Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 18 2 2024 04 16 174 182 Hassan Dariushnejad 1) Department of Medical Biotechnology, Faculty of Medicine, Lorestan University of Medical Sciences, Khorramabad, Iran 2) Cardiovascular Research Center, Shahid Rahimi Hospital, Lorestan University of Medical Sciences, Khoramabad, Iran Neda Roshanravan Cardiovascular Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Hunar Mustafa Wasman Medical Laboratory science department, University of Raparin, Kurdistan Region, Iraq Mostafa Cheraghi Cardiovascular Research Center, Shahid Rahimi Hospital, Lorestan University of Medical Sciences, Khoramabad, Iran Lale Pirzeh Cardiovascular Research Center, Shahid Rahimi Hospital, Lorestan University of Medical Sciences, Khoramabad, Iran Vajihe Ghorbanzadeh Cardiovascular Research Center, Shahid Rahimi Hospital, Lorestan University of Medical Sciences, Khoramabad, Iran 2022 09 12 2023 10 02 Background: Triple-negative breast cancer (TNBC) with a poor prognosis and survival is the most invasive subtype of breast cancer.  Usually, TNBC requires a chemotherapy regimen at all stages, but chemotherapy drugs have shown many side effects. We assumed that combination therapy of vinblastine and silibinin might reduce the vinblastine toxicity and dose of vinblastine. Materials and Methods: The MDA-MB-231 were cells subjected to MTT assay for IC50 determination and combination effects, which were measured based on  Chou-Talalay's method. The type of cell death was determined by using a Flow-cytometric assay. Cell death pathway markers, including Bcl-2, Bax, and caspase-3 were analyzed by western blot and Real-Time PCR. Results: The treatment of MDA-MB-231 cells exhibited IC50 and synergism at the combination of 30 µM of silibinin and 4 µm of vinblastine in cell viability assay (CI=0.69). YO-PRO-1/PI double staining results showed a significant induction of apoptosis when MDA-MB-231 cells were treated with a silibinin and vinblastine combination (p<0.01). Protein levels of Bax and cleaved caspase-3 were significantly upregulated, and Bcl-2 downregulated significantly. Significant upregulation of Bax (2.96-fold) and caspase-3 (3.46-fold) while Bcl-2 was downregulated by 2-fold. Conclusion: Findings established a preclinical rationale for the combination of silibinin and vinblastine. This combination produces synergistic effects in MDA-MB-231 cells by altering pro- and anti-apoptotic genes, which may reduce the toxicity and side effects of vinblastine.   https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/1908 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/1908/1030