SP1 and plasma cell myeloma: On the other hand, we report here the transcriptional repression of miR-23b by c-myc, an oncogenic TF known to regulate miRs38 and stimulate cell proliferation.27, 39 Thus MYC-dependent miR-23b repression in myeloma cells may allow activation of oncogenic TFs Sp1 and NF-κB, representing the first feed-forward loop with critical growth and survival role in myeloma.