CD44 and breast cancer: These include a high-affinity anti-IL-6 antibody, MEDI5117, which has been shown to enhance the anti-tumor efficacy of chemotherapy or gefitinib in several types of tumors that are known to be driven by the IL-6–STAT-3 signaling and especially target the CD44+CD24− CSCs in trastuzumab-resistant and HER-2+ breast cancer cells (90).