The Synergistic Effect of Ruthenium Complex Δ-Ru1 and Doxorubicin in a Mouse Breast Cancer Model

Background: Doxorubicin is a significant drug for the treatment of breast cancer, but its cardiotoxicity is an obvious obstacle. Previously, we confirmed that ruthenium complex (Δ-Ru1) and doxorubicin (Δ-Ru1/Dox) combination had a synergistic effect in MCF-7 cells, but its biological effect in vivo is unknown. Purposes: To find a way to overcome the toxicity of doxorubicin and build MCF-7 xenograft tumor mouse model to test whether this potential combination has better efficacy and less toxicity. Methods: The tumor model of nude mice was established to verify the synergistic antitumor effect of the drug combination in vivo. H staining was used to detect the toxicity of major organs in mice. Sirius red staining and transmission electron microscopy were used to detect cardiotoxicity. Prussian blue was used to measure iron accumulation in heart tissue. TUNEL staining was used to detect the antitumor effect in vivo. Immunohistochemical staining was used to detect the expression of iron death-related pathway proteins. High-throughput sequencing techniques were used to determine the molecular mechanism of ferroptosis. Results: Histopathological analysis of tumor tissues indicated that the Δ-Ru1/Dox combination significantly promoted tumor cell apoptosis. Doxorubicin damaged cardiac tissue by inducing fibrosis and iron accumulation, but it was reversed by the Δ-Ru1/Dox combination treatment. Further exploration found that doxorubicin could regulate iron accumulation in the ferroptosis pathway and the expression of lipid peroxidation-related proteins, including upregulation of Tf, DMT1, and HO-1, and downregulation of Nrf2, SLC7A11, and GPX4. Conclusion: Δ-Ru1/Dox combination synergistically inhibits tumor growth, and it can significantly reduce and alleviate the toxic side effects of doxorubicin, especially cardiac injury.