Overexpression of ΔNTCF4 prevents the response to LiCl in subcutaneous 5TGM1 tumors. Mice were inoculated subcutaneously with 5TGM1-pDNA or 5TGM1-ΔNTCF4 cells and treated with 200 mg/kg per day LiCl. LiCl significantly increased tumor volume in 5TGM1-pcDNA tumors, but not in 5TGM1-ΔNTCF4 tumors (A). Immunohistochemistry for Ki67 demonstrated an increase in the proliferation index of 5TGM1-pcDNA cells following treatment with LiCl, but not in 5TGM1-ΔNTCF4 cells. Proliferation index was calculated as the percentage of Ki67-positive cells among the total number of tumor cells (B). Data are expressed as means (± SEM). *P < .05 compared with control.