New anti-
cancer strategies have been developed with respect to proteinkinase C (PKC) as a potential target for therapeutic intervention in patients with advanced
breast cancer. Using cell lines, most of the preliminary data are encouraging but insufficient information is available concerning clinical
breast cancer cells. Thus, we decided to clarify the involvement of PKC in clinical
breast carcinoma cells. We isolated viable
tumor cells from fluids or tissue burden of eleven patients with advanced
breast cancer. Performance of short term cultures supplemented with commonly used
antineoplastics mimicked the clinical situation. We determined the ex vivo chemosensitivity pattern of each cell population. Additionally, we analysed total PKC activity and quantified the PKC-
isoform eta. All assays showed a heterogeneous highly variable distribution of the data investigated. No tendency could be observed regarding the influence of the
therapeutics on PKC activity,
PKC-eta expression or chemoresistance, respectively. Moreover, changes in neither
PKC-eta expression, PKC activity nor chemoresistance induced by a particular
drug in an individual
tumor necessarily predicted the same reaction in another
tumor to this agent. Therefore, we concluded that more explorative data concerning this topic are required prior to the development of a clinically useful
therapy regimen with PKC as the major target.