Funktionelle Analyse der Rolle von PLAC8 in neuroendokrinen Tumorzellen des Pankreas

Kaloudis, Johanna

Thesis

Open Access

Funktionelle Analyse der Rolle von PLAC8 in neuroendokrinen Tumorzellen des Pankreas

Files

djk.pdf (1.42 MB)

Date

2026-02-10

Authors

Kaloudis, Johanna

Supervisors

Person

Buchholz, Malte

Person

Schulte, Leon

Abstract

Neuroendocrine tumors (NETs) are rare neoplasms that frequently occur in the gastroenteropancreatic system. Pancreatic NETs (pNETs) are the second most common tumor entity of the pancreas after ductal adenocarcinomas. Surgical resection is currently considered the only potentially curative option, which makes pNETs an important field of research. The aim of this study is to investigate a possible relationship between the proteins PLAC8 and LIN54, as Well as the effects of transfection with GapmeRs targeting PLAC8 on BON1 cells. A targeted knockdown of PLAC8 led, consistent with previous studies, to a significant reduction in cell viability in BON1 cells, supporting the central role of this protein in cell survival and proliferation. The effects were reproducible using both siRNAs and GapmeRs, with the latter tending to be more effective due to their higher specificity. Knockdown was also achieved at the RNA level. In contrast, knockdown of LIN54 had no effect on cell viability, arguing against a functional connection between PLAC8 and LIN54. Regarding the impact on cell cycle proteins, PLAC8 knockdown using GapmeRs resulted - depending on the GapmeR used - in a significant downregulation of Cyclin D1 and an upregulation of p21. Involvement of apoptosis could be excluded based on markers such as PARP and Caspase. Due to indications of an S-phase arrest observed in flow cytometry, further investigation of the S-phase was carried out using a BrdU assay, which showed a reduced proliferation rate. DNA double-strand breaks in transfected cells were visualized by γ-H2AX foci staining. The results, showing maximal DNA damage between 24 and 48 hours post-transfection, suggest a temporally delayed, GapmeR-induced DNA damage. Overall, the results support the assumption that PLAC8 is essential for the survival and proliferation of pancreatic neuroendocrine tumor cells and could therefore serve as a therapeutic target for pNETs. GapmeRs against PLAC8 appear to exert their effects primarily through mechanisms involving cell cycle regulation and the induction of DNA double-strand breaks.