AIM: To explore the regulatory mechanism of the target gene of micro RNA-21(mi R-21), phosphatase gene(p TEN), and its downstream proteins, protein kinase B(AKT) and phosphatidylinositol 3-kinase(p I3K), in colorectal cancer(CRC) cells. METHODS: Quantitative real-time p CR(q RT-p CR) and Western blot were used to detect the expression levels of mi R-21 and p TEN in HCT116, HT29, Colo32 and SW480 CRC cell lines. Also, the expression levels of p TEN m RNA and its downstream proteins AKT and p I3 K in HCT116 cells after downregulating mi R-21 were investigated. RESULTS: Comparing the mi R-21 expression in CRC cells, the expression levels of mi R-21 were highest in HCT116 cells, and the expression levels of mi R-21 were lowest in SW480 cells. In comparing mi R-21 and p TEN expression in CRC cells, we found that the protein expression levels of mi R-21 and p TEN were inversely correlated(p < 0.05); when mi R-21 expression was reduced, m RNA expression levels of p TEN did not significantly change(p > 0.05), but the expression levels of its protein significantly increased(p < 0.05). In comparing the levels of p TEN protein and downstream AKT and p I3 K in HCT116 cells after downregulation of mi R-21 expression, the levels of AKT and p I3 K protein expression significantly decreased(p < 0.05). CONCLUSION: p TEN is one of the direct target genesof mi R-21. Thus, phosphatase gene and its downstream AKT and p I3 K expression levels can be regulated by regulating the expression levels of mi R-21, which in turn regulates the development of CRC. AIM: To explore the regulatory mechanism of the target gene of micro RNA-21 (mi R-21), phosphatase gene (p TEN), and its downstream proteins, protein kinase B (AKT) and phosphatidylinositol 3-kinase , in colorectal cancer (CRC) cells. METHODS: Quantitative real-time p CR (q RT-p CR) and Western blot were used to detect the expression levels of mi R-21 and p TEN in HCT116, HT29, Colo32 and SW480 CRC cell lines. Also, the expression levels of pTEN m RNA and its downstream proteins AKT and pI3K in HCT116 cells after downregulating mi R-21 were investigated. RESULTS: Comparing the mi R-21 expression in CRC cells, the expression Levels of mi R-21 were highest in HCT116 cells, and the expression levels of mi R-21 were lowest in SW480 cells. In comparison mi R-21 and p TEN expression in CRC cells, we found that the protein expression levels of mi R-21 and p TEN were inversely correlated (p <0.05); when mi R-21 expression was reduced, m RNA expression levels of p TEN did not significantly c (p <0.05), but the expression levels of its protein significantly increased (p <0.05). In comparing the levels of pTEN protein and downstream AKT and pI3K in HCT116 cells after downregulation of mi R-21 expression, the Levels of AKT and pI3K protein expression were significantly decreased (p <0.05). CONCLUSION: pTEN is one of the direct target genesof mi R-21. Thus, phosphatase gene and its downstream AKT and pI3K expression levels can be regulated by regulating the expression levels of mi R-21, which in turn regulates the development of CRC.