In the present study, we demonstrate that the presence of the sst5TMD4 [6–12] induces significant changes in the expression of several angiogenesis-related genes and increases the expression and/or secretion of pro-angiogenic factors such as VEGF, EGF and/or angiopoietins in the breast cancer cell lines MCF-7 and MDA-MB-231, where it also increases the capacity to form mammospheres in culture. This evidence concerns the gene EGF and breast cancer.