Ubiquitin-vermittelte Proteolyse als Steuermechanismus der DNA-Replikation und DNA-Schaden Antwort - Bedeutung für die Tumorentstehung
Pathology
Final Report Abstract
B-cell malignancies are characterized by high levels of genomic instability, which critically contribute to their pathogenesis and evolution. Recently, the fundamental role of the ubiquitin proteasome system (UPS) in maintaining genome integrity has been appreciated, thus suggesting roles in both B-cell malignancy development and as a target structures. Indeed, two major new therapeutic modalities in B- cell malignancies, proteasome inhibitors and imunomodulatory 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 genomewide aCGH and NGS studies of different human MM and 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, FBXO9 (6p12; locus of frequent amplification) and USP24 (1p32, locus of frequent deletion) as promising candidates in MM, 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. Fbxo9 With regard to MM, our studies on FBXO9 unraveled a mechanism by which the SCF ubiquitin ligase, in concert with the CK2 kinase, promotes survival in MM cells through asymmetrical mTOR activation, resulting in constitutive activation of the PI3K/mTORC2/Akt pathway. FBXO9 overexpression was present in 30% of investigated MM cases, and high Fbxo9 expression correlated with better response and higher PFS in patients treated with Bortezomib, thereby providing the first rationally developed marker for Bortezomib response and distinguishing Fbxo9 and CK2 as new therapeutic targets. Our work on USP24 revealed a critical role for this DUB in the spindle assembly checkpoint maintenance and mitotic catastrophe. We have gained evidence that these functions are mediated via stabilization of BUB1 and NOXA. Importantly, we identify significant deletion of USP24 in MM (29%), suggesting a role for USP24 as a tumor suppressor. As to MCL, our studies focused on FBXO25. We found that FBXO25 targets the pro-survival protein Hax-1 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 HAX-1. 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 haploinsufficient tumor suppressor and HAX-1 as a novel proto-oncogene in MCL. In the context of DLBCL, we studied the DUB USP9X. We identified XIAP as a mitotic substrate of USP9X and unravel a mechanism by which the USP9X-XIAP axis regulates the mitotic cell fate decision. We further identify significant overexpression of USP9X (and consecutively of XIAP) in DLBCL and show that high expression of USP9X/XIAP associates with adverse outcome in patients treated with spindle poison containing polychemotherapy. USP9X and XIAP may thus qualify as potential prognostic biomarkers and therapeutic targets. Overall, we anticipate that our interdisciplinary approach comprising functional proteomics, cell biology, mouse models, and analyses of defined patient cohorts will continue to gain further mechanistic insight into the overall role of the UPS in the pathophysiology of B-cell malignancies, and identify relevant drugable target structures of the ubiquitin proteasome system for the specific treatment of these diseases.
Publications
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(2009). betaTrCP- and Rsk1/2-mediated degradation of BimEL inhibits apoptosis. Mol Cell 33, 109-116
Dehan, E., Bassermann, F., Guardavaccaro, D., Vasiliver-Shamis, G., Cohen, M., Lowes, K., Dustin, M., Huang, D., Taunton, J., and Pagano, M.
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(2010). Dissecting the role of ubiquitylation in the DNA damage response checkpoint in G2. Cell Death Differ 17, 78-85
Bassermann, F., and Pagano, M.
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APC/C-mediated degradation of the F-box protein NIPA is regulated by its association with Skp1. PLoS One (2011) 6, e28998
Klitzing, C., Huss, R., Illert, A.L., Froschl, A., Wotzel, S., Peschel, C., Bassermann, F., and Duyster, J.
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(2012). Cks1 Promotion of S Phase Entry and Proliferation Is Independent of p27Kip1 Suppression. Mol Cell Biol 32, 2416-2427
Hoellein, A., Graf, S., Bassermann, F., Schoeffmann, S., Platz, U., Holzlwimmer, G., Kroger, M., Peschel, C., Oostendorp, R., Quintanilla-Fend, L., et al.
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Extracellular Signal-regulated Kinase 2 (ERK2) Mediates Phosphorylation and Inactivation of Nuclear Interaction Partner of Anaplastic Lymphoma Kinase (NIPA) at G2/M. J Biol Chem (2012) 287, 37997-38005
Illert, A.L., Zech, M., Moll, C., Albers, C., Kreutmair, S., Peschel, C., Bassermann, F., and Duyster, J.
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(2013). SCF-FBXO9 and CK2 direct the cellular response to growth factor withdrawal via Tel2/Tti1 degradation and promote survival in multiple myeloma. Nature Cell Biol 15, 72–81
Fernández-Sáiz, V., Targosz, B.S., Lemeer, S., Eichner, R., Langer, C., Bullinger, L., Reiter, C., Slotta- Huspenina, J., Schroeder, S., Knorn, A., Kurutz, J., Peschel, C., Pagano, M., Kuster, B., Bassermann, F.
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(2014) The ubiquitin proteasome system – Implications for cell cycle control and the targeted treatment of cancer. BBA-Mol Cell Res 184, 150-62
Bassermann, F., Eichner, R., Pagano, M.
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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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(2014). gp130 activation induces myeloma and collaborates with Myc. J. Clin. Invest. 124, 5263-5274
Dechow, T., Steidle, S., Götze, K., Rudelius, M., Behnke, K., Pechloff, K., Kratzat, S., Bullinger, L., Fend, F., Soberon, V., Mitova, N., Li, Z., Thaler, M., Bauer, J., Pietschmann, E., Albers, C., Grundler, R., Schmidt-Supprian, M., Ruland, J., Peschel, C., Duyster, J., Rose-John, S., Bassermann, F., Keller, U.
