105P Antiproliferative Effect of New Lignan from Abies Sibirica on Hormone-Dependent Breast Cancer Cells in Vitro

ABSTRACT Background Lignans is one of the main group phytoestrogens, natural compounds with estrogenic activity. Data of experimental studies suggest that lignans can exhibit tumor-protective properties and inhibit tumor growth. Here we studied the effect of lignan, secoisolariciresinol (Knotolan®) isolated from new nonfood vegetable raw material (Abies sibirica) on proliferation of hormone-dependent breast cancer cells in vitro. Material and methods Knotolan® was obtained from Abies sibirica wood. Commercial enterolaktone (Sigma) was as positive control. The final concentration of Knotolan and enterolactone in samples 1000-fold surpassed the concentration of 17-estradiol (E2) and was 1 µM, because previous studies showed that higher concentrations of enterolactone produced a growth-stimulating effect in vitro. The MCF7 cells were used as test object. The number of estrogens receptors was determined by a modified radioligand method. Cells were grown in RPMI 1640 medium without phenol red and 10% FCS containing estrogens. For the experiments cells were grown in the same conditions but without estrogens. Cell proliferation in samples was measured by MTT-test. Microscope examination was performed using Axiolmager invertal microscope. Results MCF7 cells revealed 6.1 ± 0.5 3H-E2 binding sites per cells. On day 5, incubation of cells with E2 in concentration 1nM increased proliferation of MCF7 cells by 41.7%. Incubation with Knotolan® or enterolactone in concentration 1 µM for 5 days had no effect on cell proliferation. Pre-incubation with Knotolan® or enterolactone for 2 days followed by incubation with E2 did not stimulate cell proliferation. The capacity of Knotolan® to abolish the growth stimulating effect of E2, i.e. to exhibit its antiestrogen properties was similar to the effect of enterolactone. We hypothesized that this effect can be realized in vivo and Knotolan® from Abies sibirica can serve as basis for the creation of new plant preparation with protective properties. Disclosure All authors have declared no conflicts of interest.