CD44 and cancer: CD44 is highly expressed in tumor initiating cells and regarded as a cancer stem cell maker of almost all solid cancers, such as breast cancer [23], colon cancer [24], pancreatic cancer [25], non-small cell-lung carcinoma [26], head and neck cancer [27], bladder cancer [28], ovarian cancer [29], prostate cancer [30], cervical cancer [31], gastric cancer [32], hepatocellular carcinoma [33], human nasopharyngeal carcinoma [34] and melanoma [35].