CD44 and breast carcinoma: Prior studies have also demonstrated that an increase of CD44+/CD24− phenotypes in epithelial-like luminal breast cancer subtypes lead to a heightened resistance to chemotherapy.42 The CD44+/CD24− phenotype corresponded to the proportion of CSC-like cells,43 and they were identified by immunostaining of the harvested cluster cultures after 7 days of exposure to 0.5 μM of doxorubicin (Fig. 4a, b) (Figure S8).