Loss Of IRF8 Inhibits The Growth Of Diffuse Large B-cell Lymphoma

ObjectivesDiffuse large B-cell lymphoma(DLBCL) is the most common type of aggressive nonHodgkin lymphoma in adults. DLBCL is a highly heterogeneous malignancy, which gives a great challenge to the treatment and prognosis of DLBCL, so research in DLBCL’s molecular pathology is of great clinical significance. Interferon regulatory factor 8(IRF8)is a transcription factor with a critical role in B lymphocyte development and functions. Its role in DLBCL, however, remained elusive. In our previous study, analysis of public available data suggested that the expression levels of IRF8 mRNA in human DLBCL tissues were inversely correlated with patients’ overall survival time. And this study was to further explore the molecular mechanism, hoping to provide more theoretical basis for the clinical application of IRF8.MethodsCloning IRF8 specific short hairpin RNA(shRNA) plasmids, packaging into 293 T cells by lentiviral system, collecting virus to infect DLBCL cells(OCI-Ly01 and OCI-Ly10), then detecting the expression levels of IFR8 in DLBCL cells using quantificational real-time polymerase chain reaction(qRT-PCR)and Western blot; studying the effect of IRF8 on DLBCL cell proliferation by MTS assay and carboxyfluorescein succinimidyl amino ester(CFSE) staining; checking the mitogen-activated protein kinase(MAPK) phosphorylation levels on DLBCL cells through Western blot assay; injecting DLBCL cells with shRNA-mediated IRF8 knockdown to study the effect of IRF8 on tumor growing; detecting the protein expression level of IRF8 in DLBCL patients’ tissues by immunohistochemistry(IHC) analysis and analyzing the relationship between the IRF8 expression level and DLBCL subtype.ResultsReducing levels of IRF8 decreased the proliferation of DLBCL cells in vitro. The phosphorylation of p38 MAPK and extracellular regulated protein kinase(ERK) MAPK was inhibited in DLBCL cells with IRF8 knockdown. Loss of IRF8 suppressed the growth of B-cell lymphoma in vivo. The levels of IRF8 was significantly associated with the molecular subtypes of DLBCL,in which low levels of IRF8 were associated with germinal centre B-cell-like(GCB) subtype whereas high levels of IRF8 were associated with non germinal centre B-cell-like(nonGCB) subtype.ConclusionsThe loss of IRF8 suppressed DLBCL cell proliferation in vitro and tumor growth in vivo, and the regulatory effect may be mediated by the inhibition of p38 and ERK activation. IRF8 may play an oncogenic role in human DLBCL by promoting cell proliferation.