PTCH1 and esophageal squamous cell carcinoma: In accordance with the expression levels of Shh and PTCH1, the IC50 values of TE-1 and EC109 cells on cisplatin were significantly higher than that of KYSE510 and KYSE150 cells, implying that the Shh signaling activity was negatively correlated with the sensitivity of ESCC cells to cisplatin (R = 0.9; Figure 2B).