Detecting bone marrow micrometastasis of gastric cancer by magnetic activated cell sorting combined with fluorescent activated cell sorting

BACKGROUND OBJECTIVE: Several methods are used to detect bone marrow micrometastasis of gastric cancer with different accuracies. In breast cancer, tumor cells in blood can be detected sensitively and specifically by magnetic activated cell sorting (MACS) and fluorescent activated cell sorting (FACS). This study was to investigate the clinical value of this method in detecting bone marrow micrometastasis of gastric cancer. METHODS: Thirty-five patients, who received operation for gastric cancer from Dec. 2002 to Jun. 2003, were selected. Mononuclear cells were separated from their bone marrows. After marked by MACS minibeads conjugated with cytokeratin (CK) 7/8 antibodies, anti-CK-fluorescein isothiocyanate (FITC), and anti-CD45-perdinin chlorophyll protein (PerCP), tumor cells were enriched twice by MS+/RS+ positive separation column. FACS analysis was conducted on these samples before and after MACS enrichment. The results were compared with clinicopathologic parameters. RESULTS: Disseminated tumor cells were detected in bone marrow of 3 samples(8.6%) before MACS enrichment, and 25 samples (71.4%) after enrichment. The frequencies of tumor cells were 1.4×10-8-2.4×10-5, 2.2×10-7 -3.7×10-5, and 4.0×10-6-8.6×10-5 in patients with moderately differentiated, poorly differentiated, and undifferentiated carcinoma, respectively, with significant differences (P = 0.026). Bone marrow micrometastasis positively correlated with tumor TNM stage (P = 0.008), while had no correlation with tumor size, depth of wall invasion, and other clinicopathologic parameters. CONCLUSIONS: MACS combined with FACS may improve detection rate of bone marrow micrometastasis of gastric cancer. The patients with poor differentiation and in advanced TNM stage have more disseminated tumor cells in bone marrow.