Subgroup: Tumor angiogenesis

Our projects focus primarily on hypoxic pancreatic, colon, gastric, lung and breast tumors. The serine-threonine kinase PKD2 (protein kinase D2) has been previously reported to be involved in migration, invasion, proliferation and growth of various types of cancer. Our group revealed a novel role of PKD2 in two key aspects of tumor angiogenesis: VEGF-A expression and secretion by the tumor cells; and VEGF-A stimulated blood vessel formation by the tumor associated endothelial cells. Mechanistically, we demonstrated that PKD2 regulates hypoxia-induced VEGF secretion through the induction of TR3/Nur77, an orphan member of the steroid/thyroid receptor family.

Our recent findings revealed PKD2 as a “client” for the heat shock protein 90 (HSP90) [4], a chaperone shown to stabilize various kinases, nuclear receptors and transcription factors. The fact that PKD2 is implicated in the tumor cell death evoked by the inhibition of HSP90 and that ectopic PKD2 partially restores HIF-1alpha accumulation and VEGF-A secretion following HSP90 inhibition broadens the initially described molecular mechanisms of how PKD2 might drive the formation of blood vessels in hypoxic tumors [4] (Fig. 1 and Fig. 2). With the aim of extending these findings, we currently investigate the potential role of PKD2 in hypoxia- and TGFalpha-induced epithelial to mesenchymal transition as well as in the metastatic potential of breast cancer.

Treatment of various cancer cells with ATP-competitive HSP90 inhibitors such as PU-H71 - an optimized water-soluble member of the purine class of chaperone inhibitors or STA9090 – a resorcinol-containing triazole molecule, both currently in clinical development, leads to proteasomal degradation not only of PKD2, but also of STK33, another serine/threonine kinase that we have recently described as a client of HSP90 [5]. The most important finding of this study was that inhibition of HSP90 inhibitors triggered apoptosis preferentially in KRAS mutant cells in an STK33-dependent manner, both in vitro and in vivo (CAM and mouse tumor xenografts). These observations suggest that cancer cells driven by mutant KRAS require expression of STK33 for their viability and proliferation and identify STK33 as a context-dependent therapeutic target. To substantiate these initial findings, we are currently trying to decipher the molecular mechanisms through which STK33 may directly or indirectly (as an HSP90 client) contribute to tumor-driven vascularization of hypoxic solid tumors.

 

Initially identified as a molecule that regulates the final step of glycolysis, the M2 isoform of pyruvate kinase (PKM2) was recently reported to have a central role in the metabolic reprogramming of cancer cells as well as participating in cell cycle progression and gene transcription. Despite intensive efforts, the intricate molecular mechanisms through which PKM2 regulates tumor progression remain elusive. Lately, we identified PKM2 as a molecule that interferes with NF-kappaB/p65 and HIF-1alpha signaling in hypoxic pancreatic tumors. Activation of these transcription factors results in augmented secretion of VEGF that translates to a boost in blood vessel formation that in turn contributes to tumor growth [1]. While our data favor and place NF-κB p65 subunit below PKM2 and upstream of HIF-1alpha in the hypoxia signaling axis in pancreatic tumors, we cannot exclude the contribution of VEGF secretion as a result of sole NF-kappaB activation or HIF-1alpha accumulation in other tumor entities (Fig. 3).

In our efforts to address all these questions we involve a wide range of molecular biology & biochemistry methods (western blotting, IP, ELISA, promoter assays, immunofluorescence, immunohistochemistry). Our in vitro results are subject to confirmation in various animal models like human tumor xenografts on chorionallantoic membrane (CAM), subcutaneous and/or orthotope tumor xenografts in athymic mice and knockout mice.

Staff

Postdoc / Principal Investigator

Profilbild von Dr. rer. nat Ninel Azoitei

Dr. rer. nat Ninel Azoitei

Current members of the group

Dr. med. Jun Liu

Assistenzarzt

Susanne Bobrovich

Kristina Diepold

Funding

Deutsche Forschungsgemeinschaft (DFG)

Cooperation partners

  • Prof. Dr. med. Claudia Scholl, National Center for Tumor Diseases (NCT), Heidelberg
  • Prof. Dr. med. Stefan Fröhling, National Center for Tumor Diseases (NCT), Heidelberg
  • Prof. Dr. Cornelia Brunner, HNO Clinic, University of Ulm
  • PD Dr. Marcus Cronauer, Clinic for Urology, University of Schleswig-Holstein, Lübeck
  • Dr. Gabriela Chiosis, Memorial Sloan-Kettering Cancer Institute, New York, USA
  • Prof. Dr. Johan Van Lint, Katholieke Universiteit Leuven, Belgium
  • Prof. Dr. Darie Costel, Clarkson University, New York, USA
  • Dr. Harald Maier, Center for Internal Medicine I, University of Ulm
  • Prof. Dr. med. Alexander Kleger, Center for Internal Medicine I, University of Ulm
  • Dr. med. Martin Müller, Center for Internal Medicine I, University of Ulm
  • Dr. Sander Beckeschus, Leibniz-Institute for Plasma Science and Technology, Greifswald
  • Dr. Dr. Konrad Steinestel, Gerhard-Domagk-Institut für Pathologie, Münster

Selected publications

  • Azoitei N., Becher A., Steinestel K., Rouhi A., Diepold K., Genze F., Simmet T., Seufferlein T. PKM2 promotes tumor angiogenesis by regulating HIF-1a through NF-kB activation. Molecular Cancer, (2016) Jan 6;15:3. doi: 10.1186/s12943-015-0490-2.
  • Müller M., Schröer J., Azoitei N., Eiseler T., Bergmann W., Köhntop R., Lin Q., Costa I.G., Zenke ., Genze F., Weidgand C., Seufferlein T., Liebau S., Kleger A. A time frame permissive for Protein Kinase D2 activity to direct angiogenesis in mouse embryonic stem cells. Scientific Reports, (2015), Jul 7;5:11742. doi: 10.1038/srep11742.
  • Azoitei N., Fröhling S., Scholl C. and Seufferlein T. PRKD2: A two-pronged kinase crucial for the tumor-supporting activity of HSP90. Author’s View – Invited. Molecular and Cellular Oncology (2015) Jan 7;2(2):e981444.
  • Azoitei N., Diepold K., Brunner C., Rouhi A., Genze F., Becher A., Kestler H., Van Lint J., Chiosis G., Koren J. III, Fröhling S., Scholl C. and Seufferlein T. HSP90 supports tumor growth and angiogenesis through PRKD2 protein stabilization. Cancer Research (2014), 23:7125-7136
  • Azoitei N., Hoffmann C., Ellegast J., Ball C., Obermayer K., Gößele U., Koch B., Faber K., Genze F., Schrader M., Kestler H., Döhner H., Chiosis G., Glimm H., Fröhling S. and Scholl C. Targeting of KRAS mutant tumors by HSP90 inhibitors involves degradation of STK33. Journal of Experimental Medicine (2012), 209: 697-711
  • Azoitei N., Kleger A., Schoo N., Rudolf Thal D., Brunner C., Pusapati G.V., Filatova A., Genze F., Möller P., Acker T., Kuefer R., Van Lint J., Baust H., Adler G., Seufferlein T. Protein kinase D2 is a novel regulator of glioblastoma growth and tumor formation. Neuro-Oncology (2011), 13(7): 710-724
  • Azoitei N., Pusapati G.V., Kleger A., Möller P., Küfer R., Genze F., Wagner M., van Lint J., Carmeliet P., Adler G., Seufferlein T. Protein kinase D2 is a crucial regulator of tumor cell-endothelial cell communication in gastrointestinal tumors. GUT (2010), 59(10): 1316-30.
  • Azoitei N., Brey A., Bush T., Fulda S., Adler G., Seufferlein T. Thirty-eight-negative kinase 1 (TNK1) facilitates TNFalpha-induced apoptosis by blocking NF-kappaB activation. Oncogene (2007), 26(45): 6536-6545
  • Azoitei N., Wirth T., Baumann B. Activation of the IkappaB kinase complex is sufficient for neuronal differentiation of PC12 cell. Journal of Neurochem. (2005) Jun;93(6):1487-501.
  • Huber M., Azoitei N., Baumann B., Grünert S., Sommer A., Pehamberger H., Kraut N., Beug H., and Wirth T. NF-κB is essential for epithelial-mesenchymal transition and metastasis in a model of breast cancer progression. Journal of Clinical Investigation, (2004), 114: 569-58.