ATOX1 and neoplasm: However, knockdown of CTR2 did not alter the level of CTR1.199 Application of the anti-tumor drug cisplatin (CDDP) triggers the rapid polyubiquitination and proteasomal degradation of CTR1 in a mechanism dependent on the chaperone Atox1.200 When the Atox1+/+ and Atox1−/− fibroblasts were treated with CDDP, only the wild-type fibroblasts showed a CDDP-induced downregulation of CTR1.