RIPK3 and neoplasm: However, little is known about the transcriptional regulation of Ripk3 in any cell type, other than its repression by CHD4 and by hypoxia-inducible factor 1 (HIF-1) in hypoxic ECs [10], its repression by CHD4 in muscle stem cells [17], and its methylation-dependent repression and promotion by the transcription factor SP1 in tumor cells [18,19].