Development of a quantum-dot-labelled magnetic immunoassay method for circulating colorectal cancer cell detection

Table 1 Histopathological characteristics of colorectal cancer samples at diagnosis

Characteristics	Colorectal cancer patients (n)
Tumor location
Rectum	2
Left colon	5
Right colon	2
Tumor size
≤ 4 cm	5
> 4 cm	4
Differentiation
Well	1
Moderate	7
Poor	1
TNM stage
I	0
II	1
III	3
IV	3

TNM: Classification of Malignant Tumors, T describes the size of the tumor and whether it has invaded nearby tissue, N describes regional lymph nodes that are involved, M describes distant metastasis.

Table 2 Results recorded by fluorescence-activated cell sorting, real time reverse transcriptase polymerase chain reaction, and proposed method for detection of circulating tumor cells in clinical samples

Sample	FACS (CTCs/mL blood)	Real-time PCR1	Results with MBs-EpCAM/QDs-CK192
CRC 1	34	12.96	+++
CRC 2	20	8.64	++
CRC 3	51	17.28	++++
CRC 4	57	18.52	++++
CRC 5	63	19.75	++++
CRC 6	19	9.87	++
CRC 7	9	0	+/-
CRC 8	3	0	-
CRC 9	2	0	-
Healthy 1	0	0	-
Healthy 2	0	0	-
Healthy 3	0	0	-
Healthy 4	0	0	-
Healthy 5	0	0	-
DLD-1 cells	500	100	+++++
Negative control (1X PBS)	0	0	-

¹% expression CK19/CK19 of DLD-1 normalized to GAPDH);

²The number of “+” is proportional to the fluorescence intensity (from low to high) as evaluated by two independent observers who were blinded to the patients and the fluorescence-activated cell sorting (FACS) and real-time polymerase chain reaction data. CRC: Colorectal cancer; DLD-1: Colorectal adenocarcinoma cell line; EpCAM: Epithelial cell adhesion molecule; GAPDH: Glyceraldehyde-3-phosphate dehydrogenase; MBs: Magnetic beads; PCR: Polymerase chain reaction; CTCs: Circulating tumour cells; CK19: Cytokeratin 19; QDs: Quantum dots; PBS: Phosphate buffered saline.