The IC50 values (Table 1) revealed that (i) modification of OA with hydroxyimino and lactone moieties (HIMOXOL and Br-HIMOLID, respectively) provoked a higher cytotoxicity effect in studied breast cancer cells, and (ii) blocking ER or EGFR receptors in breast cancer cells (MCF7/ER− and MDA-MB-231/EGFR− cells, respectively) decreased the sensitivity of both studied derivatives relative to the maternal compound, OA, while it provoked increased cytotoxicity of the two derivatives. This evidence concerns the gene EGFR and breast cancer.