Abstract 33: Calsequestrin 2 regulates proliferation, migration, and invasion in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is the most heterogeneous and aggressive breast tumor subtype defined by absence of receptor for estrogen, progesterone, or HER2. However, the biologic mechanism for TNBC phenotype is still unclear. Here, we show that expression of Calsequestrin 2 (CASQ2), a Ca 2+ -binding protein, correlates with increase of proliferation, migration, and invasion, suggesting that intracellular Ca 2+ may contribute to tumor growth and metastatic phenotype. CASQ2 is the main Ca 2+ -binding protein inside the sarcoplasmic reticulum of cardiomyocytes. CASQ2 forms a complex with ryodine receptor 2 (RyR2) luminal calcium release channel in cardiac muscle. Ca 2+ is a sequestor and regulator of diverse cellular processes, and specific Ca 2+ channels play important roles in cell proliferation and invasiveness of cancers. To know the role of CASQ2 TNBC cells, we established CASQ2-overexpressing stable cells in Hs578T (Hs578T-CASQ2) using retrovirus. Stimulation with caffeine triggered the remarkable increase of intracellular calcium in Hs578T-CASQ2 cells; in addition, the basal level of calcium in cells had much higher amount of Hs578T-CASQ2 than Hs578T. By contrast, calcium chelator BAPTM/AM blocked CASQ2-induced calcium release. Hs578T-CASQ2 cells showed higher level of proliferation, migration and invasion rate compared to Hs578T, which indicated that overexpression of CASQ2 related with cellular functions. We also found that CASQ2 overexpression elevates extracellular signal-related kinase (ERK) expression. In epidermal growth factor (EGF)-treated cells, Hs578T-CASQ2 cells had higher phosphorylated ERK compared to Hs578T, leading to the expression of epithelial-mesenchymal transition (EMT) marker, vimentin. These results indicate that CASQ2 overexpression increases the level of calcium and induces cell proliferation, migration and invasion through ERK signaling. Our findings from this study show a possible cause of migration and invasiveness in breast cancer cells. Taken together, these findings demonstrate that CASQ2 could be a new therapeutic target for breast cancer. Citation Format: Ju Hee Kim, Bok sil Hong, Woohang Heo, Jong Min Han, Wonsik Han, Dong-Young Noh, Hyeong-Gon Moon. Calsequestrin 2 regulates proliferation, migration, and invasion in triple-negative breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 33.