Die Rolle der Überexpression von PRMT1 im duktalen Adenokarzinom des Pankreas

This thesis aimed to analyze the role of PRMT1 in human pancreatic ductal adenocarcinoma (PDAC). Given that overexpression of PRMT1 has been reported to occur on transcript level in PDAC relative to healthy tissue, it was investigated here whether an increase of PRMT1 expression in PDAC tissue is also detectable on protein level. Immunohistochemical stainings revealed increased protein levels of PRMT1 in tumor cells as well as tumor stroma cells of the PDAC. In order to study a potential biological function of this elevated PRMT1 expression in PDAC, the proliferative capacity of the PDAC cell lines Panc1 and MiaPaCa2 was determined using growth curve assays. siRNA-mediated depletion of PRMT1 in these cells revealed an essential function of the protein for the replicative capacity. A similar growth disadvantage due to PRMT1 depletion was also observed in HeLa cells. Furthermore, the ability of PDAC cells to grow without anchorage was measured in soft agar assays. In conditions with PRMT1 depletion, this ability was inhibited. In another part of this thesis, data previously generated in the group regarding an association of the transcription factor GLI1 with PRMT1 were validated and further investigated. Expression analyses did not show compelling evidence for an influence of PRMT1 on GLI1 transcript levels. An interaction of the two proteins could not be confirmed in vivo or in vitro and methylation of GLI1 by PRMT1 was not conclusively verified. A role of PRMT1 in the coactivation of GLI1-dependent gene expression remains doubtful and needs additional research. In the literature, it has been shown that the transcription factor c-MYC activates the transcription of the PRMT1 gene in the course of developmental processes. In this work, the existence of this connection was studied in PDAC cells. Using depletion analysis of c-MYC, it was found that PRMT1 expression is enhanced by c-MYC on transcript as well as on protein level. The influence of PRMT1 on the transcriptome of Panc1 PDAC cells was analyzed by oligonucleotide microarray-based gene expression profiling of PRMT1-depleted versus controldepleted cells. So far, two of the 51 candidate genes that were more than twofold regulated upon siRNA-mediated PRMT1 depletion could be validated. The corresponding proteins GLIPR1 and ANXA8 have previously been shown to have tumor relevant functions. Further functional characterization of these proteins in PDAC is needed in the future.