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1.  Antagonistic Cross-Regulation between Sox9 and Sox10 Controls an Anti-tumorigenic Program in Melanoma 
PLoS Genetics  2015;11(1):e1004877.
Melanoma is the most fatal skin cancer, but the etiology of this devastating disease is still poorly understood. Recently, the transcription factor Sox10 has been shown to promote both melanoma initiation and progression. Reducing SOX10 expression levels in human melanoma cells and in a genetic melanoma mouse model, efficiently abolishes tumorigenesis by inducing cell cycle exit and apoptosis. Here, we show that this anti-tumorigenic effect functionally involves SOX9, a factor related to SOX10 and upregulated in melanoma cells upon loss of SOX10. Unlike SOX10, SOX9 is not required for normal melanocyte stem cell function, the formation of hyperplastic lesions, and melanoma initiation. To the contrary, SOX9 overexpression results in cell cycle arrest, apoptosis, and a gene expression profile shared by melanoma cells with reduced SOX10 expression. Moreover, SOX9 binds to the SOX10 promoter and induces downregulation of SOX10 expression, revealing a feedback loop reinforcing the SOX10 low/SOX9 high ant,m/ii-tumorigenic program. Finally, SOX9 is required in vitro and in vivo for the anti-tumorigenic effect achieved by reducing SOX10 expression. Thus, SOX10 and SOX9 are functionally antagonistic regulators of melanoma development.
Author Summary
For the development of future cancer therapies it is imperative to understand the molecular processes underlying tumor initiation and expansion. Many key factors involved in these processes have been identified based on cell culture and transplantation experiments, but their relevance for tumor formation and disease progression in the living organism is often unclear. Therefore, genetically modified mice spontaneously developing tumors present indispensable models for cancer research. Here, we address this issue by studying the formation of melanoma, the most fatal skin tumor in industrialized countries. To this end, we use a transgenic mouse model to elucidate cellular and molecular mechanisms regulating congenital nevus and melanoma initiation. We show that a transcription factor called SOX10 promotes melanoma formation by repressing an anti-tumorigenic program involving the activity of a related factor, SOX9. When SOX10 is inactivated, SOX9 becomes upregulated and induces cell cycle arrest and death in melanoma cells. Furthermore, upon experimental elevation of SOX9 levels, SOX10 activity is suppressed, revealing an antagonistic relationship between SOX9 and SOX10 in melanoma initiation. Knowledge of how an anti-tumorigenic program can be stimulated by modulating the activities of these key factors might help to design novel therapeutic strategies.
PMCID: PMC4309598  PMID: 25629959
2.  A polymorphism in IRF4 affects human pigmentation through a tyrosinase-dependent MITF/TFAP2A pathway 
Cell  2013;155(5):10.1016/j.cell.2013.10.022.
Sequence polymorphisms linked to human diseases and phenotypes in genome-wide association studies often affect non-coding regions. A single nucleotide polymorphism (SNP) within an intron of the gene encoding Interferon Regulatory Factor 4 (IRF4), a transcription factor with no known role in melanocyte biology, is strongly associated with sensitivity of skin to sun exposure, freckles, blue eyes and brown hair color. Here we demonstrate that this SNP lies within an enhancer of IRF4 transcription in melanocytes. The allele associated with this pigmentation phenotype impairs binding of the TFAP2A transcription factor which together with the melanocyte master regulator MITF, regulates activity of the enhancer. Assays in zebrafish and mice reveal that IRF4 cooperates with MITF to activate expression of Tyrosinase (TYR), an essential enzyme in melanin synthesis. Our findings provide a clear example of a non-coding polymorphism that affects a phenotype by modulating a developmental gene regulatory network.
PMCID: PMC3873608  PMID: 24267888
3.  NCI-60 Whole Exome Sequencing and Pharmacological CellMiner Analyses 
PLoS ONE  2014;9(7):e101670.
Exome sequencing provides unprecedented insights into cancer biology and pharmacological response. Here we assess these two parameters for the NCI-60, which is among the richest genomic and pharmacological publicly available cancer cell line databases. Homozygous genetic variants that putatively affect protein function were identified in 1,199 genes (approximately 6% of all genes). Variants that are either enriched or depleted compared to non-cancerous genomes, and thus may be influential in cancer progression and differential drug response were identified for 2,546 genes. Potential gene knockouts are made available. Assessment of cell line response to 19,940 compounds, including 110 FDA-approved drugs, reveals ≈80-fold range in resistance versus sensitivity response across cell lines. 103,422 gene variants were significantly correlated with at least one compound (at p<0.0002). These include genes of known pharmacological importance such as IGF1R, BRAF, RAD52, MTOR, STAT2 and TSC2 as well as a large number of candidate genes such as NOM1, TLL2, and XDH. We introduce two new web-based CellMiner applications that enable exploration of variant-to-compound relationships for a broad range of researchers, especially those without bioinformatics support. The first tool, “Genetic variant versus drug visualization”, provides a visualization of significant correlations between drug activity-gene variant combinations. Examples are given for the known vemurafenib-BRAF, and novel ifosfamide-RAD52 pairings. The second, “Genetic variant summation” allows an assessment of cumulative genetic variations for up to 150 combined genes together; and is designed to identify the variant burden for molecular pathways or functional grouping of genes. An example of its use is provided for the EGFR-ERBB2 pathway gene variant data and the identification of correlated EGFR, ERBB2, MTOR, BRAF, MEK and ERK inhibitors. The new tools are implemented as an updated web-based CellMiner version, for which the present publication serves as a compendium.
PMCID: PMC4102467  PMID: 25032700
5.  Rb1 loss modifies but does not initiate alveolar rhabdomyosarcoma 
Skeletal Muscle  2013;3:27.
Alveolar rhabdomyosarcoma (aRMS) is a myogenic childhood sarcoma frequently associated with a translocation-mediated fusion gene, Pax3:Foxo1a.
We investigated the complementary role of Rb1 loss in aRMS tumor initiation and progression using conditional mouse models.
Rb1 loss was not a necessary and sufficient mutational event for rhabdomyosarcomagenesis, nor a strong cooperative initiating mutation. Instead, Rb1 loss was a modifier of progression and increased anaplasia and pleomorphism. Whereas Pax3:Foxo1a expression was unaltered, biomarkers of aRMS versus embryonal rhabdomyosarcoma were both increased, questioning whether these diagnostic markers are reliable in the context of Rb1 loss. Genome-wide gene expression in Pax3:Foxo1a,Rb1 tumors more closely approximated aRMS than embryonal rhabdomyosarcoma. Intrinsic loss of pRb function in aRMS was evidenced by insensitivity to a Cdk4/6 inhibitor regardless of whether Rb1 was intact or null. This loss of function could be attributed to low baseline Rb1, pRb and phospho-pRb expression in aRMS tumors for which the Rb1 locus was intact. Pax3:Foxo1a RNA interference did not increase pRb or improve Cdk inhibitor sensitivity. Human aRMS shared the feature of low and/or heterogeneous tumor cell pRb expression.
Rb1 loss from an already low pRb baseline is a significant disease modifier, raising the possibility that some cases of pleomorphic rhabdomyosarcoma may in fact be Pax3:Foxo1a-expressing aRMS with Rb1 or pRb loss of function.
PMCID: PMC4177545  PMID: 24274149
Alveolar rhabdomyosarcoma; Disease modifier; Sarcoma; Rb1; Spindle cell; Retinoblastoma
6.  Exclusion of the 750-kb Genetically Unstable Region at Xq27 as a Candidate Locus for Prostate Malignancy in HPCX1-linked Families 
Genes, chromosomes & cancer  2012;51(10):933-948.
Several linkage studies provided evidence for the presence of the hereditary prostate cancer locus, HPCX1, at Xq27-q28. The strongest linkage peak of prostate cancer overlies a variable region of ~750 kb at Xq27 enriched by segmental duplications (SDs), suggesting that the predisposition to prostate cancer may be a genomic disorder caused by recombinational interaction between SDs. The large size of SDs and their sequence similarity make it difficult to examine this region for possible rearrangements using standard methods. To overcome this problem, direct isolation of a set of genomic segments by in vivo recombination in yeast (a TAR cloning technique) was used to perform a mutational analysis of the 750 kb region in X-linked families. We did not detect disease-specific rearrangements within this region. In addition, transcriptome and computational analyses were performed to search for non-annotated genes within the Xq27 region, which may be associated with genetic predisposition to prostate cancer. Two candidate genes were identified, one of which is a novel gene termed SPANXL that represents a highly diverged member of the SPANX gene family, and the previously described CDR1 gene that is expressed at a high level in both normal and malignant prostate cells, and mapped 210 kb of upstream the SPANX gene cluster. No disease-specific alterations were identified in these genes. To summarize, our results exclude the 750-kb genetically unstable region at Xq27 as a candidate locus for prostate malignancy. Adjacent regions appear to be the most likely candidates to identify the elusive HPCX1 locus.
PMCID: PMC3412920  PMID: 22733720
Xq27; hereditary prostate cancer; HPCX1; SPANXL; CDR1; TAR cloning
7.  RCircos: an R package for Circos 2D track plots 
BMC Bioinformatics  2013;14:244.
Circos is a Perl language based software package for visualizing similarities and differences of genome structure and positional relationships between genomic intervals. Running Circos requires extra data processing procedures to prepare plot data files and configure files from datasets, which limits its capability of integrating directly with other software tools such as R. Recently published R Bioconductor package ggbio provides a function to display genomic data in circular layout based on multiple other packages, which increases its complexity of usage and decreased the flexibility in integrating with other R pipelines.
We implemented an R package, RCircos, using only R packages that come with R base installation. The package supports Circos 2D data track plots such as scatter, line, histogram, heatmap, tile, connectors, links, and text labels. Each plot is implemented with a specific function and input data for all functions are data frames which can be objects read from text files or generated with other R pipelines.
RCircos package provides a simple and flexible way to make Circos 2D track plots with R and could be easily integrated into other R data processing and graphic manipulation pipelines for presenting large-scale multi-sample genomic research data. It can also serve as a base tool to generate complex Circos images.
PMCID: PMC3765848  PMID: 23937229
Software; RCircos; R package; Circos; Genomic data visualization
8.  Whole Genome and Transcriptome Sequencing of a B3 Thymoma 
PLoS ONE  2013;8(4):e60572.
Molecular pathology of thymomas is poorly understood. Genomic aberrations are frequently identified in tumors but no extensive sequencing has been reported in thymomas. Here we present the first comprehensive view of a B3 thymoma at whole genome and transcriptome levels. A 55-year-old Caucasian female underwent complete resection of a stage IVA B3 thymoma. RNA and DNA were extracted from a snap frozen tumor sample with a fraction of cancer cells over 80%. We performed array comparative genomic hybridization using Agilent platform, transcriptome sequencing using HiSeq 2000 (Illumina) and whole genome sequencing using Complete Genomics Inc platform. Whole genome sequencing determined, in tumor and normal, the sequence of both alleles in more than 95% of the reference genome (NCBI Build 37). Copy number (CN) aberrations were comparable with those previously described for B3 thymomas, with CN gain of chromosome 1q, 5, 7 and X and CN loss of 3p, 6, 11q42.2-qter and q13. One translocation t(11;X) was identified by whole genome sequencing and confirmed by PCR and Sanger sequencing. Ten single nucleotide variations (SNVs) and 2 insertion/deletions (INDELs) were identified; these mutations resulted in non-synonymous amino acid changes or affected splicing sites. The lack of common cancer-associated mutations in this patient suggests that thymomas may evolve through mechanisms distinctive from other tumor types, and supports the rationale for additional high-throughput sequencing screens to better understand the somatic genetic architecture of thymoma.
PMCID: PMC3618227  PMID: 23577124
9.  Harnessing genomics to identify environmental determinants of heritable disease 
Mutation research  2012;752(1):6-9.
Next-generation sequencing technologies can now be used to directly measure heritable de novo DNA sequence mutations in humans. However, these techniques have not been used to examine environmental factors that induce such mutations and their associated diseases. To address this issue, a working group on environmentally induced germline mutation analysis (ENIGMA) met in October 2011 to propose the necessary foundational studies, which include sequencing of parent–offspring trios from highly exposed human populations, and controlled dose–response experiments in animals. These studies will establish background levels of variability in germline mutation rates and identify environmental agents that influence these rates and heritable disease. Guidance for the types of exposures to examine come from rodent studies that have identified agents such as cancer chemotherapeutic drugs, ionizing radiation, cigarette smoke, and air pollution as germ-cell mutagens. Research is urgently needed to establish the health consequences of parental exposures on subsequent generations.
PMCID: PMC3556182  PMID: 22935230
Germ cell; Heritable mutation; Next generation sequencing; Copy number variants
10.  SRAdb: query and use public next-generation sequencing data from within R 
BMC Bioinformatics  2013;14:19.
The Sequence Read Archive (SRA) is the largest public repository of sequencing data from the next generation of sequencing platforms including Illumina (Genome Analyzer, HiSeq, MiSeq, .etc), Roche 454 GS System, Applied Biosystems SOLiD System, Helicos Heliscope, PacBio RS, and others.
SRAdb is an attempt to make queries of the metadata associated with SRA submission, study, sample, experiment and run more robust and precise, and make access to sequencing data in the SRA easier. We have parsed all the SRA metadata into a SQLite database that is routinely updated and can be easily distributed. The SRAdb R/Bioconductor package then utilizes this SQLite database for querying and accessing metadata. Full text search functionality makes querying metadata very flexible and powerful. Fastq files associated with query results can be downloaded easily for local analysis. The package also includes an interface from R to a popular genome browser, the Integrated Genomics Viewer.
SRAdb Bioconductor package provides a convenient and integrated framework to query and access SRA metadata quickly and powerfully from within R.
PMCID: PMC3560148  PMID: 23323543
11.  NCBI GEO: archive for functional genomics data sets—update 
Nucleic Acids Research  2012;41(Database issue):D991-D995.
The Gene Expression Omnibus (GEO, is an international public repository for high-throughput microarray and next-generation sequence functional genomic data sets submitted by the research community. The resource supports archiving of raw data, processed data and metadata which are indexed, cross-linked and searchable. All data are freely available for download in a variety of formats. GEO also provides several web-based tools and strategies to assist users to query, analyse and visualize data. This article reports current status and recent database developments, including the release of GEO2R, an R-based web application that helps users analyse GEO data.
PMCID: PMC3531084  PMID: 23193258
12.  Comparative exome sequencing of metastatic lesions provides insights into the mutational progression of melanoma 
BMC Genomics  2012;13:505.
Metastasis is characterized by spreading of neoplastic cells to an organ other than where they originated and is the predominant cause of death among cancer patients. This holds true for melanoma, whose incidence is increasing more rapidly than any other cancer and once disseminated has few therapeutic options. Here we performed whole exome sequencing of two sets of matched normal and metastatic tumor DNAs.
Using stringent criteria, we evaluated the similarities and differences between the lesions. We find that in both cases, 96% of the single nucleotide variants are shared between the two metastases indicating that clonal populations gave rise to the distant metastases. Analysis of copy number variation patterns of both metastatic sets revealed a trend similar to that seen with our single nucleotide variants. Analysis of pathway enrichment on tumor sets shows commonly mutated pathways enriched between individual sets of metastases and all metastases combined.
These data provide a proof-of-concept suggesting that individual metastases may have sufficient similarity for successful targeting of driver mutations.
PMCID: PMC3500261  PMID: 23006843
13.  Identification of an Inhibitor of the EWS-FLI1 Oncogenic Transcription Factor by High-Throughput Screening 
Chromosomal translocations generating oncogenic transcription factors are the hallmark of a variety of tumors, including many sarcomas. Ewing sarcoma family of tumors (ESFTs) are characterized by the t(11;22)(q24;q12) translocation that generates the Ewing sarcoma breakpoint region 1 and Friend leukemia virus integration 1 (EWS-FLI1) fusion transcription factor responsible for the highly malignant phenotype of this tumor. Although continued expression of EWS-FLI1 is believed to be critical for ESFT cell survival, a clinically effective small-molecule inhibitor remains elusive likely because EWS-FLI1 is a transcription factor and therefore widely felt to be “undruggable.”
We developed a high-throughput screen to evaluate more than 50 000 compounds for inhibition of EWS-FLI1 activity in TC32 ESFT cells. We used a TC32 cell–based luciferase reporter screen using the EWS-FLI1 downstream target NR0B1 promoter and a gene signature secondary screen to sort and prioritize the compounds. We characterized the lead compound, mithramycin, based on its ability to inhibit EWS-FLI1 activity in vitro using microarray expression profiling, quantitative reverse transcription–polymerase chain reaction, and immunoblot analysis, and in vivo using immunohistochemistry. We studied the impact of this inhibition on cell viability in vitro and on tumor growth in ESFT xenograft models in vivo (n = 15–20 mice per group). All statistical tests were two-sided.
Mithramycin inhibited expression of EWS-FLI1 downstream targets at the mRNA and protein levels and decreased the growth of ESFT cells at half maximal inhibitory concentrations between 10 (95% confidence interval [CI] = 8 to 13 nM) and 15 nM (95% CI = 13 to 19 nM). Mithramycin suppressed the growth of two different ESFT xenograft tumors and prolonged the survival of ESFT xenograft–bearing mice by causing a decrease in mean tumor volume. For example, in the TC32 xenograft model, on day 15 of treatment, the mean tumor volume for the mithramycin-treated mice was approximately 3% of the tumor volume observed in the control mice (mithramycin vs control: 69 vs 2388 mm3, difference = 2319 mm3, 95% CI = 1766 to 2872 mm3, P < .001).
Mithramycin inhibits EWS-FLI1 activity and demonstrates ESFT antitumor activity both in vitro and in vivo.
PMCID: PMC3119649  PMID: 21653923
14.  Evidence for an Unanticipated Relationship Between Undifferentiated Pleomorphic Sarcoma and Embryonal Rhabdomyosarcoma 
Cancer cell  2011;19(2):177-191.
Embryonal rhabdomyosarcoma (eRMS) shows the most myodifferentiation amongst sarcomas, yet the precise cell of origin remains undefined. Using Ptch1, p53 and/or Rb1 conditional mouse models and controlling prenatal or postnatal myogenic cell of origin, we demonstrate that eRMS and undifferentiated pleomorphic sarcoma (UPS) lie in a continuum, with satellite cells predisposed to giving rise to UPS. Conversely, p53 loss in maturing myoblasts gives rise to eRMS, which have the highest myodifferentiation potential. Irrespective of origin, Rb1 loss modifies tumor phenotype to mimic UPS. In human sarcomas that lack pathognomic chromosomal translocations, p53 loss of function is prevalent whereas Shh or Rb1 alterations likely act primarily as modifiers. Thus, sarcoma phenotype is strongly influenced by cell of origin and mutational profile.
PMCID: PMC3040414  PMID: 21316601
15.  Exome sequencing identifies GRIN2A as frequently mutated in melanoma 
Nature genetics  2011;43(5):442-446.
The incidence of melanoma is increasing more than any other cancer, and knowledge of its genetic alterations is limited. To systematically analyze such alterations, we performed whole-exome sequencing of 14 matched normal and metastatic tumor DNAs. Using stringent criteria, we identified 68 genes that appeared to be somatically mutated at elevated frequency, many of which are not known to be genetically altered in tumors. Most importantly, we discovered that TRRAP harbored a recurrent mutation that clustered in one position (p. Ser722Phe) in 6 out of 67 affected individuals (~4%), as well as a previously unidentified gene, GRIN2A, which was mutated in 33% of melanoma samples. The nature, pattern and functional evaluation of the TRRAP recurrent mutation suggest that TRRAP functions as an oncogene. Our study provides, to our knowledge, the most comprehensive map of genetic alterations in melanoma to date and suggests that the glutamate signaling pathway is involved in this disease.
PMCID: PMC3161250  PMID: 21499247
16.  Interferon-γ links UV to melanocyte activation and promotes melanomagenesis 
Nature  2011;469(7331):548-553.
Cutaneous malignant melanoma is a highly aggressive and frequently chemoresistant cancer, whose incidence continues to rise. Epidemiological studies reveal that the major etiological melanoma risk factor is ultraviolet (UV) solar radiation, with the highest risk associated with intermittent burning doses, especially during childhood1,2. We have experimentally validated these epidemiological findings using the hepatocyte growth factor/scatter factor (HGF/SF) transgenic mouse model, which develops lesions in stages highly reminiscent of human melanoma with respect to biological, genetic and etiologic criteria, but only when irradiated as neonatal pups with UVB, not UVA3,4. However, mechanisms underlying UVB-initiated, neonatal-specific melanomagenesis remain largely unknown. Here we introduce a mouse model permitting fluorescence-aided melanocyte imaging and isolation following in vivo UV irradiation. We use expression profiling to show that activated neonatal skin melanocytes isolated following a melanomagenic UVB dose bear a distinct, persistent interferon response signature, including genes associated with immunoevasion. UVB-induced melanocyte activation, characterized by aberrant growth and migration, was abolished by antibody-mediated systemic blockade of interferon-γ (IFN-γ), but not type-I interferons. IFN-γ was produced by macrophages recruited to neonatal skin by UVB-induced ligands to the chemokine receptor Ccr2. Admixed recruited skin macrophages enhanced transplanted melanoma growth by inhibiting apoptosis; notably, IFN-γ blockade abolished macrophage-enhanced melanoma growth and survival. IFN-γ-producing macrophages were also identified in 70% of human melanomas examined. Our data reveal an unanticipated role for IFN-γ in promoting melanocytic cell survival/immunoevasion, and suggest that IFN-γ-R signaling represents a novel therapeutic melanoma target.
PMCID: PMC3140101  PMID: 21248750
17.  Preferential Localization of Human Origins of DNA Replication at the 5′-Ends of Expressed Genes and at Evolutionarily Conserved DNA Sequences 
PLoS ONE  2011;6(5):e17308.
Replication of mammalian genomes requires the activation of thousands of origins which are both spatially and temporally regulated by as yet unknown mechanisms. At the most fundamental level, our knowledge about the distribution pattern of origins in each of the chromosomes, among different cell types, and whether the physiological state of the cells alters this distribution is at present very limited.
Methodology/Principal Findings
We have used standard λ-exonuclease resistant nascent DNA preparations in the size range of 0.7–1.5 kb obtained from the breast cancer cell line MCF–7 hybridized to a custom tiling array containing 50–60 nt probes evenly distributed among genic and non-genic regions covering about 1% of the human genome. A similar DNA preparation was used for high-throughput DNA sequencing. Array experiments were also performed with DNA obtained from BT-474 and H520 cell lines. By determining the sites showing nascent DNA enrichment, we have localized several thousand origins of DNA replication. Our major findings are: (a) both array and DNA sequencing assay methods produced essentially the same origin distribution profile; (b) origin distribution is largely conserved (>70%) in all cell lines tested; (c) origins are enriched at the 5′ends of expressed genes and at evolutionarily conserved intergenic sequences; and (d) ChIP on chip experiments in MCF-7 showed an enrichment of H3K4Me3 and RNA Polymerase II chromatin binding sites at origins of DNA replication.
Our results suggest that the program for origin activation is largely conserved among different cell types. Also, our work supports recent studies connecting transcription initiation with replication, and in addition suggests that evolutionarily conserved intergenic sequences have the potential to participate in origin selection. Overall, our observations suggest that replication origin selection is a stochastic process significantly dependent upon local accessibility to replication factors.
PMCID: PMC3094316  PMID: 21602917
18.  Assessment of Automated Image Analysis of Breast Cancer Tissue Microarrays for Epidemiologic Studies 
A major challenge in studies of etiologic heterogeneity in breast cancer has been the limited throughput, accuracy and reproducibility of measuring tissue markers. Computerized image analysis systems may help address these concerns but published reports of their use are limited. We assessed agreement between automated and pathologist scores of a diverse set of immunohistochemical (IHC) assays performed on breast cancer TMAs.
TMAs of 440 breast cancers previously stained for ER-α, PR, HER-2, ER-β and aromatase were independently scored by two pathologists and three automated systems (TMALabII, TMAx, Ariol). Agreement between automated and pathologist scores of negative/positive was measured using the area under the receiver operator characteristics curve (AUC) and weighted kappa statistics (κ) for categorical scores. We also investigated the correlation between IHC scores and mRNA expression levels.
Agreement between pathologist and automated negative/positive and categorical scores was excellent for ER-α and PR (AUC range =0.98-0.99; κ range =0.86-0.91). Lower levels of agreement were seen for ER-β categorical scores (AUC=0.99-1.0; κ=0.80-0.86) and both negative/positive and categorical scores for aromatase (AUC=0.85-0.96; κ=0.41-0.67) and HER2 (AUC=0.94-0.97; κ=0.53-0.72). For ER-α and PR, there was strong correlation between mRNA levels and automated (ρ=0.67-0.74) and pathologist IHC scores (ρ=0.67-0.77). HER2 mRNA levels were more strongly correlated with pathologist (ρ=0.63) than automated IHC scores (ρ=0.41-0.49).
Automated analysis of IHC markers is a promising approach for scoring large numbers of breast cancer tissues in epidemiologic investigations. This would facilitate studies of etiologic heterogeneity which ultimately may allow improved risk prediction and better prevention approaches.
PMCID: PMC2852578  PMID: 20332278
Tissue Microarray; Immunohistochemistry; Automated Scoring; Breast Cancer; Reproducibility
19.  Assessment of Automated Image Analysis of Breast Cancer Tissue Microarrays for Epidemiologic Studies 
A major challenge in studies of etiologic heterogeneity in breast cancer has been the limited throughput, accuracy and reproducibility of measuring tissue markers. Computerized image analysis systems may help address these concerns but published reports of their use are limited. We assessed agreement between automated and pathologist scores of a diverse set of immunohistochemical (IHC) assays performed on breast cancer TMAs.
TMAs of 440 breast cancers previously stained for ER-α, PR, HER-2, ER-β and aromatase were independently scored by two pathologists and three automated systems (TMALabII, TMAx, Ariol). Agreement between automated and pathologist scores of negative/positive was measured using the area under the receiver operator characteristics curve (AUC) and weighted kappa statistics (κ) for categorical scores. We also investigated the correlation between IHC scores and mRNA expression levels.
Agreement between pathologist and automated negative/positive and categorical scores was excellent for ER-α and PR (AUC range =0.98-0.99; κ range =0.86-0.91). Lower levels of agreement were seen for ER-β categorical scores (AUC=0.99-1.0; κ=0.80-0.86) and both negative/positive and categorical scores for aromatase (AUC=0.85-0.96; κ=0.41-0.67) and HER2 (AUC=0.94-0.97; κ=0.53-0.72). For ER-α and PR, there was strong correlation between mRNA levels and automated (ρ=0.67-0.74) and pathologist IHC scores (ρ=0.67-0.77). HER2 mRNA levels were more strongly correlated with pathologist (ρ=0.63) than automated IHC scores (ρ=0.41-0.49).
Automated analysis of IHC markers is a promising approach for scoring large numbers of breast cancer tissues in epidemiologic investigations. This would facilitate studies of etiologic heterogeneity which ultimately may allow improved risk prediction and better prevention approaches.
PMCID: PMC2852578  PMID: 20332278
Tissue Microarray; Immunohistochemistry; Automated Scoring; Breast Cancer; Reproducibility
20.  Analyses of Resected Human Brain Metastases of Breast Cancer Reveal the Association between Up-regulation of Hexokinase 2 and Poor Prognosis 
Molecular cancer research : MCR  2009;7(9):1438-1445.
Brain metastases of breast cancer appear to be increasing in incidence as systemic therapy improves. Metastatic disease in the brain is associated with high morbidity and mortality. We present the first gene expression analysis of laser captured epithelial cells from resected human brain metastases of breast cancer compared to unlinked primary breast tumors. The tumors were matched for histology, TNM stage and hormone receptor status. Most differentially expressed genes were down-regulated in the brain metastases which included, surprisingly, many genes associated with metastasis. Q-PCR analysis confirmed statistically significant differences or strong trends in the expression of six genes: BMP1, PEDF, LAMγ3, SIAH, STHMN3 and TSPD2. Hexokinase 2 (HK2) was also of interest because of its increased expression in brain metastases. HK2 is important in glucose metabolism and apoptosis. In agreement with our microarray results, HK2 levels (both mRNA and protein) were elevated in a brain metastatic derivative (231-BR) of the human breast carcinoma cell line MDA-MB-231 relative to the parental cell line (231-P), in vitro. Knockdown of HK2 expression in 231-BR cells using shRNA reduced cell proliferation when cultures were maintained in glucose limiting conditions. Finally, HK2 expression was analyzed in a cohort of 123 resected brain metastases of breast cancer. High HK2 expression was significantly associated with poor patient survival post-craniotomy (P=0.028). The data suggest that HK2 overexpression is associated with metastasis to the brain in breast cancer and it may be a therapeutic target.
PMCID: PMC2746883  PMID: 19723875
21.  TRAIL induces apoptosis in triple-negative breast cancer cells with a mesenchymal phenotype 
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in some but not all breast cancer cell lines. Breast cancers can be divided into those which express the estrogen (ER) and progesterone (PR) receptors, those with HER-2 amplification, and those without expression of ER, PR, or HER-2 amplification (referred to as basal or triple-negative breast cancer). We tested a panel of 20 breast cancer cell lines representing the different types of breast cancer to evaluate if the molecular phenotype of the breast cancer cells determined their response to TRAIL. The most striking finding was that eight of eleven triple-negative cell lines are sensitive to TRAIL-mediated apoptosis. The eight TRAIL-sensitive triple-negative cell lines have a mesenchymal phenotype while the three TRAIL-resistant triple-negative cell lines have an epithelial phenotype. Two of five cell lines with HER-2 amplification were sensitive to TRAIL and none of the five ER positive cell lines were sensitive. RNAi-mediated knockdown of TRAIL receptor expression demonstrated that TRAIL Receptor 2 (TRAIL-R2) mediates the effects of TRAIL, even when both TRAIL-R1 and TRAIL-R2 are expressed. Finally, inhibition of EGFR, expressed in both TRAIL-sensitive and TRAIL-resistant triple-negative breast cancer cell lines, using a small molecule tyrosine kinase inhibitor (AG1478) enhanced TRAIL-induced apoptosis in TRAIL-sensitive cell lines but did not convert resistant cells into TRAIL-sensitive cells. Together, these findings suggest that a subset of triple-negative breast cancer, those with mesenchymal features, may be the most likely to benefit from TRAIL targeted therapy. These findings could form the basis to select breast cancer patients for clinical trials of TRAIL-R2 ligands.
PMCID: PMC2615075  PMID: 18266105
TRAIL; apoptosis; basal breast cancer; triple-negative breast cancer
22.  Zoom‐in comparative genomic hybridisation arrays for the characterisation of variable breakpoint contiguous gene syndromes 
Journal of Medical Genetics  2007;44(1):e59.
Contiguous gene syndromes cause disorders via haploinsufficiency for adjacent genes. Some contiguous gene syndromes (CGS) have stereotypical breakpoints, but others have variable breakpoints. In CGS that have variable breakpoints, the extent of the deletions may be correlated with severity. The Greig cephalopolysyndactyly contiguous gene syndrome (GCPS‐CGS) is a multiple malformation syndrome caused by haploinsufficiency of GLI3 and adjacent genes. In addition, non‐CGS GCPS can be caused by deletions or duplications in GLI3. Although fluorescence in situ hybridisation (FISH) can identify large deletion mutations in patients with GCPS or GCPS‐CGS, it is not practical for identification of small intragenic deletions or insertions, and it is difficult to accurately characterise the extent of the large deletions using this technique. We have designed a custom comparative genomic hybridisation (CGH) array that allows identification of deletions and duplications at kilobase resolution in the vicinity of GLI3. The array averages one probe every 730 bp for a total of about 14 000 probes over 10 Mb. We have analysed 16 individuals with known or suspected deletions or duplications. In 15 of 16 individuals (14 deletions and 1 duplication), the array confirmed the prior results. In the remaining patient, the normal CGH array result was correct, and the prior assessment was a false positive quantitative polymerase chain reaction result. We conclude that high‐density CGH array analysis is more sensitive than FISH analysis for detecting deletions and provides clinically useful results on the extent of the deletion. We suggest that high‐density CGH array analysis should replace FISH analysis for assessment of deletions and duplications in patients with contiguous gene syndromes caused by variable deletions.
PMCID: PMC2597909  PMID: 17098889
GLI3 ; oligonucleotide array; comparative genomic hybridization
23.  Canine tumor cross-species genomics uncovers targets linked to osteosarcoma progression 
BMC Genomics  2009;10:625.
Pulmonary metastasis continues to be the most common cause of death in osteosarcoma. Indeed, the 5-year survival for newly diagnosed osteosarcoma patients has not significantly changed in over 20 years. Further understanding of the mechanisms of metastasis and resistance for this aggressive pediatric cancer is necessary. Pet dogs naturally develop osteosarcoma providing a novel opportunity to model metastasis development and progression. Given the accelerated biology of canine osteosarcoma, we hypothesized that a direct comparison of canine and pediatric osteosarcoma expression profiles may help identify novel metastasis-associated tumor targets that have been missed through the study of the human cancer alone.
Using parallel oligonucleotide array platforms, shared orthologues between species were identified and normalized. The osteosarcoma expression signatures could not distinguish the canine and human diseases by hierarchical clustering. Cross-species target mining identified two genes, interleukin-8 (IL-8) and solute carrier family 1 (glial high affinity glutamate transporter), member 3 (SLC1A3), which were uniformly expressed in dog but not in all pediatric osteosarcoma patient samples. Expression of these genes in an independent population of pediatric osteosarcoma patients was associated with poor outcome (p = 0.020 and p = 0.026, respectively). Validation of IL-8 and SLC1A3 protein expression in pediatric osteosarcoma tissues further supported the potential value of these novel targets. Ongoing evaluation will validate the biological significance of these targets and their associated pathways.
Collectively, these data support the strong similarities between human and canine osteosarcoma and underline the opportunities provided by a comparative oncology approach as a means to improve our understanding of cancer biology and therapies.
PMCID: PMC2803201  PMID: 20028558
24.  A Single IGF1 Allele Is a Major Determinant of Small Size in Dogs 
Science (New York, N.Y.)  2007;316(5821):112-115.
The domestic dog exhibits greater diversity in body size than any other terrestrial vertebrate. We used a strategy that exploits the breed structure of dogs to investigate the genetic basis of size. First, through a genome-wide scan, we identified a major quantitative trait locus (QTL) on chromosome 15 influencing size variation within a single breed. Second, we examined genetic variation in the 15-megabase interval surrounding the QTL in small and giant breeds and found marked evidence for a selective sweep spanning a single gene (IGF1), encoding insulin-like growth factor 1. A single IGF1 single-nucleotide polymorphism haplotype is common to all small breeds and nearly absent from giant breeds, suggesting that the same causal sequence variant is a major contributor to body size in all small dogs.
PMCID: PMC2789551  PMID: 17412960
25.  Analysis of the matrix metalloproteinase family reveals that MMP8 is often mutated in melanoma 
Nature genetics  2009;41(5):518-520.
A mutational analysis of the matrix metalloproteinase (MMP) gene family in human melanoma identified somatic mutations in 23% of melanomas. Five mutations in one of the most commonly mutated genes, MMP8, reduced MMP enzyme activity. Expression of wild-type but not mutant MMP8 in human melanoma cells inhibited growth on soft agar in vitro and tumor formation in vivo, suggesting that wild-type MMP-8 has the ability to inhibit melanoma progression.
PMCID: PMC2748394  PMID: 19330028

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