Objective        To determine the expression of embryonic stem cells key transcription factor Nanog in bladder cancer tissues and its role in human bladder cancer cell line 5637.        Methods      Immunohistochemical assay were performed to detect the expression of Nanog gene in 46 tissue samples of  bladder cancer. Nanog was over-expressed through lentivirus vector LV-Nanog  in 563

7 cells. Plate colony formation assay and MTT assay were used to evaluate the effects of Nanog over-expression on the proliferation and chemo-sensitivity in 5637 cells.        Results        The positive rate of Nanog was 50％ in bladder cancer tissues

and increased expression of Nanog in bladder cancer was significantly associated with pathological grade (correlation coefficient=0.989

P

0.05). Real-time PCR and Western blotting showed that the Nanog expression was obviously higher in the 5637 cells infected with LV-Nanog than those infected with LV-Con lentivirus. The colony formation rate of 5637-C cells and 5637-Nanog cells was (4.6±0.9)％ and (9.0±1.0)％

respectively

indicating that over-expression Nanog can increase colony formation rate in 5637 cells (

P

0.01). After cisplatin treatment at 5

10

20 and 40 μmol/L for 72 h

the survival rate of 5637-C cells was (64.5±4.9)%

(53.1±4.6)％

(43.4±3.9)％ and (21.0±2.7)％ respectively

while the 5637-Nanog cells was (80.9±5.6)％

(68.5±4.2)％

(47.9±5.1)％ and (25.2±4.2)％

respectively. The chemo-sensitivity assay showed exogenous Nanog expression was significantly decreased the chemo-sensitivity of 5637 cells to cisplatin (5 and 10 μmol/L) compared with the control cells.        Conclusion       Nanog protein expression is significantly correlated with the histological grade. Over-expression of Nanog increases the proliferation and decreases the cisplatin sensitivity in 5637 cells.