Figure 5. CEBPB is an NPM-ALK and STAT3 target gene.

(A) Identification of genes whose expression strongly correlated with TNFRSF8 expression. Genes from the list obtained by the supervised analysis of TS-TTA-A5 (untreated+A1) versus A2+A3 cells (268 genes) were hierarchically clustered in all experimental conditions (33 samples). The plot represents a portion of the list, which includes transcripts with the highest degree of correlation to TNFRSF8 expression (green rectangle). (B) CEBPB expression is correlated with TNFRSF8. TNFRSF8 and CEBPB mRNA expression levels are represented in the histogram as assessed by microarray analysis of 12 TS-TTA-A5 samples. The statistical significance was ranked according to the z score. (C) C/EBPβ protein expression is strongly repressed following NPM-ALK silencing. TS-TTA and Su-DHL1-TTA cells were transduced with A5 or A5M and treated with DOX (84 hours). Western blot analysis was carried out on whole-cell lysates with specific antibodies, as indicated. Different bands represent multiple C/EBPβ isoforms. (D) STAT3 and ERK1/ERK2 regulate C/EBPβ expression. TS-TTA cells were transduced with pLVTH-STAT3, pLVTH-ERK1 and pLVTH-ERK2, pLVTH-AKT1, or pLVTH-PLC-γ shRNA interfering constructs and treated with DOX (96 hours). Western blot analysis was carried out on whole-cell lysates with the specified antibodies. (E) C/EBPβ protein expression is restricted to ALK-positive ALCL cell lines. C/EBPβ and NPM-ALK expression was determined by Western blot analysis on a panel of lymphoma/leukemia cell lines. α-Tubulin protein expression was included for protein normalization.