Three subtypes of human breast cancer cell lines (ER+ MCF7, HER2+ SK-BR-3, triple-negative HCC1806 and MDA-MB-231) were exposed to ω-3 FFAs and ATRA at a range of dose (20 μmol/L to 160 μmol/L for ω-3 FFAs, and 5 μmol/L to 40 μmol/L for ATRA), respectively. This evidence concerns the gene ERBB2 and breast cancer.