CD44 and breast carcinoma: Other studies have shown that CD44+/CD24−/low stem-like drug-resistant breast cancer cells that survive after neoadjuvant chemotherapy have low levels of ROS, which is mediated by the loss of activity in the TIS-related p21 and 26s proteasomes, leading to increased stability and transcriptional activity of the downstream target protein NRF2 [17] (Figure 4).