Objective:To investigate transmembrane transduction mechanism of a peptide(PI)with high affinity to human breast cancer cell line MDA-MB-231.Methods:PI was synthesized and labeled with FITC at its N-terminus.The MHC-I antigen in the MDA-MB-231 cells and human lung cancer Calu-1 cells was blocked using anti-MHC-Ⅰ antibody

respectively.HLA-allele analysis was performed by polymerase chain reaction-sequence specific primers.To investigate whether the transmembrane transduction mechanism of PI is associated with the caveolin-mediated endocytosis

the distribution of FITC-PI in MDA-MB-231 cells were detected using inverted fluorescence microscope and flow cytometry after pre-incubation with an inhibitor of endocytosis

nystatin.To investigate whether the transmembrane transduction mechanism of PI is associated with the same membrane protein of the two cell lines

the membrane proteins were detected by two-dimensional electrophoresis.Results:FITC-PI was observed in the two cells with MHC-Ⅰ antigen being blocked.Gene typing-analysis revealed that the alleles of the HLA-A and B locis were different.The inhibitor nystatin suppressed FITC-PI distribution.Two-dimensional electrophoresis analysis showed that membrane protein profiles of the two cell lines had 11 same protein spots.Conclusions:The transduction of PI is mediated by the caveolin-mediated endocytosis.The same proteins of the two cell lines may be also involved in this process.This study provides experimental evidence for further investigation of the transmembrane transduction mechanism.