E2F1 and esophageal squamous cell carcinoma: In 41 primary ESCC investigated with CGH (Fujita et al. 2003), the expression of numerous genes, including the cell cycle-regulator kinase gene BTAK (20q13.2-3) and E2F1 (20q11.2), which plays a crucial role in cell cycle regulation, was enhanced in ~10% of tumors.