Fig. 5

miR-203 transitory exposure promotes a morphological and molecular switch to epithelial differentiation on PyMT mammary tumor-derived organoids. A Left panel, Representative bright-field images and the corresponding H&E and Ki67 IHC staining of tumor-derived organoids (tumors from miR-203 wild-type or miR-203 knock-in; PyMT mice treated in vivo with Dox). Right panel, Violin plot showing the quantification of Ki67 staining. B Left panel, Representative bright-field images of tumor-derived organoids (tumors from miR-203 knock-in; PyMT mice treated in vivo either with vehicle or Dox), exposed in vitro to vehicle or miR-203 (Dox) during 5 days and followed by miR-203 withdrawal for 2 more weeks (indicated as “miR-203 5d” in the figure). Right panel, Quantification of the percentage of organoids exhibiting dense versus cystic (luminal-like) morphology in every condition tested. C Left panel, Representative images of H&E and ALDH1/2 IHC staining of control tumor-derived organoids, exposed to vehicle or miR-203 in vitro during 5 days and followed by miR-203 withdrawal, as in (B). Right panel, Violin plot showing the quantification of ALDH1/2 staining. D Representative bright-field images of healthy mammary gland-derived organoids (from miR-203 wild-type; PyMT wild-type mice). E Violin plots showing the quantification of H3K27me3, prolactin, progesterone receptor (PGR), estrogen receptor alpha (ERα) and smooth muscle actin (SMA) staining in control tumor-derived organoids (control), control tumor-derived organoids treated in vitro with miR-203 during 5 days (miR-203) and healthy mammary gland-derived organoids (non-tumor). Representative images are shown in Additional file 1: Fig. 2B. Scale bar 100 µm. In violin plots, six different fields from three independent tumor samples were analyzed. ****p < 0.0001; ***p < 0.001; ** < 0.01; n.s. not statistically different (Student’s t test for panels A–C; One-way ANOVA for E)