Extended Data Fig. 1: Pre-malignant EpdSCs are serine auxotrophs.
From: Extracellular serine controls epidermal stem cell fate and tumour initiation
a. Representative immunofluorescence of progenitor markers α6 and K14 and tumor SC markers CD44 and SOX2 in K14-CreER;SOX2+ pre-tumorigenic lesions in second telogen mice two weeks after tamoxifen administration. Three mice per genotype were analyzed with similar results. Scale bars = 50 μm. b, Relative levels of amino acids from conditioned medium relative to unconditioned medium measured by GC-MS (n = 6 biologically independent samples). Data are mean ±SEM. c, Fractional labeling of intracellular serine from [U-13C]serine (n = 3 biologically independent samples). Data are mean ±SD. d, Population doublings of H-RasG12V-expressing pre-malignant keratinocytes following 48 h of Ser/Gly starvation (n = 3 biologically independent samples). Data are mean ±SD. e, Immunoblot of serine synthesis enzymes in WT and SOX2+ cells following 24 h of culture in control or Ser/Gly-free medium. See Supplementary Table 1 for quantification of immunoblot from triplicate independent experiments. f, Labeling of intracellular serine from [U-13C]glycine (left) and intracellular glycine from [U-13C]serine (right) (n = 3 biologically independent samples). Data are mean ±SD. Statistical significance was determined using a two-way ANOVA with Sidak’s multiple comparison test for panels b, c, and f, and an unpaired two-tailed student’s t-test for panel d. Scanned images of unprocessed blots are shown in Source Data Extended Fig. 1. Numerical data are provided in Statistics Source Data Extended Fig. 1.
