Funktionelle Charakterisierung von BCKDK im Hinblick auf seine Funktion im Pankreaskarzinom

Pancreatic ductal adenocarcinoma (PDAC) is characterized by its high mortality: the five-year overall survival is only 8%. One of the reasons for this is the usually late diagnosis as early symptoms rarely occur. Thus, when first diagnosed, the tumor is often already metastasized and surgery is no longer possible. Another important factor is its high resistance against chemotherapeutic intervention. According to the current state of research, PDAC develops from precursor lesions due to an accumulation of characteristic genetic mutations. The exact molecular mechanisms are not yet understood. Hence, research tries to identify proteins with relevance for the pathogenesis of pancreatic cancer, which might be targeted by new anticancer therapies. One of those proteins is the Branched-Chain α-Ketoacid Dehydrogenase-Kinase (BCKDK). In a kinome-wide screening, pancreatic cancer cells showed an increase in apoptotic activity after suppression of BCKDK. Additionally, an elevated BCKDK-expression was found in primary human PDAC tissues. The BCKDK regulates the Branched-Chain α-Ketoacid Dehydrogenase and therefore functions as a major regulator of the branched-chain amino acid catabolism. Different functions could not be identified to date. In this thesis, the pro-oncogenic effect of the BCKDK in PDAC was investigated. For this purpose, the expression of BCKDK was suppressed by transfecting three different siRNAs (siRNA 1, 3 and 5) in two pancreatic carcinoma cell lines. Subsequently, the effects of the knockdown on apoptosis, proliferation and protein expression were analyzed. The experiments showed different results depending on the employed siRNA. When using siRNA 1, cell viability in both cell lines decreased as a result of increased apoptosis induction. Additionally, the proliferation rate dropped and cells arrested in the G2-phase of the cell cycle. Likewise, repression of the target gene with siRNA 3 led to a decrease of cell viability as well as an elevated apoptotic rate. However, only one of the two cell lines showed a decrease in proliferation. Those cells transfected with siRNA 5 did not show any differences to the control cells, neither in cell viability nor in proliferation. These diverse results can possibly be explained by off-target-effects of the siRNA. The underlying pathologic mechanisms could not be revealed entirely in this thesis and further research is required.