The Evolutionary History of Metastatic Pancreatic Neuroendocrine Tumours Reveals a Therapy Driven Route to High-Grade Transformation.

Tumour evolution with acquisition of more aggressive disease characteristics is a hallmark of disseminated cancer. Metastatic pancreatic neuroendocrine tumours (PanNETs) in particular, show frequent progression from a low/intermediate to a high-grade disease. To understand the molecular mechanisms underlying this phenomenon, we performed multi-omics analysis of 32 longitudinal samples from six metastatic PanNET patients. Following MEN1 inactivation, PanNETs exhibit genetic heterogeneity on both spatial and temporal dimensions with parallel and convergent tumuor evolution involving the ATRX/DAXX and mTOR pathways. Following alkylating chemotherapy treatment, some PanNETs develop mismatch repair deficiency and acquire a hypermutator phenotype. This DNA hypermutation phenotype was only found in cases that also showed transformation into a high-grade PanNET. Overall, our findings contribute to broaden the understanding of metastatic PanNET, and suggests that therapy driven disease evolution is an important hallmark of this disease.

Matched Analyses of Brain Metastases versus Primary Non-Small Cell Lung Cancer Reveal a Unique microRNA Signature.

Distant spreading of tumor cells to the central nervous system in non-small cell lung cancer (NSCLC) occurs frequently and poses major clinical issues due to limited treatment options. RNAs displaying differential expression in brain metastasis versus primary NSCLC may explain distant tumor growth and may potentially be used as therapeutic targets. In this study, we conducted systematic microRNA expression profiling from tissue biopsies of primary NSCLC and brain metastases from 25 patients. RNA analysis was performed using the nCounter Human v3 miRNA Expression Assay, NanoString technologies, followed by differential expression analysis and in silico target gene pathway analysis. We uncovered a panel of 11 microRNAs with differential expression and excellent diagnostic performance in brain metastasis versus primary NSCLC. Five microRNAs were upregulated in brain metastasis (miR-129-2-3p, miR-124-3p, miR-219a-2-3p, miR-219a-5p, and miR-9-5p) and six microRNAs were downregulated in brain metastasis (miR-142-3p, miR-150-5p, miR-199b-5p, miR-199a-3p, miR-199b-5p, and miR-199a-5p). The differentially expressed microRNAs were predicted to converge on distinct target gene networks originating from five to twelve core target genes. In conclusion, we uncovered a unique microRNA profile linked to two target gene networks. Our results highlight the potential of specific microRNAs as biomarkers for brain metastasis in NSCLC and indicate plausible mechanistic connections.

Evaluation of NTRK immunohistochemistry as a screening method for NTRK gene fusion detection in non-small cell lung cancer.

PURPOSE: The small molecule inhibitors larotrectinib and entrectinib have recently been approved as cancer agnostic drugs in patients with tumours harbouring a rearrangement of the neurotrophic tropomyosin receptor kinase (NTRK). These oncogenic fusions are estimated to occur in 0.1-3 % of non-small cell lung cancers (NSCLC). Although molecular techniques are most reliable for fusion detection, immunohistochemical analysis is considered valuable for screening. Therefore, we evaluated the newly introduced diagnostic immunohistochemical assay (clone EPR17341) on a representative NSCLC cohort. METHODS: Cancer tissue from 688 clinically and molecularly extensively annotated NSCLC patients were comprised on tissue microarrays and stained with the pan-TRK antibody clone EPR17341. Positive cases were further analysed with the TruSight Tumor 170 RNA assay (Illumina). Selected cases were also tested with a NanoString NTRK fusion assay. For 199 cases, NTRK RNA expression data were available from previous RNA sequencing analysis. RESULTS: Altogether, staining patterns for 617 NSCLC cases were evaluable. Of these, four cases (0.6 %) demonstrated a strong diffuse cytoplasmic and membranous staining, and seven cases a moderate staining (1.1 %). NanoString or TST170-analysis could not confirm an NTRK fusion in any of the IHC positive cases, or any of the cases with high mRNA levels. In the four cases with strong staining intensity in the tissue microarray, whole section staining revealed marked heterogeneity of NTRK protein expression. CONCLUSION: The presence of NTRK fusion genes in non-small cell lung cancer is exceedingly rare. The use of the immunohistochemical NTRK assay will result in a small number of false positive cases. This should be considered when the assay is applied as a screening tool in clinical diagnostics.

An immune gene expression signature distinguishes central nervous system metastases from primary tumours in non-small-cell lung cancer.

BACKGROUND: Dissemination of non-small-cell lung cancer (NSCLC) in the central nervous system is a frequent and challenging clinical problem. Systemic or local therapies rarely prolong survival and have modest activity regarding local control. Alterations in gene expression in brain metastasis versus primary tumour may increase aggressiveness and impair therapeutic efforts. METHODS: We identified 25 patients with surgically removed NSCLC brain metastases in two different patient cohorts. For 13 of these patients, primary tumour samples were available. Gene expression analysis using the nCounter® PanCancer Immune Profiling gene expression panel (nanoString technologies Inc.) was performed in brain metastases and primary tumour samples. Identification of differentially expressed genes was conducted on normalized data using the nSolver analysis software. RESULTS: We compared gene expression patterns in brain metastases with primary tumours. Brain metastasis samples displayed a distinct clustering pattern compared to primary tumour samples with a statistically significant downregulation of genes related to immune response and immune cell activation. Results from KEGG term analysis on differentially expressed genes revealed a concomitant enrichment of multiple KEGG terms associated with the immune system. We identified a 12-gene immune signature that clearly separated brain metastases from primary tumours. CONCLUSIONS: We identified a unique gene downregulation pattern in brain metastases compared with primary tumours. This finding may explain the lower intracranial efficacy of systemic therapy, especially immunotherapy, in brain metastasis of patients with NSCLC.

PATZ1 down-regulates FADS1 by binding to rs174557 and is opposed by SP1/SREBP1c.

The FADS1 and FADS2 genes in the FADS cluster encode the rate-limiting enzymes in the synthesis of long-chain polyunsaturated fatty acids (LC-PUFAs). Genetic variation in this region has been associated with a large number of diseases and traits many of them correlated to differences in metabolism of PUFAs. However, the causative variants leading to these associations have not been identified. Here we find that the multiallelic rs174557 located in an AluYe5 element in intron 1 of FADS1 is functional and lies within a PATZ1 binding site. The derived allele of rs174557, which is the common variant in most populations, diminishes binding of PATZ1, a transcription factor conferring allele-specific downregulation of FADS1. The PATZ1 binding site overlaps with a SP1 site. The competitive binding between the suppressive PATZ1 and the activating complex of SP1 and SREBP1c determines the enhancer activity of this region, which regulates expression of FADS1.

Genetic prevention of hepatitis C virus-induced liver fibrosis by allele-specific downregulation of MERTK.

AIM: Infection by hepatitis C virus (HCV) can result in the development of liver fibrosis and may eventually progress into cirrhosis and hepatocellular carcinoma. However, the molecular mechanisms for this process are not fully known. Several genome-wide association studies have been carried out to pinpoint causative variants in HCV-infected patient cohorts, but these variants are usually not the functional ones. The aim of this study was to identify the regulatory single nucleotide polymorphism associated with the risk of HCV-induced liver fibrosis and elucidate its molecular mechanism. METHODS: We utilized a bioinformatics approach to identify a non-coding regulatory variant, located in an intron of the MERTK gene, based on differential transcription factor binding between the alleles. We validated the results using expression reporter assays and electrophoresis mobility shift assays. RESULTS: Chromatin immunoprecipitation sequencing indicated that transcription factor(s) bind stronger to the A allele of rs6726639. Electrophoresis mobility shift assays supported these findings and suggested that the transcription factor is interferon regulatory factor 1 (IRF1). Luciferase report assays showed lower enhancer activity from the A allele and that IRF1 may act as a repressor. CONCLUSIONS: Treatment of hepatitis C with interferon-α results in increased IRF1 levels and our data suggest that this leads to an allele-specific downregulation of MERTK mediated by an allelic effect on the regulatory element containing the functional rs6726639. This variant also shows the hallmarks for being the driver of the genome-wide association studies for reduced risk of liver fibrosis and non-alcoholic fatty liver disease at MERTK.

Allele-specific transcription factor binding in liver and cervix cells unveils many likely drivers of GWAS signals.

Genome-wide association studies (GWAS) point to regions with associated genetic variants but rarely to a specific gene and therefore detailed knowledge regarding the genes contributing to complex traits and diseases remains elusive. The functional role of GWAS-SNPs is also affected by linkage disequilibrium with many variants on the same haplotype and sometimes in the same regulatory element almost equally likely to mediate the effect. Using ChIP-seq data on many transcription factors, we pinpointed genetic variants in HepG2 and HeLa-S3 cell lines which show a genome-wide significant difference in binding between alleles. We identified a collection of 3713 candidate functional regulatory variants many of which are likely drivers of GWAS signals or genetic difference in expression. A recent study investigated many variants before finding the functional ones at the GALNT2 locus, which we found in our genome-wide screen in HepG2. This illustrates the efficiency of our approach.

Allele-specific transcription factor binding to common and rare variants associated with disease and gene expression.

Genome-wide association studies (GWAS) have identified a large number of disease-associated SNPs, but in few cases the functional variant and the gene it controls have been identified. To systematically identify candidate regulatory variants, we sequenced ENCODE cell lines and used public ChIP-seq data to look for transcription factors binding preferentially to one allele. We found 9962 candidate regulatory SNPs, of which 16 % were rare and showed evidence of larger functional effect than common ones. Functionally rare variants may explain divergent GWAS results between populations and are candidates for a partial explanation of the missing heritability. The majority of allele-specific variants (96 %) were specific to a cell type. Furthermore, by examining GWAS loci we found >400 allele-specific candidate SNPs, 141 of which were highly relevant in our cell types. Functionally validated SNPs support identification of an SNP in SYNGR1 which may expose to the risk of rheumatoid arthritis and primary biliary cirrhosis, as well as an SNP in the last intron of COG6 exposing to the risk of psoriasis. We propose that by repeating the ChIP-seq experiments of 20 selected transcription factors in three to ten people, the most common polymorphisms can be interrogated for allele-specific binding. Our strategy may help to remove the current bottleneck in functional annotation of the genome.

Novel regulatory variant detected on the VKORC1 haplotype that is associated with warfarin dose.

AIM: Warfarin dose requirement is associated with VKORC1 rs9923231, and we studied whether it is a functional variant. MATERIALS & METHODS: We selected variants in linkage disequilibrium with rs9923231 that bind transcription factors in an allele-specific way. Representative haplotypes were cloned or constructed, nuclear protein binding and transcriptional activity were evaluated. RESULTS: rs56314408C>T and rs2032915C>T were detected in a liver enhancer in linkage disequilibrium with rs9923231. The rs56314408-rs2032915 C-C haplotype preferentially bound nuclear proteins and had higher transcriptional activity than T-T and the African-specific T-C. A motif for TFAP2A/C was disrupted by rs56314408T. No difference in transcriptional activity was detected for rs9923231G>A. CONCLUSION: Our results supported an activating role for rs56314408C, while rs9923231G>A had no evidence of being functional.

Looking beyond GWAS: allele-specific transcription factor binding drives the association of GALNT2 to HDL-C plasma levels.

BACKGROUND: Plasma levels of high-density lipoprotein cholesterol (HDL-C) have been associated to cardiovascular disease. The high heritability of HDL-C plasma levels has been an incentive for several genome wide association studies (GWASs) which identified, among others, variants in the first intron of the GALNT2 gene strongly associated to HDL-C levels. However, the lead GWAS SNP associated to HDL-C levels in this genomic region, rs4846914, is located outside of transcription factor (TF) binding sites defined by chromatin immunoprecipitation followed by DNA sequencing (ChIP-seq) experiments in the ENCODE project and is therefore unlikely to be functional. In this study we apply a bioinformatics approach which rely on the premise that ChIP-seq reads can identify allele specific binding of a TF at cell specific regulatory elements harboring allele specific SNPs (AS-SNPs). EMSA and luciferase assays were used to validate the allele specific binding and to test the enhancer activity of the regulatory element harboring the AS-SNP rs4846913 as well as the neighboring rs2144300 which are in high LD with rs4846914. FINDINGS: Using luciferase assays we found that rs4846913 and the neighboring rs2144300 displayed allele specific enhancer activity. We propose that an inhibitor binds preferentially to the rs4846913-C allele with an inhibitory boost from the synergistic binding of other TFs at the neighboring SNP rs2144300. These events influence the transcription level of GALNT2. CONCLUSIONS: The results suggest that rs4846913 and rs2144300 drive the association to HDL-C plasma levels through an inhibitory regulation of GALNT2 rather than the reported lead GWAS SNP rs4846914.

lobChIP: from cells to sequencing ready ChIP libraries in a single day.

BACKGROUND: ChIP-seq is the method of choice for genome-wide studies of protein-DNA interactions. We describe a new method for ChIP-seq sample preparation, termed lobChIP, where the library reactions are performed on cross-linked ChIP fragments captured on beads. RESULTS: The lobChIP method was found both to reduce time and cost and to simplify the processing of many samples in parallel. lobChIP has an early incorporation of barcoded sequencing adaptors that minimizes the risk of sample cross-contamination and can lead to reduced amount of adaptor dimers in the sequencing libraries, while allowing for direct decross-linking and amplification of the sample. CONCLUSIONS: With results for histone modifications and transcription factors, we show that lobChIP performs equal to or better than standard protocols and that it makes it possible to go from cells to sequencing ready libraries within a single day.

Novel amplifications in pediatric medulloblastoma identified by genome-wide copy number profiling.

Medulloblastoma (MB) is a WHO grade IV, invasive embryonal CNS tumor that mainly affects children. The aggressiveness and response to therapy can vary considerably between cases, and despite treatment, ~30% of patients die within 2 years from diagnosis. Furthermore, the majority of survivors suffer long-term side-effects due to severe management modalities. Several distinct morphological features have been associated with differences in biological behavior, but improved molecular-based criteria that better reflect the underlying tumor biology are in great demand. In this study, we profiled a series of 25 MB with a 32K BAC array covering 99% of the current assembly of the human genome for the identification of genetic copy number alterations possibly important in MB. Previously known aberrations as well as several novel focally amplified loci could be identified. As expected, the most frequently observed alteration was the combination of 17p loss and 17q gain, which was detected in both high- and standard-risk patients. We also defined minimal overlapping regions of aberrations, including 16 regions of gain and 18 regions of loss in various chromosomes. A few noteworthy narrow amplified loci were identified on autosomes 1 (38.89-41.97 and 84.89-90.76 Mb), 3 (27.64-28.20 and 35.80-43.50 Mb), and 8 (119.66-139.79 Mb), aberrations that were verified with an alternative platform (Illumina 610Q chips). Gene expression levels were also established for these samples using Affymetrix U133Plus2.0 arrays. Several interesting genes encompassed within the amplified regions and presenting with transcript upregulation were identified. These data contribute to the characterization of this malignant childhood brain tumor and confirm its genetic heterogeneity.

Recurrent genomic alterations in benign and malignant pheochromocytomas and paragangliomas revealed by whole-genome array comparative genomic hybridization analysis.

Pheochromocytomas and abdominal paragangliomas are adrenal and extra-adrenal catecholamine-producing tumours. They arise due to heritable cancer syndromes, or more frequently occur sporadically due to an unknown genetic cause. The majority of cases are benign, but malignant tumours are observed. Previous comparative genomic hybridization (CGH) and loss of heterozygosity studies have shown frequent deletions of chromosome arms 1p, 3q and 22q in pheochromocytomas. We applied high-resolution whole-genome array CGH on 53 benign and malignant pheochromocytomas and paragangliomas to narrow down candidate regions as well as to identify chromosomal alterations more specific to malignant tumours. Minimal overlapping regions (MORs) were identified on 16 chromosomes, with the most frequent MORs of deletion (> or = 32%) occurring on chromosome arms 1p, 3q, 11p/q, 17p and 22q, while the chromosome arms 1q, 7p, 12q and 19p harboured the most common MORs of gain (> or = 14%). The most frequent MORs (61-75%) in the pheochromocytomas were identified at 1p, and the four regions of common losses encompassed 1p36, 1p32-31, 1p22-21 and 1p13. Tumours that did not show 1p loss generally demonstrated aberrations on chromosome 11. Gain of chromosomal material was significantly more frequent among the malignant cases. Moreover, gain at 19q, trisomy 12 and loss at 11q were positively associated with malignant pheochromocytomas, while 1q gain was commonly observed in the malignant paragangliomas. Our study revealed novel and narrow recurrent chromosomal regions of loss and gain at several autosomes, a prerequisite for identifying candidate tumour suppressor genes and oncogenes involved in the development of adrenal and extra-adrenal catecholamine-producing tumours.

Focal amplifications are associated with high grade and recurrences in stage Ta bladder carcinoma.

Urinary bladder cancer is a heterogeneous disease with tumors ranging from papillary noninvasive (stage Ta) to solid muscle infiltrating tumors (stage T2+). The risk of progression and death for the most frequent diagnosed type, Ta, is low, but the high incidence of recurrences has a significant effect on the patients' quality of life and poses substantial costs for health care systems. Consequently, the purpose of this study was to search for predictive factors of recurrence on the basis of genetic profiling. A clinically well characterized cohort of Ta bladder carcinomas, selected by the presence or absence of recurrences, was evaluated by an integrated analysis of DNA copy number changes and gene expression (clone-based 32K, respectively, U133Plus2.0 arrays). Only a few chromosomal aberrations have previously been defined in superficial bladder cancer. Surprisingly, the profiling of Ta tumors with a high-resolution array showed that DNA copy alterations are relatively common in this tumor type. Furthermore, we observed an overrepresentation of focal amplifications within high-grade and recurrent cases. Known (FGFR3, CCND1, MYC, MDM2) and novel candidate genes were identified within the loci. For example, MYBL2, a nuclear transcription factor involved in cell-cycle progression; YWHAB, an antiapoptotic protein; and SDC4, an important component of focal adhesions represent interesting candidates detected within two amplicons on chromosome 20, for which DNA amplification correlated with transcript up-regulation. The observed overrepresentation of amplicons within high-grade and recurrent cases may be clinically useful for the identification of patients who will benefit from a more aggressive therapy.

Characterization of novel and complex genomic aberrations in glioblastoma using a 32K BAC array.

Glioblastomas (GBs) are malignant CNS tumors often associated with devastating symptoms. Patients with GB have a very poor prognosis, and despite treatment, most of them die within 12 months from diagnosis. Several pathways, such as the RAS, tumor protein 53 (TP53), and phosphoinositide kinase 3 (PIK3) pathways, as well as the cell cycle control pathway, have been identified to be disrupted in this tumor. However, emerging data suggest that these aberrations represent only a fraction of the genetic changes involved in gliomagenesis. In this study, we have applied a 32K clone-based genomic array, covering 99% of the current assembly of the human genome, to the detailed genetic profiling of a set of 78 GBs. Complex patterns of aberrations, including high and narrow copy number amplicons, as well as a number of homozygously deleted loci, were identified. Amplicons that varied both in number (three on average) and in size (1.4 Mb on average) were frequently detected (81% of the samples). The loci encompassed not only previously reported oncogenes (EGFR, PDGFRA, MDM2, and CDK4) but also numerous novel oncogenes as GRB10, MKLN1, PPARGC1A, HGF, NAV3, CNTN1, SYT1, and ADAMTSL3. BNC2, PTPLAD2, and PTPRE, on the other hand, represent novel candidate tumor suppressor genes encompassed within homozygously deleted loci. Many of these genes are already linked to several forms of cancer; others represent new candidate genes that may serve as prognostic markers or even as therapeutic targets in the future. The large individual variation observed between the samples demonstrates the underlying complexity of the disease and strengthens the demand for an individualized therapy based on the genetic profile of the patient.

A segmental maximum a posteriori approach to genome-wide copy number profiling.

MOTIVATION: Copy number profiling methods aim at assigning DNA copy numbers to chromosomal regions using measurements from microarray-based comparative genomic hybridizations. Among the proposed methods to this end, Hidden Markov Model (HMM)-based approaches seem promising since DNA copy number transitions are naturally captured in the model. Current discrete-index HMM-based approaches do not, however, take into account heterogeneous information regarding the genomic overlap between clones. Moreover, the majority of existing methods are restricted to chromosome-wise analysis. RESULTS: We introduce a novel Segmental Maximum A Posteriori approach, SMAP, for DNA copy number profiling. Our method is based on discrete-index Hidden Markov Modeling and incorporates genomic distance and overlap between clones. We exploit a priori information through user-controllable parameterization that enables the identification of copy number deviations of various lengths and amplitudes. The model parameters may be inferred at a genome-wide scale to avoid overfitting of model parameters often resulting from chromosome-wise model inference. We report superior performances of SMAP on synthetic data when compared with two recent methods. When applied on our new experimental data, SMAP readily recognizes already known genetic aberrations including both large-scale regions with aberrant DNA copy number and changes affecting only single features on the array. We highlight the differences between the prediction of SMAP and the compared methods and show that SMAP accurately determines copy number changes and benefits from overlap consideration.

Profiling of copy number variations (CNVs) in healthy individuals from three ethnic groups using a human genome 32 K BAC-clone-based array.

To further explore the extent of structural large-scale variation in the human genome, we assessed copy number variations (CNVs) in a series of 71 healthy subjects from three ethnic groups. CNVs were analyzed using comparative genomic hybridization (CGH) to a BAC array covering the human genome, using DNA extracted from peripheral blood, thus avoiding any culture-induced rearrangements. By applying a newly developed computational algorithm based on Hidden Markov modeling, we identified 1,078 autosomal CNVs, including at least two neighboring/overlapping BACs, which represent 315 distinct regions. The average size of the sequence polymorphisms was approximately 350 kb and involved in total approximately 117 Mb or approximately 3.5% of the genome. Gains were about four times more common than deletions, and segmental duplications (SDs) were overrepresented, especially in larger deletion variants. This strengthens the notion that SDs often define hotspots of chromosomal rearrangements. Over 60% of the identified autosomal rearrangements match previously reported CNVs, recognized with various platforms. However, results from chromosome X do not agree well with the previously annotated CNVs. Furthermore, data from single BACs deviating in copy number suggest that our above estimate of total variation is conservative. This report contributes to the establishment of the common baseline for CNV, which is an important resource in human genetics.