TJP1 and endometrial cancer: Therefore, to examine the potential effects of arecoline on expression of the ZO-1 tight junction protein and HER2 member of the EGF receptor gene family, cultured human Ishikawas endometrial cancer cells were treated with concentrations of arecoline ranging between 0.1 mM and 0.5 mM and the production of ZO-1 and HER2 protein determined by western blot analysis.