expression in ER-negative breast cancer cells. SUM-229PE cells were cultured in the presence of different calcitriol (circles) and calcipotriol (triangles) concentrations or vehicle alone (C, ethanol) for 24 hr. Afterwards, mRNA was extracted and qPCR was performed. Results are shown as the mean ± S.D. of ERα/GAPDH mRNA normalized ratio. Data were normalized setting a value of 1 for vehicle-treated cells. *P ≤ 0.05 vs. C.