Main research topics:

• Studies on the functional role of the PI3K/Akt/mTOR pathway in cancer and circulating tumor cells (CTCs).
• Development of combination therapies with AKT and mTOR inhibitors in preclinical studies in hepatocellular carcinoma, breast carcinoma and head and neck tumors
• Identification of molecular mechanisms that may lead to the emergence of therapy resistance
• Identification of biomarkers to predict recurrent liver metastases in colorectal carcinoma
• Development of micro-bioreactors (lab-on-a-chip) for quantitative analysis of specific inhibitors in 3D tumor cultures (tumoroids) (cooperation with Prof. Trieu, Institute of Microsystems Engineering, TU Hamburg-Harburg)
• Studies on the functional role of SHIP1 as a tumor suppressor of leukemogenesis and carcinogenesis in solid tumor entities
• Structural analysis of the inositol-5-phosphatase SHIP1 as well as of patient-derived SHIP1 mutants and their role as oncogenes in carcinogenesis (cooperation with Prof. Kirchmair, Center for Bioinformatics, University of Hamburg and Dr. Witt, CSSB/DESY)

The PI3K/AKT/mTOR pathway as a druggable molecular target in circulating tumor cells (Supervision: Dr. Daniel J. Smit / Prof. Dr. Manfred Jücker)

Circulating tumor cells (CTCs) are cells that have lost the adhesion to the primary tumor and circulate in the peripheral blood. Recent research suggests that circulating tumor cells are the initiators of metastasis formation and therefore a noteworthy target for new therapeutic strategies. The PI3K/AKT/mTOR signaling pathway was shown to be often hyperactivated in cancer. Activation of the pathway leads to proliferation, angiogenesis, reduced apoptosis, epithelial-mesenchymal transition and increased metastatic potential. Many possible targets for inhibition inside the pathway have been identified in the past, including the key proteins AKT and mTOR.

In our most recent publication (Smit et al., 2020), we analyzed in cooperation with the groups of Prof. Catherine Alix-Panabières (Laboratory of Rare Human Circulating Cells, University Medical Center of Montpellier) and Prof. Klaus Pantel (Department of Tumor Biology, University Medical Center Hamburg-Eppendorf) the functional role of the PI3K/AKT/mTOR signaling pathway in the circulating tumor cell line ‘CTC-MCC-41’ derived from a patient with colorectal cancer. We could demonstrate that this cell line is susceptible to AKT and mTOR inhibition using MK2206 and RAD001 within the nanomolar range. Stable AKT isoform specific knockdowns of AKT1 and AKT2 significantly impaired proliferation of this cell line. These data demonstrate that the PI3K/AKT/mTOR signaling pathway plays a key role in the proliferation of CTC-MCC-41 cells and suggests that specific inhibition of this pathway in CTCs may be a promising approach to inhibit metastasis.

Selected recent contributions:

Smit, D.J.; Pantel, K.; Jücker, M. Circulating tumor cells as a promising target for individualized drug susceptibility tests in cancer therapy. Biochemical Pharmacology 2021, 188, 114589, doi: 10.1016/j.bcp.2021.114589.

Smit, D. J., Cayrefourcq, L., Haider, M.-T., Hinz, N., Pantel, K., Alix-Panabières, C., Jücker, M. High Sensitivity of Circulating Tumor Cells Derived from a Colorectal Cancer Patient for Dual Inhibition with AKT and mTOR Inhibitors. Cells 2020, 9, 2129. doi: 10.3390/cells9092129.

Koch, C.; Kuske, A.; Joosse S. A.; Yigit, G.; Sflomos, G.; Thaler, S.; Smit, D.J.; Werner, S.; Borgmann, K.; Gärtner, S.; Mossahebi Mohammadi, P.; Battista, L.; Cayrefourcq, L.; Altmüller, J.; Salinas-Riester, G.; Raithatha, K.; Zibat, A.; Goy, Y.; Ott, L.; Bartkowiak, K.; Tan, T. Z.; Zhou, Q.; Speicher, M. R.; Müller, V.; Gorges, T. M.; Jücker, M.; Thiery, J.-P.; Brisken, C.; Riethdorf, S.; Alix-Panabières, C.; Pantel, K. Characterization of circulating breast cancer cells with tumorigenic and metastatic capacity. EMBO Mol. Med. 2020, 12, e11908. doi: 10.15252/emmm.201911908.

Isoform-specific effects of AKT in breast cancer bone metastasis (Supervision: Prof. Dr. Manfred Jücker)

Breast cancer is the most common cancer in women and the development of bone metastasis is associated with poor prognosis and impaired survival. AKT, also known as protein kinase B, is a key regulator of cellular processes and plays a crucial role in breast cancer bone metastasis. AKT consists of three isoforms (i.e., AKT1, AKT2 and AKT3). These isoforms demonstrated in some extend different effects on signal transduction of cancer cells. Thus, we are investigating the role of AKT isoforms on breast cancer cells e.g. on proliferation, migration, chemotaxis and bone metastasis in a mouse model by stable sh-RNA-mediated isoform-specific knockdowns of AKT isoforms in bone-seeking sublines of breast cancer cells. Our purpose is, to get further insights into AKT-isoform mediated signal transduction in bone metastasis and reveal clinical implications for AKT-isoform inhibition in breast cancer treatment.

Selected recent contributions

Hinz, N.; Jücker, M. AKT in Bone Metastasis of Solid Tumors: A Comprehensive Review. Cancers (Basel) 2021, 13, 2287, doi:10.3390/cancers13102287.

Hinz, N.; Baranowsky, A.; Horn, M.; Kriegs, M.; Sibbertsen, F.; Smit, D.J.; Clezardin, P.; Lange, T.; Schinke, T.; Jücker, M. Knockdown of AKT3 Activates HER2 and DDR Kinases in Bone-Seeking Breast Cancer Cells, Promotes Metastasis In Vivo and Attenuates the TGFβ/CTGF Axis. Cells 2021, 10, 430, doi:10.3390/cells10020430.

Hinz, N.; Jücker, M. Distinct functions of AKT isoforms in breast cancer: a comprehensive review. Cell Commun Signal 2019, 17, 154, doi:10.1186/s12964-019-0450-3.

Analysis of SHIP1 as a tumor suppressor of leukemogenesis

The PI3-kinase/AKT pathway is constitutively activated in approximately 50-70% of patients with acute myeloid leukemia (AML) and mediates both proliferation promoting and anti-apoptotic signals. The inositol 5-phosphatase SHIP1 is a negative regulator of the PI3K/AKT signaling pathway in hematopoietic cells (Helgason et al., 1998, Li et al., 1999). In our group, we are investigating the functional role of SHIP1 in leukemogenesis.

We have shown that restoration of SHIP1 expression in the human T cell line Jurkat leads to decreased proliferation by prolonging the G1 phase of the cell cycle (Horn, et al 2004) and that vector-mediated overexpression of SHIP1 in CD34+ cells from AML patients reduces proliferation of these cells in vitro (Metzner, et al 2009). In a xenograft mouse model, we demonstrated that overexpression of SHIP1 in the human AML cell line UKE-1 leads to prolonged mouse survival after transplantation into NSG mice (Täger 2017).

A hallmark of tumor suppressors is their mutational inactivation in cells. Various mutations have also been found for the SHIP1-encoding gene INPP5D in AML patients. Our group was able to show that some of these SHIP1 mutations have a strongly reduced enzymatic activity and can no longer negatively regulate the PI3K/AKT signaling pathway (Brauer, et al 2012) thereby also losing their tumor suppressing effect on the growth of human AML cells in a xenograft mouse model (Täger et al 2017).

We have now identified phosphorylation of SHIP1 at tyrosine residue 1021 by SRC family tyrosine kinases as the molecular mechanism for inactivation of SHIP1, which can lead to proteasomal degradation of SHIP1 and thus to its inactivation (Ehm et al, unpublished data). In further studies using an inducible leukemia mouse model, we will now investigate the role of SHIP1 as a tumor suppressor in the initiation and development of AML in vivo by deleting SHIP1 in multipotent hematopoietic stem and progenitor cells. In addition, we plan to identify the underlying signaling pathways by gene expression studies.

3R-Project (BMBF): Reduction of animal experiments in preclinical studies for the analyis of drugs for individualized cancer therapy by using in vitro methods with tumor tissues (tumoroids) (Projektleitung Prof. Dr. Manfred Jücker)

In the current application, we will analyze the possibility to reduce animal experiments in drug testing by using an in vitro method to predict drug sensitivity. Tumor cells from patients with colorectal cancer (CRC) will be analyzed for the effect of distinct drugs in a xenotransplantation mouse model (PDX) in comparison to the effect of the same drugs analyzed in in vitro assays. For this purpose, we will analyze patients with synchronous hepatic metastasis after written consent and with approved ethic vote. In the in vitro assays we will analyze proliferation, vitality, apoptosis, migration, invasion and three dimensional tumoroid growth. These data will be compared with the growth of the primary tumor after subcutaneous transplantation in the mice. The drugs analyzed in this project will be FOLFOX, a combination of the substances 5-Fluoruracil, Folic acid und Oxaliplatin which are applied intravenously in patients. This so called FOLFOX regime is the current state of the art therapy for patients with colorectal cancer.

If any of these in vitro methods will give comparable results to the mouse experiments, this method can be used to replace at least partially some of the many animal experiments currently performed in drug screening.

Training

- Project studies (for molecular life sciences students)

- bachelor theses

- master theses

- doctoral theses (PhD, Dr. rer. nat., Dr. med., Dr. med. dent., Dr. rer. biol. hum.)

- Internship