Thapsigargin, the SERCA ATPase inhibitor, effectively suppresses the expression of metastasis marker S100A4 in breast cancer cells MDA-MB231. It has been demonstrated that transcription of the S100A4 gene is controlled by Ca2+-signaling pathways. It has been shown that synthesis of S100A4 mRNA and protein in the MDA-MB231 cell line is effectively inhibited by thapsigargin at a concentration of 0.4-4 µM, while preserving cell survival. We assume that a change in gene transcription in response to the disruption of Ca2+ homeostasis plays a direct role in the remodeling of Ca2+-signaling pathways.