Application of highly efficient and lowly toxic bufadienolides screened from toad skin in lymphatic chemotherapy for colorectal cancer through a lymphatic metastatic model

Background: Lymph node metastasis (LNM) remains a major obstacle to treat colorectal cancer (CRC). Increasing evidences have suggested that bufadienolides contain several fractions displaying antitumor activity and may be applied in lymphatic chemotherapy. However, effects of the highly efficient and lowly toxic (HELT) bufadienolides on CRC in lymphatic chemotherapy have not been reported. Methods: Adenosine triphosphate tumor chemosensitivity assays (ATP-TCA) was performed to detect the inhibition rate (IR) of fractions of bufadienolides to cytokine-induced killer (CIK) cells and tumor cells. HELT fraction-loaded emulsions of different concentrations were prepared. Nude mouse bearing HCT116 tumors in footpad received high-dose emulsion (HD-E), middle-dose emulsion (MD-E), low-dose emulsion (LD-E), control emulsion (CE), Cinobufacini Injection (CI), or normal saline (NS), respectively. Hematoxylin and eosin (H&E) staining, Flow Cytometry (FCM), enzyme-linked immune sorbent assay (ELISA) and hematological examination were applied to evaluate therapeutic effects and potential toxicity. Results: F18 and F19 were screened out as HELT fractions in vivo and F18-loaded emulsions of different concentrations for lymphatic administration were prepared. We confirmed that HD-E and MD-E produced obvious antitumor activities in footpad tumors and LNM compared with other groups in vitro. We also verified the effects of F18-loaded emulsions on activating hematopoietic function, stimulating proliferation of the spleen and natural killer (NK) cells, and promoting the secretion of IFN-gamma and IgG1, although HD-E performed mild toxicity on liver. Conclusion: The present study demonstrated that lymphatic chemotherapy with HELT fraction of bufadienolides could be an effective approach to the treatment of CRC patients with LNM.