Enhanced Anti-cancer Effect Of MAP30-S3 By Endosomal Escape Medicating By Cyclosproin A

A major challenge in the clinical application of anti-tumor drug proteins is the intracellular release after delivering.Cyclosporin A(CsA)is an immunosuppressive agent and a calcium antagonist and it also has been reported that enhanced the efficacy of some immunotoxins,while its mechanism remains unknown.In this study,MAP30,a ribosome inactivating protein reported to have apoptotic effects on cancer cells,was fused with S3,an EGFR-targeting peptide.CsA was incorporated to investigate if it can further promote the apoptotic effects of S3 fused MAP30(MAP30-S3).CsA(2μM)significantly and specifically enhanced the cytotoxicity of MAP30-S3 on the EGFR-overexpressing tumor cell lines HeLa.SMMC-7721 and MGC803,especially on the HeLa cells,it promoted the anti-tumor effect of MAP30-S3 by at least 125-fold.In comparison,CsA did not further decrease the cytotoxicity of MS3 on noncancerous cells MRC-5 derived from normal lung tissue,indicating that the enhanced effect of CsA retained the selectivity of MAP30-S3,and 2 μM CsA itself has no toxicity on the cells.Our results also showed that CsA further increased the apoptotic activity of MAP30-S3 in HeLa cells.CsA was capable of promoting the endosomal escape of FITC-MAP30-S3 with a diffused pattern in the cytoplasm.Further investigation of the endocytosis pathway revealed that the promoting endosomal escape effect of CsA on targeted toxins might be associated with whether the targeted toxin depended on clathrin-mediated endocytosis.Our study indicated that CsA could be used as a novel chemical endosomal escape enhancer to improve the anti-tumor effect of targeted toxin.