Identification of copy number alterations in colon cancer from analysis of amplicon-based next generation sequencing data

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Abstract

The objective of this study was to determine the feasibility to detect copy number alterations in colon cancer samples using Next Generation Sequencing data and to elucidate the association between copy number alterations in specific genes and the development of cancer in different colon segments. We report the successful detection of somatic changes in gene copy number in 37 colon cancer patients by analysis of sequencing data through Amplicon CNA Algorithm. Overall, we have found a total of 748 significant copy number alterations in 230 significant genes, of which 143 showed CN losses and 87 showed CN gains. Validation of results was performed on 20 representative genes by quantitative qPCR and/or immunostaining. By this analysis, we have identified 4 genes that were subjected to copy number alterations in tumors arising in all colon segments (defined “common genes”) and the presence of copy number alterations in 14 genes that were significantly associated to one specific site (defined “site-associated genes”). Finally, copy number alterations in ASXL1, TSC1 and IL7R turned out to be clinically relevant since the loss of TSC1 and IL7R was associated with advanced stages and/or reduced survival whereas copy number gain of ASXL1 was associated with good prognosis.

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Most cited references 55

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Controlling the False Discovery Rate: A Practical and Powerful Approach to Multiple Testing

Yoav Benjamini, Yosef Hochberg (1995)

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Global variation in copy number in the human genome.

Richard Redon, Shumpei Ishikawa, Karen R Fitch … (2006)

Copy number variation (CNV) of DNA sequences is functionally significant but has yet to be fully ascertained. We have constructed a first-generation CNV map of the human genome through the study of 270 individuals from four populations with ancestry in Europe, Africa or Asia (the HapMap collection). DNA from these individuals was screened for CNV using two complementary technologies: single-nucleotide polymorphism (SNP) genotyping arrays, and clone-based comparative genomic hybridization. A total of 1,447 copy number variable regions (CNVRs), which can encompass overlapping or adjacent gains or losses, covering 360 megabases (12% of the genome) were identified in these populations. These CNVRs contained hundreds of genes, disease loci, functional elements and segmental duplications. Notably, the CNVRs encompassed more nucleotide content per genome than SNPs, underscoring the importance of CNV in genetic diversity and evolution. The data obtained delineate linkage disequilibrium patterns for many CNVs, and reveal marked variation in copy number among populations. We also demonstrate the utility of this resource for genetic disease studies.

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Is Open Access

Ki67 Index, HER2 Status, and Prognosis of Patients With Luminal B Breast Cancer

Maggie C. U. Cheang, Stephen Chia, David Voduc … (2009)

Background Gene expression profiling of breast cancer has identified two biologically distinct estrogen receptor (ER)-positive subtypes of breast cancer: luminal A and luminal B. Luminal B tumors have higher proliferation and poorer prognosis than luminal A tumors. In this study, we developed a clinically practical immunohistochemistry assay to distinguish luminal B from luminal A tumors and investigated its ability to separate tumors according to breast cancer recurrence-free and disease-specific survival. Methods Tumors from a cohort of 357 patients with invasive breast carcinomas were subtyped by gene expression profile. Hormone receptor status, HER2 status, and the Ki67 index (percentage of Ki67-positive cancer nuclei) were determined immunohistochemically. Receiver operating characteristic curves were used to determine the Ki67 cut point to distinguish luminal B from luminal A tumors. The prognostic value of the immunohistochemical assignment for breast cancer recurrence-free and disease-specific survival was investigated with an independent tissue microarray series of 4046 breast cancers by use of Kaplan–Meier curves and multivariable Cox regression. Results Gene expression profiling classified 101 (28%) of the 357 tumors as luminal A and 69 (19%) as luminal B. The best Ki67 index cut point to distinguish luminal B from luminal A tumors was 13.25%. In an independent cohort of 4046 patients with breast cancer, 2847 had hormone receptor–positive tumors. When HER2 immunohistochemistry and the Ki67 index were used to subtype these 2847 tumors, we classified 1530 (59%, 95% confidence interval [CI] = 57% to 61%) as luminal A, 846 (33%, 95% CI = 31% to 34%) as luminal B, and 222 (9%, 95% CI = 7% to 10%) as luminal–HER2 positive. Luminal B and luminal–HER2-positive breast cancers were statistically significantly associated with poor breast cancer recurrence-free and disease-specific survival in all adjuvant systemic treatment categories. Of particular relevance are women who received tamoxifen as their sole adjuvant systemic therapy, among whom the 10-year breast cancer–specific survival was 79% (95% CI = 76% to 83%) for luminal A, 64% (95% CI = 59% to 70%) for luminal B, and 57% (95% CI = 47% to 69%) for luminal–HER2 subtypes. Conclusion Expression of ER, progesterone receptor, and HER2 proteins and the Ki67 index appear to distinguish luminal A from luminal B breast cancer subtypes.

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Journal

Journal ID (nlm-ta): Oncotarget

Journal ID (iso-abbrev): Oncotarget

Journal ID (publisher-id): Oncotarget

Journal ID (publisher-id): ImpactJ

Title: Oncotarget

Publisher: Impact Journals LLC

ISSN (Electronic): 1949-2553

Publication date Collection: 17 April 2018

Publication date (Electronic): 17 April 2018

Volume: 9

Issue: 29

Pages: 20409-20425

Affiliations

¹ Dipartimento di Medicina Sperimentale e Clinica, Università Magna Graecia, Catanzaro, Italy

² Dipartimento di Scienze della Salute, Università Magna Graecia, Catanzaro, Italy

³ Dipartimento di Scienze Mediche e Chirurgiche, Università Magna Graecia, Catanzaro, Italy

⁴ Fred Hutchinson Cancer Research Center, Seattle, WA, USA

⁵ University of California Los Angeles (UCLA), Los Angeles, CA, USA

⁶ UOC Chirurgia Generale, Azienda Ospedaliera dei Colli, Napoli, Italy

Author notes

Correspondence to: Giuseppe Viglietto, viglietto@ 123456unicz.it

Donatella Malanga, malanga@ 123456unicz.it

[*]

These authors contributed equally to this work

Article

Publisher ID: 24912

DOI: 10.18632/oncotarget.24912

PMC ID: 5945505

PubMed ID: 29755661

SO-VID: 6a0f6e2b-1196-45d0-a540-01341a620f91

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This is an open-access article distributed under the terms of the Creative Commons Attribution License 3.0 (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Identification of copy number alterations in colon cancer from analysis of amplicon-based next generation sequencing data

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Karger: Oncology

Most cited references 55

Controlling the False Discovery Rate: A Practical and Powerful Approach to Multiple Testing

Global variation in copy number in the human genome.

Ki67 Index, HER2 Status, and Prognosis of Patients With Luminal B Breast Cancer

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