Our recent study has demonstrated that SHH signaling activation is involved in tumor repopulation after radiotherapy (Ma et al., 2013), and Sims-Mourtada et al. has reported that SHH signaling pathway is extensively activated in residual tumors after chemo-radiotherapy and that blocking SHH signaling in esophageal cancer could enhance radiation cytotoxicity (Sims-Mourtada et al., 2006). The gene discussed is SHH; the disease is esophageal cancer.