Calcium-activated nucleotidase 1 (CANT1) is a member of apyrase family of enzymes which are responsible for hydrolysis of extracellular nucleoside tri-phosphate and di-phosphate to nucleoside monophosphates. The mutation in CANT1 gene causes an autosomal recessive disorder known as Desbuquois dysplasia, revealing skeletal growth abnormalities. CANT1 is an endoplasmic reticulum (ER)-resident protein so that previous studies have suggested roles for CANT1 which are related to ER functions and mechanisms such as protein quality control or unfolded protein response. The first CANT1 expression study in cancer has emerged in prostate cancer research due to the high expression level of CANT1 in prostate tissue. In this study, we aimed to identify the regulation of CANT1 expression during ER stress-activated cell death in breast cancer cell lines MCF7, SK-BR-3, and MDA-MB-468. We induced ER stress-related cell death by Thapsigargin and investigated how the protein expression, mRNA level and subcellular localization of CANT1 change in breast cancer cell lines. Immunoblot results indicate that CANT1 protein expression was altered during ER stress while we did not observe any change in CANT1 mRNA level. Additionally, subcellular localization of CANT1 protein upon ER stress was detected by laser scanning confocal microscope and we obtained increasing colocalization of CANT1 protein with ER but not with mitochondria. Here, first time, we reported how CANT1 expression levels and its subcellular localization change in breast cancer cells upon drug-mediated ER stress-induced cell death
