Hedgehog signaling activation in the development of squamous cell carcinoma and adenocarcinoma of esophagus.

Hedgehog (Hh) signaling is frequently activated in human cancer, including esophageal cancer. Most esophageal cancers are diagnosed in the advanced stages, therefore, identifying the very alterations that drive esophageal carcinogenesis may help designing novel strategies to diagnose and treat the disease. Analysis of Hh signaling in precancerous lesions is a critical first step in determining the significance of this pathway for carcinogenesis. Here we report our data on Hh target gene expression in 174 human esophageal specimens [28 esophageal adenocarcinomas (EAC), 19 Barrett's esophagus, 103 cases of esophageal squamous cell carcinoma (ESCC), and 24 of squamous dysplastic lesions], and in two rat models of esophageal cancer. We found that 96% of human EAC express Hh target genes. We showed that PTCH1 expression is the most reliable biomarker. In contrast to EAC, only 38% of ESCC express Hh target genes. We found activation of Hh signaling in precancerous lesions of ESCCs and EACs in different degrees (21% and 58% respectively). Expression of Hh target genes is frequently detected in severe squamous dysplasia/ carcinoma in situ (p=0.04) and Barrett's esophagus (p=0.01). Unlike EAC, sonic hedgehog (Shh) expression was rare in ESCCs. Consistent with the human specimen data, we found a high percentage of Hh signaling activation in precancerous lesions in rat models. These data indicate that Hh signaling activation is an early molecular event in the development of esophageal cancer, particularly EAC.