Isolation and characterization of circulating tumor cells from human gastric cancer patients.

Circulating tumor cells (CTCs) have been proved to be responsible for tumor metastasis and resistant to anticancer therapies. This study aims to isolate and characterize circulating tumor cells from human gastric cancer patients, and investigate characteristic differences between gastric CTCs and gastric cancer cell lines. We analyzed 31 cases of gastric cancer patients using anti-CD45 antibody-conjugated magnetic microbeads negative separation, combined with fluorescence activated cell sorter CD44 positive screening. Abilities of tumor formation, metastasis, invasion, migration, irradiation and drug sensitivity of CTCs and gastric cancer cell lines were detected and compared. Of all the 31 patients, CD44(+)/CD45(-)CTCs were isolated in 14 patients, of which 3 cases were stage IIA, 2 cases stage IIB, 2 cases stage IIIC and 7 cases stage IV. The malignant behavior was demonstrated by both clonogenetic assay and tumor xenograft in nude mice. Compared with human gastric cancer cell lines, the migration and invasion abilities of CTCs increased to 3.21-12.6-fold and 2.3-6.7-fold, respectively (all p values <0.05). In addition, the metastatic potential of CTCs is much higher in vivo than that of the control. Furthermore, CTCs were found to be relatively sensitive to FU, cisplatin and paclitaxel, but relatively resistant to irradiation, oxaliplatin, cetuximab and trastuzumab. CD44(+)/CD45(-) gastric CTCs were isolated and found to exhibit stronger malignant behavior when compared with human gastric cancer cell lines. Furthermore, CTCs cultured in vitro have potential implications in drug sensitivity screening for the future anticancer treatments.