Effects of beta-sitosterol on microtubular systems in cervical cancer cells

Abstract

To investigate beta-sitosterol's inhibitory effects on SiHa cells' growth, and the effects on microtubular system in SiHa cell. Proliferation inhibition of SiHa cell line was evaluated by MTT assay. Cell cycle of SiHa cells treated with beta-sitosterol was analyzed by flow cytometry. The expression and distribution of microtubule and microtubule associated protein 2 in SiHa cells were investigated by confocal microscopy. Immunoblotting analysis was used to determine tubulin alpha, microtubule associated protein 2, and the proportion of polymerization of tubulin. beta-sitosterol could obviously inhibit the proliferation of SiHa cells, and induce the accumulation of cells in S phase (rather than the G2/M phase) and mitotic arrest in the cell cycle. Confocal microscopy showed an abnormal microtubular network in SiHa cell treated with beta-sitosterol for 5 days, and the expression of microtubule associated protein 2 was marked down-regulated. Further analysis by immunoblotting confirmed the down-regulation of beta-sitosterol on the expression for both microtubule associated protein 2 and tubulin alpha. Moreover, beta-sitosterol reduced the proportion of polymerization of microtubule in a time-dependent manner. beta-sitosterol could down-regulate the expression of tubulin alpha and microtubule associated protein 2 in SiHa cells, and inhibit the microtubular polymerization. Our results suggested an anti-microtubule characteristic of beta-sitosterol which might contribute to the proliferation inhibition of SiHa cells.