Beyond Capture: Circulating Tumor Cell Release and Single‐Cell Analysis

Abstract

As the most promising “liquid biopsy”, analysis of circulating tumor cells (CTCs) provides noninvasive access to obtain biological information of solid tumors. It not only advances the understanding of the mechanisms underlying tumor metastasis, relapse, and chemoresistance, but also promotes the development of precision medicine. Over the past decade, the rapid advances in micro/nanomaterials and microfluidics have overcome the technical challenges of capturing CTCs, allowing efficient enrichment and sensitive detection. Beyond the capture of CTCs, major challenges of in‐depth CTC analysis are the release of CTCs from capture platforms and the inherent heterogeneity in CTCs. A variety of technologies have now emerged for release and single‐cell analysis of CTCs. This review focuses on recent progress along this direction. First, different release strategies are outlined and discussed, including their design principles and characteristics (merits and limitations). Then, existing methods for single CTC analysis at the genomic, transcriptomic, proteomic, and functional level are summarized. Finally, some perspectives are provided on current development trends, future research directions, and challenges of CTC studies.

Nanotechnology-Assisted Isolation and Analysis of Circulating Tumor Cells on Microfluidic Devices

“…Thermosensitive gelatin hydrogel was uniformly coated on the scaffold, which, modified with the anti-EpCAM antibody, dissolves at 37 °C quickly, and the captured cells are gently released from the chip, with high viability (>90%) and 86% release efficiency ( Figure 6 A). In general, strategies based on thermally responsive polymers can release CTCs under mild temperature stimuli, providing almost complete CTCs for downstream analysis [ 33 ].…”

“…Genomic analysis of CTCs advances our understanding of the molecular mechanisms underlying tumor metastasis, relapse and drug resistance and helps us to develop new targeted anticancer therapies [ 5 , 33 ]. Conventional preprocessing techniques for CTC sequencing include limited dilution, micromanipulation, fluorescence-activated cell flow cytometry, etc.…”

“…The isolated CTCs are often adhered to or trapped on the device based on either their biophysical or biochemical properties, as described above. The best way to release these target CTCs from the device still remains a daunting challenge and affects downstream in-depth analysis, such as cell culture or precise manipulation at a single-cell level [ 31 , 32 , 33 ].…”

“…These reports either focused on the different methodologies of CTC isolation based on their physical properties [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ] or CTC detection using microfluidic devices based on the newly discovered CTC biomarkers and their affinity reaction. Among these studies, nanotechnology-assisted CTC isolation and analysis using microfluidic devices has attracted more and more attention as it combines the advantages of both nanotechnology and microfluidic areas [ 15 , 16 , 33 ]. Nanostructured-assisted devices for CTC capture provide increased contact area between the cell surface and the nanofeatures of the device, thus allowing for more binding sites and more efficient affinity capture [ 16 ].…”

Detecting Ultralow Frequency Mutation in Circulating Cell‐Free DNA of Early‐Stage Nonsmall Cell Lung Cancer Patients with Unique Molecular Identifiers

“…According to the United States National Institutes of Health Surveillance, Epidemiology and End Result Program, only 16% of the newly diagnosed lung cancers are at the early‐stage . Hence, in order to improve cancer detection in early‐stage lung cancer patients, immense efforts have been invested in exploring potential molecular biomarkers and developing novel strategies for screening and early detection of the disease.…”