ESR1 and skin basal cell carcinoma: To identify whether NAF-dependent proliferation of ER+BCCs is mediated by secreted factors, ER+BCCs were placed in organoid cultures for 2 days and subsequently growth medium was replaced with conditioned media (CM) obtained from NAF-ER+BCC organoid co-cultures or organoid cultures containing each cell type separately for an additional 8 days when BCC (EpCAM+) and NAF (EpCAM−) cell numbers were analyzed (Figures 1D and 1E).