Molekulare Charakterisierung von »Tumor-Dormancy« beim Pankreaskarzinom Molecular characterization of tumor dormancy in pancreatic carcinoma

Objective:Ahumanpancreaticadenocarcinomacellline(A818-6)-whichshowsalltypicalgenetic alterationsofmalignantcells-developssinglelayerepithelialhollowspheresresemblingnormal pancreaticductalstructures in vitro.Inthishighlydifferentiationstateofhollowsphereformation, A818-6cellsareshowinggrowtharrestandadecreaseoftelomeraseactivity.Thisdifferentiation statusofhollowsphereformationisreversible. Material and methods:A818-6cellswerecultivated asmonolayerandunderthree-dimensionalgrowthconditions.Toexaminehowgrowthinhibi­ tion/reductionoftelomeraseactivitywasmediatedinhollowspheres,we checkedexpression/ phosphorylationofmembersofMAP-kinasepathwaybywestern-blottinginhollowspheresin comparisontomonolayer.ThesameexperimentswerecarriedoutwithhTERT(catalyticsubunit oftelomerase)-transduced A818-6 cells andconstitutivelyactive TGF~-receptor I-transduced A818-6cells. Additionally,relativetelomeraseactivity(TRAP-assay)andexpression/activityof members ofMAP-kinase pathway (Western blot) were tested in constitutively active TGF~­ receptor I-transducedA818-6 cells. Results: A818-6, A818-6/hTERTandA818-6/constitutively active TGF~-receptorIcellsshowedunderthree-dimensionalgrowthconditionsastrongdecrease