Figure 4. Altered Ca²⁺ homeostasis is sufficient to induce clusterin (CLU) gene expression. Two experiments were performed using 1403 MCF-7 cells: (1) increasing doses of BAPTA-AM (0–20 µM) were administered with a single dose of thapsigargin (TG) (10 nM); and (2) cells were pre-treated with one dose of BAPTA-AM (3 µM) followed by subsequent increasing doses of TG (0–20 nM, 1 h). CLU promoter activity was assessed as described in Figure 3 and in the Materials and Methods section. Experiments were performed three times in triplicate, and statistical analyses of the data were performed using the Student's t-test. NT, no treatment.