ISET® enables lable-free enrichment of CTC and CTM as intact cells from all types of solid cancers and allows to identify CCC and CCM.
Lymphocytes are the smallest cells in the body, they are 8 microns in size and have a very compact nucleus and minimal cytoplasm. The vast majority of lymphocytes and neutrophils are eliminated by the Rarecells® filtration system. Larger cells are enriched by ISET® and can be analyzed by cytomorphology and immuno-molecular characterization. Each spot on the filter enriches and shows the large cells isolated from 1 mL of blood allowing easy counting.
ISET® technique’s high sensitivity is related to its efficiency: 10 mL of blood are diluted with the Rarecells buffer, incubated for 10 minutes under mild agitation then transferred to the Rarecells® Block and treated. CTC and CTM collection on the filter takes 3 minutes or less. CTC and CTM are then available for staining and further analyses. The ISET® sensitivity threshold is unparalleled and is one CTC in 10mL of blood. To maintain this high sensitivity, blood has to be treated within 5 hours after collection. This also allows practically no cell loss during the filtration.
- Tumor cell
- Filter’s pore
Fixed CTC workflow
Fixed CTC Applications
After blood filtration, CTC are enriched on the ten circular filtration areas (spots) of the filter. Each spot of the filter can be analysed independently, therefore the Rarecells® System can allow multiplexing. The Rarecells® System is an open system that allows performing all types of CTC analyses, as listed in the next paragraphs (all publications below report on ISET®)
Because the ISET® filtration process isolates intact CTC, it has been possible to validate that classical cytopathological criteria used in exfoliative cytopathology are reliable for CTC diagnosis (Hofman et al. 2011 Am J Clin Pathol, Hofman et al. 2012 Cytopathology).Nuclear size equal or larger than 16 microns, irregularity of the nuclear contour, irregularity of the chromatin, presence of a visible cytoplasm and high nuclear to cytoplasmic ratio (>0.8) are the cytopathological criteria used for CTC diagnosis (Hofman et al. 2011 Clin Cancer Res).ISET® isolates and identifies all types of CTC and clusters of tumor cells called CTM (Vona et al. 2000 Am J Pathol, Khoja et al. 2014 Melanoma Res, Mazzini et al. 2014 Cancers, Chinen et al. 2014 Oncotargets Ther, Massard et al. 2016 Oncotarget, Long et al. 2016 Cancer Med, Fanelli et al. 2017 Head and Neck).
Following CTC identification by cytopathology, further CTC characterization is possible through immunocytochemistry (ICC) to identify epithelial-mesenchymal transition (EMT) markers (Hou et al. 2011 Am J Pathol, Lecharpentier et al. 2011 Brit J Cancer), proliferation markers (Hou et al. 2012 J Clin Oncol) and various theranostic markers (Hofman et al. 2013 J Invest Dermatol, Cummings et al. 2014 BMC Cancer).
ISET® enables assessment of PD-L1 expression on CTC, demonstrating concordant PD-L1 staining in tumor tissue and corresponding ISET® filters from selected NSCLC patients (Ilie et al. 2017 Ann Oncol).
Single-cell targeted Sanger sequencing following laser capture microdissection of individual CTC can help further characterizing them (Vona et al. 2000 Am J Pathol, Vona et al. 2004 Hepatology).Quantitative real-time PCR for assessment of messenger RNA expression (De Giorgi et al. 2010 J Invest Dermatol) and targeted sanger sequencing of KRAS mutations on pools of CTC (Buim et al. 2015 Cancer Biol Ther) are also possible following ISET®.Single-cell high throughput sequencing following laser capture microdissection and whole genome amplification can help characterizing CTC heterogeneity using either targeted panels or whole exome sequencing (Laget et al. 2017 Plos One).
ISET® enables immunofluorescent staining of CTC, thereby helping automated or semi-automated imaging methods for an efficient and reliable computational analysis of CTC on ISET® filters (Pailler et al. 2016 BMC Cancer, Williamson et al. 2016 Nat Commun, Kallergi et al. 2018 Ther Adv Med Oncol, Poruk et al. 2016 Cancer Med)
Fluorescence In Situ Hybridization (FISH) applied to CTC recovered by ISET® enables identification of oncogenic fusions, rearrangements and gene amplifications with relevance to therapeutic decision-making and follow-up of potential recurrence (Ilie et al. 2012 Ann Oncol, Pailler et al. 2013 J Clin Oncol, Massard et al. 2016 Oncotarget, Pailler et al. 2017 Cancer Res, Ilie et al. 2018 Clin Chem Lab Med).