XDH and colorectal carcinoma: The CD44v expressed in HT-29 cells is v3 or v6, and these two variants are involved in tumor formation, metastatic progression and/or chemoresistance in CRC.(30,32–34) Hydrogen peroxide (H2O2) produced by xanthine/xanthin oxidase is suggested as an antiproliferative inducer in CRC cells.(35) CD44v is reported to protect cells from such an antiproliferative inducer through interaction with xCT, a subunit of a cysteine-glutamate transporter.