الفهرس 
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Abstract
Cancer is driven by genetic and epigenetic changeswhich allow cells to escape from the apoptosis mechanisms and continue to proliferate uncontrollably, which leads to increased mass oftumor. Therefore inducing apoptosis in tumer cells without affecting the normal cells is a major process for controlling cancer development and progression.
In this study, The efficacy of BetA in MCF-7 and triple-negative breast carcinoma MDA-MB-231 cell lines was investigated. Bet A has been used totreat human diseases including cancer for thousands of years because ofits wide range of biological properties.Which interplay between; the induction of cell cycle arrest, inhibition of angiogenesis, inhibition of topoisomerase I and II function,down-regulate (Sp) transcription factors, Inhibition of NF-κB signaling pathway and overcoming multidrug resistance (MDR).In addition, studies have demonstrated that BA selectively acts ontumor cells, not normal cells.
To achieve our aim, cell viability and cytotoxicity by MTT, cell cycle analysis by flow cytometry as well as apoptotic analysis by annexin were performed in breast cancer cell lines MCF-7 and MDA-MB-231 treated with BA.Also, we tried to explore whether the apoptotic potential of BA is proceeding via modulation of the gene expression of zinc finger protein Kaiso and its targets i.e. as oncogene c-myc as well as the tumor suppressor gene p16 which regulate and subsequently induce cell death in breast cancer cell lines
MCF-7 and MDA-MB-231. The effect of BA on the methylation status of oncogene c-myc and tumor suppressor gene p16was detected by MSP. Since their epigenetic alterations by methylation affect their regulation by Kaiso, we also studied its gene expression by RT-PCR.
Our results confirmed the cytotoxic activity of betulinic acid on MDA-MB-231 and MCF-7 cell lines, with more sensitivity of MCF-7 to BA than MDA-MB-231.
Our data also revealed that BA promotes the arrest of breast cancer cells at the G0 / G1 phase and forces cells to proceed to irreversible late apoptosis at a lower dose for MCF-7 compared to that needed for the same effect in MDA-MB-231.
By measuring kaiso mRNA expression levels, we observed that IC50 treatment with MCF-7 induces overexpression of Kaiso (14-fold) vs (9-fold) in MDA-MB-231, respectively , indicating that Kaiso acts as a tumor suppressor because its overexpression was parallel to BA cytotoxicity on MCF-7 and MDA-MB-231.
Finally, after analyzing the DNA methylation status within the p16 and c-myc promoter by methylation-specific PCR;we observed the hypermethylation of c-myc and the hypomethylation stronger in MCF-7 upon treatment with 10%IC50 and IC50 compared to these effects in MDA-MB-231. Which indicate that BA may be a crucial modulator of breast cells proliferation and differentiation via modulation of methylation status of the targets of Kaiso; c-myc and p16 in human breast cancer cell lines, MCF-7 and MDA-MB-231 cells.