A potential peptide vector that allows targeted delivery of a desired fusion protein into the human breast cancer cell line MDA-MB-231

Abstract

Effective control of breast cancer has been primarily hampered by a lack of tumor specificity in treat­ments. One potential way to improve targeting specificity is to develop novel vectors that specifically bind to and are internalized by tumor cells. Through a phage display library, an 11-L-amino acid peptide, PI (sequence, CASPSGALRSC), was selected. PI was labeled with fluorescein isothiocyanate (FITC) and named PI-FITC. Subsequently, the specific affinity of PI-FITC to MDA-MB-231 human breast cancer cells and other cancer cell lines was observed by confocal microscopy. Our previous study established that PI-FITC also shows affinity to Calu-1 human lung carcinoma cells and major histocompatibility complex class I antigen molecules; therefore, the cytomembrane proteins of the cell lines were analyzed to determine those that were common to the two cell lines and may be associated with transmembrane transduc­tion. To further test the delivery ability of PI to MDA-MB-231 cells, PI-glutathione-S-transferase (GST) was constructed and the internalization of this fusion protein was visualized by immunofluorescence microscopy. The results revealed that PI exhibited specific affinity to MDA-MB-231 cells. Use of membrane transport inhibitors indicated that macropinocy­tosis and caveolin-mediated endocytosis may be involved in the endocytosis of PI. In addition, 11 membrane proteins common to MDA-MB-231 and Calu-1 may be associated with trans­membrane transduction. In summary, PI was able to deliver PI-GST into MDA-MB-231 cells. Thus, PI could be modified to be a potential vector, and may contribute to the development of targeted therapeutic strategies for breast cancer.