Cytotoxic and proapoptotic effects of alizarin in mice with Ehrlich solid tumor: novel insights into ERα-mediated MDM2/p-Rb/E2F1 signaling pathway.

The role of estrogen receptor (ER) and its related effects is crucial for growth of breast cancer cells. This study aimed to assess the cytotoxic impact of alizarin in models of breast cancer in vivo and investigate its antiestrogenic and apoptotic properties. MTT assay was used to evaluate alizarin cytotoxic effect against MCF7 and MDA-MB-231. In vivo, 30 mice were insulted with Ehrlich tumor cells. They were randomly allocated into 3 groups, 10 mice each. Alizarin was orally administered to two treatment groups (50 mg/kg and 100 mg/kg), respectively. The third group was considered as a positive control group. Western blot was used to evaluate the expression of mouse double minute 2 (MDM2), phosphorylated retinoblastoma (pRb), and E2F1. Caspase threefold change was measured by RT-PCR. ERα, Bax, and p53 expressions were investigated by immunohistochemistry. Molecular docking study of alizarin effect on ER was performed. Alizarin demonstrated dose dependent cytotoxicity against MCF7 and MDA-MB cell lines. Alizarin decreased tumor weight in mice, prompted cell cycle arrest, and stimulated cell apoptosis by impeding ERα-mediated tumorigenic effects, and inactivating its related MDM2/p-Rb/E2F1 signaling cascade with upregulation of target genes involved in cell apoptosis (Bax, caspase 3, and p53). Molecular docking proposed that alizarin is a very promising inhibitor to ER. Alizarin represented a promising approach to inhibit cell proliferation of breast cancer by modulating estrogen receptor mediated effects on MDM2/p-Rb/E2F1 axis concomitantly with activating apoptosis of cancer cells.