The mechanism of downregulation of CYGB in TOC is unclear, as no mutations have been identified in affected tissue (Shahabi et al, 2004), although there is evidence that CYGB promoter methylation may occur in sporadic oesophageal cancer (McRonald et al, 2006) and possibly also in ovarian cancer (Presneau et al, 2005). Here, CYGB is linked to carcinoma of esophagus.