MYD88-independent growth and survival effects of Sp1 transactivation in Waldenström macroglobulinemia

Abstract

• Sp1 transcription factor (TF) is activated in WM.• Dual inhibition of Sp1 and MYD88 pathways induces synergistic cell death in WM cells.Sp1 transcription factor controls a pleiotropic group of genes and its aberrant activation has been reported in a number of malignancies, including multiple myeloma. In this study, we investigate and report its aberrant activation in Waldenström macroglobulinemia (WM). Both loss of and gain of Sp1 function studies have highlighted a potential oncogenic role of Sp1 in WM. We have further investigated the effect of a small molecule inhibitor, terameprocol (TMP), targeting Sp1 activity in WM. Treatment with TMP inhibited the growth and survival and impaired nuclear factor-kB and signal transducer and activator of transcription activity in WM cells. We next investigated and observed that TMP treatment induced further inhibition of WM cells in MYD88 knockdown WM cells. Moreover, we observed that Bruton's tyrosine kinase, a downstream target of MYD88 signaling pathway, is transcriptionally regulated by Sp1 in WM cells. The combined use of TMP with Bruton's tyrosine kinase or interleukin-1 receptor-associated kinase 1 and 4 inhibitors resulted in a significant and synergistic dose-dependent antiproliferative effect in MYD88-L265P-expressing WM cells. In summary, these results demonstrate Sp1 as an important transcription factor that regulates proliferation and survival of WM cells independent of MYD88 pathway activation, and provide preclinical rationale for clinical development of TMP in WM alone or in combination with inhibitors of MYD88 pathway. (Blood. 2014;123(17):2673-2681

miR-29s: a family of epi-miRNAs with therapeutic implications in hematologic malignancies

“…To explore additional mechanisms of miR-29b action, we focused on the transcription factor SP1. In fact, high SP1 activity was previously shown to be relevant for sustaining survival and proliferation of MM [ 129 ] and WM cells [ 130 ]. Indeed, we demonstrated direct targeting of SP1 at 3′UTR along with the existence of a feed-back loop between SP1 and miR-29b, since both pharmacological or genetic inhibition of SP1 led to miR-29b transcriptional activation.…”

miR-23b/SP1/c-myc forms a feed-forward loop supporting multiple myeloma cell growth

“… 3 Moreover, we have demonstrated increased activity of the TF Sp1, a ubiquitous zinc-finger TF that binds guanine–cytosine-rich elements in the promoter region of inducible genes, 4 , 5 in MM 7 , 6 and Waldeström's macroglobulinemia (WM). 8 In these malignancies, Sp1 was found to trigger the nuclear factor-κB (NF-kB) pathway, which sustains proliferation, survival and drug resistance in tumor cells. Importantly, genetic as well as pharmacological targeting of Sp1 was able to reduce tumor growth both in vitro and in vivo, 6 , 8 thus indicating that Sp1 is a suitable target for therapeutic intervention in MM and WM.…”

Dual NAMPT and BTK Targeting Leads to Synergistic Killing of Waldenström Macroglobulinemia Cells Regardless of MYD88 and CXCR4 Somatic Mutation Status

“…Residual CD19-negative BM mononuclear cells were cultured in Dulbecco Modified Eagle medium (DMEM) with 20% FCS for 3 to 6 weeks to generate BMSCs, as previously described. (30), (31) Peripheral blood mononuclear cells (PBMCs) were obtained from healthy subjects by Ficoll-Hypaque density gradient sedimentation, and subsequently, CD19 + selection was performed. Approval for these studies was obtained from the Dana-Farber Cancer Institute's Institutional Review Board.…”