CD44 and breast cancer: The evaluation of in‐vitro tumorigenesis properties in sorted populations of CD24+‐breast cancer cells (Figure 3C,D) and CD24−/CD44+‐breast CSCs (Figure 3C,E) of MDA‐MB‐231 depicted a significant decrease in the mammosphere forming efficiency in the presence of doxorubicin (0.01 μM) with the EGFR inhibitor/compound 1e that was comparable to the commercial EGFR inhibitor (PD153035), which in turn was comparable to the doxorubicin alone at a high dose (0.1 μM) (Figure 3D,E).