Project Details
Projekt
Targeting oncogene-driven translation and integrated stress response signaling in Cancer
Subject Area
Hematology, Oncology
Term
from 2015 to 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 267467939
Colorectal and hepatocellular carcinomas (CRC and HCC, respectively) are characterized by high intrinsic levels of protein translation. This constitutes a pre-sensitized state for therapies which aim at interfering with mechanisms of proteostasis. Based on our previous work focusing on the role of eIF2B5 in colon- and on CDH1 in liver carcinomas, we will target components of the protein translation machinery in CRC and HCC. Both avenues identified the regulation of eukaryotic translation initiation factor 2α (eIF2α) phosphorylation to be essential for the proliferation and survival of CRC and HCC. We will now address several aspects of the molecular regulation of the integrated stress response (ISR) network in greater detail to further the development of these novel treatment options.In a focused shRNA screen we have identified the eIF2α guanine exchange factor (GEF) eIF2B5 as essential for CRC cell survival with oncogenic WNT signaling. We could further show that the induction of MYC leads to overwhelming proteotoxicity in these cells upon loss of eIF2B5. Furthermore, in a CRC mouse model, APCmin mice survived significantly longer when the eIF2α-GEF expression was reduced. As constitutive suppression of eIF2B5 function may result in compensatory activation of rescue pathways, we aim to investigate the potentially therapeutic effects of acute eIF2B5 knockdown in CRC in vivo. We will furthermore determine which of the four eIF2α kinases is dominant in CRC, and whether the inhibition of this kinase can mimick the effects of eIF2B5 knockdown. Using organoid cultures, it will be investigated if there are additional mutations of the WNT pathway which sensitize to loss of eIF2B5, or if oncogenic MYC levels are the major downstream target of activated WNT signaling and facilitate this vulnerability. These results will be correlated to genetic and phenotypic investigations on a biobank that is currently established from up to 100 human CRC organoid cultures. In a yeast-2-hybrid screen, we have identified the anaphase promoting complex co-activator CDH1 to interact with GADD34, the major regulator of eIF2α dephosphorylation under stress. In mammalian cells, CDH1 facilitates the ubiquitylation of GADD34. Loss of CDH1 led to a reduction in GADD34 turnover, increased proteotoxicity, and hypersensitivity towards endoplamatic reticulum stress induced cell death, both in vitro and in a xenograft mouse model. We found that CDH1 is induced in NRAS-driven liver cancer, and that inhibition of CDH1 induction significantly prolonged the survival of the animals. Here we aim to investigate the mechanisms of regulation of CDH1 by oncogenic NRAS and other HCC drivers. Using an in vivo screen, we will investigate which effectors of the ISR are majorily involved in liver carcinogenesis. Finally, we aim to investigate if there is a synergism in the mechanism of action of loss of eIF2B5 and CDH1, both in CRC and HCC.
DFG Programme
Research Units
