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The whole transcriptional landscape of circulating tumor cells compared to metastases in stage IV breast cancer

ABSTRACT: Metastasis is responsible for the vast majority of breast cancer related deaths. Metastatic breast cancer (MBC) is inherently different than primary breast cancer (BC), evolving under selection pressure at different organ sites or during systemic therapy. The current ASCO guidelines call for biopsy of a metastatic site to guide decision making for systemic therapy. Yet, biopsies of macro metastasis are oftentimes not feasible in the clinical setting. Circulating tumor cells (CTCs) have been shown to be prognostic in MBC, but their use as clinical biomarker beyond CTC enumeration has been limited. A better understanding of CTC-biology compared to metastasis may shed light on treatment opportunities and help advance the application of CTCs as liquid biopsies in clinical practice. The ANGLE Parsortix system is a microfluidics device that separates CTCs based on size and deformability, without the need for cell-surface marker selection. Our lab has previously demonstrated the feasibility of gene expression profiling of rare CTCs. Here, we evaluated whether whole transcriptome sequencing (RNA Seq) gene expression profiling of ANGLE Parsortix isolated CTCs may serve as a surrogate for biopsies of macro metastases. CTCs from 21 MBC patients were enumerated and captured from 10mL peripheral blood (PB) via the ANGLE Parsortix system. RNA Seq was performed on fresh metastatic tumor biopsies (mets), CTCs and peripheral blood from all patients. Biopsy sites included: skin (n=1), lung (n=1), pleural effusion (n=5), pericardial effusion (n=1), breast (n=3), lymph node (n=2), brain (n=4), liver (n=1), ascites (n=3), cerebrospinal fluid (n=2) and bone (n=1). 19/21 patients were included in subsequent data analysis. We present the whole transcriptomic landscape of CTCs with comparison to metastases and peripheral blood all acquired prior to treatment of Stage IV breast cancer. Multiple genes, including oncogenes, breast epithelial, mesenchymal genes and cancer stem cell genes were found with higher expression in CTCs versus metastases. When focusing on 66 known potentially clinically actionable genes in breast cancer, represented by 7 molecular signaling pathways, CTCs did not show significantly different patterns of expression versus mets compared to PB. RNA Seq of CTCs may be utilized to identify alterations in MBC patients that are potentially clinically actionable.

ORGANISM(S): Homo sapiens

PROVIDER: GSE113890 | GEO | 2022/05/01

REPOSITORIES: GEO

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Project description:Circulating tumor cells (CTCs) are critical in the development of distant organ tumor metastasis, and are associated with advanced cancer stage and poor patient outcome. Here, we present the first genome-wide nucleotide-level characterization of CTCs. Our single-nucleotide polymorphism (SNP) analysis in patients with melanoma involved: 1) global comparative genomic analysis of CTCs and matched regional metastases, 2) identification of key genomic aberrations in CTCs, 3) verification of these target genes in aggressive distant tumor metastases, and 4) evidence of selective expression and functional consequence of CTC-associated genes in melanomas. We report 131 aberrant loci in CTCs that are potentially pro-metastatic, and show that such expression of a 5-marker gene panel (CSMD2, CNTNAP5, FLJ14051, ADAM6, TRPM2) in melanomas confers prognostic utility. Successful treatment of melanoma requires understanding of the metastatic process and identification of patients with tumors most likely to develop aggressive metastatic disease. Melanomas are heterogeneous, and CTCs have long been recognized as vehicles for cancer spread, representing particularly aggressive tumor clones that can evolve into successful clinical metastases. Elucidation of genomic aberrations in CTCs will aid in the development of prognostic biomarkers and therapeutic strategies to target CTCs to prevent or control distant cancer spread. This study provides the first detailed genomic confirmation of the close relation between CTCs and tumor metastases, and illustrates how CTCs can be utilized as a novel approach and rational source for identification of pro-metastatic genes in cancer research. Three individual patient cohorts were utilized in the study. CNV and LOH loci were evaluated initially in metastatic melanoma patients (n=13) in a discovery cohort. SNP loci that harbored CNV/LOH in CTCs were then separately verified for: (a) presence in distant organ metastasis (AJCC Stage IV melanoma) (n=27), and (b) relevance to prognosis in regional melanoma metastasis (AJCC Stage III melanoma) (n=35). The first discovery patient cohort group was utilized for capture of CTCs, and consisted of peripheral blood mononuclear cell (PBMC) and tumor specimens from metastatic melanoma patients (n=13). CTC-related loci were verified in a second cohort of patients with Stage IV distant organ metastases (n=27), including 15 brain, 4 lung, and 8 gastrointestinal (bowel, liver) metastases. The third patient cohort consisted of early passage (<12) established melanoma cell lines derived from 35 regional melanoma metastases (Stage III) for evaluation of the prognostic utility of the CTC-associated aberrant loci.

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The whole transcriptional landscape of circulating tumor cells compared to metastases in stage IV breast cancer

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