SHH and esophageal squamous cell carcinoma: In order to investigate whether the activation of Shh signaling was correlated to platinum resistance of ESCC, we first used immunohistochemistry (IHC) to measure the expression of Shh and Sox2, where Shh is a ligand and Sox2 is a target in canonical Shh signaling (Rimkus et al., 2016), in paraffin-embedded tumor tissues from 59 ESCC patients who were treated with platinum-based regimens.