To assess whether the I3C regulation of MDM2 protein interactions with p53 and/or nucleostemin occurs in other indole-carbinol-sensitive breast cancer cells, three well-established cell lines, SKBR3, MCF-7 and MDA-MB-231, were treated with or without I3C for 48 hours and MDM2–p53 and nucleostemin–MDM2 co-immunoprecipitations carried out as described above for 10AT-Her2 cells. This evidence concerns the gene ERBB2 and breast cancer.