Although elevated mRNA levels have been reported for CERS2, CERS4, and CERS6 in human breast cancer [21, 22], the present study specifically focused on CerS4 because this protein was upregulated in not only TCGA-BRCA data but also MCF-7/ADR cells among all CerS proteins, indicating that CerS4 is expected to play an important role in breast cancer. Here, CERS6 is linked to breast cancer.