Objective To explore the inhibitive effects of microRNA - 133b (miR - 133b) on the growth of implanted subcutaneous tumors in human colorectal tumor - bearing nude mice

and to investigate whether miR - 133b is a new tumor suppressor

in vivo

. Methods Thirty nude mice

were randomized into 3 groups

SW - 620 group

SW - 620 - HK group and SW - 620 - 133b group. The animal model of subcutaneous implantation tumor in nude mice was established by corresponding injecting 5 × 10

6

SW - 620 cells

SW - 620 - HK (transfected with nonsense sequence) and SW - 620 - 133b (transfected with miR - 133b) subcutaneously

and the model was established when the tumor was 3 to 4 mm in diameter. The tumor growth in each group was recorded and compared. The mice was killed in 30 d. The cell apoptosis of implantation tumor was tested by TUNEL assay. The expression of miR - 133b and c - met in each group were examined by real - time PCR and Western blotting

respectively. Results The model animals of human colorectal tumor - bearing mice were successfully established

with a tumor - formation rate of 100%. The growth curves of planted tumor showed that the tumor growth rate of SW - 620 - 133b group was much slower than those of SW - 620 and SW - 620 - HK groups (

P

0 . 05). At the end point time

the average tumor volume of SW - 620 - 133b group was smaller than those of SW - 620 and SW - 620 - HK groups [(0.85 ± 0.14) cm

3

vs

(3.56 ± 0.79) cm

3

and (3.24 ± 0.68) cm

3

P

0 . 05

]

. The average tumor weight of SW - 620 - 133b group was lighter than those of SW - 620 and SW - 620 - HK groups [(1.15 ± 0.16) g

vs

(4.02 ± 0.64) and (3.81 ± 0.61) g

P

0 . 05

]

. The cell apoptosis of SW - 620 - 133b group was significantly higher than those of SW - 620 and SW - 620 - HK groups [(30.28 ± 3.47)%

vs

(7.96 ± 0.92)% and (7 . 26 ± 0 . 84)%

P

0 . 05

]

. The expression of c - met in SW - 620 - 133b group was significantly deceased compared with those of SW - 620 and SW - 620 - HK groups [(0.19 ± 0.02)

vs

(0.52 ± 0.04) and (0.51 ± 0.04)

P

0 . 05

]

. Conclusion  The ectopic expression of miR - 133b can effectively inhibit the growth of tumor in human colorectal tumor - bearing nude mice.