Transglutaminase 2 Mediates the Cytotoxicity of Resveratrol in a Human Cholangiocarcinoma and Gallbladder Cancer Cell Lines

Resveratrol is a polyphenolic compound extracted from plants and is also a constituent of red wine. Our aim was to evaluate if the cytotoxic effect of resveratrol (RES) on cholangiocarcinoma (CC) and gallbladder cancer (GBC) cell lines could be abolished by TG2 inhibition. Human CC and GBC cell lines (SK-ChA-1 and MZ-ChA-1), grown in a three-dimensional cell culture system (MCTS, multicellular tumor spheroids), were treated for 72 h with RES (32, 64 µM) alone or combined with different TG2 inhibitors (Cystamine, B003, T101). We investigated: cells viability; cell morphology with light microscopy (LM) and transmission electron microscopy (TEM); immunoreactivity with immunohistochemistry; Q-Banding karyotype analysis; TG2 activity; Western blotting. RES treatment induced a significant inhibition of cell growth, ranging from 24% to 76% in both cell lines. The inhibitors successfully reduced TG2 activity without any variation of protein quantity as demonstrated by immunohistochemistry and Western blot. TG2 inhibition resulted in cell growth normalization. In addition, morphologic analysis by light and transmission electron microscopy confirmed the cytotoxic effect of RES and its reduction consequent to TG2 inhibition. Our data demonstrated a connection between the cytotoxic effect of RES in SK-ChA-1 and MZ-ChA-1 and TG2 activity.