Project description:Background: Gene expression profiling has been used extensively within breast cancer research. Patient matched transcriptomic studies of tumour samples before and after treatment offer great potential and have been initiated, but tend not to include a control group. Here we examine gene expression changes between patient-matched core biopsies and surgical resection samples in the absence of treatment, to consider sampling methods and tumour heterogeneity. Patients and Methods: Illumina BeadArray technology was used to measure dynamic changes in gene expression from thirty-seven paired baseline and surgically excised breast tumour samples obtained from women receiving no treatment prior to surgery. Results: Patient-matched sample pairs had significantly higher correlations than samples between different individuals, demonstrating that tumour heterogeneity and intra-tumour differences are less prominent than inter-tumour/patient differences. Perhaps surprisingly, consistent changes in gene expression were identified during the diagnosis-surgery interval, despite a lack of treatment. 50 genes were significantly differentially expressed (48 up, 2 down; FDR 0.05) in a manner that appears independent of both subtype and the sampling-interval length. Gene set enrichment analysis using four independent treated datasets has implicated the tumour sampling method as the likely cause of these expression changes which include increases in early growth response genes such as EGR1, 2 and 3 along with DUSP1 and FOS. Our data does not support the idea that there is a significant wounding or immune response. Conclusion: This is the largest cohort of patient-matched transcriptome profiling of tumours from patients receiving no treatment between diagnosis and surgery to date. It has revealed that consistent changes in gene expression do exist between diagnostic core biopsy and the surgical excision sample. We have confirmed these findings in a number of published breast cancer datasets. Ultimately, researchers should be aware of the potential for the tumour sampling method to introduce a confounding factor in future neoadjuvant studies. 37 paired patient-matched whole-transcriptome profiled primary breast tumours from patients receiving no treatment between diagnosis and surgery. Superseries is a product of two integrated individual batches.

Project description:Background: Gene expression profiling has been used extensively within breast cancer research. Patient matched transcriptomic studies of tumour samples before and after treatment offer great potential and have been initiated, but tend not to include a control group. Here we examine gene expression changes between patient-matched core biopsies and surgical resection samples in the absence of treatment, to consider sampling methods and tumour heterogeneity. Patients and Methods: Illumina BeadArray technology was used to measure dynamic changes in gene expression from thirty-seven paired baseline and surgically excised breast tumour samples obtained from women receiving no treatment prior to surgery. Results: Patient-matched sample pairs had significantly higher correlations than samples between different individuals, demonstrating that tumour heterogeneity and intra-tumour differences are less prominent than inter-tumour/patient differences. Perhaps surprisingly, consistent changes in gene expression were identified during the diagnosis-surgery interval, despite a lack of treatment. 50 genes were significantly differentially expressed (48 up, 2 down; FDR 0.05) in a manner that appears independent of both subtype and the sampling-interval length. Gene set enrichment analysis using four independent treated datasets has implicated the tumour sampling method as the likely cause of these expression changes which include increases in early growth response genes such as EGR1, 2 and 3 along with DUSP1 and FOS. Our data does not support the idea that there is a significant wounding or immune response. Conclusion: This is the largest cohort of patient-matched transcriptome profiling of tumours from patients receiving no treatment between diagnosis and surgery to date. It has revealed that consistent changes in gene expression do exist between diagnostic core biopsy and the surgical excision sample. We have confirmed these findings in a number of published breast cancer datasets. Ultimately, researchers should be aware of the potential for the tumour sampling method to introduce a confounding factor in future neoadjuvant studies.

Project description:Triple Negative Breast Cancer (TNBC) is an aggressive subtype of breast cancer with high intra-tumoral heterogeneity, frequently resistant to treatment and no known targeted therapy available to improve patient outcomes. It has been hypothesized that the genomic architecture of a TNBC tumour evolves over time, both before, and during therapy, leading to therapy resistance and a high propensity to relapse. Whether this is an inherent property of the tumour or acquired over time is not well characterized. Despite this important clinical implication, limited studies have been carried out to unravel temporal evolution of TNBC over time. Herein, we report an OMICS based analysis of three TNBC patients who were longitudinally sampled during their treatment at different times of relapse. We recruited three TNBC patients at the time of their first relapse who were then followed-up through the course of their treatment. We obtained retrospective samples (tumour samples) from patient tumours at diagnosis (before neo-adjuvant chemotherapy - NACT) at surgery (post NACT) and prospectively sampled them at each subsequent relapse (tumour, blood plasma, and buffy coat) as determined by RECIST criteria. Tumor and buffy coat DNA were subjected to whole exome sequencing (WES) at 200x, and SNP arrays for copy number variation (CNV) analysis. RNA from tumour samples at relapse was subjected to whole transcriptome sequencing. Pathogenic germline BRCA1 variants identified in WES were validated using Sanger sequencing. 1084 somatic mutations identified in whole exome sequencing of all tumour tissues (n=13) from three patients, were subjected to a custom amplicon ultra-deep sequencing assay at 30,000X in their germline DNA (n=3), tumour DNA (n=10), and cfDNA from plasma samples at relapse (n=8). Copy number corrected allele frequencies, tumour ploidy, tumour purity, and ultra-deep sequencing assay derived variant allele frequencies were used to infer clonal and phylogenetic architecture of each patient as it evolved under selective pressure of therapy over time. Clonality analysis incorporating allele fractions from ultra-deep sequencing identified clones comprising of mutations that are present throughout the course of therapy which we term as founding clones and stem mutations respectively. Such founding clones comprising of stem mutations in all 3 patients were present throughout the course of treatment, irrespective of change in treatment modalities. These stem clones included well characterized cancer related genes like PDGFRB & ARID2 (Patient 02), TP53, BRAF & CSF3R (Patient 04) and ESR1, APC, EZH2 & TP53 (Patient 07). Such branching evolution is seen in all three patients wherein the dominant clone (stem clone) acquires additional mutations to form sub-clones, while persisting over time. These sub-clones may be chemo and radio resistant, while also providing for organ specific metastatic potential. Allele fractions of expressed variants inferred from RNA-Seq data co-related with allele fractions from WES data indicating that all somatic.

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Tumour sampling method can significantly influence gene expression profiles derived from neoadjuvant window studies I

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Tumour sampling method can significantly influence gene expression profiles derived from neoadjuvant window studies.

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