[Single-cell detection of EGFR gene mutation in circulating tumor cells in lung cancer]

Circulating tumor cells (CTCs) are cells that shed from a primary tumor and enter the peripheral blood circulation. The CTCs are closely associated with tumor development and metastasis because of its high heterogeneity. However, there are still no effective methods to detect single-cell heterogeneity of the CTCs. To this end, we developed a method to detect gene mutation in CTCs at the single-cell level and applied it to the detection of EGFR gene mutation in single lung cancer CTC. Specifically, the rare CTCs were captured from blood using an integrated microfluidic system, and then were released into a microchip with thousands of nanoliter wells to isolate single CTC. The single CTC was then transferred into a PCR tube under the microscope for single-cell genome amplification and detection of EGFR gene mutation. We firstly modified chip and capillary and optimized PCR conditions (annealing temperature, number of cycles) using non-small-cell lung cancer (NSCLC) cell lines A549, NCI-H1650 and NCI-H1975 as samples, which showed maximal amplification after 30 cycles with an annealing temperature at 59℃. We then successfully detected blood samples from NSCLC patients using this method. 5 CTCs were obtained from 2 mL patient's blood and the sequencing of EGFR exons 18, 19, 20 and 21 showed no mutations. Our results demonstrated that this method is sensitive enough to detect gene mutation in single CTC and has guiding significance in clinic research.