STAT1 and esophageal squamous cell carcinoma: In the same study, gene transfection of STAT1C (a constitutively-activated form of STAT1) into two ESCC cell lines (EC1 and EC109), resulted in significant apoptosis, and this biological change correlated with a marked reduction in the expression of several anti-apoptotic proteins and a cell-cycle facilitator (including Bcl-2, Bcl-xL survivin and cyclin D1) as well as an upregulation of p21Waf1, a negative regulator of G1 cell-cycle progression [4].