The 10AT-Her2 cell line, which has a stable phenotype and is highly enriched with cells that display breast cancer stem/progenitor cell-like properties, will be used to characterize the precise functional role of signal-regulated alterations in nucleostemin–protein interactions that are part of the anti-proliferative response to I3C, and can be employed to assess the efficiency by which other classes of anti-cancer agents can target specific stem/progenitor cell components in cancer cell populations. This evidence concerns the gene ERBB2 and breast cancer.