ESR1 and breast cancer: Because of the complementarity of their antitumor action and the known antiproliferative effects of n-3FA in estrogen receptor negative breast cancer cell lines [15, 16, 24], we believe that the chemopreventive effect of the combination of n-3FA and antiestrogens will not be restricted to ER positive tumors but will extend to ER negative tumors which are more aggressive and associated with shorter survival.