Objective   To investigate the therapeutic effect of herceptin to  rat bladder cancer.    Methods   Totally 50 SD rats were randomly divided into experimental group (n=40) and control group (n=10). The rats of experimental group received a perfusion into the bladder with N-methyl-N-nitrosourea (MNU) at 2.5 mg every time

once per 3 weeks for 4 times in all

while those of the control group underwent a perfusion with normal saline instead of MNU. In 1 week after the last perfusion

the bladders were slited for gross observation and the biopsies were carried out for pathological observation with HE staining. Immunohistochemical SP method and RT-PCR were applied to detect HER-2 protein and mRNA expression in tumor tissues. Then 16 rats with HER-2 positive bladder cancer were randomly and equally divided into treatment group (herceptin

20 mg/kg by intraperitoneal injection

once per week for 6 weeks) and non-treatment group (normal saline

0.5 ml). Tumor weight

size and shape were measured and calculated for the inhibitory rate of herceptin. HE staining was carried out for the morphology of the tumor mass. The expression of HER-2 protein was detected with immunohistochemical SP method

and apoptosis in bladder tumor tissues with TUNEL method.    Results   The results of inhibitory rate was 50.0%

and it showed that the differences were statistically significant in treatment group compared with non-treatment group (P0.05). Immunohistochemical SP staining showed that the expression of HER-2 protein was significantly decreased after herceptin treatment. TUNEL assay indicated that the apoptotic index was higher in treatment group  (64.0±6.3)% than in nontreatment group (47.9±5.4)% with significant difference (P0.05).    Conclusion   Herceptin suppresses the growth of tumor mass and improved apoptosis of tumor cells in experimental HER-2-positive bladder tumor in SD rats.