Synergistic Enhancement of Apo2L/TRAIL and DR4-Induced Apoptosis by Arsenic Trioxide in Triple-Negative Breast Cancer Cells: A Comparison to Conventional Chemotherapy

Abstract

Triple-negative breast cancer (TNBC) is an aggressive subtype lacking hormonal and HER2 receptors, making it highly resistant to treatment. Apo2L/TRAIL, a tumor necrosis factor-related ligand, induces apoptosis in cancer cells via the death receptor DR4. However, TNBC often develops resistance to TRAIL-mediated apoptosis, limiting its therapeutic potential. This study investigates whether arsenic trioxide (ATO) can overcome TRAIL resistance by modulating the Apo2L/TRAIL pathway and enhancing the effects of carboplatin (CP) and cyclophosphamide (CY). TNBC cell lines BT-20 and MDA-MB-231 were treated with ATO, CP, CY, and their combinations. Cell viability was measured using the MTT assay, while real-time PCR and Western blot analysis assessed Apo2L/TRAIL and DR4 expression. Statistical analysis was performed using ANOVA with Dunnett's post hoc test. ATO induced dose-dependent cytotoxicity in TNBC cells, which was significantly enhanced in combination treatments. The highest reductions in cell viability were observed with 3 µM ATO plus 5000 µM CP or 500 µM CY (p < 0.0001). ATO markedly upregulated Apo2L/TRAIL and DR4 at both mRNA and protein levels, with the most pronounced effects seen in ATO-CY combinations. These findings indicate that ATO sensitizes TNBC cells to TRAIL-mediated apoptosis by upregulating DR4 and Apo2L/TRAIL, while also exhibiting strong synergistic cytotoxicity with CP and CY. This highlights ATO's potential as an adjuvant therapy to improve TNBC treatment efficacy and overcome chemoresistance, warranting further clinical exploration.

Keywords: Apo2L/TRAIL; Arsenic trioxide; Breast cancer therapy; Synergistic apoptosis; Triple-negative breast cancer.