Abstract: Objective In order to explore the possible mechanism between bufalin and colorectal cancer, we have observed the effects that bufalin inhibits the epithelial mesenchymal transformation on colorectal cell HCT-116. Methods We induce the colorectal cell HCT-116 to take effect of epithelial-mesenchymal transition (EMT) by TGF-β1 to prepare the EMT models. The experiment is divided into control groups, model groups and bufalin groups. After 72h of intervention, observe the morphological difference of each groups; evaluate the effect of the invasion and migration capabilities of bufalin on HCT-116 by using transwell-invasion and transwell-migration models; To detect the expressions of EMT-related protein including E-cadherin，Vimentin and β-catenin by using Western blot; To observe the distribution of β-catenin protein by using immunofluorescence method. Results 1. Changes of cellular morphology: Compared with the control groups, the cells of the model groups became elongated and spindle, the connections between cells are relatively lax. 2. Transwell-invasion experiment shows: After 72h , the cell numbers of permeation(under ×200, 3 view) of control groups, model groups and bufalin groups are: (86.67±11.72), (413.33±41.63) and (110.00±26.46), which show significant difference(P<0.05). Transwell-migration experiment shows: After 72h , the cell numbers of permeation(under ×200, 3 view) of control groups, model groups and bufalin groups are: (475±69.41), (898±49.49) and (507±38.16), which show significant difference(P<0.05). 3. The expressions of EMT-related protein E-cadherin/Vimentin/β-catenin by Western blot: Compared with the control groups, the model groups have lower expressions of E-cadherin and higher expressions of Vimentin; compared with model groups, the Bufalin groups have higher expressions of E-cadherin while the expressions of Vimentin are significantly lower. There is no significant difference between the expressions of β-catenin. 4. The distribution of β-catenin under immunofluorescence method: The experiment shows, compared with the control groups, the model groups have β-catenin expressions moving from the cell membrane and the cytoplasm to nucleus; compared with the model groups, the Bufalin groups have more expressions in cytoplasm than in nucleus. Conclusion 1. TGF-β1 can induce the epithelial mesenchymal transformation of colorectal cell HCT-116. 2. The inhibiting ability of Bufalin to the invasion and migration of HCT-116 is related to the epithelial mesenchymal transformation. 3. Bufalin probably inhibits the EMT of HCT-116 by inhibiting the nuclear translocation of β-catenin, and thus inhibit the invasion and migration of cells.

Key words: Colorectal cancer, Bufalin, Epithelial mesenchymal transformation, TGF-β1, Invasion and migration