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Although Insulin-like growth factor (IGF-I) has been intensively studied, the functions of E-domain peptides of pro-IGF-I, however, have been overlooked. In our laboratory, several anti-cancer activities of the E-peptide of pro-IGF-I have been identified for the longest isoforms of human and rainbow trout E-peptides. These activities include dose-dependent inhibition of colony formation, inhibition of cancer cell metastasis and invasion through matrigel, suppression of cancer-induced angiogenesis, and attenuation of expression of apoptotic genes in favor of cell death. In this study, we were able to produce two-tagged recombinant human Eb-peptide (hEb) of pro-IGF-I with a purity over 99%. With its antimicrobial peptide (AMP)-like characteristics such as binding to the cytoplasmic membrane, and the affinity to the substratum of culture plate, hEb forms a layer of interface rapidly which facilitates the attachment of breast carcinoma cells, MDA-MB-231. Furthermore, the likely conformational change of homo-dimerized hEb through a single disulfide bond, as well as the ability to trigger clathrin-mediated endocytosis may play important roles for inducing lamellipodia outspread in MDA-MB-231 cells. With the highly purified hEb-peptide, not only could we study its function(s) in detail but also the minimum requirement for cancerous cells to metastasize to a suitable environment and grow.Highly purified (>99%) recombinant hEb was produced.hEb has a structural and characteristic resemblance to antimicrobial peptides.hEb interacts with hydrophobic and negatively charged tissue culture substratum and MDA-MB-231 cell plasma membrane.hEb enters MDA-MB-231 cells via clathrin-media endocytosis, which is a key player for cell lamellipodia outspread.