eIF3d as a therapeutic target for the regulation of oncogenic MYC levels in colorectal carcinoma

• Applicants: Dr. Alberto Cebrian-Serrano; Professor Dr. Armin Wiegering
• Subject Area: General and Visceral Surgery
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 554428301

Colorectal carcinomas (CRC) are the most common tumors of the gastrointestinal tract. At the molecular level, almost all CRCs exhibit upregulation of the oncogene MYC and are dependent on it. However, due to its structure and function, MYC is difficult to inhibit directly. It is therefore of interest to identify biological processes by which the expression/function of MYC can be indirectly inhibited. The literature clearly shows that protein biosynthesis (translation) in tumors is altered in many ways and differs significantly from translation in normal tissue. This includes the use of different translation initiation and elongation factors as well as translation via 5'-cap and eIF4F-independent structures such as internal ribosomal entry sites (IRES). These differences result in tumor-specific therapeutic approaches. In published preliminary work, we have shown that MYC protein expression in CRC is regulated at the translational level, that this regulation is at least partially independent of previously published pathways and that this results in a therapeutic window. To identify factors that regulate MYC translation in CRC, we performed mass spectrometry of proteins bound to the 5' UTR (untranslated region) of MYC mRNA and identified 69 MYC 5' UTR-binding proteins. In a subsequent siRNA screen, these identified factors were analyzed for their regulation of MYC protein expression. We identified eIF3d as the best hit. Knockdown of eIF3d leads to a significant decrease in MYC protein levels, downregulation of MYC target genes and a reduction in the global translation rate. In addition, depletion of eIF3d reduces the growth of APC-mutated intestinal tumor organoids, whereas the growth of organoids from wild-type mucosa is unaffected. The central hypothesis of the proposed project is that (i) protein translation in CRC is dependent on eIF3d, whereas eIF3d is not essential in normal tissue. (ii) a knockdown of eIF3d specifically affects the translation of MYC and possibly other oncogenic mRNAs in CRC. (iii) thus, modulation of eIF3d represents a therapeutic approach for CRC and colorectal liver metastases (CRLM). In the context of this application, the following points will be addressed: (i) on the molecular level, the underlying mechanism of regulation of MYC mRNA translation by eIF3d in CRC will be investigated. (ii) at the cellular level, how eIF3d regulates growth in CRC, whether there are specific cell populations in normal mucosa and in CRC that are eIF3d dependent and whether human CRC organoids are dependent on eIF3d. (iii) At the organism level, the effect of eIF3d knockdown in vivo on the whole organism and on CRLM growth will be investigated.

• DFG Programme: Research Grants