IRF4 addiction in multiple myeloma

Abstract

The transcription factor IRF4 is required during an immune response for lymphocyte activation and the generation of immunoglobulin-secreting plasma cells 1-3 . Multiple myeloma, a malignancy of plasma cells, has a complex molecular etiology with several subgroups defined by gene expression profiling and recurrent chromosomal translocations 4,5 . Moreover, the malignant clone can sustain multiple oncogenic lesions, accumulating genetic damage as the disease progresses 6,7 . Current therapies for myeloma can extend survival but are not curative 8,9 . Hence, new therapeutic strategies are needed that target molecular pathways shared by all subtypes of myeloma. Using a loss-offunction, RNA-interference-based genetic screen we show here that IRF4 inhibition was toxic to myeloma cell lines, regardless of transforming oncogenic mechanism. Gene expression profiling and genome-wide chromatin immunoprecipitation analysis uncovered an extensive network of IRF4 target genes and identified MYC as a direct target of IRF4 in activated B cells and myeloma. Unexpectedly, IRF4 was itself a direct target of MYC transactivation, generating an autoregulatory circuit in myeloma cells. Though IRF4 is not genetically altered in most myelomas, they are nonetheless addicted to an aberrant IRF4 regulatory network that fuses the gene expression programs of normal plasma cells and activated B cells.Recently, we developed a genetic method to identify therapeutic targets in cancer in which small hairpin RNAs (shRNAs) that mediate RNA interference are screened for their ability to block cancer cell proliferation and/or survival 10 . Here we report the results of such an "Achilles heel" screen in multiple myeloma (Supplementary Table 3). We used myeloma cell lines from three molecular subtypes: KMS12 (CCND1 translocation), H929 (FGFR3/MMSET * Corresponding author: Louis M. Staudt, MD, PhD 9000 Rockville Pike Building 10, Room 4N114 Bethesda, MD 20892 301-402-1892 Fax: 301-496-9956 e-mail: lstaudt@mail.nih.gov Reprints and permissions information can be found at www.nature.com/reprints. Author contributions were as follows: Experimental design/discussion, A.L.S., V.N.N., J.E., L.M.S.; preparation and performance of experiments, A.L.S, N.C.T.E, L.L., V.N.N., S.D., X.Y., H.Z., Y.Z., B.C.; data analysis/interpretation, A.L.S., N.C.T.E., W.X., G.W., J.P., J.E., L.M.S.; manuscript preparation, A.L.S., L.M.S. New datasets have been deposited under GEO accessions GSE8958, GSE9067 (gene expression), and GSE9367 (ChIP-CHIP).Full Methods are available in the Supplementary Materials in the online version of the paper at www.nature.com/nature.Supplementary Information is linked to the online version of this paper at www.nature.com/nature.The authors declare no competing financial interests. NIH Public Access Author ManuscriptNature. Author manuscript; available in PMC 2009 July 10. Published in final edited form as:Nature. (Fig.1a). Lymphoma cell lines were largely unaffected by IRF4 knockdown, with the exception of OCILy3, an activated B cell-like...

Bone morphogenetic proteins induce apoptosis in multiple myeloma cells by Smad-dependent repression of MYC

“…9 However, overexpression of MYC has been reported in a larger fraction of myeloma patients than the patients carrying MYC translocations. 6,12 Importantly, knockdown of MYC was shown to be toxic to myeloma cell lines, 13 indicating that myeloma cell lines may be addicted to MYC expression.…”

Alternate pathways for Bcl6‐mediated regulation of B cell to plasma cell differentiation

“…Interestingly, we observed strong binding of Bcl6 to the IRF4 gene, but we could not detect any significant changes in IRF4 expression in BCL6 knockout cells. This may be due to the fact that DT40 cells have high c-myc expression, which has been shown to promote IRF4 expression [60]. However, together these data suggest that in addition to PRDM1, Bcl6 has a double-negative regulatory circuit with IRF4.…”

Critical role for transcriptional repressor Snail2 in transformation by oncogenic RAS in colorectal carcinoma cells

“…Functional RNA interference cell-based screens for genes that are differentially required, dependent on a particular genotype or phenotype, have been performed recently by several groups (Ngo et al, 2006;Shaffer et al, 2008;Luo et al, 2009;Scholl et al, 2009). The primary screen in this study was similar in design to that of Luo et al, using a pooled shRNA library and an isogenic colon cancer cell line pair differing only in the presence or absence of an activated mutant KRAS allele.…”

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