Defining deregulated ubiquitylation events in B-NHL
Final Report Abstract
B-cell malignancies such as MCL, DLBCL and MM remain to have an adverse prognosis, particularly in the relapsed/refractory setting. Therefore, novel treatment modalities and concepts are urgently needed to improve outcome. Two major new therapeutic modalities in B-cell malignancies, proteasome inhibitors and immunomodulatory drugs (IMiDs), target the UPS, suggesting the presence of aberrant ubiquitylation events. Their identities have however remained mostly elusive. We started from systematic analyses of genome-wide aCGH and NGS studies of different human B-cell lymphoma cohorts with regard to significantly altered chromosomal regions (gains and losses), and correlated with chromosomal loci of orphan, previously uncharacterized F-box proteins and DUBs. This strategy identified FBXO25 (8p23) as a promising candidate deleted in MCL, and USP9X (Xp11) as a candidate amplified in DLBCL. Using unbiased mass-spectrometric based functional proteomic screens, we subsequently identified the relevant substrates of each candidate, and unraveled both the physiological activities as well as the pathophysiological functions in the context of B-cell malignancies for each candidate. As to MCL, our studies focused on FBXO25. We found that FBXO25 targets the pro-survival protein HAX1 for proteasomal degradation in response to apoptotic stimuli, and specified PKCδ as the kinase that spatially and temporally regulates this process via phosphorylation of both FXO25 and HAX1. Studies in B-NHL cell lines and different murine lymphoma models demonstrate that deletions of FBXO25 contribute to lymphomagenesis through Hax-1 stabilization. Indeed, we find monoallelic deletions of FBXO25 (32%) and stabilizing HAX-1 degron mutations (5%) in human mantle cell lymphoma (MCL) samples. These findings distinguish FBXO25 as a novel haplo-insufficient tumor suppressor and HAX1 as a novel proto-oncogene in MCL. In the context of DLBCL, we studied the DUB USP9X. We identified XIAP and WT1 as substrates of USP9X, which are targeted for deubiquitylation specifically in mitosis. As an upstream regulatory means, we specify mitotic phosphorylation of USP9X at serine residue 2563, which is in turn directed by opposing activities of the phosphatase CDC14B and the kinase CDK1. Functionally, we show that this novel signaling axis regulates the mitotic cell fate decision that mediates cell survival in cellular contexts that challenge mitotic survival. Furthermore, we identify significant overexpression of USP9X in DLBCL and show that high expression of USP9X/XIAP associates with adverse outcome in patients treated with spindle poison containing polychemotherapy. Finally, we investigated the molecular mode of action of IMiDs. These studies revealed an unexpected ubiquitin-independent chaperone-like function of CRBN that promotes maturation and activation of two transmembrane proteins, CD147 and MCT1, which form a transmembrane complex that promotes angiogenesis, invasion and proliferation (via CD147) and lactate export (via MCT1). We show that IMiDs interfere with this chaperone-like function of CRBN in a competitive manner to mediate both their anti-tumor and their teratotoxic effects.
Publications
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(2014). Disruption of the PRKCD-FBXO25-HAX-1 axis attenuates the apoptotic response and drives lymphomagenesis. Nature Medicine 20, 1401-1409
Baumann, U., Fernandez-Saiz, V., Rudelius, M., Lemeer, S., Rad, R., Knorn, A.M., Slawska, J., Engel, K., Jeremias, I., Li, Z., Tomiatti, V., Illert, A.L., Targosz, B.S., Braun, M., Perner, S., Leitges, M., Klapper, W., Dreyling, M., Miething, C., Lenz, G., Rosenwald, A., Peschel, C., Keller, U., Kuster, B., Bassermann, F.
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(2016). Immunomodulatory drugs disrupt the CRBN-CD147/MCT1 axis to exert anti-tumor activity and teratogenicity. Nature Medicine 22, 735-743
Eichner, R., Heider, M., Fernández-Sáiz, V., van Bebber, F., Garz, A.K., Lemeer, S., Rudelius, M., Targosz, B.S., Jacobs, L., Knorn, A.M., Slawska, J., Platzbecker, U., Germing, U, Langer, C., Knop, S., Einsele, H., Peschel, C., Haass, C., Keller, U., Schmid, B., Götze, K.S., Kuster, B., Bassermann, F.
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(2016). USP9X stabilizes XIAP to regulate mitotic cell death and chemoresistance in aggressive B-cell lymphoma. EMBO Mol. Med. 8, 851-862
Engel, K., Rudelius, M., Slawska, J., Ahangarian Abhari, B., Altmann, B., Kurutz, J., Ratha-krishnan, A., Fernandez-Sáiz, V., Brunner, A., Targosz, B.S., Loewecke, F., Gloeckner, C.J., Ueffing, M., Fulda, S., Pfreundschuh, M., Trümper, L., Klapper, W., Keller, U., Jost, P.J., Rosenwald, A., Peschel, C., Bassermann, F.
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(2017) IKZF1 expression is a prognostic marker in newly diagnosed standard-risk multiple myeloma treated with lenalidomide and intensive chemotherapy: a study of the German Myeloma Study Group (DSMM). Leukemia, 31, 1363-1367
Kronke, J., Kuchenbauer, F., Kull, M., Teleanu, V., Bullinger, L., Bunjes, D., Greiner, A., Kolmus, S., Kopff, S., Schreder, M., Mügge, L.O., Straka, C., Engelhardt, M., Döhner, H., Einsele, H., Bassermann, F., Bargou, R., Knop, S., Langer, C.
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(2018). FBXL13 directs the proteolysis of CEP192 to regulate centrosome homeostasis and cell migration. EMBO Rep 19, e44799
Fung, E., Richter, C., Yang, H.B., Schaffer, I., Fischer, R., Kessler, B.M., Bassermann, F., and D'Angiolella, V.
