Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz

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Gewählte Publikation:

Stiegelbauer, V.
Characterization of novel predictive biomarkers in colorectal cancer
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] Graz Medical University; 2016. pp. [OPEN ACCESS]


Autor*innen der Med Uni Graz:
Gerger Armin
Hutterer Georg
Pichler Martin

MicroRNAs (miRNAs) are small, non-coding, single-stranded RNAs that are known to be important regulators of carcinogenesis and might be useful potential prognostic factors and therapeutic targets in colorectal cancer (CRC). In the current study we focused on two specific miRNAs, namely miR-196b-5p and miR-188-3p, and analysed their role as potential prognostic biomarkers, their biological functions and their molecular mechanisms of action. In the first part of this study miR-196b-5p expression was quantified by qRT-PCR in two independent cohorts comprising 292 CRC patients in total to investigate its potential as biomarker. In the second part of this thesis an analysis of genome-wide miRNA sequencing data of 228 CRC patients from the cancer genome atlas (TCGA) was performed and identified miR-188-3p as significantly associated with survival. This observation was further validated in a large independent validation cohort (n=332). Transient and stable gain and loss of function experiments were performed in a panel of CRC cell lines, to evaluate the impact of miR-196b-5p and miR-188-3p on proliferation, chemo-sensitivity, migration, invasion and metastases formation in vitro and in vivo. The molecular pathways influenced by these miRNAs were characterized using mRNA transcriptome profiling, in silico target prediction tools, luciferase-interaction assays and pheno-copy gene knock-down experiments. Low miR-196b-5p expression was significantly associated with metastases and poor survival in both independent CRC patient cohorts (p<0.05). Inhibition of miR-196b-5p resulted in increased cancer cell migration/invasion and metastases formation in nude mice (p<0.05). We showed that HOXB7 and GalNT5 mRNAs are regulated by miR-196b-5p via targeting their 3´UTR, which in turn led to a decrease of CRC cell migration. We identified high miR-188-3p expression as an independent prognostic factor (screening cohort: hazard ratio = 4.137, 95%CI=1.568-10.917, p=0.004; validation cohort: hazard ratio HR=1.538, 95%CI=1.107-2.137, p=0.010, respectively). Enhanced miR-188-3p expression resulted in increased migratory behavior of CRC cells in vitro and metastases formation in vivo (p<0.05). The pro-migratory phenotype of miR-188-3p is regulated by direct interaction with MLLT4, a novel migration related gene in CRC. In conclusion, the results of this thesis suggest that miR-196b-5p and miR-188-3p are novel independent prognostic factors in CRC patients which can be party explained by the direct interaction with genes involved in cancer cell migration.

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