Auswirkung von MYCN auf die Tumorprogression von Retinoblastomen und Blockade des Signalweges als zielgerichtete Therapie (MYtargetRB)
Zusammenfassung der Projektergebnisse
Retinoblastoma is the most common eye tumor in childhood. It is the paradigm of a tumor that is initiated by biallelic inactivation of a tumor suppressor gene, the retinoblastoma gene 1, RB1. Additional genetic alterations are rare, but amplification of the transcription factor MYCN is common and MYCN mRNA expression exceeds levels observed in other tumor entities. Amplification of the proto-oncogene MYCN has been identified in some retinoblastomas with RB1 inactivation (RB1-/-, MYCN-amplified [MYCNA]) and in a rare subgroup of RB1-proficient retinoblastoma (RB1wtMYCNA). In MYtargetRB, we aimed to characterize the role of MYCN in retinoblastoma tumorigenesis using a retinoblastoma cell line model and primary retinoblastoma samples. In retinoblastoma cell lines, we targeted MYCN expression using MYCN-directed shRNA to characterize the effect of MYCN on proliferation, apoptosis, cell cycle, tumor cell invasiveness and metastatic potential in vitro and in in ovo assays. Knockdown of MYCN in human MYCNA retinoblastoma cell lines induced growth arrest, downregulation of gene expression of MYCN targets and upregulation of photoreceptor gene signature. Upregulation of photoreceptor signature was significantly stronger in RB1-/- cell lines than in RB1wt. Based on the characteristics in gene expression profiles, we defined a MYCN signature, referred to as MYCN244-RB, which could be useful to identify MYCN-dependent tumors. This MYCN244 RB signature was then applied to RNA-seq profiling data from a cohort of 52 retinoblastomas - 50 primary retinoblastomas and two extraocular relapsed retinoblastomas. In a parallel approach, genome-wide DNA methylation profiles from 61 retinoblastomas were obtained. These data were used as input for an unsupervised hierarchical clustering that separated MYCNA (RB1- /-MYCNA and RB1wtMYCNA) and two non-MYCNA tumors (MYCNA-like) from all other non-MYCNA retinoblastoma. Combining the clustering data that are based on global methylation and the MYCN244- RB signature revealed that the MYCNA and MYCNA-like retinoblastoma group was characterized by low gene expression of photoreceptor gene signature and high expression of stemness markers and MYC(N) targets. Thus, our results obtained in MYtargetRB contributed to a more complete understanding of the functional consequences and molecular mechanisms of dysregulated MYCN in retinoblastoma. Beyond classification purposes, the MYCN244-RB signature could serve as a predictive biomarker capable of selecting MYCN-dependent tumors that respond to MYCN-directed therapies, which are currently in early clinical development.
Projektbezogene Publikationen (Auswahl)
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Characterization of retinoblastoma cell lines with different genetic backgrounds, Jahrestagung der Gesellschaft für Humangenetik, 2018
M. Schwermer, L. Steenpass, A. Rieb & P.Temming
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Comprehensive characterization of RB1 mutant and MYCN amplified retinoblastoma cell lines. Experimental Cell Research, 375(2), 92-99.
Schwermer, M.; Hiber, M.; Dreesmann, S.; Rieb, A.; Theißen, J.; Herold, T.; Schramm, A.; Temming, P. & Steenpass, L.
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RNAi of MYCN provides a first glimpse into MYCN signature in retinoblastoma; Essen Translational Oncology Symposium (ETOS) 2021
Tatsiana Ryl1, Melanie Schwermer, Markus Schneider, Anja Rieb, Artur Bister, Helmut Hanenberg, Alexander Schramm & Petra Ketteler
