CD44 and malignant colon neoplasm: Using EpCAM+/CD44+ colon cancer xenografts, Dylla and colleagues showed that this was the only tumor-initiating cell population remaining following treatment with the cytotoxic drugs irinotecan and cyclophosphamide, and that these cells express high levels of ALDH1, a gene implicated in chemoresistance and a marker of CSCs [41,77-79].