BAK1 and esophageal squamous cell carcinoma: In addition, knockdown of GPC1 in TE8 and TE14 cells decreased levels of the anti-apoptotic protein Bcl-w, and increased levels of the pro-apoptotic proteins Bim in TE8 cells and Bak in TE14 cells (Figure 2D), suggesting that suppression of GPC1 protein expression by siRNA resulted in increased apoptosis in these ESCC cell lines.