Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Golob-Schwarzl, N.
New liver cancer and colorectal cancer biomarkers: PI3K/AKT/mTOR pathway members and eukaryotic translation initiation factors
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] Graz Medical University; 2017. pp. 186
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Haybäck Johannes
- Schicho Rudolf
- Altmetrics:
- Abstract:
- Theoretical background & aim: The most common type of liver cancer is hepatocellular carcinoma (HCC). Despite progressive achievements in management and diagnosis, the mean survival of patients with HCC is less than 8 months. 90% of HCCs arise from hepatic injury and inflammation. Therefore, biomarkers differentiating HCC from inflammation and cirrhosis are needed in order to improve the prognosis of the respective patients. Colorectal cancer (CRC) is the third most common cause of cancer-related death worldwide. With more than 1.2 million cases registered per year, it constitutes the third most frequently diagnosed cancer entity worldwide. Protein deregulation has received considerable attention as a major step in cancer development and progression. The step of initiation, regulated by eukaryotic initiation factors (eIFs), is regarded as rate-limiting step in protein synthesis. eIFs become major targets for cancer therapy and are functionally linked to PI3K/AKT/mTOR signaling. However, little is known about their contribution to CRC. The first part of this thesis focuses on eIF5 to find out if this gene could serve as a prognostic biomarker in chronic hepatitis B (HBV) and C (HCV), HBV- and HCV-associated HCC, non-virus related HCC, ASH, and Wilson´s disease. In the second part, the thesis focuses on eIF1, eIF5, and eIF6 in CRC. The aim of the in vitro studies was to establish a siRNA knockdown system in CRC cell lines to down-regulate the levels of eIF1, eIF5, and eIF6. Methods: eIF and mTOR expression was analysed in HBV and HCV, HBV- and HCV-associated HCC, non-virus related HCC, ASH, and Wilson´s disease. A comparison was made with non-neoplastic tissue on the protein level using immunohistochemistry and immunoblot. eIF and mTOR expression was analysed in primary low and high grade colon carcinoma (CC) and rectum carcinoma (RC) samples, and compared with non-neoplastic tissue on the protein and mRNA level. To assess the therapeutic potential of targeting eIF1, eIF5, and eIF6, siRNA knockdown in HCT116 and HT29 cells was performed. We evaluated the eIF knockdown on protein and mRNA level, and investigated proliferation, apoptosis, invasion, colony-forming, and polysome-associated fractions. In addition, CC and RC liver metastasis and non- neoplastic liver tissue served as controls, and were studied by immunohistochemistry investigating 9 eIF subunits on tissue micro-arrays (TMAs). Results: On the protein level, eIF5 turned out to be a prognostic biomarker in HBV, HCV, HBV- and HCV-associated HCC, non-virus related HCC, ASH, and Wilson´s disease. Protein and mRNA levels of low and high grade CC and RC patients revealed a significant up-regulation for mTOR members and most eIF subunits. As the eIF subunits 1, 5, and 6 turned out to be the most promising candidates in targeting CRC, we investigated them in more detail in silencing experiments. After successful down-regulation of eIF1, eIF5, and eIF6, both the proliferation rate and the clonogenicity of HCT116 and HT29 cells were significantly reduced. In addition to chemosensitivity testing, CRC PDX models were analyzed on the protein level. No significant changes in eIF expression pattern could be observed when comparing CRC and control tissues upon treatment. Conclusion: eIF5 turned out to serve as a predictive and prognostic biomarker in HBV, HCV, HBV- and HCV-associated HCC, non-virus related HCC, ASH, and Wilson´s disease. Various eIF subunits were found to be significantly overexpressed in liver metastases of primary CRC. To gain a deeper mechanistic insight into the multifaceted role of eIF1, eIF5, and eIF6 in carcinogenesis, future studies are needed. However, it can be concluded that eIF1, 5, and 6 might serve as prognostic tumor markers especially in low and high grade CRC.