Objective: To investigate the antitumor effects and it's mechanism of steroidal saponins from Cestrum nocturnum

Linn (SSCN) on human hepatocellular carcinoma xenografts in nude mice in vivo. Method: SSCN was separated and identified their structure. The animal model of human hepatocellular carcinoma xenografts was established by subcutaneous inoculation of hepatocellular carcinoma HepG2 cells into nude mice. The mice were randomly divided into five groups:NS group

thalidomide (TLD) group

and SSCN 4

6

8 mg·kg-1·d-1group ip

every the other day for 30 days. During treatment

tumor size was measured. The mice were killed 30 days later to observe tumor morphology. The tumor samples were observed and analyzed using HE staining and immunohistochemical staining. The protein expression of proliferating cell necliar antigen(PCNA) and Ki-67 in transplantation tumor was detected. Result: The relative proliferation rate in TLD group in tumor nude mice was 42.19%. The relative proliferation rate in SSCN high

middle and low dose in tumor nude mice was 48.26%

42.94%

41.57% accordingly. Along with the increase of the dose of SSCN the relative tumor proliferation rate decrease gradually

explaining the inhibition of tumor growth by SSCN in dose dependence manner. A large number of necrotic cells in tumor tissue sections could be viewed in SSCN 8 mg·kg-1 group. Some tumor cells were smaller

and nuclear staining was dense. The protein expression of proliferating cell nuclear antigen (PCNA) and Ki-67 in transplantation tumor was markedly higher. Compared with the NS group

the protein expression of PCNA and Ki-67 was markedly lower in TLD group and SSCN 8 mg·kg-1 group(P<0.05). Conclusion: SSCN show certain inhibitory effect on human hepatocellular carcinoma xenografts in nude mice in vivo. The anti-tumor mechanism is probably related to down-regulation of the protein expression of PCNA and Ki-67 gene

thus inhibiting tumor cell proliferation.