Anoikis is a form of apoptosis induced upon cell detachment from extracellular matrix.It has been determined that acquisition of resistance to anoikis is a critical step for tumor cell metastasis.MiR-21,the most prominent oncomiR,plays an important role in tumor progression.In this study,we revealed that up-regulation of miR-21 in human esophageal adenocarcinoma (EA) is associated with lymph node metastasis and poor survival rate.Because of the established anti-apoptosis effect of miR-21,it is tempting to speculate that miR-21 might contribute to tumor metastasis by regulating anoikis,qRT-PCR analysis demonstrated that miR-21 expression in OE33/AR cells (subpopulation of human EA OE33 cells that acquired resistance to anoikis) was significantly increased.Also,transfection of miR-21 mimics provided OE33 cells resisting to anoikis.By luciferase assays,we verified that PDCD4 and PTEN were the functional targets of miR-21.In mouse model,via tail vein injection experiment,we showed that the metastasis formation of OE33 cells in vivo could be mediated by changing the miR-21 expression patt.Taken together,our findings suggested that miR-21 was involved in the regulation of anoikis in human EA cells.Targeting miR-21 may provide a novel strategy to prevent metastasis.