Global expression analysis of DLBCL cell lines with LITAF over-expression or silencing

The multifunctional protein lipopolysaccharide-induced TNFalpha factor (LITAF) induces the secretion of inflammatory cytokines in monocytes and regulates protein degradation in neural cells. In B-cell lymphomas, LITAF is frequently inactivated by epigenetic mechanisms, but beyond these data little is known about its regulation and function. Immunohistochemical and gene expression profiling analyses of normal and malignant B-cells revealed that LITAF and BCL6 exhibited opposite expression patterns. Accordingly, chromatin immunoprecipitation and luciferase experiments showed that LITAF is transcriptionally repressed by BCL6 in germinal center (GC) lymphocytes and in B-cell lymphoma cells. Gain- and-loss-of-function assays demonstrated that LITAF does not exert any of its previous roles. Conversely, LITAF co-localized with autophagosomes in B-cells whereby activated autophagic responses, which were abrogated upon LITAF silencing. Therefore, BCL6-mediated transcriptional repression of LITAF may contribute to an appropriate GC reaction by suppressing autophagy in GC lymphocytes, whereas constitutive repression of autophagic responses may promote B-cell lymphoma development. Analysis of global gene expression in the diffuse large B-cell lymphoma (DLBCL) cell lines KARPAS-231 and VAL treated with a specific siRNA for LITAF or a scrambled control, and analysis of global gene expression in the DLBCL cell lines RL and SC-1 stably transfected with a tetracycline-inducible LITAF expression vector in the presence or absence of 4 mg/ml doxycycline in the culture medium. The over-expression experiments were performed in duplicate and the silencing experiments in triplicate, resulting in a total of 20 microarrays.