NFKB1 and AL amyloidosis: On the other hand, miR-21 levels are increased in multiple myeloma cells when the proteasome 20S subunit beta type-4 (PSMB4) is overexpressed; there is evidence that this is due to increase in proteasomal degradation of the inhibitor of NF-κB, as NF-κB promotes the transcription of miR-21 [180].