@phdthesis{Reissland2024,
  author    = {Reissland, Michaela},
  title     = {USP10 is a \(de\) \(novo\) tumour-specific regulator of β-Catenin and contributes to cancer stem cell maintenance and tumour progression},
  doi       = {10.25972/OPUS-31957},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-319579},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {Colorectal Cancer (CRC) is the third most common cancer in the US. The majority of CRC cases are due to deregulated WNT-signalling pathway. These alterations are mainly caused by mutations in the tumour suppressor gene APC or in CTNNB1, encoding the key effector protein of this pathway, β-Catenin. In canonical WNT-signalling, β-Catenin activates the transcription of several target genes, encoding for proteins involved in proliferation, such as MYC, JUN and NOTCH. Being such a critical regulator of these proto-oncogenes, the stability of β-Catenin is tightly regulated by the Ubiquitin-Proteasome System. Several E3 ligases that ubiquitylate and degrade β-Catenin have been described in the past, but the antagonists, the deubiquitylases, are still unknown. By performing an unbiased siRNA screen, the deubiquitylase USP10 was identified as a de novo positive regulator of β-Catenin stability in CRC derived cells. USP10 has previously been shown in the literature to regulate both mutant and wild type TP53 stability, to deubiquitylate NOTCH1 in endothelial cells and to be involved in the regulation of AMPKα signalling. Overall, however, its role in colorectal tumorigenesis remains controversial. By analysing publicly available protein and gene expression data from colorectal cancer patients, we have shown that USP10 is strongly upregulated or amplified upon transformation and that its expression correlates positively with CTNNB1 expression. In contrast, basal USP10 levels were found in non-transformed tissues, but surprisingly USP10 is upregulated in intestinal stem cells. Endogenous interaction studies in CRC-derived cell lines, with different extend of APCtruncation, revealed an APC-dependent mode of action for both proteins. Furthermore, by utilising CRISPR/Cas9, shRNA-mediated knock-down and overexpression of USP10, we could demonstrate a regulation of β-Catenin stability by USP10 in CRC cell lines. It is widely excepted that 2D cell culture systems do not reflect complexity, architecture and heterogeneity and are therefore not suitable to answer complex biological questions. To overcome this, we established the isolation, cultivation and genetically modification of murine intestinal organoids and utilised this system to study Usp10s role ex vivo. By performing RNA sequencing, dependent on different Usp10 levels, we were able to recapitulate the previous findings and demonstrated Usp10 as important regulator of β-dependent regulation of stem cell homeostasis. Since genetic depletion of USP10 resulted in down-regulation of β-Catenin-dependent transcription, therapeutic intervention of USP10 in colorectal cancer was also investigated. Commercial and newly developed inhibitors were tested for their efficacy against USP10, but failed to significantly inhibit USP10 activity in colorectal cancer cells. To validate the findings from this work also in vivo, development of a novel mouse model for colorectal cancer has begun. By combining CRISPR/Cas9 and classical genetic engineering with viral injection strategies, WT and genetically modified mice could be transformed and, at least in some animals, intestinal lesions were detectable at the microscopic level. The inhibition of USP10, which we could describe as a de novo tumour-specific regulator of β-Catenin, could become a new therapeutic strategy for colorectal cancer patients.},
  subject      = {Biomedizin},
  language  = {en}
}
@phdthesis{Hahn2024,
  author    = {Hahn, Sarah},
  title     = {Investigating non-canonical, 5' UTR-dependent translation of MYC and its impact on colorectal cancer development},
  doi       = {10.25972/OPUS-36420},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-364202},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {Colorectal cancer (CRC) is the second most common tumour disease in Germany, with the sequential accumulation of certain mutations playing a decisive role in the transition from adenoma to carcinoma. In particular, deregulation of the Wnt signalling pathway and the associated deregulated expression of the MYC oncoprotein play a crucial role. Targeting MYC thus represents an important therapeutic approach in the treatment of tumours. Since direct inhibition of MYC is challenging, various approaches have been pursued to date to target MYC indirectly. The MYC 5' UTR contains an internal ribosomal entry site (IRES), which has a particular role in the initiation of MYC translation, especially in multiple myeloma. As basis for this work, it was hypothesised on the basis of previous data that translation of MYC potentially occurs via its IRES in CRC as well. Based on this, two IRES inhibitors were tested for their potential to regulate MYC expression in CRC cells. In addition, alternative, 5' UTR-dependent translation of MYC and interacting factors were investigated. EIF3D was identified as a MYC 5' UTR binding protein which has the potential to regulate MYC expression in CRC. The results of this work suggest that there is a link between eIF3D and MYC expression/translation, rendering eIF3D a potential therapeutic target for MYC-driven CRCs.},
  subject      = {Myc},
  language  = {en}
}