RIPK1 and malignant colon neoplasm: In cells in which the RIPK3 kinase predominantly signals to necroptosis, like in human colon cancer HT29 cells, the RIPK3 chaperone Hsp90/CDC37 level is relatively high, which allows RIPK3 to fold into a configuration that can only be activated by upstream signaling molecules, be that either RIPK1 in response to TNF receptor family members, or TRIF and ZBP1/DAI in response to toll-like receptors or Z-RNA, respectively.