NFKB1 and cancer: KPC1 has been shown to function as an E3 ubiquitin ligase for NF-κB1 p105, which facilitates the ubiquitinating and proteasomal processing of NF-κB1 p105 to p50 in multiple human cancer cells, and then leads to generation of excessive transcriptional repressor p50:p50 homodimers in place of the transcriptional activator p50:p65 heterodimers [36].