Unlike p53, mutations are not frequently found in Kras or Pten; however, enhanced RTK/Ras/PI3K/Akt signaling and p53 mutations are characteristic of altered signaling pathways found in human ESCC and are hypothesized to be sufficient to induce murine foregut tumor formation from basal progenitors20,21. Here, PTEN is linked to esophageal squamous cell carcinoma.