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"Epigenetic plasticity" refers to the capability of mammalian cells to alter their differentiation status via chromatin remodeling-associated alterations in gene expression. While epigenetic plasticity has been best associated with lineage commitment of embryonic stem cells, recent studies have demonstrated chromatin remodeling even in terminally differentiated normal cells, and advanced-stage melanoma and breast cancer cells, in context-dependent responses to alterations in their microenvironment. In the current study, we extend this attribute of epigenetic plasticity to aggressive ovarian cancer cells, by using an integrative approach to associate cellular phenotypes with chromatin modifications ("ChIP-chip") and mRNA and microRNA expression. While we identified numerous gene promoters possessing the well-known "bivalent mark" of H3K27me3/H3K4me2, we also report 14 distinct, lesser-known bi-, tri-, and tetravalent combinations of activating and repressive chromatin modifications, in platinum-resistant CP70 ovarian cancer cells. The vast majority (>90%) of all the histone marks studied localized to regions within 2000 bp of transcription start sites, supporting a role in gene regulation. Upon a simple alteration in the microenvironment, transition from two- to three-dimensional culture, an increase (17% to 38%) in repressive-only marked promoters was observed, concomitant with a decrease (31% to 21%) in multivalent (i.e., juxtaposed permissive and repressive histone marked) promoters. Like embryonic/tissue stem and other (non-ovarian) carcinoma cells, ovarian cancer cell epigenetic plasticity reflects an inherent transcriptional flexibility for context-responsive alterations in phenotype. It is possible that this plasticity could be therapeutically exploited for the management of this lethal gynecologic malignancy.

Half of all human transcription factors use C2H2 zinc finger domains to specify site-specific DNA binding and yet very little is known about their role in gene regulation. Based on in vitro studies, a zinc finger code has been developed that predicts a binding motif for a particular zinc finger factor (ZNF). However, very few studies have performed genome-wide analyses of ZNF binding patterns, and thus, it is not clear if the binding code developed in vitro will be useful for identifying target genes of a particular ZNF. We performed genome-wide ChIP-seq for ZNF263, a C2H2 ZNF that contains 9 finger domains, a KRAB repression domain, and a SCAN domain and identified more than 5000 binding sites in K562 cells. Our results suggest that ZNF263 binds to a 24-nt site that differs from the motif predicted by the zinc finger code in several positions. Interestingly, many of the ZNF263 binding sites are located within the transcribed region of the target gene. Although ZNFs containing a KRAB domain are thought to function mainly as transcriptional repressors, many of the ZNF263 target genes are expressed at high levels. To address the biological role of ZNF263, we identified genes whose expression was altered by treatment of cells with ZNF263-specific small interfering RNAs. Our results suggest that ZNF263 can have both positive and negative effects on transcriptional regulation of its target genes.

Epigenetic alterations, including gain or loss of DNA methylation, are a hallmark of nearly every malignancy. Changes in DNA methylation can impact expression of cancer-related genes including apoptosis regulators and tumor suppressors. Because such epigenetic changes are reversible, they are being aggressively investigated as potential therapeutic targets. Here we use the Eμ-TCL1 transgenic mouse model of chronic lymphocytic leukemia (CLL) to determine the timing and patterns of aberrant DNA methylation, and to investigate the mechanisms that lead to aberrant DNA methylation. We show that CLL cells from Eμ-TCL1 mice at various stages recapitulate epigenetic alterations seen in human CLL. Aberrant methylation of promoter sequences is observed as early as 3 months of age in these animals, well before disease onset. Abnormally methylated promoter regions include binding sites for the transcription factor FOXD3. We show that loss of Foxd3 expression due to an NF-κB p50/p50:HDAC1 repressor complex occurs in TCL1-positive B cells before methylation. Therefore, specific transcriptional repression is an early event leading to epigenetic silencing of target genes in murine and human CLL. These results provide strong rationale for the development of strategies to target NF-κB components in CLL and potentially other B-cell malignancies.

3H-1,2-dithiole-3-thione (D3T) and its analogues 4-methyl-5-pyrazinyl-3H-1,2-dithiole-3-thione (OLT) and 5-tert-butyl-3H-1,2-dithiole-3-thione (TBD) are chemopreventive agents that block or diminish early stages of carcinogenesis by inducing activities of detoxication enzymes. While OLT has been used in clinical trials, TBD has been shown to be more efficacious and possibly less toxic than OLT in animals. Here, we utilize a robust and high-resolution chemical genomics procedure to examine the pharmacological structure-activity relationships of these compounds in livers of male rats by microarray analyses. We identified 226 differentially expressed genes that were common to all treatments. Functional analysis identified the relation of these genes to glutathione metabolism and the nuclear factor, erythroid derived 2-related factor 2 pathway (Nrf2) that is known to regulate many of the protective actions of dithiolethiones. OLT and TBD were shown to have similar efficacies and both were weaker than D3T. In addition, we identified 40 genes whose responses were common to OLT and TBD, yet distinct from D3T. As inhibition of cytochrome P450 (CYP) has been associated with the effects of OLT on CYP expression, we determined the half maximal inhibitory concentration (IC(50)) values for inhibition of CYP1A2. The rank order of inhibitor potency was OLT >> TBD >> D3T, with IC(50) values estimated as 0.2, 12.8 and >100 microM, respectively. Functional analysis revealed that OLT and TBD, in addition to their effects on CYP, modulate liver lipid metabolism, especially fatty acids. Together, these findings provide new insight into the actions of clinically relevant and lead dithiolethione analogues.

Myc proteins have long been modeled to operate strictly as classic gene-specific transcription factors; however, we find that N-Myc has a robust role in the human genome in regulating global cellular euchromatin, including that of intergenic regions. Strikingly, 90% to 95% of the total genomic euchromatic marks histone H3 acetylated at lysine 9 and methylated at lysine 4 is N-Myc–dependent. However, Myc regulation of transcription, even of genes it directly binds and at which it is required for the maintenance of active chromatin, is generally weak. Thus, Myc has a much more potent ability to regulate large domains of euchromatin than to influence the transcription of individual genes. Overall, Myc regulation of chromatin in the human genome includes both specific genes, but also expansive genomic domains that invoke functions independent of a classic transcription factor. These findings support a new dual model for Myc chromatin function with important implications for the role of Myc in cancer and stem cell biology, including that of induced pluripotent stem cells. [Cancer Res 2008;68(23):9654–62]

Using ChIP–chip assays (employing ENCODE arrays and core promoter arrays), we examined the binding patterns of three members of the E2F family in five cell types. We determined that most E2F1, E2F4, and E2F6 binding sites are located within 2 kb of a transcription start site, in both normal and tumor cells. In fact, the majority of promoters that are active (as defined by TAF1 or POLR2A binding) in GM06990 B lymphocytes and Ntera2 carcinoma cells were also bound by an E2F. This very close relationship between E2F binding sites and binding sites for general transcription factors in both normal and tumor cells suggests that a chromatin-bound E2F may be a signpost for active transcription initiation complexes. In general, we found that several E2Fs bind to a given promoter and that there is only modest cell type specificity of the E2F family. Thus, it is difficult to assess the role of any particular E2F in transcriptional regulation, due to extreme redundancy of target promoters. However, Ntera2 carcinoma cells were exceptional in that a large set of promoters were bound by E2F6, but not by E2F1 or E2F4. It has been proposed that E2F6 contributes to gene silencing by recruiting enzymes involved in methylating histone H3. To test this hypothesis, we created Ntera2 cell lines harboring shRNAs to E2F6. We found that reduction of E2F6 only induced minimal alteration of the transcriptome of Ntera2 transcriptome. Our results support the concept of functional redundancy in the E2F family and suggest that E2F6 is not critical for histone methylation.

Background: Epigenetic alterations are frequently encountered in many malignancies. Control of DNA methylation is thought to play a critical role in the global epigenetic reprogramming observed during development and carcinogenesis. DNA demethylation is initiated by the transition from 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). While 5mC patterns are relatively well characterized in many malignancies, not much is known about 5hmC patterns and the potential usefulness as biomarkers. We thus sought out to identify 5hmC alterations in renal cell carcinoma (RCC) and assess their potential usefulness as urine biomarkers. Results: We performed genome-wide 5hmC MethylCap-seq on one pooled RCC tissue sample (n = 3) and the corresponding pooled matched normal kidney tissue (n = 3), as well as on one pooled urine sample obtained from RCC patients (n = 52) and one pooled urine sample obtained from control patients without malignancy (n = 65). Global 5hmC levels were dramatically reduced in RCC tissues compared to matched normal adjacent kidney tissues, and in urine samples compared to tissue samples. Assessing histone marked regions we found 5hmC levels to be highly enriched in H3K9me3 marked repressive genomic regions of RCC tissue compared to normal adjacent tissues. Given the low 5hmC signal in these regions in normal tissues, this difference was also clearly identified comparing urine samples from RCC patients to control patients without RCC. Conclusions: We characterized the 5hmC distribution of RCC and normal human renal tissue as well as of urine samples from RCC patients and control patients without RCC. We identified dramatic genome-wide 5hmC changes to occur during carcinogenesis, which have potential for development as non-invasive urine biomarkers. Citation Format: Wei Meng, Tim Lautenschlaeger, David Frankhouser, Zhenqing Ye, Alexander Huebner, Victor Jin, Pearlly Yan, Arnab Chakravarti. 5-hydroxymethylcytosine alterations at H3K9me3 marked genomic regions serve as potential biomarker for renal cell carcinoma patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2963. doi:10.1158/1538-7445.AM2015-2963

Recruitment of transcriptional machinery to target promoters for aberrant gene expression has been well studied, but underlying control directed by distant-acting enhancers remains unclear in cancer development. Our previous study demonstrated that distant estrogen response elements (DEREs) located on chromosome 20q13 were frequently amplified (50∼60 copies) and translocated to other chromosomes in ERα-positive breast cancer cells. In this study, we used three-dimensional interphase fluorescence in situ hybridization to decipher spatiotemporal gathering of multiple DEREs in the nucleus. Upon estrogen stimulation, the majority of 20q13 DEREs were mobilized to form regulatory depots for synchronized regulation of target loci. A chromosome conformation capture assay coupled with chromatin immunoprecipitation further uncovered that ERα-bound regulatory depots are tethered to heterochromatin protein 1 (HP1) for coordinated chromatin movement and subsequent facilitation of histone modifications of target loci, resulting in transcription repression. Neutralizing HP1 function dissembled these regulatory depots and reversed this transcription inactivation of candidate tumor-suppressor genes. Deletion of amplified DEREs using the CRISPR/Cas9 genomic-editing system profoundly altered transcriptional profiles of JAK/STAT signaling networks, leading to proliferation inhibition of cancer cells with beneficial outcome of breast cancers. These findings reveal a formerly uncharacterized feature of oncogenic amplicons that multiple copies of the amplicon congregate as transcriptional unions in the nucleus for synchronous regulation of function-related loci in tumorigenesis. Disruption of their assembly can be a new strategy for treating breast cancers and other malignancies. Citation Format: Pei-Yin Hsu, Hang-Kai Hsu, Victor X. Jin, Zelton D. Sharp, Tim H.-M. Huang. HP1-mediated spatiotemporal control of estrogen-responsive transcription in breast cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4778. doi:10.1158/1538-7445.AM2015-4778

Fields such as genomics and systems biology are built on the synergism between computational and experimental techniques. This type of synergism is especially important in accomplishing goals like identifying all functional transcription factor binding sites in vertebrate genomes. Precise detection of these elements is a prerequisite to deciphering the complex regulatory networks that direct tissue specific and lineage specific patterns of gene expression. This review summarizes approaches for in silico, in vitro, and in vivo identification of transcription factor binding sites. A variety of techniques useful for localized- and high-throughput analyses are discussed here, with emphasis on aspects of data generation and verification.

Repeated sequences account for a significant fraction of Eukaryotic genomes - nearly half of the human genome consists of repeated sequence elements. Several elements have been linked to diseases. Consequently, identifying and characterizing repeated elements is essential for understanding diseases at the molecular level. Repeated sequences vary from one genome to another and are therefore difficult to identify using sequence comparison methods alone. Certain gene families, such as the interferon gene family or the natural killer gene complex, have been found to be clustered together in the genome. Several observations have lead to the hypothesis that specific sequence repeats could be playing an important role in generating multigene families. Here, we define the concept of localized interspersed motifs and present a computational approach for detecting them

The estrogen receptor (ER) plays an important role in several physiologic functions of both the reproductive and non-reproductive systems. Malignancies of the ER have been associated with the development of cancers, including those of the prostate and breast. Hence it has become of significant importance to characterize the transcriptional regulation of ER target genes. We have created ERTargetDB in order to integrate the previously published ER target gene information that is available in various publications and databases. This information resource provides researchers with an easy access to ER target genes and the regulatory mechanisms in the corresponding promoters. The current version contains 40 genes with experimentally verified estrogen response elements (EREs), 32 experimentally verified ERE tethering sites, 40 genes identified by the chromatin immunoprecipitation microarray, 381 genes from gene expression microarray and 2948 genes from computational prediction. ERTargetDB provides an integral information resource for direct target genes of ERs for the endocrinology research community. It should prove useful in the investigation of gene regulation and aid the development of computational tools for the prediction of ER target genes.

Summary: Sequence comparisons between human and rodents are increasingly being used for the identification of gene regulatory regions. The effectiveness of such an approach largely depends on the quality and availability of promoter sequences. We developed OMGProm by integrating three data sources: (1) experimentally supported full-length cDNA, promoter and first exon sequences; (2) homology information from HomoloGene and (3) the human and mouse genomic sequences. The current version of OMGProm contains 8550 promoter pairs of 6373 orthologous human and mouse genes, where supporting experimental evidence for transcription start site annotation exists in at least one species. Availability: OMGProm can be accessed from http://bioinformatics.med.ohio-state.edu/OMGProm Contact: davuluri-1@medctr.osu.edu Supplementary information: Additional information on methods and implementation is available at http://bioinformatics.med.ohio-state.edu/OMGProm/si.jsp.

Since the first amplified gene, MYCN, was identified in neuroblastomas, considerable effort has been directed toward discovery of oncogenes in amplified genomic regions. However, there is no significant correlation between copy number gains and increased expression of corresponding genes within amplicons. We demonstrate that amplification of distant-acting regulatory elements, or enhancers, may be an alternative mechanism contributing to an oncogenic event. Enhancers comprise transcription factor binding sites known to remotely regulate transcription through chromatin looping or transvection. Using a “Seq-to-Seek” strategy integrating three next-generation sequencing approaches, we comprehensively mapped distant estrogen response elements (DEREs) that remotely control transcription of target genes through chromatin proximity. Surprisingly, a densely mapped DERE region located on chromosome 20q13 frequently amplifies in ERα-positive breast cancer with poor prognosis. Progressive accumulation of DERE copies was observed in normal breast progenitor and cancer cells chronically exposed to estrogen or estrogenic chemicals. Pharmacological studies with either an ERα antagonist or an ataxia telangiectasia mutated (ATM) kinase inhibitor further showed that ATM-dependent DNA repair pathway participates in ERα-driven increase of 20q13 DERE copies, suggesting involvement of breakage-fusion-bridge mechanism in DERE amplification. Furthermore, these aberrantly amplified DEREs altered chromatin interactions, leading to transcriptional repression of genes that are associated with tumor-suppressor and apoptosis pathways and potentially linked to cancer development and tamoxifen resistance. Correlation analyses of copy-number variation, occupancy of the repressive histone mark, H3K27me3, and methylation profiling of 20q13 DEREs in ERα-positive cancer cells support a model in which amplified DEREs preferentially induce repressive epigenetic modulation of target genes. In addition, interphase fluorescence in situ hybridization coupled with immunofluorescence analyses revealed that estrogen stimulation leads to DERE clustering in a transcriptional hub nearby in a heterochromatic region. These findings indicate that the 20q13 DERE region is a potential transcriptionally repressive domain whose aberrant amplification can result in suppressing expression of tumor suppressor genes. To determine the precise role of amplified DEREs in epigenetic transcription and their biological significance, our ongoing studies use CRISPR/Cas genomic editing system to delete candidate DEREs at 20q13. In summary, our findings suggest that amplification of DNA regulatory elements can profoundly alter target transcriptome during tumorigenesis and amplified DEREs can be used as potential prognostic markers for endocrine resistance. Citation Format: PEI-YIN HSU, HANG-KAI HSU, Victor X. Jin, Zelton D. Sharp, Tim H.-M. Huang. Amplification of distant estrogen response elements epigenetically deregulates target genes in ERα-mediated breast tumorigenesis. [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 4783. doi:10.1158/1538-7445.AM2014-4783

Endometrial cancer (EC) is the most common gynecologic malignancy, with approximately 20% of EC patients developing advanced stage recurrent tumors and frequent metastasis. Our goal was to investigate whether DNA methylation signatures associated with low promoter methylation (hypomethylation) and specific oncogenic signaling delineate predictive markers of endometrial cancer recurrence. Global screening by Methyl-CpG-capture sequencing revealed aberrant DNA methylation in our endometrial cancer cohort and identified a subset of bone morphogenetic protein family (BMP1, 2, 3, 4, and 7) exhibiting frequent hypomethylation in primary tumors with subsequent recurrence compared with non-recurrent tumors. This epigenetic signature correlated with poor survival and was validated in The Cancer Genome Atlas endometrial cancer cohort. Our functional studies also implicated epidermal growth factor receptor (EGFR) pathway in the transcriptional activation of these BMPs and inducing epithelial-mesenchymal transition (EMT). In addition to AKT and MAPK, the epithelial cell adhesion molecule (EpCAM) mediated these actions by EGFR. EpCAM involvement in cancer progression includes nuclear co-translocation of its intracellular domain EpICD with Lef-1 complexes and targeting oncogene promoter activation. In this study, EGF stimulated EpICD-Lef-1 binding on BMP genes accompanied with histone active modification marks. EpICD knockdown resulted in increased repressive histone marks and DNA methylation at these loci, suggesting that EpICD occupancy is involved in their epigenetic modification to an open transcriptional conformation. Knockdown of candidate BMPs led to decreased endometrial cancer cell invasiveness, implicating them in aggressive growth. Extending our studies, we performed ChIP-Seq analysis to identify global regulation by the EpICD-Lef-1 complexes in endometrial cancer. Interestingly, under basal levels only about 28% of loci targeted by either EpICD or Lef-1 were commonly targeted by EpICD-Lef-1, with common targets increasing to about 50% in 24 hrs and 73% in 48 hrs post EGF treatment. This indicates that EGFR signaling stimulates a time-course dependent enrichment of EpICD-Lef-1 convergence on target loci. Our initial studies of these EpICD target pathways included genes with cell adhesion functions. Future studies on the regulation of the EpICD-Lef-1 regulated genes and their mechanisms of action in aggressive endometrial cancer will provide a better understanding of this gene network in endometrial cancer. Hypomethylation signatures of candidate loci in this regulatory network may present putative predictive markers of poor survival and which may be used to tailor individualized therapy. Citation Format: Ya-Ting Hsu, Fei Gu, Yi-Wen Huang, Joseph Liu, Jianhua Ruan, Rui-Lan Huang, Chiou-Miin Wang, Chun-Liang Chen, Rohit R. Jadhav, Yao Wang, Victor X. Jin, Hung-Cheng Lai, David G. Mutch, Paul J. Goodfellow, Ian M. Thompson, Nameer B. Kirma, Tim H.M. Huang. EpCAM-mediated hypomethylation of BMP and cell adhesion genes is associated with advanced endometrial cancer. [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 1376. doi:10.1158/1538-7445.AM2014-1376

The phosphatidylinositol 3-kinase (PI3K)/AKT pathway is a critical survival cascade in tumor progression. Our previous study demonstrated that combinational treatment of a potent PI3K inhibitor, LY294002 (LY), and DNA methyltransferase inhibitor, 5’-Aza-deoxycytidine (DAC), compounds effectively reduce tumor formation in the immunodeficiency mouse model, suggesting that PI3K/AKT signaling suppresses tumorigenesis through the epigenetic modulation. While tumor size of the LY-treated xenografts is dramatically decreased compared to the control group, the tumor growth cannot be completely attenuated by either LY or LY/DAC treatment, indicating that there is an alternative route for tumor survival. Here, we performed a microarray analysis to identify LY-mediated expression profiling on an ERα-positive breast cancer cell line, T-47D, the cell line applied in the previous xenograft experiments. A subset of 24 LY-activated genes associated with better clinical outcome are found to be not only direct targets of PI3K/AKT but involved in estrogen (E2)/ERα signaling by ingenuity pathway analysis, suggesting the involvement of ERα signaling in PI3K/AKT-mediated tumor growth. To clarify their relationship, pharmacological experiments using an ERα antagonist, ICI 182, 780 (ICI) and LY coupled with E2 was conducted. We observed that E2 stimulation induces both AKT and ERα activation in a time-dependent manner. Either ICI or LY treatment cannot repress the activation levels of AKT or ERα, respectively. Though, either single or combined inhibitor treatment can effectively restore E2-suppressed gene expression. These findings indicate that cross-talk between PI3K/AKT and ERα signaling cascades may cooperatively regulate cell growth and associated gene expression. In addition, transcription factor motif analysis showed that signal transducer and activator of transcription 3 and 6 (STAT3/6) binding motifs are enriched with highest prediction score on the promoter regions of the examined AKT-directed targets. Inhibitors prohibit E2-mediated assembly of STAT3/6 with ERα and STAT3/6 recruitment onto the promoter regions of target loci using co-immunoprecipitation (co-IP) and chromatin IP-qPCR. Moreover, repressive histone marks, H3K27me3 and H3K9me3, are found to occupy on the same regions as STAT3/6 upon E2 treatment. DAC treatment can effectively restore E2-induced suppression of AKT-directed target genes. Further association studies are ongoing to interrogate whether STAT3/6 is part of repressive transcription complex with H3K27me3 and H3K9me3. In summary, we propose that cross-talk of ERα with PI3K/AKT signaling represents the potential function switch of ERα from genomic binding to no-genomic binding. Combined treatment of PI3K/AKT inhibitors with hormone therapy may shed a light of therapeutic strategy to patients with aggressive or metastatic breast tumors. Citation Format: Hang-Kai Hsu, Pei-Yin Hsu, Yao Wang, Zelton D. Sharp, Tim H.-M. Huang, Victor X. Jin. Cross-talk between PI3K/AKT and ERα signaling leads to STAT3/6-modulated epigenetic transcription in aggressive breast cancer. [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 3341. doi:10.1158/1538-7445.AM2014-3341

Mutation of the APC tumor suppressor gene occurs in approximately 75% of colorectal cancers (CRC) and is considered the central event driving tumor initiation in the large intestine. The APC protein controls gene expression indirectly through the canonical WNT signaling pathway as a component of a cytoplasmic complex that promotes the proteolysis of the transcriptional co-regulator β-catenin. Recent studies have shown that APC is also a chromatin-associated protein that interacts with the promoter of the MYC proto-oncogene to downregulate its transcription. We have tested the hypothesis that APC similarly regulates other genes relevant to tumorigenesis, and that the 75% of CRCs that are deficient in APC may show abnormal activation or suppression of these genes, in comparison to the other 25% of CRCs. These differences could potentially underlie differences in tumor progression and/or responses to chemotherapy, and could enable the identification of new therapeutic targets. The APC genotype of two CRC cell lines was manipulated using siRNA to reduce APC expression in one cell line wild-type for APC and using an APC transgene to induce exogenous APC expression in a second cell line mutated for APC. NanoString and RNA-seq technologies have generated gene expression datasets from these cell lines and identify more than 700 genes that could be directly regulated at the transcriptional level by APC. RT-PCR and in silico analyses have validated a smaller subset of these genes. Functional pathway analysis has led to the hypothesis that APC loss facilitates evasion of apoptosis, with a subset of 17 pro- and anti-apoptotic candidate genes implicated in this effect. Critical experiments in progress will confirm the extent to which the aberrant expression of these genes in vivo is specific to colon tumors lacking APC, using Apc-deficient and Apc-wild-type mouse models of intestinal cancer, and will identify direct chromatin binding sites of APC by ChIP-seq. These approaches will validate our gene expression analyses and identify a set of direct gene targets that APC regulates. Citation Format: William Hankey, Michael A. McIlhatton, Xun Lan, Anil G. Jegga, Victor X. Jin, Bruce J. Aronow, Joanna Groden. Direct transcriptional functions of the APC tumor suppressor in regulating gene expression. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr A21.

One big limitation of computational tools for analyzing ChIP-seq data is that most of them ignore non-unique tags (NUTs) that match the human genome even though NUTs comprise up to 60% of all raw tags in ChIP-seq data. Effectively utilizing these NUTs would increase the sequencing depth and allow a more accurate detection of enriched binding sites, which in turn could lead to more precise and significant biological interpretations. In this study, we have developed a computational tool, LOcating Non-Unique matched Tags (LONUT), to improve the detection of enriched regions from ChIP-seq data. Our LONUT algorithm applies a linear and polynomial regression model to establish an empirical score (ES) formula by considering two influential factors, the distance of NUTs to peaks identified using uniquely matched tags (UMTs) and the enrichment score for those peaks resulting in each NUT being assigned to a unique location on the reference genome. The newly located tags from the set of NUTs are combined with the original UMTs to produce a final set of combined matched tags (CMTs). LONUT was tested on many different datasets representing three different characteristics of biological data types. The detected sites were validated using de novo motif discovery and ChIP-PCR. We demonstrate the specificity and accuracy of LONUT and show that our program not only improves the detection of binding sites for ChIP-seq, but also identifies additional binding sites.

7573 Background: In this study we performed genome-wide microRNA-seqencing (miRNA-seq) in lung adenocacinoma (ADC) patient samples and used bioinformatic analyses to identify novel and annotated microRNAs that are differentially expressed between patients with and patients without lymph node metastasis, as well as examining their potential prognostic value. Methods: Sixty four frozen tissue specimens from lung ADC patients collected between 2003 and 2012 were obtained through the OSUCCC Tissue Procurement Shared Resource, approved by internal review board (IRB). Total RNA samples were processed and loaded on the Applied Biosystems SOLiD 4 sequencing system for data acquisition. 249 patients from the TCGA lung ADC cohort were used for results validation. Human lung ADC cell lines H23 and H1573 were used for in vitro functional assays. Results: We identified several microRNAs that were associated with the presence of lymph node metastasis in primary lung adenocarcinoma tissues using genome-wide miRNA-seq. We confirmed miR-31 to be up-regulated in lung ADC tissues from patients with lymph node metastasis in a separate patient cohort (p=0.009, t-test), and to be expressed higher in ADC tissues than in matched normal adjacent lung tissues (p

Thyroid cancer shows high heritability but causative genes remain largely unknown. According to a common hypothesis the genetic predisposition to thyroid cancer is highly heterogeneous; being in part due to many different rare alleles. Here we used linkage analysis and targeted deep sequencing to detect a novel single-nucleotide mutation in chromosome 4q32 (4q32A>C) in a large pedigree displaying non-medullary thyroid carcinoma (NMTC). This mutation is generally ultra-rare; it was not found in 38 NMTC families, in 2676 sporadic NMTC cases or 2470 controls. The mutation is located in a long-range enhancer element whose ability to bind the transcription factors POU2F and YY1 is significantly impaired, with decreased activity in the presence of the C- allele compared with the wild type A-allele. An enhancer RNA (eRNA) is transcribed in thyroid tissue from this region and is greatly downregulated in NMTC tumors. We suggest that this is an example of an ultra-rare mutation predisposing to thyroid cancer with high penetrance.

Background The TCF7L2 transcription factor is linked to a variety of human diseases, including type 2 diabetes and cancer. One mechanism by which TCF7L2 could influence expression of genes involved in diverse diseases is by binding to distinct regulatory regions in different tissues. To test this hypothesis, we performed ChIP-seq for TCF7L2 in six human cell lines. Results We identified 116,000 non-redundant TCF7L2 binding sites, with only 1,864 sites common to the six cell lines. Using ChIP-seq, we showed that many genomic regions that are marked by both H3K4me1 and H3K27Ac are also bound by TCF7L2, suggesting that TCF7L2 plays a critical role in enhancer activity. Bioinformatic analysis of the cell type-specific TCF7L2 binding sites revealed enrichment for multiple transcription factors, including HNF4alpha and FOXA2 motifs in HepG2 cells and the GATA3 motif in MCF7 cells. ChIP-seq analysis revealed that TCF7L2 co-localizes with HNF4alpha and FOXA2 in HepG2 cells and with GATA3 in MCF7 cells. Interestingly, in MCF7 cells the TCF7L2 motif is enriched in most TCF7L2 sites but is not enriched in the sites bound by both GATA3 and TCF7L2. This analysis suggested that GATA3 might tether TCF7L2 to the genome at these sites. To test this hypothesis, we depleted GATA3 in MCF7 cells and showed that TCF7L2 binding was lost at a subset of sites. RNA-seq analysis suggested that TCF7L2 represses transcription when tethered to the genome via GATA3. Conclusions Our studies demonstrate a novel relationship between GATA3 and TCF7L2, and reveal important insights into TCF7L2-mediated gene regulation.

We previously reported in a Phase I clinical trial that black raspberry (BRB) powder is well tolerated by humans when administered in a slurry of water at 45g/day for 7 days. We then undertook a study to determine if BRB might regress rectal polyps in familial adenomatous polyposis (FAP) patients. Fourteen FAP patients who had undergone a colectomy were treated with BRB daily for a period of nine months. Seven patients received BRB powder (20g/3x/day) orally in water plus two suppositories (each composed of 700 mg BRB) that patients inserted into the rectum one hour before bedtime. The other seven patients were randomized to receive an oral placebo plus the two rectal suppositories. Rectal polyp counts were taken at time zero and after nine months of BRB treatment. The number of rectal polyps was reduced by a median of 43% at nine months overall including a median reduction of 59% in patients treated by both routes and 36% in patients treated with the suppositories only. Polyps and aberrant crypt foci, both were histopathologically identified as tubular adenomas, and adjacent normal tissues were collected both before and after berry treatment. Promoter methylation of CDKN2A, also known as p16, in collected specimens was measured using MassARRAY. Global methylation LINE-1 was determined by Pyrosequencing. MBDCap-seq genome-wide methylation analysis was used to discover other genes demethylated by berries. Further, the specimens were evaluated for p16, Ki-67, TUNEL, DNMT1 and DNMT3B expression by semi-quantitative immunohistochemistry. Our results showed that treatment with BRB powder, both orally and in the form of a BRB suppository, significantly reduced cell proliferation in the tubular adenomas. The suppository alone was sufficient to decrease promoter methylation of p16 leading to an increase in p16 protein expression in adjacent normal rectum and in tubular adenomas. This was associated with decreased protein expression of DNMT1 and DNMT3B. Based on MBDCap-seq data, BRBs significantly demethylated promoter CpGs of 44 genes in tubular adenomas. These genes are involved in the regulation of important cellular functions; e.g., cell proliferation, Wnt signaling and Notch pathway, etc. Lastly, berry treatment did not induce changes in global methylation LINE-1. In conclusion, our data provide evidence that one of the mechanisms for BRB-induced rectal polyp regression in FAP patients is through the demethylation and reactivation of tumor suppressor genes.(Supported by NCI grants CA148818 and CA103180, and USDA grant 38903-03560). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1009. doi:1538-7445.AM2012-1009

Methyl-CpG binding domain protein sequencing (MBD-seq) is widely used to survey DNA methylation patterns. However, the optimal experimental parameters for MBD-seq remain unclear and the data analysis remains challenging. In this study, we generated high depth MBD-seq data in MCF-7 cell and developed a bi-asymmetric-Laplace model (BALM) to perform data analysis. We found that optimal efficiency of MBD-seq experiments was achieved by sequencing ∼100 million unique mapped tags from a combination of 500 mM and 1000 mM salt concentration elution in MCF-7 cells. Clonal bisulfite sequencing results showed that the methylation status of each CpG dinucleotides in the tested regions was accurately detected with high resolution using the proposed model. These results demonstrated the combination of MBD-seq and BALM could serve as a useful tool to investigate DNA methylome due to its low cost, high specificity, efficiency and resolution.

Background DNA methylation and repressive histone modifications cooperate to silence promoters. One mechanism by which regions of methylated DNA could acquire repressive histone modifications is via methyl DNA-binding transcription factors. The zinc finger protein ZBTB33 (also known as Kaiso) has been shown in vitro to bind preferentially to methylated DNA and to interact with the SMRT/NCoR histone deacetylase complexes. We have performed bioinformatic analyses of Kaiso ChIP-seq and DNA methylation datasets to test a model whereby binding of Kaiso to methylated CpGs leads to loss of acetylated histones at target promoters. Results Our results suggest that, contrary to expectations, Kaiso does not bind to methylated DNA in vivo but instead binds to highly active promoters that are marked with high levels of acetylated histones. In addition, our studies suggest that DNA methylation and nucleosome occupancy patterns restrict access of Kaiso to potential binding sites and influence cell type-specific binding. Conclusions We propose a new model for the genome-wide binding and function of Kaiso whereby Kaiso binds to unmethylated regulatory regions and contributes to the active state of target promoters.

Poster presentation Advances in high-throughput technologies such as ChIPchip and the completion of human genomic sequences allow analysis of the mechanisms of gene regulation on a systems level. In this study, we have developed a computational genomics approach (ChIPModules) and a motif discovery approach (ChIPMotifs) to mine the ChIP-chip data. The ChIPModules approach begins with experimentally determined binding sites and integrates positional weight matrices, a comparative genomics approach, and statistical learning methods to identify transcriptional regulatory modules. Using E2F1 ChIP-chip data performed on ENCODE regions in both HeLa and MCF7 cells, we have identified five regulatory modules for E2F1. One of modules was validated by using ChIP-chip with arrays containing ~14,000 human promoters. The ChIPMotifs approach incorporates a bootstrap re-sampling method to statistically infer the optimal cutoff threshold for a position weight matrix (PWM) of a motif identified from ChIP-chip data by ab initio motif discovery programs. Using OCT4 ChIP-chip data, we developed an in vivo OCT4 PWM. We then used this PWM and our ChIPModules to identify transcription factors co-localizing with OCT4 in a testicular germ cell tumor (Ntera2 cells).