ST8SIA1 and breast cancer: ST8SIA1 (GD3 synthase) knockdown enhances cytotoxicity of gefitinib (an EGFR kinase inhibitor) in resistant MDA-MB468 cells, both in vitro and in vivo, indicating that ST8SIA1 contributes to gefitinib resistance in EGFR-positive breast cancer cells and its potential as a therapeutic target in drug-resistant breast cancers [81].