The Algal Antioxidant Carotenoid Diatoxanthin as a Modulator of Inflammation and Angiogenesis in Triple-Negative Breast Cancer Cells

Algal carotenoids play a promising role in handling chronic diseases due to their diverse bioactive properties, including anti-inflammatory, antioxidant, and anticancer effects. This study assesses the activity of the antioxidant xanthophyll diatoxanthin (Dt), derived from marine diatoms, against triple-negative breast cancer (TNBC) cells using in vitro models, gene expression evaluation, and explores its role in potentiating the cytotoxic effect of chemotherapy. Dt exhibited selective activity against MDA-MB-231 and BT-549 TNBC cells at concentrations ≥12.5 ng/mL, with maximal effects observed at 25 ng/mL while sparing human umbilical vein endothelial cells (HUVECs) at these doses. When combined with doxorubicin (0.1–0.5 μM), Dt enhanced the anti-tumor efficacy in both TNBC cell lines, further reducing cell viability compared with doxorubicin alone (p < 0.05–0.001). Dt also exerted its activity in inhibiting migration and chemotaxis by approximately 30–50% compared with the controls (p < 0.01) and suppressing 3D-tumor spheroid growth at day 12 (up to >50% reduction, p < 0.001). Notably, secretome analysis revealed Dt-induced changes in inflammatory, oxidative and angiogenic mediators, highlighting its ability to modulate the TNBC microenvironment. Dt also downregulated key pro-survival, pro-angiogenic and pro-tumorigenic genes in both TNBC cell lines, supporting its role in disrupting oncogenic pathways. Angiogenesis-related genes were significantly reduced. Dt also decreased the expression of angiogenic mediators in HUVECs, supporting Dt’s role in inhibiting tumor vascularization. Results on gene expression regulation were also confirmed by RNA-Seq analysis. These findings pose Dt as a promising chemopreventing candidate in the challenging fight against TNBC, a well-known type of cancer that is aggressive and resistant to conventional therapies, targeting critical pathways for tumor survival, such as inflammation, angiogenesis, tumor cell growth, and cell migration. Given its selective activity against TNBC cells, ability to enhance chemotherapy efficacy, and modulation of the tumor microenvironment, Dt holds promise as a complementary drug for cancer prevention and interception. Future studies should focus on validating these effects in vivo and exploring Dt’s potential in combinatorial treatment strategies for cancer.