[Diagnostic and Therapeutic Potential of Membrane HSP90].

BACKGROUND: Heat shock protein (HSP90) is a molecular chaperone involved in maintaining protein homeostasis by modulating stability of de novo synthesized proteins. Neoplastic cells with high metabolic rate have higher expression of HSP90 and develop so called "chaperone addiction". Specific inhibition of HSP90 has been therefore discussed as a viable therapeutic strategy and several inhibitors of HSP90 have already entered clinical trials. Recently, a novel role for HSP90 was found on plasma membrane of cancer cells. Since then, extracellular HSP90 has been implicated in increased tumor invasiveness and metastasis, but better understanding of its regulation is needed to fully explore its potential in early detection of malignity and import of specific HSP90 inhibitors. We have therefore analyzed correlation of extracellular HSP90 level with import of fluorescently-labeled inhibitor of HSP90 and total expression of HSP90.

METHODS: Flow cytometry was used to analyze cell uptake of FITC-Geldanamycin as well as level of extracellular HSP90, while total expression of HSP90 was analyzed by SDS-PAGE and subsequently Western blotting. Data was then subjected to statistical analysis to analyze possible correlation.

RESULTS: We have analyzed import of fluorescently labeled HSP90 inhibitor together with total and membrane level of HSP90 on a panel of selected breast carcinoma cell lines (BT-474, BT-549, BT-20, MCF-7, MDA-MB-468, SK-BR-3 a T-47D). Acquired data were subjected to statistical analysis that revealed a correlation between total and membrane level of HSP90 as well as correlation of ectopic HSP90 with uptake of HSP90 inhibitor.

CONCLUSIONS: Our analysis has shown that import of HSP90 inhibitors is likely dependent on membrane level of HSP90 as well as its total expression, and therefore can potentially reflect HSP90 addiction of cancer cells.Key words: breast neoplasms - HSP90 - heat shock proteins - geldanamycin This work was supported by MEYS - NPS I - LO1413. The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 13. 3. 2017Accepted: 26. 3. 2017.