Table 3.

Microfluidics technologies for CTCs isolation and single cell sequencing

Sample type	Microfluidics device	Markers	Capture (%)	Sequencing technique	Key findings	Refs.
Breast cancer	Single-cell RNA sequencing (SCR-Chip)	EpCAM	93	SMART-Seq II	The sequencing data showed significant genetic differences between tumor cells and white blood cells. Tumor cells maintained a high consistency in the RNA panel, while there were large variations in WBC genes panel, which might be due to the presence of different subtypes in WBCs	[157]
Pancreatic cancer	CTC-iChip	CK CD45	95	ABI 5500XL	CTCs clustered separately from primary tumors and tumor-derived cell lines, showing enrichment for gene Aldh1a2 and Igfbp5. Pancreatic CTCs exhibit a very high expression of stromal-derived extracellular matrix proteins, including SPARC	[158]
Lung cancer	Deterministic lateral displacement (DLD chip)	CK CD45	90	Illumina HiSeq	Six new somatic gene mutations in both single CTC and surgical specimen of this patient, namely HIVEP2, SPATA21A, TUBGCP2, KCNG1, MIR4756, and ASMTL	[159]
Breast cancer	ClearCell FX	CD45 CD31	80	Illumina MiSeq	Compared to peripheral blood mononuclear cell (PBMCs), CTCs showed elevated expression of breast cancer-specific markers BRCA1 and MDM2, and a canonical epithelial cell marker CDH1	[160]
Prostate cancer	CTC-iChip	EpCAM CDH11 CD45	92	RNA-seq	A total of 711 genes were highly expressed in CTCs compared to primary tumors, with the most enriched being the molecular chaperone HSP90AA1 and the non-coding RNA transcript MALAT1	[161]
Ovarian/colorectal/prostate/breast/pancreatic cancer	Sinusoidal microfluidics chip	EpCAM FAPα	80	Illumina HiSeq	KRAS mutational status in CTCs has been shown a high concordance with the primary tumor (~ 90%). KRAS mutations were detected in CTCFAPα and CTCEpCAM but not always in both CTC subpopulations	[162]
Lung cancer	Microfluidic chip with micropore arrayed filtration membrane	CK CD45	85	Illumina HiSeq X	Four common mutation sites were found between tissue and ctDNA samples before treatment, including CREBBP, ROS1, TP53 and EGFR. Moreover, oncogene HRAS mutated both in single CTC sample and ctDNA sample after treatment, rather than samples before treatment	[163]
Breast cancer	ClearCell FX	CK CD45	32.31	Single-cell whole-exome sequencing (WES)	There were a few hundreds of somatic mutations in the three CTCs, with only 16 overlapping mutations. Significantly mutated genes in pan-cancer BRCA1 and EPHA3 were found in CTC-1, and mutations in FGFR2 and ATM were found in CTC-3, indicating genomic heterogeneity among the CTCs	[164]
Prostate cancer	CTC-iChip	CD45 CD16 CD66b	93.8	Illumina NextSeq 500	No significant differences were evident between fresh and preserved blood for any of the 40 genes except for KRT18. Select genes in certain patients showed a trend toward increased expression	[165]
Prostate cancer	Celsee PREP100	CK CD45	79	Sanger sequencing	The p.K139fs*3 deletion of TP53 and p.T877A mutation of AR could be detected in the captured PC3 and LNCaP cells, respectively	[166]