Synergistische Wirkung des Farnesyltransferaseinhibitors Lonafarnib und des Kinaseinhibitors Flavopiridol auf Proliferation und Zellzyklus von Ovarialkarzinomzellen in vitro

Table of Contents: In women ovarian cancer is one of the most frequently cancers leading to death. For the primary therapy a radical surgical resection still remains most relevant; followed by a platin-based combined chemotherapy. Despite initial therapeutic success the rate of relapse stays high. Also because of chemoresistency there is a need for e.g. targeted therapeutics. Drugs of the so-called targeted therapy operate selectively by either inhibiting receptors and ligands or molecules of the signaltransduction. Lonafarnib inhibits the farnesylation of H-Ras and the attachment of Ras to the cell membrane. Further points of attack seams to be other farnesylated proteins like small G-proteins, RHEB and centromer-binding-proteins. Lonafarnib is also able to induce apoptosis via a CHOP-dependent upregulation of the DR-5-expression and a following caspase-8-activation. Lonafarnib works as an orally available farnesyltransferase inhibitor against tumor growth in ras-dependent and ras-independent neoplasia. Lonafarnib seems to be less efficient in solid tumors with a high ras-mutation-incidence; one reason for this could be the alternative prenylation and a different point of attack than ras. In-vitro-treatment with Lonafarnib leads to a dose-dependent G2-arrest of glioblastomacells, lungcancer- and fibrosarcomacells. Flavopiriol blocks the ATP-binding site of cyclin-dependent cinases and leads to a G1- respectively G2-cellcycle arrest in vitro. Furthermore it can induce p53-indepent apoptosis. Diverse models show that Flavoprirol inhbitis the TNF-mediated NF-κB-activation and the AP-1-activation, suppresses the expression of a multiplicity of antiapoptotic proteins and the TNF-induced AKT-activation. The mechanisms influenced by Flaoprirol and Lonafarnib are relevant on ovarian cancer cells. The aim of this study is to investigate potential synergistic effects of Flavopiridol and Lonfarnib inhibiting the proliferation of human ovarian cancer cells in vitro. End points are proliferation, cell cycle allocation, induction of apoptosis and necrosis. SKOV-3 and BG1 were used as ovarian cancer cell lines. The following methods were applied: at first proliferation assays with photometric analysis were conducted, then an annexin-V-detection was applied for differentiation of the treated cells in vital, necrotic and apoptotic groups. Cellcycle-analysis was applied via flow cytometry. Antibodies used for the western blotting as housekeeping genes were HDJ-2, HIF1 and anti-ß-Aktin. Analysing the results of the proliferation assays synergistic effects when combining Flavorpiridol and Lonafarnib could not be shown in SKOV3-cells but in BG1-cells. This result was confirmed in the annexin-V-assay. No syngergistic effects could be observed in SKOV-3-cells; in BG1-cells combining both drugs led to a rise of necrosis and a reduction of vital cells. Via flow cytometry in both cell lines a clear transformation of cell cycle induced by treatment with the drugs could be demonstrated, but these effects seem to be rather a single effect of flavopiridol. The combined treatment of Flavopiriol and Lonafarnib in BG1-cells showed a slightly increased cell cycle arrest in the subG1-fraction in selected concentrations. The western blots demonstrated an upregulation of HDJ2 by single use of Lonafarnib and combination with Flavopiridol. Relevant effects of Flaovpiridol and Lonafarnib are detectable in the selected model of human ovarian cancer cells in vitro; in BG1-cells evidence for a synergism of Flavopiridol and Lonafarnib was found. This study supports evidence in literature pointing to a certain activity of these drugs and at the same time emphasizes the different sensibility of human ovarian cancer cell lines to targeted therapeutics in vitro.