Fig 1: Examination of cellular changes in Meta4 organoids after MEK inhibition.a Meta4 organoids were treated with either DMSO containing control media or Selumetinib (1 µM) containing media for 3 days. Phase contrast images were captured before and 3 days after the DMSO vehicle or Selumetinib treatment. Scale bars indicate 500 µm. b Diameters of Meta4 organoids were manually measured before and after either DMSO vehicle or Selumetinib treatment. Data are presented as mean values with standard deviation. P-values were calculated using unpaired two-tailed t-test. ****P < 0.0001. c Co-immunostaining for markers of enterocyte apical membrane, UEAI, Villin and F-actin in paraffin sections of Meta4 treated with either DMSO vehicle or Selumetinib. Scale bars indicate 50 µm. d Expression of intestinal lineage marker transcripts after Selumetinib treatment. Quantitative PCR showing relative expression of intestinal lineage marker genes (Lgr5, Lys, Tff3, Cdx1, Cdx2, Gpx2, Ctfr, Villin, and Muc2), a CSC marker (panCD44) and metaplasia markers (CD44v9 and Clu) 3 days after Selumetinib treatment. Lys, Cdx1, Cdx2, and Muc2 were not detected. Data are presented as mean values with standard deviation (n = 3). P-values were calculated using unpaired two-tailed t-test. *P < 0.05 (0.01; Gpx2), **P < 0.005 (0.002; Cftr, 0.009; CD44v9), ***P < 0.005 (0.0003; Villin), ****P < 0.0001 (Lgr5, Tff3, panCD44). e Transmission electron micrographs (TEM) of Meta4 organoids treated with either DMSO vehicle (above) or Selumetinib (below) for 3 days. Dotted boxes indicate enlarged area. Scale bars indicate 2 microns or 500 nm. Source data are provided as a Source Data file.