Distinct mutation profiles between primary bladder cancer and circulating tumor cells warrant the use of circulating tumors cells as cellular resource for mutation follow-up.
Author(s): Kim TM, Yoo JS, Moon HW, Hur KJ, Choi JB, Hong SH, Lee JY, Ha US
Publication: BMC Cancer, 2020, Vol. 20, Page 1203
PubMed ID: 33287735 PubMed Review Paper? No
Purpose of Paper
This paper investigated the concordance of somatic mutations between circulating tumor cells (CTCs) and primary tumor tissue from bladder cancer patients.
Conclusion of Paper
Mutation abundances of primary tumors and CTCs were not significantly correlated and highly variable between patients. Ratios of missense mutations to silent mutations (NS/S ratios) were similar for common, tumor-specific, and CTC-specific mutations. However, mutation spectra analysis showed that CTC-specific mutations were distinct from common and primary tumor-specific mutations.
Studies
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Study Purpose
This study investigated the concordance of somatic mutations between CTCs and primary tumor tissue from bladder cancer patients. Specimens were collected from 20 patients undergoing surgery for bladder cancer. Tumor tissue was collected by transurethral resection of the bladder, snap-frozen, hematoxylin and eosin (H&E) stained, examined by pathologists, and blocks with >70% tumor purity were used for DNA extraction. CTCs were isolated from blood collected in acid citrate dextrose (ACD) tubes before surgery using the CytoGen Cell Isolation Kit. Enriched CTCs were cultured 16-18 days in mesenchymal stem cell growth medium for sequencing or fixed onto slides in 4% paraformaldehyde for 5 min at room temperature and kept at 4°C until immunostaining with CD45, cytokeratin, and vimentin antibodies and analysis by fluorescent microscopy. Whole-exome enrichment and sequencing was performed with the Agilent SureSelect Human All Exome 50Mb Kit and paired-end 100 bp sequencing reads were generated on an Illumina HiSeq 2500 platform. Sequencing reads were aligned with human reference genomes (UCSC hg19), local realignment and score recalibration were done using Genome Analysis ToolKit. Sequencing data of primary tumor and CTCs were compared with data of matched normal blood. Point mutations and short insertions/deletions (indels) were identified using MuTect and Indelocator, respectively.
Summary of Findings:
A total of 14,864 exonic mutations were identified across both specimen types. Mutation abundances of primary tumors (20–1515 exonic mutations, median=231) and CTCs (28–1217 exonic mutations, median=217) were not significantly correlated (r=0.16, P=0.499) and highly variable between patients. Only 8-89 (2.7 to 23.9%) of the mutations were found in primary tumor and CTC from the same case. Ratios of missense mutations to silent mutations (NS/S ratios) were similar for common, tumor-specific, and CTC-specific mutations (1.1–6.0, 1.2–4.2, and 1.1–3.7, respectively). Mutation spectra analysis showed that CTC-specific mutations were distinct from common and primary tumor-specific mutations. CTC-specific mutations were characterized by a depletion of C-to-G transversions and an overrepresentation of C-to-T transitions.
Biospecimens
Preservative Types
- None (Fresh)
- Frozen
Diagnoses:
- Neoplastic - Carcinoma
- Normal
Platform:
Analyte Technology Platform Cell count/volume Fluorescent microscopy DNA Next generation sequencing Morphology H-and-E microscopy Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Biospecimen Acquisition Biospecimen location Circulating tumor cells (CTCs)
Primary tumor tissue