ESR1 and breast cancer: In ER-positive MCF7 human breast cancer cells, overexpression of IGF-1R increased receptor tyrosine kinase activity in response to IGF-1 ligand stimulation, promoting resistance to tamoxifen and fulvestrant.33 NAFLD has been shown to be associated with decreased circulating IGF-1 levels,34,35 which might partially explain why NAFLD was associated with better breast cancer outcomes during SERMs treatment.