5-FU treatment of human colon carcinoma cells resulted in the generation of 5-FU-resistant cells that are enriched for CD133+ tumor cells, and to a lesser degree, CD44+ tumor cells [11], suggesting that enrichment of colon CSCs might be an underlying mechanism of colon cancer chemoresistance [11, 14, 49]. Here, CD44 is linked to malignant colon neoplasm.