CD44 and breast cancer: It is known that the dual-activation of TrkA and CD44 by NGF is involved in drug resistance to lestaurtinib in MDA-MB-231 human breast cancer cells [46]; the increase in phosphorylated p38 MAPK is associated with OxPt-R occurring in H29-D4 human colorectal cancer cells [47]; the increased caspase-2 expression in certain types of tumor has been linked to the promotion of tumorigenesis [48]; CD44 promotes resistance to etoposide-induced apoptosis in SW620 human colon cancer cells [49]; and the decreased NPM caused by trastuzumab reduces the drug resistance of gastric cancer to OxPt [50].