الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Methyl paraben (MP) is one of endocrine disrupting chemicals that exhibits an estrogenic effect which contribute to unusual cargo of estrogen signaling in the human breast with subsequent intensification in the risks for development of breast cancer. The definite exposure along with the safe concentrations are up till now not well established. The human breast adenocarcinoma cell line MCF-7 is used as a standard model for in vitro cancer research.
Tamoxifen citrate is a known nonsteroidal agent that has established powerful antiestrogenic properties in animal test systems. It is a selective estrogen-receptor modulator (SERM) that inhibit the growth of breast cells. Ellagic acid is a natural phenol antioxidant found in several fruits and vegetables. The antiproliferative and antioxidant properties of ellagic acid have provoked research into its possible health benefits.
The aim of the present study was to determine the toxicological effect of MP on the behavior of MCF-7 breast cancer cells and to evaluate the potential antagonizing effects of Tamoxifen and ellagic acid on stimulated breast cancer cells by MP.
The study elaborated five days exposure of cultured MCF-7 breast cancer cells to seven concentrations of MP, ranging from 40 to 800 µM. The cell viability and proliferation were correspondingly assessed using crystal violet assay and flow cytometric analysis for expression of Ki-67 proliferative marker confirmed by Realtime PCR. Moreover, the estradiol (E2) secretion and oxidative stress markers were also measured and evaluated in correlation to the proliferation and cytotoxicity capacities of MP.
Furthermore, the IC50 of both ellagic acid and tamoxifen were determined before co-incubation with the highest dose of MP to explore their counteracting effects, after five days of MP incubation on MCF7 cells IC50 of EA and Tam were added for successive three days. The consequences of co-incubation with both antiestrogenic agents and the degree of inhibition of stimulation by MP were evaluated by Crystal violet technique and flow cytometry assay of Ki-67 expression with estimation of estradiol level in culture media.