The coordinated loss of IRF4 and gain of Bim sensitize myeloma tumor cells to bortezomib-induced apoptosis in pG1 in the absence of Noxa and more profoundly in pG1-S in cooperation with Noxa in vitro.
These data confirm the central role of IRF4 in MM pathogenesis; indicate that this is an important mechanism by which lenalidomide exerts its antitumour effects; and may provide a mechanistic biomarker to predict response to lenalidomide.
In addition, malignant cells strongly stained with CD138 in all the cases, whereas leukocyte common antigen and multiple myeloma 1/interferon regulatory factor 4 were completely negative, nor immunoreactivity was seen for either κ or λ light chains.
The cellular interferon regulatory factor-4 (IRF-4), which is a member of IRF family, is involved in the development of multiple myeloma and Epstein-Barr virus (EBV)-mediated transformation of B lymphocytes.
We hypothesized that MUM1 may be dysregulated/up-regulated in these tumors by a chromosomal translocation, as is seen in many cases of plasma cell myeloma [where MUM1 is juxtaposed with the immunoglobulin heavy chain gene (IgH)].
Molecular targeting of the PKC-beta inhibitor enzastaurin (LY317615) in multiple myeloma involves a coordinated downregulation of MYC and IRF4 expression.
Here we show, using a loss-of-function, RNA-interference-based genetic screen, that IRF4 inhibition is toxic to myeloma cell lines, regardless of transforming oncogenic mechanism.
Diffuse large B-cell lymphoma (DLBCL) can be assigned to prognostic subgroups, including germinal center B-cell (GCB) and activated B-cell subgroups, by using gene expression profiling and, reportedly, immunohistochemistry for CD10, Bcl-6, and multiple myeloma-1/interferon regulatory factor-4 (MUM1/IRF4).
MUM1 (multiple myeloma oncogene 1)/IRF4 (interferon regulatory factor 4) is a transcription factor that is activated as a result of t(6;14)(p25;q32) in multiple myeloma.
MUM1/IRF4 is a myeloma-associated oncogene transcriptionally activated as a result of t(6;14)(p25,q32) chromosomal translocation and by virtue of its juxtaposition to the immunoglobulin heavy chain gene (IgH) locus.
With similar results, fusions between MUM1 and IgH loci were observed by means of interphase DCFISH in eight (21.1%) out of the 38 MM cases, although no definite relationships between MUM1 status and specific clinical findings could be established.