Telomere length alterations in microsatellite stable colorectal cancer and association with the immune response

Telomeres are repetitive sequences (TTAGGG) located at the end of chromosomes. Telomeres progressively shorten with each cell replication cycle, ultimately leading to chromosomal instability and loss of cell viability. Telomere length anomaly appears to be one of the earliest and most prevalent genetic alterations in malignant transformation. Here we aim to estimate telomere length from whole-exome sequencing data in colon tumors and normal colonic mucosa, and to analyze the potential association of telomere length with clinical factors and gene expression in colon cancer. Reads containing at least five repetitions of the telomere sequence (TTAGGG) were extracted from the raw sequences of 42 adjacent normal-tumor paired samples. The number of reads from the tumor sample was normalized to build the Tumor Telomere Length Ratio (TTLR), considered an estimation of telomere length change in the tumor compared to the paired normal tissue. We evaluated the associations between TTLR and clinical factors, gene expression and copy number (CN) aberrations measured in the same tumor samples. Colon tumors showed significantly shorter telomeres than their paired normal samples. No significant association was observed between TTLR and gender, age, tumor location, prognosis, stromal infiltration or molecular subtypes. The functional gene set enrichment analysis showed pathways related to immune response significantly associated with TLLR. By extracting a relative measure of telomere length from whole-exome sequencing data, we have assessed that colon tumor cells predominantly shorten telomeres, and this alteration is associated with expression changes in genes related to immune response and inflammation in tumor cells

ICO amplicon NGS data analysis: a web tool for variant detection in common high-risk hereditary cancer genes analyzed by amplicon GS junior next-Generation Sequencing

Next-generation sequencing (NGS) has revolutionized genomic research and is set to have a major impact on genetic diagnostics thanks to the advent of benchtop sequencers and flexible kits for targeted libraries. Among the main hurdles in NGS are the difficulty of performing bioinformatic analysis of the huge volume of data generated and the high number of false positive calls that could be obtained, depending on the NGS technology and the analysis pipeline. Here, we present the development of a free and user-friendly Web data analysis tool that detects and filters sequence variants, provides coverage information, and allows the user to customize some basic parameters. The tool has been developed to provide accurate genetic analysis of targeted sequencing of common high-risk hereditary cancer genes using amplicon libraries run in a GS Junior System. The Web resource is linked to our own mutation database, to assist in the clinical classification of identified variants. We believe that this tool will greatly facilitate the use of the NGS approach in routine laboratories.Peer ReviewedPostprint (published version

Comprehensive analysis of copy number aberrations in microsatellite stable colon cancer in view of stromal component

Background: Somatic copy number aberrations (CNA) are common acquired changes in cancer cells playing an important role in the progression of colon cancer (CRC). This study aimed to perform a characterization of CNA and their impact in gene expression.Methods: CNA were inferred from SNP array data in a series of 99 CRC. CNA events were calculated and used to assess the association between copy number dosage, clinical and molecular characteristics of the tumours, and gene expression changes. All analyses were adjusted for the quantity of stroma in each sample, that was inferred from gene expression data.Results: High heterogeneity among samples was observed, the proportion of altered genome ranged between 0.04 and 26.6%. Recurrent CNA regions with gains were frequent in chromosomes 7p, 8q, 13q, and 20 while 8p, 17p, and 18 cumulated loses. A significant positive correlation was observed between the number of somatic mutations and total CNA (Spearman r=0.42, P=0.006). Approximately 37% of genes located in CNA regions changed their level of expression, and the average partial correlation (adjusted for stromal content) with copy number was 0.54 (inter-quartile range 0.20 to 0.81). Altered genes showed enrichment in pathways relevant for colorectal cancer. Tumours classified as CMS2 and CMS4 by the consensus molecular subtyping showed higher frequency of CNA. Loses of one small region in 1p36.33, with gene CDK11B, were associated with poor prognosis. More than 66% of the recurrent CNA were validated in the TCGA data when analysed with the same procedure. Also 79% of the genes with altered expression in our data were validated in the TCGA.Conclusion: Though CNA are frequent events in MSS CRC, few focal recurrent regions were found. These aberrations have strong effects on gene expression and contribute to deregulate relevant cancer pathways. Due to the diploid nature of stromal cells, it is important to consider the purity of tumour samples to accurately calculate CNA events in CRC

Comprehensive analysis of copy number aberrations in microsatellite stable colon cancer in view of stromal component

Background: Somatic copy number aberrations (CNA) are common acquired changes in cancer cells playing an important role in the progression of colon cancer (CRC). This study aimed to perform a characterization of CNA and their impact in gene expression.Methods: CNA were inferred from SNP array data in a series of 99 CRC. CNA events were calculated and used to assess the association between copy number dosage, clinical and molecular characteristics of the tumours, and gene expression changes. All analyses were adjusted for the quantity of stroma in each sample, that was inferred from gene expression data.Results: High heterogeneity among samples was observed, the proportion of altered genome ranged between 0.04 and 26.6%. Recurrent CNA regions with gains were frequent in chromosomes 7p, 8q, 13q, and 20 while 8p, 17p, and 18 cumulated loses. A significant positive correlation was observed between the number of somatic mutations and total CNA (Spearman r=0.42, P=0.006). Approximately 37% of genes located in CNA regions changed their level of expression, and the average partial correlation (adjusted for stromal content) with copy number was 0.54 (inter-quartile range 0.20 to 0.81). Altered genes showed enrichment in pathways relevant for colorectal cancer. Tumours classified as CMS2 and CMS4 by the consensus molecular subtyping showed higher frequency of CNA. Loses of one small region in 1p36.33, with gene CDK11B, were associated with poor prognosis. More than 66% of the recurrent CNA were validated in the TCGA data when analysed with the same procedure. Also 79% of the genes with altered expression in our data were validated in the TCGA.Conclusion: Though CNA are frequent events in MSS CRC, few focal recurrent regions were found. These aberrations have strong effects on gene expression and contribute to deregulate relevant cancer pathways. Due to the diploid nature of stromal cells, it is important to consider the purity of tumour samples to accurately calculate CNA events in CRC

ICO amplicon NGS data analysis: a web tool for variant detection in common high-risk hereditary cancer genes analyzed by amplicon GS junior next-Generation Sequencing

Next-generation sequencing (NGS) has revolutionized genomic research and is set to have a major impact on genetic diagnostics thanks to the advent of benchtop sequencers and flexible kits for targeted libraries. Among the main hurdles in NGS are the difficulty of performing bioinformatic analysis of the huge volume of data generated and the high number of false positive calls that could be obtained, depending on the NGS technology and the analysis pipeline. Here, we present the development of a free and user-friendly Web data analysis tool that detects and filters sequence variants, provides coverage information, and allows the user to customize some basic parameters. The tool has been developed to provide accurate genetic analysis of targeted sequencing of common high-risk hereditary cancer genes using amplicon libraries run in a GS Junior System. The Web resource is linked to our own mutation database, to assist in the clinical classification of identified variants. We believe that this tool will greatly facilitate the use of the NGS approach in routine laboratories.Peer Reviewe

Mutations in JMJD1C are involved in Rett syndrome and intellectual disability

Purpose: autism spectrum disorders are associated with defects in social response and communication that often occur in the context of intellectual disability. Rett syndrome is one example in which epilepsy, motor impairment, and motor disturbance may co-occur. Mutations in histone demethylases are known to occur in several of these syndromes. Herein, we aimed to identify whether mutations in the candidate histone demethylase JMJD1C (jumonji domain containing 1C) are implicated in these disorders. Methods: we performed the mutational and functional analysis of JMJD1C in 215 cases of autism spectrum disorders, intellectual disability, and Rett syndrome without a known genetic defect. Results: we found seven JMJD1C variants that were not present in any control sample (~ 6,000) and caused an amino acid change involving a different functional group. From these, two de novo JMJD1C germline mutations were identified in a case of Rett syndrome and in a patient with intellectual disability. The functional study of the JMJD1C mutant Rett syndrome patient demonstrated that the altered protein had abnormal subcellular localization, diminished activity to demethylate the DNA damage-response protein MDC1, and reduced binding to MECP2. We confirmed that JMJD1C protein is widely expressed in brain regions and that its depletion compromises dendritic activity. Conclusions: our findings indicate that mutations in JMJD1C contribute to the development of Rett syndrome and intellectual disability

Mutations in JMJD1C are involved in Rett syndrome and intellectual disability

Purpose: autism spectrum disorders are associated with defects in social response and communication that often occur in the context of intellectual disability. Rett syndrome is one example in which epilepsy, motor impairment, and motor disturbance may co-occur. Mutations in histone demethylases are known to occur in several of these syndromes. Herein, we aimed to identify whether mutations in the candidate histone demethylase JMJD1C (jumonji domain containing 1C) are implicated in these disorders. Methods: we performed the mutational and functional analysis of JMJD1C in 215 cases of autism spectrum disorders, intellectual disability, and Rett syndrome without a known genetic defect. Results: we found seven JMJD1C variants that were not present in any control sample (~ 6,000) and caused an amino acid change involving a different functional group. From these, two de novo JMJD1C germline mutations were identified in a case of Rett syndrome and in a patient with intellectual disability. The functional study of the JMJD1C mutant Rett syndrome patient demonstrated that the altered protein had abnormal subcellular localization, diminished activity to demethylate the DNA damage-response protein MDC1, and reduced binding to MECP2. We confirmed that JMJD1C protein is widely expressed in brain regions and that its depletion compromises dendritic activity. Conclusions: our findings indicate that mutations in JMJD1C contribute to the development of Rett syndrome and intellectual disability

Mutations in JMJD1C are involved in Rett syndrome and intellectual disability

Purpose: autism spectrum disorders are associated with defects in social response and communication that often occur in the context of intellectual disability. Rett syndrome is one example in which epilepsy, motor impairment, and motor disturbance may co-occur. Mutations in histone demethylases are known to occur in several of these syndromes. Herein, we aimed to identify whether mutations in the candidate histone demethylase JMJD1C (jumonji domain containing 1C) are implicated in these disorders. Methods: we performed the mutational and functional analysis of JMJD1C in 215 cases of autism spectrum disorders, intellectual disability, and Rett syndrome without a known genetic defect. Results: we found seven JMJD1C variants that were not present in any control sample (~ 6,000) and caused an amino acid change involving a different functional group. From these, two de novo JMJD1C germline mutations were identified in a case of Rett syndrome and in a patient with intellectual disability. The functional study of the JMJD1C mutant Rett syndrome patient demonstrated that the altered protein had abnormal subcellular localization, diminished activity to demethylate the DNA damage-response protein MDC1, and reduced binding to MECP2. We confirmed that JMJD1C protein is widely expressed in brain regions and that its depletion compromises dendritic activity. Conclusions: our findings indicate that mutations in JMJD1C contribute to the development of Rett syndrome and intellectual disability