Self-assembled nanocomposites of carboxymethyl β-dextran/protamine sulfate for enhanced chemotherapeutic drug sensitivity of triple-negative breast cancer by autophagy inhibition via a ternary collaborative strategy

Drug resistance in cancer chemotherapy is a major confounding factor affecting the effectiveness of chemo-therapeutic agents, thereby leading to poor clinical outcomes. Most chemotherapeutic drugs can induce pro-tective autophagy and increase the resistance of tumors to chemotherapeutic drugs and reduce effective drug delivery to tumor cells. In this study, a tri-drug nanocomposite (NP) delivery system was devised using car-boxymethyl beta-dextran (CMD) and protamine sulfate (PS), two natural materials with good bio-compatibility. They were designed to carry the chemotherapeutic drug docetaxel (DTX), the autophagy inhibitor chloroquine (CQ), and Atg5 siRNA to cancer cells. The CQ + DTX + Atg5 siRNA NPs was driven by electrostatic interaction and self-assembly methods. The breast cancer cell line MDA-MB-231 was used for both cell culture and estab-lishing mouse xenograft model. Our findings demonstrated that CQ and Atg5 siRNA encapsulated in NPs could enhance the sensitivity of tumor cells to DTX. The NPs exhibited remarkable considerable therapeutic effects for treating triple-negative breast cancer (TNBC) and good biosafety. Therefore, we established a novel multifunc-tional nanoplatform based on CMD and PS that enhances chemotherapeutic drug sensitivity through an auto-phagy inhibition strategy, providing new opportunities to overcome conventional drug resistance and enhance therapeutic efficiency against TNBC.