Research

The Trumpp group is well known for its finding that that hematopoietic stem cells (HSCs) in the bone marrow and also several other stem cells in adult tissues are retained as a deeply dormant population (Cabezas-Wallscheid et al., 2017 Cell; Essers et al., 2009 Nature; Scognamiglio et al., 2016 Cell; Tesio et al., 2015 Journal of Experimental Medicine; Velten et al., 2017 Nat Cell Biol; Walter et al., 2015 Nature; Wilson et al., 2008 Cell). The majority of HSCs divide regularly and slowly to generate sufficient new cells to replace the ones which are constantly lost due to normal turnover. However, the most potent adult HSCs during homeostasis reside in a status of deep dormancy as single cells in distinct bone marrow niches. In a healthy mammal, these cells usually divide only five times per lifetime. Their metabolism and replication machinery are completely silenced, while their stem cell identity is maintained. The original hallmark papers describing these findings were published in Cell 2008 and in Nature 2009 and are cited together almost 2000 times. Together with the follow-up studies cited above, they established the general concept of tissue regeneration based on dormant stem cells in response to injury of tissues and organs. Most importantly, in response to stressors such as bacterial/viral infection, severe blood loss or chemotherapy induced toxicity, dormant HSCs are activated in a graded manner to generate billions of new blood cells to regenerate the blood system and bring it back to homeostasis. The activated HSCs then return to dormancy. Recent work of the group showed that the dormancy phase is controlled by Vitamin A derived retinoic acid, suggesting that dietary component are also controlling stem cell activity (Cabezas-Wallscheid et al., 2017 Cell). In addition, by combining single cell RNA-Seq with functional single cell analyses they could show that development from dormant HSCs occurs as a continuous flow of differentiation in which lineage priming and unipotency is established much earlier than previously anticipated. These data challenge the original tree model of hematopoiesis and the paper is already cited 140 times within the two years of publication (Velten et al., 2017 Nat Cell Biol).

These findings have by now been confirmed by many international research groups, expanded to many other systems and became textbook knowledge of stem cell biology. Strikingly, stem cell dormancy goes along with a remarkable resistance of these cells to anti-proliferative chemotherapy. Similarly, this mechanism may also be used by cancer- and metastasis stem cells and possibly explains their resistance to anti-cancer drugs in the clinic. Based on these results, our group also reported that chemotherapy resistant stem cells can be converted and targeted by pre-treatment with interferon-alpha (IFNa), which activates stem cells out of dormancy (Essers et al., 2009 Nature). These data indicate that pre-treatment of cancer patients with IFNa followed by chemotherapy may target also so far resistant dormant cancer stem cells. These findings are now the basis of currently developed sequential therapies to target therapy resistant leukemic stem cells in the clinic (Trumpp, Essers, & Wilson, 2010 Nature Reviews Immunology).

To find the reason why potent stem cells are preserved in dormancy in our body, we worked together with our colleagues in the Milsom lab at HI-STEM to show that the dormancy status protects the stem cell genome from DNA damage and accumulation of mutations. This is of critical importance as mutations in stem cells would propagate these to billions of its progeny and thus would be the seed for the development of leukemias (Walter et al., 2015 Nature). An additional link to cancer has been provided showing that the process of entry and exit of dormancy is controlled by the activity of one of the most vicious oncogenes we know of: MYC, encoding a master transcription factor. MYC activity is controlled by hormones, signaling molecules and environmental cues in adult stem cells but also in embryonic stem cells and pre-implantation embryos. The data suggest that MYC serves as the gas-pedal of cellular activity without influencing the fate or identity of the stem cell. These findings have widespread implications for the understanding of the role of the Myc oncogene in dormant cancers and metastasis (Bahr et al., 2018 Nature; Scognamiglio et al., 2016 Cell).

In another approach focusing on cancer disease mechanisms, Trumpp’s group has identified the branched chain amino acid (BCAA) transaminase 1 (BCAT1) as being essential for the function of human Acute Myeloid Leukemia (AML) stem cells. BCAT1 links BCAA catabolism to the control of intracellular α-ketoglutarate (αKG) level, the latter being an essential co-factor for many dioxygenases including TET. They found that the BCAA-BCAT-αKG pathway mimics the effects of IDH and TET2 mutations and is associated with poor overall survival in IDH^wtTET2^wt AML patients. The team is currently developing BCAT1 inhibitors to treat AMLs without TET2/IDH mutations and used in combination with IDH inhibitors to prevent the development of therapy resistance (Raffel et al., 2017 Nature).

Andreas Trumpp and colleagues were the first to identify metastasis-initiating cells directly from peripheral blood of breast cancer patients. They could show that these circulating tumor cells (CTCs) induce metastatic growth in bone and liver (Baccelli et al., 2013 Nat Biotechnol). Evaluation of the identified markers MET and CD47 in over 200 breast cancer patients could show that expression of both correlates with a reduction in survival of over 10 years and indicates the presence of metastasis stem cells already in the primary tumors of these patients with poor outcome (Baccelli et al., 2014 Oncotarget). In collaboration with the NCT Heidelberg as well as pharmaceutical companies these results are currently clinically translated. Projects are ongoing using single cell transcriptomic analysis to decipher the heterogeneity of CTCs of breast cancer patients and to expand CTCs ex vivo.

In another cancer entity, pancreatic ductal adenocarcinoma (PDAC), one of the deadliest cancers known, the group of Martin Sprick (Group Leader at HI-STEM) and Andreas Trumpp has uncovered a novel mechanism of resistance of PDAC cells to tyrosine kinase inhibitors and clinically used chemotherapeutics. The resistance is caused by up-regulation of CYP3A5 pathway activity, which metabolizes and inactivates these drugs intracellularly. Pharmaceutical inhibition or CYP3A5 knockdown sensitizes PDAC cells to paclitaxel, both in vitro and in vivo as was shown by a preclinical intervention trial. Subsets of other cancers, including hepatocellular carcinoma, express CYP3A5 at high levels suggesting that this is a more common drug resistance mechanism. Two different CYP3A5 inhibitors have been identified and investigator-initiated trials are being planned at the NCT to evaluate a combination treatment of nab-paclitaxel plus gemcitabine with/without CYP3A5 inhibitor to test their efficacy to break resistance in PDACs (Noll et al., 2016 Nature Medicine).

• Baccelli, I., Schneeweiss, A., Riethdorf, S., Stenzinger, A., Schillert, A., Vogel, V., Klein, C., Saini, M., Bauerle, T., Wallwiener, M., Holland-Letz, T., Hofner, T., Sprick, M., Scharpff, M., Marme, F., Sinn, H.P., Pantel, K., Weichert, W., & Trumpp, A. (2013). Identification of a population of blood circulating tumor cells from breast cancer patients that initiates metastasis in a xenograft assay. Nat Biotechnol, 31(6), 539-544. doi: 10.1038/nbt.2576
• Baccelli, I., Stenzinger, A., Vogel, V., Pfitzner, B.M., Klein, C., Wallwiener, M., Scharpff, M., Saini, M., Holland-Letz, T., Sinn, H.P., Schneeweiss, A., Denkert, C., Weichert, W., & Trumpp, A. (2014). Co-expression of MET and CD47 is a novel prognosticator for survival of luminal-type breast cancer patients. Oncotarget, 5(18), 8147-8160. doi: 10.18632/oncotarget.2385
• Bahr, C., von Paleske, L., Uslu, V.V., Remeseiro, S., Takayama, N., Ng, S.W., Murison, A., Langenfeld, K., Petretich, M., Scognamiglio, R., Zeisberger, P., Benk, A.S., Amit, I., Zandstra, P.W., Lupien, M., Dick, J.E., Trumpp, A., & Spitz, F. (2018). A Myc enhancer cluster regulates normal and leukaemic haematopoietic stem cell hierarchies. Nature, 553(7689), 515-520. doi: 10.1038/nature25193
• Cabezas-Wallscheid, N., Buettner, F., Sommerkamp, P., Klimmeck, D., Ladel, L., Thalheimer, F.B., Pastor-Flores, D., Roma, L.P., Renders, S., Zeisberger, P., Przybylla, A., Schonberger, K., Scognamiglio, R., Altamura, S., Florian, C.M., Fawaz, M., Vonficht, D., Tesio, M., Collier, P., Pavlinic, D., Geiger, H., Schroeder, T., Benes, V., Dick, T.P., Rieger, M.A., Stegle, O., & Trumpp, A. (2017). Vitamin A-Retinoic Acid Signaling Regulates Hematopoietic Stem Cell Dormancy. Cell, 169(5), 807-823 e819. doi: 10.1016/j.cell.2017.04.018
• Essers, M.A., Offner, S., Blanco-Bose, W.E., Waibler, Z., Kalinke, U., Duchosal, M.A., & Trumpp, A. (2009). IFNalpha activates dormant haematopoietic stem cells in vivo. Nature, 458(7240), 904-908. doi: 10.1038/nature07815
• Noll, E.M., Eisen, C., Stenzinger, A., Espinet, E., Muckenhuber, A., Klein, C., Vogel, V., Klaus, B., Nadler, W., Rosli, C., Lutz, C., Kulke, M., Engelhardt, J., Zickgraf, F.M., Espinosa, O., Schlesner, M., Jiang, X.Q., Kopp-Schneider, A., Neuhaus, P., Bahra, M., Sinn, B.V., Eils, R., Giese, N.A., Hackert, T., Strobel, O., Werner, J., Buchler, M.W., Weichert, W., Trumpp, A., & Sprick, M.R. (2016). CYP3A5 mediates basal and acquired therapy resistance in different subtypes of pancreatic ductal adenocarcinoma. Nature Medicine, 22(3), 278-287. doi: 10.1038/nm.4038
• Raffel, S., Falcone, M., Kneisel, N., Hansson, J., Wang, W., Lutz, C., Bullinger, L., Poschet, G., Nonnenmacher, Y., Barnert, A., Bahr, C., Zeisberger, P., Przybylla, A., Sohn, M., Tönjes, M., Erez, A., Adler, L., Jensen, P., Scholl, C., Fröhling, S., Cocciardi, S., Wuchter, P., Thiede, C., Flörcken, A., Westermann, J., Ehninger, G., Lichter, P., Hiller, K., Hell, R., Herrmann, C., Ho, A.D., Krijgsveld, J., Radlwimmer, B., & Trumpp, A. (2017). BCAT1 restricts αKG levels in AML stem cells leading to IDHmut-like DNA hypermethylation. Nature, 551(7680), 384-388. doi: 10.1038/nature24294
• Scognamiglio, R., Cabezas-Wallscheid, N., Thier, M.C., Altamura, S., Reyes, A., Prendergast, A.M., Baumgartner, D., Carnevalli, L.S., Atzberger, A., Haas, S., von Paleske, L., Boroviak, T., Worsdorfer, P., Essers, M.A., Kloz, U., Eisenman, R.N., Edenhofer, F., Bertone, P., Huber, W., van der Hoeven, F., Smith, A., & Trumpp, A. (2016). Myc Depletion Induces a Pluripotent Dormant State Mimicking Diapause. Cell, 164(4), 668-680. doi: 10.1016/j.cell.2015.12.033
• Tesio, M., Tang, Y.L., Mudder, K., Saini, M., von Paleske, L., Macintyre, E., Pasparakis, M., Waisman, A., & Trumpp, A. (2015). Hematopoietic stem cell quiescence and function are controlled by the CYLD-TRAF2-p38MAPK pathway. Journal of Experimental Medicine, 212(4), 525-538. doi: 10.1084/jem.20141438
• Trumpp, A., Essers, M., & Wilson, A. (2010). Awakening dormant haematopoietic stem cells. Nature Reviews Immunology, 10(3), 201-209. doi: 10.1038/nri2726
• Velten, L., Haas, S.F., Raffel, S., Blaszkiewicz, S., Islam, S., Hennig, B.P., Hirche, C., Lutz, C., Buss, E.C., Nowak, D., Boch, T., Hofmann, W.-K., Ho, A.D., Huber, W., Trumpp, A., Essers, M.A.G., & Steinmetz, L.M. (2017). Human haematopoietic stem cell lineage commitment is a continuous process. Nat Cell Biol, 19(4), 271-281. doi: 10.1038/ncb3493
• Walter, D., Lier, A., Geiselhart, A., Thalheimer, F.B., Huntscha, S., Sobotta, M.C., Moehrle, B., Brocks, D., Bayindir, I., Kaschutnig, P., Muedder, K., Klein, C., Jauch, A., Schroeder, T., Geiger, H., Dick, T.P., Holland-Letz, T., Schmezer, P., Lane, S.W., Rieger, M.A., Essers, M.A., Williams, D.A., Trumpp, A., & Milsom, M.D. (2015). Exit from dormancy provokes DNA-damage-induced attrition in haematopoietic stem cells. Nature, 520(7548), 549-552. doi: 10.1038/nature14131
• Wilson, A., Laurenti, E., Oser, G., van der Wath, R.C., Blanco-Bose, W., Jaworski, M., Offner, S., Dunant, C.F., Eshkind, L., Bockamp, E., Lio, P., Macdonald, H.R., & Trumpp, A. (2008). Hematopoietic stem cells reversibly switch from dormancy to self-renewal during homeostasis and repair. Cell, 135(6), 1118-1129. doi: 10.1016/j.cell.2008.10.048