ESR1 and cancer: CAF subpopulations can have contrasting effects: CD146-positive CAFs support ER expression and tamoxifen sensitivity in ER-positive breast cancer, while CD146-negative CAFs contribute to tamoxifen resistance, highlighting the complexity and context-dependent roles of CAFs in cancer progression and therapy response (Wang et al., 2023; Costa et al., 2018; Liu et al., 2022).