CCND1 and esophageal squamous cell carcinoma: Among several molecules, gene amplification of CCND1 mapped to the 11q13 region, which is a key regulator of the G1 phase of the cell cycle, has been defined as one of the most common genetic aberrations in ESCC, and has been shown to correlate with advanced stage and poor prognosis (Jiang et al, 1992; Kyomoto et al, 1997).