CerS2 Overexpression Enhances Palmitoyl-CoA-Induced Cytotoxicity and Alters Ceramide Species Composition in Breast...

Sphingolipid metabolism, particularly the balance between pro-apoptotic ceramide and pro-survival sphingosine-1-phosphate (S1P), has been associated with breast cancer progression. The aim of the present study was to examine whether ceramide synthase 2 (CerS2) overexpression is associated with changes in increased palmitoyl-CoA (PCA) based ceramide buildup and cell fate changes in MCF-7 breast cancer cells, a hormone receptor-positive model. CERS2 plasmid transfected cells were treated with PCA and/or the CerS inhibitor, fumonisin B1 (FB1). Cell viability, the proliferation marker proliferating cell nuclear antigen (PCNA), apoptosis (TUNEL and cleaved caspase-3), and sphingolipid profiles were evaluated. High-dose PCA (100 μM) significantly reduced MTT signal and PCNA expression and increased apoptotic markers, with stronger effects in CerS2-overexpressing cells. Across short- and longer-term exposures, the response pattern was concentration- and time-responsive but not uniformly monotonic. Lipidomic analysis revealed that PCA and CerS2 overexpression increased C16 ceramide and very-long-chain ceramides (C22-C24), respectively. FB1 decreased the level of ceramide, elevated S1P and partly counteracted PCA-induced cytotoxicity. FB1 pre-treatment which was applied sequentially restricted but did not eliminate apoptosis. These findings indicate that CerS2 overexpression reshapes the cellular response to substrate-driven sphingolipid stress by altering acyl-chain-specific ceramide composition and the balance between ceramide- and S1P-associated signaling. Rather than reflecting isolated pathway effects, the results support a context-dependent role for CerS2 in modulating apoptotic sensitivity in MCF-7 breast cancer cells.