Taken together, these data imply that the mechanism of action of GIP-8 in the growth suppression of E-stimulated breast cancer is the result of: (1) blockage of voltage-gated K+ ion channels; (2) interference of EGFR- and E2-stimulated MAPK-kinase activities; (3) inhibition of serine-118 human ER phosphorylation; (4) interference of P53 tumor suppressor phosphorylation and (5) increase in p21 Cip levels that impede cell cycle stage progression. This evidence concerns the gene TP53 and breast cancer.