CD24 and breast carcinoma: First, we determined CD24 expression at the transcript level in five breast cancer cell lines representing the subtypes of breast cancer (MCF7 for the luminal A subtype, HCC1419 for the luminal B subtype, SK-BR3 for the HER2 subtype, and MDA-MB–231 and MDA-MB–435 for the TNBC subtype) (Fig 4A).