MiR-181a promoted tumor growth of SMMC-7721 cells in nude mice. (A) P-miR-181a cells produced larger tumors than control cells at 14 days after implantation. (B) Representative picture of tumors formed. (C) Growth curve of tumor volumes. Each piece of data represented the mean ± SD of 5 mice. (D) Ki-67 and E2F5 stained sections of transplanted tumors. *P < 0.05, **P < 0.01.