Malignant mesothelioma is a poor prognosis
cancer in urgent need of
alternative therapies.
Oleuropein, the major phenolic of olive tree (Olea europaea L.), is believed to have therapeutic potentials for various diseases, including
tumors. We obtained an
oleuropein-enriched fraction, consisting of 60% w/w
oleuropein, from olive leaves, and assessed its effects on intracellular Ca(2+) and cell viability in
mesothelioma cells. Effects of the
oleuropein-enriched fraction on Ca(2+) dynamics and cell viability were studied in the REN
mesothelioma cell line, using
fura-2 microspectrofluorimetry and MTT assay, respectively. Fura-2-loaded cells, transiently exposed to the
oleuropein-enriched fraction, showed dose-dependent transient elevations of cytosolic Ca(2+) concentration ([Ca(2+)]i). Application of standard
oleuropein and
hydroxytyrosol, and of the inhibitor of low-voltage T-type Ca(2+) channels
NNC-55-0396, suggested that the effect is mainly due to
oleuropein acting through its
hydroxytyrosol moiety on T-type Ca(2+) channels. The
oleuropein-enriched fraction and standard
oleuropein displayed a significant antiproliferative effect, as measured on REN cells by MTT cell viability assay, with IC50 of 22 μg/mL
oleuropein. Data suggest that our
oleuropein-enriched fraction from
olive leaf extract could have pharmacological application in
malignant mesothelioma anticancer
therapy, possibly by targeting T-type Ca(2+) channels and thereby dysregulating intracellular Ca(2+) dynamics.