20q13 were frequently amplified in estrogen receptor-α-positive luminal breast cancer. These aberrantly amplified DEREs deregulated target gene expression potentially linked to cancer development and tamoxifen resistance. Progressive accumulation of DERE copies was observed in normal breast progenitor cells chronically exposed to estrogenic chemicals. These findings may extend to other DNA regulatory elements, the amplification of which can profoundly alter target transcriptome during tumorigenesis.
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Antoon JW, Martin EC, Lai R, Salvo VA, Tang Y, Nitzchke AM, Elliott S, Nam SY, Xiong W, Rhodes LV, Collins-Burow B, David O, Wang G, Shan B, Beckman BS, Nephew KP, Burow ME. MEK5/ERK5 signaling suppresses estrogen receptor expression and promotes hormone-independent tumorigenesis. PLoS One 2013; 8:e69291. [PMID: 23950888 PMCID: PMC3739787 DOI: 10.1371/journal.pone.0069291] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 06/12/2013] [Indexed: 01/20/2023] Open
Abstract
Endocrine resistance and metastatic progression are primary causes of treatment failure in breast cancer. While mitogen activated protein kinases (MAPKs) are known to promote ligand-independent cell growth, the role of the MEK5-ERK5 pathway in the progression of clinical breast carcinoma remains poorly understood. Here, we demonstrated increased ERK5 activation in 30 of 39 (76.9%) clinical tumor samples, as well as across breast cancer cell systems. Overexpression of MEK5 in MCF-7 cells promoted both hormone-dependent and hormone-independent tumorigenesis in vitro and in vivo and conferred endocrine therapy resistance to previously sensitive breast cancer cells. Expression of MEK5 suppressed estrogen receptor (ER)α, but not ER-β protein levels, and abrogated downstream estrogen response element (ERE) transcriptional activity and ER-mediated gene transcription. Global gene expression changes associated with upregulation of MEK5 included increased activation of ER-α independent growth signaling pathways and promotion of epithelial-to-mesenchymal transition (EMT) markers. Taken together, our findings show that the MEK5-ERK5 pathway mediates progression to an ER(-), mesenchymal and endocrine therapy resistant phenotype. Given the need for new clinical therapeutic targets, our results demonstrate the therapeutic potential of targeting the MEK5-ERK5 pathway in breast cancer.
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Rhee JK, Kim K, Chae H, Evans J, Yan P, Zhang BT, Gray J, Spellman P, Huang THM, Nephew KP, Kim S. Integrated analysis of genome-wide DNA methylation and gene expression profiles in molecular subtypes of breast cancer. Nucleic Acids Res 2013; 41:8464-74. [PMID: 23887935 PMCID: PMC3794600 DOI: 10.1093/nar/gkt643] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Aberrant DNA methylation of CpG islands, CpG island shores and first exons is known to play a key role in the altered gene expression patterns in all human cancers. To date, a systematic study on the effect of DNA methylation on gene expression using high resolution data has not been reported. In this study, we conducted an integrated analysis of MethylCap-sequencing data and Affymetrix gene expression microarray data for 30 breast cancer cell lines representing different breast tumor phenotypes. As well-developed methods for the integrated analysis do not currently exist, we created a series of four different analysis methods. On the computational side, our goal is to develop methylome data analysis protocols for the integrated analysis of DNA methylation and gene expression data on the genome scale. On the cancer biology side, we present comprehensive genome-wide methylome analysis results for differentially methylated regions and their potential effect on gene expression in 30 breast cancer cell lines representing three molecular phenotypes, luminal, basal A and basal B. Our integrated analysis demonstrates that methylation status of different genomic regions may play a key role in establishing transcriptional patterns in molecular subtypes of human breast cancer.
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Huang RL, Gu F, Kirma NB, Ruan J, Chen CL, Wang HC, Liao YP, Chang CC, Yu MH, Pilrose JM, Thompson IM, Huang HC, Huang THM, Lai HC, Nephew KP. Comprehensive methylome analysis of ovarian tumors reveals hedgehog signaling pathway regulators as prognostic DNA methylation biomarkers. Epigenetics 2013; 8:624-34. [PMID: 23774800 PMCID: PMC3857342 DOI: 10.4161/epi.24816] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Women with advanced stage ovarian cancer (OC) have a five-year survival rate of less than 25%. OC progression is associated with accumulation of epigenetic alterations and aberrant DNA methylation in gene promoters acts as an inactivating ?hit? during OC initiation and progression. Abnormal DNA methylation in OC has been used to predict disease outcome and therapy response. To globally examine DNA methylation in OC, we used next-generation sequencing technology, MethylCap-sequencing, to screen 75 malignant and 26 normal or benign ovarian tissues. Differential DNA methylation regions (DMRs) were identified, and the Kaplan?Meier method and Cox proportional hazard model were used to correlate methylation with clinical endpoints. Functional role of specific genes identified by MethylCap-sequencing was examined in in vitro assays. We identified 577 DMRs that distinguished (p < 0.001) malignant from non-malignant ovarian tissues; of these, 63 DMRs correlated (p < 0.001) with poor progression free survival (PFS). Concordant hypermethylation and corresponding gene silencing of sonic hedgehog pathway members ZIC1 and ZIC4 in OC tumors was confirmed in a panel of OC cell lines, and ZIC1 and ZIC4 repression correlated with increased proliferation, migration and invasion. ZIC1 promoter hypermethylation correlated (p < 0.01) with poor PFS. In summary, we identified functional DNA methylation biomarkers significantly associated with clinical outcome in OC and suggest our comprehensive methylome analysis has significant translational potential for guiding the design of future clinical investigations targeting the OC epigenome. Methylation of ZIC1, a putative tumor suppressor, may be a novel determinant of OC outcome.
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Huang Z, Li H, Huang Q, Chen D, Han J, Wang L, Pan C, Chen W, House MG, Nephew KP, Guo Z. SERPINB2 down-regulation contributes to chemoresistance in head and neck cancer. Mol Carcinog 2013; 53:777-86. [PMID: 23661500 DOI: 10.1002/mc.22033] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 02/22/2013] [Accepted: 03/12/2013] [Indexed: 12/13/2022]
Abstract
Resistance to cisplatin-based chemotherapy is responsible for the majority of deaths from head and neck squamous cell carcinoma (HNSCC). In this study, using genome-wide gene expression analysis to investigate potential molecular mediators of HNSCC chemoresistance, we identified SERPINB2, a known inhibitor of extracellular serine proteinase urokinase-type plasminogen activator (uPA), as an important candidate. Whereas SERPINB2 is known to function as a suppressor of uPA molecular cascades, many of which play important roles in tumor invasion and metastasis, a role for SERPINB2 in cancer drug resistance has not been examined. By using quantitative real-time PCR and Western blot analysis, we determined that SERPINB2 mRNA and protein levels correlated with chemoresistance in HNSCC cell lines, and significantly lower SERPINB2 expression levels were observed in two cisplatin resistant HNSCC subclones compared to their isogenic drug-sensitive parental lines. Immunohistochemical analysis of HNSCC tumor tissues from patients treated with neoadjuvant cisplatin-based chemotherapy (n = 67 cases) revealed a significant association between SERPINB2 protein levels, tumor differentiation and patient relapse. Moreover, SERPINB2 down-regulation was a strong predictor of reduced overall survival in patients with HNSCC who received cisplatin-based chemotherapy (P = 0.001, log rank test). Studies using either siRNA-mediated down-regulation or forced over-expression of SERPINB2 in HNSCC cell lines confirmed a functional role for SERPINB2 in drug resistance. The findings were further supported using chemical inhibitors of STAT3 activity (a downstream effecter of uPAR signaling pathway), showing that STAT3 suppression altered HNSCC cell line cisplatin sensitivity. This is the first report on a role for SERPINB2 in acquired resistance to cisplatin in patients with HNSCC.
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Cardenas H, Goswami C, Nephew KP, Matei D. Abstract 2978: DNA methylation changes during epithelial-to-mesenchymal transition in ovarian cancer cells. Cancer Res 2013. [DOI: 10.1158/1538-7445.am2013-2978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Epithelial-to-mesenchymal transition (EMT) is a required step in the process of metastasis and has been linked to cancer cell stemness. We hypothesized that aside from defined genetic changes associated with EMT, epigenetic mechanisms are also involved. We determined DNA methylation changes in SKOV3 ovarian cancer (OC) cells undergoing TGFβ-induced EMT by using the Infinium HumanMethylation450 array. Methylation of sites was expressed as ß-values ranging from 0 (completely unmethylated) to 1 (completely methylated). Methylation of 468 and 390 sites changed significantly (P<.01, ANOVA and FDR<0.05) after 48h and 120h of TGFβ stimulation, of which 31 and 72 sites changed >1.25-fold. The majority of changes (∼66%) reflected TGFβ-induced demethylation. Methylation of 160 sites changed similarly at 48 and 120h indicating that approximately 40% of changes were sustained. PCA analysis demonstrated that the removal of TGFβ was associated with reversal of DNA methylation changes at most sites and restitution of the baseline methylome. Pathway analysis identified DNA methylated genes involved in functional networks relevant to EMT and cancer progression, including: 1) cell morphology and development (39 genes), 2) cell growth and proliferation, and cell death and survival (34 genes), 3) cellular assembly and organization (22 genes), 4) DNA replication, recombination and repair (17 genes), and 5) gene expression, cell signaling, and cellular movement (15 genes). Validation of the relevant genes is ongoing. Treatment of OC cells with the DNA methyl transferase inhibitor SGI-110 prevented TGFβ-induced EMT and reduced by two-fold the number of cells with stem cell characteristics (ALDH1+). These results demonstrate that DNA methylation is a dynamic process involved in regulation of genes implicated in EMT and metastasis.
Citation Format: Horacio Cardenas, Chirayu Goswami, Kenneth P. Nephew, Daniela Matei. DNA methylation changes during epithelial-to-mesenchymal transition in ovarian cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2978. doi:10.1158/1538-7445.AM2013-2978
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Miller DFB, Yan PS, Buechlein A, Rodriguez BA, Yilmaz AS, Goel S, Lin H, Collins-Burow B, Rhodes LV, Braun C, Pradeep S, Rupaimoole R, Dalkilic M, Sood AK, Burow ME, Tang H, Huang TH, Liu Y, Rusch DB, Nephew KP. A new method for stranded whole transcriptome RNA-seq. Methods 2013; 63:126-34. [PMID: 23557989 DOI: 10.1016/j.ymeth.2013.03.023] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 03/21/2013] [Accepted: 03/23/2013] [Indexed: 11/18/2022] Open
Abstract
This report describes an improved protocol to generate stranded, barcoded RNA-seq libraries to capture the whole transcriptome. By optimizing the use of duplex specific nuclease (DSN) to remove ribosomal RNA reads from stranded barcoded libraries, we demonstrate improved efficiency of multiplexed next generation sequencing (NGS). This approach detects expression profiles of all RNA types, including miRNA (microRNA), piRNA (Piwi-interacting RNA), snoRNA (small nucleolar RNA), lincRNA (long non-coding RNA), mtRNA (mitochondrial RNA) and mRNA (messenger RNA) without the use of gel electrophoresis. The improved protocol generates high quality data that can be used to identify differential expression in known and novel coding and non-coding transcripts, splice variants, mitochondrial genes and SNPs (single nucleotide polymorphisms).
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120
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Chae H, Park J, Lee SW, Nephew KP, Kim S. Comparative analysis using K-mer and K-flank patterns provides evidence for CpG island sequence evolution in mammalian genomes. Nucleic Acids Res 2013; 41:4783-91. [PMID: 23519616 PMCID: PMC3643570 DOI: 10.1093/nar/gkt144] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
CpG islands are GC-rich regions often located in the 5′ end of genes and normally protected from cytosine methylation in mammals. The important role of CpG islands in gene transcription strongly suggests evolutionary conservation in the mammalian genome. However, as CpG dinucleotides are over-represented in CpG islands, comparative CpG island analysis using conventional sequence analysis techniques remains a major challenge in the epigenetics field. In this study, we conducted a comparative analysis of all CpG island sequences in 10 mammalian genomes. As sequence similarity methods and character composition techniques such as information theory are particularly difficult to conduct, we used exact patterns in CpG island sequences and single character discrepancies to identify differences in CpG island sequences. First, by calculating genome distance based on rank correlation tests, we show that k-mer and k-flank patterns around CpG sites can be used to correctly reconstruct the phylogeny of 10 mammalian genomes. Further, we used various machine learning algorithms to demonstrate that CpG islands sequences can be characterized using k-mers. In addition, by testing a human model on the nine different mammalian genomes, we provide the first evidence that k-mer signatures are consistent with evolutionary history.
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Di Leva G, Piovan C, Gasparini P, Ngankeu A, Taccioli C, Briskin D, Cheung DG, Bolon B, Anderlucci L, Alder H, Nuovo G, Li M, Iorio MV, Galasso M, Ramasamy S, Marcucci G, Perrotti D, Powell KA, Bratasz A, Garofalo M, Nephew KP, Croce CM. Estrogen mediated-activation of miR-191/425 cluster modulates tumorigenicity of breast cancer cells depending on estrogen receptor status. PLoS Genet 2013; 9:e1003311. [PMID: 23505378 PMCID: PMC3591271 DOI: 10.1371/journal.pgen.1003311] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 12/24/2012] [Indexed: 02/06/2023] Open
Abstract
MicroRNAs (miRNAs), single-stranded non-coding RNAs, influence myriad biological processes that can contribute to cancer. Although tumor-suppressive and oncogenic functions have been characterized for some miRNAs, the majority of microRNAs have not been investigated for their ability to promote and modulate tumorigenesis. Here, we established that the miR-191/425 cluster is transcriptionally dependent on the host gene, DALRD3, and that the hormone 17β-estradiol (estrogen or E2) controls expression of both miR-191/425 and DALRD3. MiR-191/425 locus characterization revealed that the recruitment of estrogen receptor α (ERα) to the regulatory region of the miR-191/425-DALRD3 unit resulted in the accumulation of miR-191 and miR-425 and subsequent decrease in DALRD3 expression levels. We demonstrated that miR-191 protects ERα positive breast cancer cells from hormone starvation-induced apoptosis through the suppression of tumor-suppressor EGR1. Furthermore, enforced expression of the miR-191/425 cluster in aggressive breast cancer cells altered global gene expression profiles and enabled us to identify important tumor promoting genes, including SATB1, CCND2, and FSCN1, as targets of miR-191 and miR-425. Finally, in vitro and in vivo experiments demonstrated that miR-191 and miR-425 reduced proliferation, impaired tumorigenesis and metastasis, and increased expression of epithelial markers in aggressive breast cancer cells. Our data provide compelling evidence for the transcriptional regulation of the miR-191/425 cluster and for its context-specific biological determinants in breast cancers. Importantly, we demonstrated that the miR-191/425 cluster, by reducing the expression of an extensive network of genes, has a fundamental impact on cancer initiation and progression of breast cancer cells. MicroRNAs are small noncoding RNAs that act as posttranscriptional repressors of gene expression. A pivotal role for miRNAs in all the molecular processes driving initiation and progression of various malignancies, including breast cancer, has been described. Divergent miRNA expression between normal and neoplastic breast tissues has been demonstrated, as well as differential miRNA expression among the molecular subtypes of breast cancer. Over half of all breast cancers overexpress ERα, and several studies have shown that miRNA expression is controlled by ERα. We assessed the global change in microRNA expression after estrogen starvation and stimulation in breast cancer cells and identified that miR-191/425 and the host gene DALRD3 are positively associated to ERα-positive tumors. We demonstrated that ERα regulates the miR-191/425 cluster and verified the existence of a transcriptional network that allows a dual effect of estrogen on miR-191/425 and their host gene. We show that estrogen induction of miR-191/425 supports in vitro and in vivo the estrogen-dependent proliferation of ERα positive breast cancer cells. On the contrary, miR-191/425 cluster reprograms gene expression to impair tumorigenicity and metastatic potential of highly aggressive ERα negative breast cancer cells.
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Antoon JW, Nitzchke AM, Martin EC, Rhodes LV, Nam S, Wadsworth S, Salvo VA, Elliott S, Collins-Burow B, Nephew KP, Burow ME. Inhibition of p38 mitogen-activated protein kinase alters microRNA expression and reverses epithelial-to-mesenchymal transition. Int J Oncol 2013; 42:1139-50. [PMID: 23403951 PMCID: PMC3622654 DOI: 10.3892/ijo.2013.1814] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 09/21/2012] [Indexed: 12/26/2022] Open
Abstract
Acquired chemoresistance and epithelial-to-mesenchymal transition (EMT) are hallmarks of cancer progression and of increasing clinical relevance. We investigated the role of miRNA and p38 mitogen-activated protein kinase (MAPK) signaling in the progression of breast cancer to a drug-resistant and mesenchymal phenotype. We demonstrate that acquired death receptor resistance results in increased hormone-independent tumorigenesis compared to hormone-sensitive parental cells. Utilizing global miRNA gene expression profiling, we identified miRNA alterations associated with the development of death receptor resistance and EMT progression. We further investigated the role of p38 MAPK in this process, showing dose-dependent inactivation of p38 by its inhibitor RWJ67657 and decreased downstream ATF and NF-κB signaling. Pharmacological inhibition of p38 also decreased chemoresistant cancer tumor growth in xenograft animal models. Interestingly, inhibition of p38 partially reversed the EMT changes found in this cell system, as illustrated by decreased gene expression of the EMT markers Twist, Snail, Slug and ZEB and protein and mRNA levels of Twist, a known EMT promoter, concomitant with decreased N-cadherin protein. RWJ67657 treatment also altered the expression of several miRNAs known to promote therapeutic resistance, including miR-200, miR-303, miR-302, miR-199 and miR-328. Taken together, our results demonstrate the roles of multiple microRNAs and p38 signaling in the progression of cancer and demonstrate the therapeutic potential of targeting the p38 MAPK pathway for reversing EMT in an advanced tumor phenotype.
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Lee H, Yang Y, Chae H, Nam S, Choi D, Tangchaisin P, Herath C, Marru S, Nephew KP, Kim S. BioVLAB-MMIA: a cloud environment for microRNA and mRNA integrated analysis (MMIA) on Amazon EC2. IEEE Trans Nanobioscience 2013; 11:266-72. [PMID: 22987133 DOI: 10.1109/tnb.2012.2212030] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
MicroRNAs, by regulating the expression of hundreds of target genes, play critical roles in developmental biology and the etiology of numerous diseases, including cancer. As a vast amount of microRNA expression profile data are now publicly available, the integration of microRNA expression data sets with gene expression profiles is a key research problem in life science research. However, the ability to conduct genome-wide microRNA-mRNA (gene) integration currently requires sophisticated, high-end informatics tools, significant expertise in bioinformatics and computer science to carry out the complex integration analysis. In addition, increased computing infrastructure capabilities are essential in order to accommodate large data sets. In this study, we have extended the BioVLAB cloud workbench to develop an environment for the integrated analysis of microRNA and mRNA expression data, named BioVLAB-MMIA. The workbench facilitates computations on the Amazon EC2 and S3 resources orchestrated by the XBaya Workflow Suite. The advantages of BioVLAB-MMIA over the web-based MMIA system include: 1) readily expanded as new computational tools become available; 2) easily modifiable by re-configuring graphic icons in the workflow; 3) on-demand cloud computing resources can be used on an "as needed" basis; 4) distributed orchestration supports complex and long running workflows asynchronously. We believe that BioVLAB-MMIA will be an easy-to-use computing environment for researchers who plan to perform genome-wide microRNA-mRNA (gene) integrated analysis tasks.
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Rawlinson JW, Vaden K, Hunsaker J, Miller DF, Nephew KP. Adenoviral-delivered HE4-HSV-tk sensitizes ovarian cancer cells to ganciclovir. GENE THERAPY & MOLECULAR BIOLOGY 2013; 15:120-130. [PMID: 26005395 PMCID: PMC4440683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Ovarian cancer (OC) is most often contained within the peritoneal cavity, making it an ideal disease for adenoviral-delivered gene therapies. In effort to develop a safe and effective gene therapy for OC, we created a replication deficient adenovirus bearing the herpes simplex thymidine kinase (HSV-tk) gene under direction of the tumor specific promoter human epididymis protein 4 (HE4). The purpose of this study was to investigate the ability of our adenoviral construct to transduce OC cells in vitro and mediate transgene expression of HSV-tk, thereby sensitizing OC to the pro-drug ganciclovir. Cisplatin-sensitive (CS) and -resistant (CR) A2780 OC cells, infected with virus for 6 hours at 100, 500, and 1000 multiplicity of infection followed by ganciclovir treatment every other day for 5 days, were assayed for cell viability. Adenoviral-mediated transgene expression increased with increasing amounts of virus and peaked at 48 hours after transduction in both A2780-CS and -CR. Unexpectedly, ganciclovir alone was slightly toxic to both A2780 cell lines (IC50 of 234.9 μg/mL and 257.2 μg/mL in A2780-CS and -CR, respectively). Transduction with ADV-HE4-HSV-tk followed by ganciclovir treatment increased (P<0.05) cell killing up to ten-fold, lowering the IC50 to 23.9 μg/mL and 32.6 μg/mL in A2780-CS and -CR, respectively, at 1000 multiplicity of infection. The results support the potential use of this approach as a gene therapy for OC, a disease that accounts for more deaths than any other cancer of the female reproductive system.
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Nam S, Long X, Kwon C, Kim S, Nephew KP. An integrative analysis of cellular contexts, miRNAs and mRNAs reveals network clusters associated with antiestrogen-resistant breast cancer cells. BMC Genomics 2012; 13:732. [PMID: 23270413 PMCID: PMC3560207 DOI: 10.1186/1471-2164-13-732] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Accepted: 12/20/2012] [Indexed: 12/28/2022] Open
Abstract
Background A major goal of the field of systems biology is to translate genome-wide profiling data (e.g., mRNAs, miRNAs) into interpretable functional networks. However, employing a systems biology approach to better understand the complexities underlying drug resistance phenotypes in cancer continues to represent a significant challenge to the field. Previously, we derived two drug-resistant breast cancer sublines (tamoxifen- and fulvestrant-resistant cell lines) from the MCF7 breast cancer cell line and performed genome-wide mRNA and microRNA profiling to identify differential molecular pathways underlying acquired resistance to these important antiestrogens. In the current study, to further define molecular characteristics of acquired antiestrogen resistance we constructed an “integrative network”. We combined joint miRNA-mRNA expression profiles, cancer contexts, miRNA-target mRNA relationships, and miRNA upstream regulators. In particular, to reduce the probability of false positive connections in the network, experimentally validated, rather than prediction-oriented, databases were utilized to obtain connectivity. Also, to improve biological interpretation, cancer contexts were incorporated into the network connectivity. Results Based on the integrative network, we extracted “substructures” (network clusters) representing the drug resistant states (tamoxifen- or fulvestrant-resistance cells) compared to drug sensitive state (parental MCF7 cells). We identified un-described network clusters that contribute to antiestrogen resistance consisting of miR-146a, -27a, -145, -21, -155, -15a, -125b, and let-7s, in addition to the previously described miR-221/222. Conclusions By integrating miRNA-related network, gene/miRNA expression and text-mining, the current study provides a computational-based systems biology approach for further investigating the molecular mechanism underlying antiestrogen resistance in breast cancer cells. In addition, new miRNA clusters that contribute to antiestrogen resistance were identified, and they warrant further investigation.
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