Chansu inhibits the expression of cortactin in colon cancer cell lines in vitro and in vivo

BACKGROUND: Chansu is a transitional Chinese medicine that has been used for centuries as therapy for inflammation, anaesthesia and arrhythmia in China and other Asian countries. Recently, it has also been used for anti-cancer purposes. We have previously shown that Chansu has a huge pro-apoptotic potential on colon cancer cells, but to date the detailed mechanism of this action is not well understood. METHODS: One of the major components of Chansu, Cinobufagin (CBF) was used to treat cancer cells. The expressions of levels of cortactin, an important factor in tumour progression and cancer invasion, were assessed in in vitro and in vivo experiments. Additional analyses were performed in subcellular protein fractions and immune-fluorescent staining was used to define cortactin protein expression and the changes of location in CBF-treated cells. RESULTS: CBF strongly inhibited the expression of cortactin in HCT116 cells. There were reductions of both mRNA transcription and protein synthesis, which were more significant in the absence of oxygen in vitro. In addition, nuclear translocation of cortactin was observed in HCT116 cells post CBF exposure but not in the negative control, indicating that CBF is likely to interrupt co-localisation of cortactin to cytoskeletal proteins. Most importantly, CBF could diminish the expression of cortactin in human HCT116 xenograft tumours in nude mouse in vivo. CONCLUSIONS: CBF inhibits cortactin expression and nuclear translocation in colon cancer cells in vitro and in mouse models bearing human colon tumour in vivo, suggesting it might disrupt actin-regulated cell movement. Thus, CBF or Chansu could be developed as an effective anti-cancer therapy to stop local invasion and metastasis.