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The oncoprotein NPM-ALK of anaplastic large-cell lymphoma induces JUNB transcription via ERK1/2 and JunB translation via mTOR signaling

Philipp B. Staber, Paul Vesely, Naznin Haq, Rene G. Ott, Kotaro Funato, Isabella Bambach, Claudia Fuchs, Silvia Schauer, Werner Linkesch, Andelko Hrzenjak, Wilhelm G. Dirks, Veronika Sexl, Helmut Bergler, Marshall E. Kadin, David W. Sternberg, Lukas Kenner and Gerald Hoefler

Data supplements

Article Figures & Data

  • Figure 1

    AP-1 transcription factor activity is increased in NPM-ALK–containing cells. (A) Hierarchic clustering using gene expression data of 84 genes differentially expressed in NPM-ALK–negative (blue) and NPM-ALK–positive (red) ALCL cell lines. The dendrogram at the right demonstrates clustering of cell lines using complete linkage. (B) Hierarchic clustering using mRNA expression of 6 AP-1 target genes separating NPM-ALK–negative (blue) and NPM-ALK–positive (red) ALCL cell lines. (C) EMSA of NPM-ALK–negative (MAC-2A, FE-PD) and–positive (SR-786, Karpas 299) ALCL cell lines. Cell lysates were incubated with a [32P]-labeled AP-1 consensus DNA probe (A) or a [32P]-labeled mutated probe (M) (representative results of 3 independent experiments). (D top panel) Western blots using ALK and β-actin antibodies on lysates from vector control (VC) and NPM-ALK–expressing Ba/F3 cells, as well as TonBaF.1-NPM-ALK cells inducibly expressing NPM-ALK without (unind) and 48 hours after addition of 2 μg/mL doxycycline (+ dox). (Bottom panel) EMSA of cell lysates incubated with AP-1 consensus DNA probe (A) or mutated probe (M) (representative results of 3 independent experiments). (E top panel) Western blots of wild-type NPM-ALK and kinase-negative (KN) NPM-ALK–expressing HEK293 cells. Lysates of control (VC) and stably expressing NPM-ALK and KN transfectants were analyzed for presence of fusion protein (bottom) and for NPM-ALK phosphorylated at the pY342/pY343 position. (Bottom panel) EMSA of HEK293 KN and HEK293 NPM-ALK incubated with AP-1 consensus DNA probe (A) and mutated probe (M). (F) Supershift analysis. Cell lysates were incubated with an AP-1 consensus DNA probe and various anti–AP-1 antibodies (c-Jun, JunB, JunD, Fos, Fra-1, Fra-2, and ATF2) (representative results of 3 independent experiments). (G) JUNB mRNA and protein are increased in TonBaF.1-NPM-ALK cells induced for 48 hours with doxycycline. (Left) mRNA expression levels relative to a calibrator (c-JUN mRNA level of Mac2A cells compared with β-actin) are given to facilitate comparison between AP-1 factors (bars indicate standard deviation [SD] of triplicate experiments). (Right) Immunoblotting using antibodies indicated on lysates of uninduced and induced TonBaF.1-NPM-ALK cells.

  • Figure 2

    Knockdown of JUNB impairs cell-cycle progression in NPM-ALK–expressing cells. (A) Small hairpin (sh) RNA knockdown of JUNB in doxycycline-induced TonBaF.1-NPM-ALK cells. (Right) JUNB mRNA is decreased in 24-hour doxycycline-induced TonBaF.1-NPM-ALK cells stably transduced with JUNB sh-RNA–producing vector (sh-JUNB) compared with cells producing scrambled sh-RNA (sh-control). JUNB expression levels of sh-control–treated cells were set as 1 to facilitate comparison with sh-JUNB cells (bars indicate standard deviation [SD] of triplicate experiments). (Left) Cell counts (normalized to control at t = 0) demonstrate a decreased cellular proliferation of sh-JUNB–treated TonBaF.1-NPM-ALK cells at time points indicated (representative results of 3 independent experiments). (B) Knockdown experiments using small interfering (si) RNA in the human NPM-ALK–positive ALCL cell line Karpas-299. (Top panel left) Immunoblot demonstrating changes in protein levels upon transfection with scrambled siRNA (siControl), GAPDH siRNA (siGAPDH), JUNB siRNA (siJUNB), and c-JUN siRNA (si c-JUN), respectively. (Top panel right) Cell counts (normalized to control at t = 0) demonstrate a decreased cellular proliferation of Karpas-299 transfected with siJUNB at time points indicated (representative results of 6 independent experiments. SDs for 2 biologic replicates are given). (Bottom panel) Cell-cycle analysis assessed by propidium iodide staining and flow cytometry shows a decrease in the G2/M fraction associated with an increase of the G0/G1 fraction after siJUNB transfection (representative results of 3 independent experiments). (C) EMSA of Karpas-299 cytoplasmic lysates, 24 hours after siRNA transfection with siControl, siGAPDH, siJUNB, and si c-JUN. Cell lysates were incubated with a [32P]-labeled AP-1 consensus DNA (representative results of 3 independent experiments).

  • Figure 3

    NPM-ALK regulates JunB via mTOR and MAPK signaling. (A) NPM-ALK induces activation of AKT, ERK, and mTOR. Whole-cell lysates from vector control or NPM-ALK–expressing BA/F3 cells were immunoblotted with antibodies against proteins indicated on the right. (B) JunB protein expression is attenuated in NPM-ALK–expressing cells by mTOR or MEK inhibition. SR-786: NPM-ALK–positive ALCL cell line (top panel); TB-NA: TonBaF.1-NPM-ALK cells 24 hours after induction with 2 μg/mL doxycycline (+ dox), or without doxycycline (− dox) (bottom panel). Western blot analysis was performed with antibodies indicated on the right after treatment for 24 hours with 20 nM rapamycin, 12.5 μM U0126, both agents, or control (DMSO). (C) JUNB mRNA is decreased by MEK but not mTOR inhibition. qRT-PCR was performed on SR-786 cells and doxycycline-induced TB-NA cells upon treatment as indicated (20 nM rapamycin, 12.5 μM U0126, both agents, control [DMSO]). Logarithmic scale of mean JUNB expression levels related to expression of a housekeeping gene (β-actin) as 2−ΔCT (bars indicate SEM of triplicate experiments). (D) Following 24-hour treatment with 20 nM rapamycin, 12.5 μM U0126, both agents, 48.8 μM LY294002, or control (DMSO), whole-cell lysates from SR-786 cells were blotted with antibodies against proteins indicated on the right. (E) Cell counts (normalized to control at t = 0) at indicated time points: Treatment conditions as in panel D resulted in reduced cell growth.

  • Figure 4

    Activation of mTOR and ERK in NPM-ALK–positive ALCL patient samples. Immunohistochemistry of ALCL samples using antibodies against (phospho-) proteins indicated on the left. Representative images from 9 NPM-ALK–positive ALCL (left) and 14 NPM-ALK–negative ALCL (right) patient samples. ALK antibody staining demonstrates expression of NPM-ALK in ALCL cells. JunB antibody staining is shown as minimum and maximum signal intensities of NPM-ALK–positive (left) and NPM-ALK–negative samples (right). See “Immunohistochemistry” for image acquisition information.

  • Figure 5

    Rapamycin inhibits polysomal partitioning of JUNB mRNA. Ribosomal 17.1% to 51% sucrose gradients were prepared from NPM-ALK–positive ALCL cell line SR-786 treated with 20 nM rapamycin or control (DMSO). Twelve fractions of each gradient were collected from bottom to top after ultracentrifugation, with online monitoring of RNA content via an OD254 UV-flow cell (gray shaded areas). RNA was isolated from each fraction and analyzed by gel electrophoresis (bottom panels), and quantities of JUNB as well as β-actin mRNA were determined using Northern blot analysis on the same blot membranes. As indicated by the photometric OD254 measurement, fractions 3 and 4 represent monosomes; fraction 5, disomes; and fractions 6 and higher, higher polysomes. Mono-polysomal β-actin and JUNB mRNA distribution correspond to the number of ribosomes that translate each molecule.

Supplementary Materials

  • Figure S1

    Supplementary PDF file available online.

  • Figure S2

    Supplementary PDF file available online.

  • Figure S3

    Supplementary PDF file available online.

  • Figure S4

    Supplementary PDF file available online.

  • Figure S6

    Supplementary PDF file available online.

  • Table S1

    Supplementary PDF file available online.

  • Document S1

    Supplementary PDF file available online.