Synergistic effects and competitive relationships between DOC and DOX as acting on DNA molecules: Studied with confocal Raman spectroscopy and molecular docking technology

Docetaxel (DOC) is one of the second-generation antineoplastic drugs of the taxanes family with excellent antitumor activity. However, the mechanism of DOC inducing tumor cell apoptosis and treating cancer diseases, especially its interaction with DNA in the nucleus, and its adjuvant or combined Doxorubicin (DOX) acting on DNA molecules are unclear. In this study, the interaction mechanism between DOC and DNA, as well as the synergistic effects and competitive relationships among DOC and DOX when they simultaneously interact with DNA molecules were studied by laser confocal Raman spectroscopy combined with UV-visible absorption spectroscopy and molecular docking technology. The spectroscopic results showed that the binding constant of DOC to DNA is 5.25 × 10³ M^-1, the binding modes of DOC and DNA are non-classical intercalation and electrostatic binding, and the DNA-DOC complex has good stability. When DOC or DOX interacts with DNA alone, both of them can bind with bases and phosphate backbone of DNA, and also lead to DNA conformation changes; when DOC and DOX interact with DNA at the same time, the orders of interaction not only affect their binding sites with DNA, but also cause changes in the surrounding environment of the binding sites. In addition, the molecular docking results further verified that DOC and DOX have synergy and competition when they interact with DNA molecules simultaneously. The docking energies of DNA-DOC and DNA-DOX indicate the important role of van der Waals forces and hydrogen bonds. This study has practical significance for the design and development of antitumor drugs with less toxic based on the taxanes family and the combination with other drugs for the treatment of cancer.