en Cell, Stem Cell and Cancer Cell, Stem Cell and Cancer Experimental research article Experimental research article <div style="text-align: justify;"><strong>Introduction:</strong> Recently, the therapeutic and antioxidant effects of simvastatin on 7,12-dimethylbenz[a] anthracene (DMBA) induced breast cancer have been studied. To gain further understanding of the molecular mechanisms of simvastatin, this study investigated its effects on the expression of c-myc, cyclin D1 and p53 in normal mammary glands and tumors. <strong>Methods:</strong> Female albino mice were divided into two groups: 1) N group, healthy mice without DMBA and 2) D group, mice with DMBA administration. After the appearance of tumors, D group mice are subdivided into 3 groups, as control (C), simvastatin- treated group (S) which received 80 mg/kg/day, orally and tamoxifen-treated group (T) with 50 mg/kg/day, orally. After 4 weeks, animals were sacrificed. Also, the tumors and normal mammary glands were removed for histopathological evaluations and analysis of gene expression by qRT-PCR. <strong>Results:</strong> The results showed the up-regulation of c-myc and cyclin D1 in tumors of the control group compared with mammary glands of the N group. Similar to tamoxifen, the simvastatin treatment could normalize the expression of c-myc and cyclin D1; however, the expression of p53 did not change in the treated groups. <strong>Conclusion:</strong> Down-regulation of c-myc and cyclin D1 in treated tumors with simvastatin could be a possible molecular mechanism for its therapeutic effects in DMBA-induced breast cancer in mice.</div> Breast cancer, Simvastatin, Cyclin D1, C-myc, P53. 152 158 http://ppj.phypha.ir/browse.php?a_code=A-10-1297-1&slc_lang=en&sid=1 Behnaz Karimi 3200319475328460029429 3200319475328460029429 No Division of Biochemistry, Department of Basic Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran Mahboobeh Ashrafi mashrafi@shirazu.ac.ir 3200319475328460029430 3200319475328460029430 Yes Division of Biochemistry, Department of Basic Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran Malihe Masoudian 3200319475328460029431 3200319475328460029431 No Division of Biotechnology, Department of Pathobiology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran