Developmental Neuro-Oncology Group
Daisuke Kawauchi, Ph.D. (Group Leader)
Daniel Haag, Ph.D. (Postdoctoral Fellow)
Mikaella Vouri, Ph.D. (Postdoctoral Fellow)
Jessica Clark, Ph.D. (Postdoctoral Fellow)
Patricia Benites, Ph.D. (Postdoctoral Fellow)
Marcus Giese (Clinician Scientist)
Linda Linke (Technical Assistant)
Laura Sieber (Technical Assistant)
Britta Statz (Technical Assistant)
With the advances of molecular genetics in recent years our understanding of genetic alterations in brain tumors has been greatly expanded. This has led to the discovery of tumor-specific recurrent aberrations in genes for which an oncogenic role had already been described in other malignancies but also in genes that have not been implicated in tumorigenic processes previously. With the wealth of new genomic information about pediatric brain tumors at hand it is now of significant importance to distinguish oncogenic genomic alterations from so called passenger mutations. A versatile and flexible in vivo validation pipeline is thus an integral part of the process of translational medicine. Our aim is to investigate these newly identified alterations in an in vivo context and thereby provide a new insight into tumor biology and provide models for preclinical testing in order to facilitate the bench-to-bedside translation of these novel findings.
Medulloblastoma (MB) is one of the most common malignant brain tumors in children. The molecular heterogeneity of this disease has been revealed as classification into 4 subgroups (WNT, SHH, Group3 and Group4). The survival rate of patients with these tumor entities are getting better for decades, but still not 100% curable. Even for cured patients, there can be a risk of side effect caused by current therapies. Thus, more efficient and safer therapeutic methods have been explored. Toward establishment of better therapies, our group is studying etiology of this disease using animal models. Profound understanding of how MB develops would identify critical signaling pathways for tumor initiation and progression, leading to discovery of novel chemotherapeutic approaches.
1. Identification of novel genetic pathways in SHH-subgroup medulloblastomas
The mechanisms underlying initiation of SHH-subgroup medulloblastoma has been relatively well-characterized so far. It has been thought that this subgroup arises from cerebellar granule cell precursors (GNPs) by aberrant SHH signaling activation. Nevertheless, recent intensive genomics studies revealed heterogeneous recurrent mutations of chromatin modifiers in addition to genes regulating SHH signaling pathways, raising the possibility that such chromatin modifiers could be involved in tumor initiation and progression. To understand how these chromatin modifiers are influence GNP proliferation, transformation into malignant tumor cells and drug resistance, we are currently using state-of-art approaches, including in vivo electroporation, mouse genetics, primary neuronal culture, iPSC technology, viral gene transduction, RNA-seq, ChIP-seq and CRISPR technologies.
2. Cell of origin of non-WNT/SHH subgroup medulloblastomas
Non-WNT/SHH subgroups, so-called Group3 and Group4 medulloblastoma have been known as the most aggressive subgroup. Compared to the other two subgroups, the etiology of these subgroups has been relatively less known. Biological questions regarding the cell of origin and oncogenic impacts behind the entities still remains to be defined. With international collaborations, we have screened and identified candidate genes/signaling pathways. With germline and non-germline genetically engineered mouse models, we are developing animal models for these entities and validating function of potential oncogenic hits.
3. Single cell analysis on the developing cerebellum and SHH subgroup medulloblastoma
The cancer is supposed to develop from normal cells via multistep mutations in tumor suppressors and oncogenes. Nevertheless, accumulation of non-oncogenic “passive” mutations hinders discovery of causal factors for cancers. Recent advances of the single cell analysis technology could be a powerful tool to understand how normal cells transform into pre-neoplastic and subsequently malignant tumor cells. We are currently applying the single cell technology to SHH-medulloblastoma murine models and exploring novel markers for tumor-propagating cells as well as specific treatments targeting these cells.
Ependymoma (EPN) is the third most common malignant brain tumor in children. Recent DNA-methylation-based molecular classification have classified the EPNs into 9 major subgroups. Among them, two main subgroups in supratentorial EPNs, so-called RELA and YAP1 subgroups are closely associated with unique gene-fusion breakpoints of the RELA and YAP1 genes, respectively. While recent our and others’ studies revealed oncogenic impacts of these fusion proteins in neural cells of the developing brain, little is known about how these fusion proteins play the roles in tumorigenesis of EPN. We are exploring the molecular mechanisms of fusion-dependent oncogenic signaling using in vivo tumor models. These projects are on-going in collaboration with Dr. Kristian Pajtler’s research group in the pediatric neuro-oncology division.
1. Identification of novel genetic pathways driven by YAP1-fusion genes for EPN tumorigenesis
YAP1 is found as a fusion gene in YAP1 subgroup EPNs. Its expression level in the tumors is not extraordinarily high, indicating that these fusion proteins could have structure-specific oncogenic mechanisms. Interestingly, various fusion partners for YAP1 have been identified in this type of tumors, suggesting common/distinct oncogenic signaling could be activated in each tumor type. Profound understanding of the roles of respective fusion partners in tumor formation could established fusion partner-based personalized medicine in the near future. We are now testing functional domains of fusion proteins using in utero electroporation-engineered mouse models and are exploring fusion-specific cofactors to activate oncogenic signaling using biochemical and molecular biology techniques. Based on these biological findings, we are aiming at preclinical studies using the mouse models mentioned above. Since no cell lines and no other mouse models are available for YAP1 subgroup EPNs, our new moue model is a powerful tool to understand YAP1-EPNs.
2. Identification of oncogenic pathways driven by RELA-fusion genes
The RELA fusion is usually found to be fused to unknown C11orf95 protein in the supratentorial EPNs, but how the fusion induces tumors in the developing brain remains elusive, regardless of its oncogenic capacity. We recently developed electroporation-based RELA tumor model in combination with CRISPR-based Cdkn2a deletion. Using this model system, we are exploring essential domain(s) of the C11orf95-RELA fusion gene for tumor formation. Also, we are testing newly identified fusion genes in supratentorial EPNs, leading to generation of novel preclinical models and the following therapeutic avenues.
Forget A*, Martignetti L, Puget S, […], Kawauchi D*, Barillot E*, Remke M* and Ayrault O*. Aberrant ERBB4-SRC signaling as a novel hallmark of Group 4 medulloblastoma revealed by integrative phosphoproteomic profiling. Cancer Cell, accepted *corresponding authors
Kawauchi D#, Ogg RJ, Liu L, Shih DJ, Finkelstein D, Murphy BL, Rehg JE, Korshunov A, Calabrese C, Zindy F, Phoenix T, Kawaguchi Y, Gronych J, Gilbertson RJ, Lichter P, Gajjar A, Kool M, Northcott PA, Pfister SM and Roussel MF#. Novel MYC-driven medulloblastoma models from multiple embryonic cerebellar cells. Oncogene. 2017. 36: 5231-5242 (#corresponding authors)
Feng W*, Kawauchi D*#, Körkel-Qu H, Deng H, Serger E, Sieber L, Lieberman JA, Jimeno-González S, Lambo S, Hanna BS, Harim Y, Jansen M, Neuerburg A, Friesen O, Zuckermann M, Rajendran V, Gronych J, Ayrault O, Korshunov A, Jones DT, Kool M, Northcott PA, Lichter P, Cortés-Ledesma F, Pfister SM#, Liu HK#. Chd7 is indispensable for mammalian brain development through activation of a neuronal differentiation programme. Nat Commun. 2017. 8:14758 (*Equal contribution, #corresponding authors)
Zuckermann M, Hovestadt V, Knobbe-Thomsen CB, Zapatka M, Northcott PA, Schramm K, Belic J, Jones DT, Tschida B, Moriarity B, Largaespada D, Roussel MF, Korshunov A, Reifenberger G, Pfister SM, Lichter P, Kawauchi D#, Gronych J#. Somatic CRISPR/Cas9-mediated tumour suppressor disruption enables versatile brain tumour modelling. Nat Commun. 2015. 6:7391. (#corresponding authors)
Kawauchi D, Robinson G, Uziel T, Gibson P, Rehg J, Gao C, Finkelstein D, Qu C, Pounds S, Ellison DW, Gilbertson RJ, Roussel MF. A mouse model of the most aggressive subgroup of human medulloblastoma. Cancer Cell. 2012. 21(2):168-80.