Ca2+ signaling promotes reactive oxygen species (ROS) in mitochondria and the phosphorylation and translocation to the cell nucleus of signal transducer and activator of transcription 3 (STAT3), which is a transcriptional activator in breast cancer that regulates the activation of several target oncogenes associated with immunosuppression, malignant transformation, tumor growth, apoptosis, metastasis and chemoresistance [156]. This evidence concerns the gene STAT3 and breast cancer.