Studies On The Anti-tumor Activity Of Cinobufagin And Its Toxiclogical Evaluation Of Safety

Chansu which is a traditional Chinese medicine product of the skin secretions of local toads such as Bufo bufo gargarzians Cantor or Bufo bufo melanostictus Schneider, possesses a wide range of biological and pharmacological activity including cardiotonic, anti-arrhythmia and blood pressure stimulation. Recently, the effects of Chansu in tumor cells have been focused on. This study aimed to examin the effects of cinobufagin, the steroid compound isolated from chansu, on proliferation and apoptosis in human gastric cancer BGC-823 cells, and to explore its potential action mechanism.The results from MTT assay showed that cinobufagin could inhibits the growth of six human tumor cells (human gastric cancer BGC-823 and SGC-7901 cell lines, human hepatoma cell line SMMC-7721, human breast cancer cell line MCF-7, human cervical carcinoma cell line He La, and human promyelocytic leukemia cell line HL-60) in a time and dose-dependent manner. Among the cancer cell lines tested, BGC-823 cells were the most vulnerable to cinobufagin with an IC50 value of approximately 0.095μM.Results from Hoechst 33258 staining and sub-G1 DNA measurement showed cinobufagin could induce apoptosis in BGC-823 cells. Cinobufagin could increase the expression of NF-κB significantly. Pyrrolidine dithiocarbamate (PDTC), a potent NF-κB inhibitor, could suppress the induction of apoptosis and activation of NF-κB in BGC-823 cells by cinobufagin.Results from whole-cell patch-clamp recording showed that potassium current in BGC-823 was inhibited by cinobufagin in a voltage-dependent manner and percent inhibitions for the blocking action of cinobufagin (0.05μM and 0.25μM) on Ik was 82.7±2.9%and 51.3±1.7%, respectively.To evaluate the safety of cinobufagin, mice were given to two doses of cinobufagin by intraperitoneal injection. After 30 days injection, organs were examined for damages. Results from water maze showed that cinobufagin (>1.5 mg/kg) could be damage on rats'memory. And histological analysis of cinobufagin treated mice showed that cardiac muscle was the target organ of this toxin.These results suggest that cinobufagin has the ability to induce apoptosis in BGC-823 cells via to NF-κB activation. The present study might provide scientific foundation for cinobufagin to be exploited to be an agent for tumor.