MiR-421 is a functional marker of circulating tumor cells in gastric cancer patients.

The detection of circulating tumor cells (CTCs) has recently received great attention. To evaluate if miR-421 could be used as a specific marker for CTCs, the level of miR-421 in mononuclear cells (MNCs) from peripheral blood were determined by reverse transcription-polymerase chain reaction. Transfection of miR-421 inhibitor significantly suppressed tumor growth in vivo. The level of miR-421 in MNCs from gastric cancer was significantly higher than in those from healthy controls. The area under the receiver operating characteristic curve was 0.773 ± 0.0736. In conclusion, miR-421 may be used as a biomarker for monitoring CTCs in patients with gastric cancer.