ESR1 and breast cancer: Moreover, Allred et al. demonstrated that trigonelline, a natural constituent of coffee accounting for ∼1% of dry matter in roasted beans, can function as an estrogen receptor (ER) agonist in estrogen-responsive breast cancer cells and that the compound results in transcriptional activation of the ER, which alters the gene expression of downstream target genes, and finally exerts potential benefits for human health [35, 36].