The role of TLR-4 in chemoresistance of cancer.

Chemotherapy, which aims to eradicate tumor cells and enhance patient survival, is a prevalent approach for tumor treatment. Nevertheless, recurrence and drug resistance resulting from consecutive chemotherapy regimens have emerged as significant factors contributing to the high fatality rates among cancer patients. Numerous studies have revealed that chemicals discharged by injured and deceased cells can trigger the host repair program mediated by toll-like receptor-4 (TLR-4), enhancing tumor resistance. TLR-4 is not only expressed in immune cells but also in various malignant tumor cells, especially inflammation-associated tumor cells, and plays a crucial role in tumor formation, development, and chemoresistance. Endogenous ligands are released upon the killing of tumor cells by chemotherapy drugs, binding to and activating TLR-4, subsequently activating downstream NF-κB and other essential molecules, leading to the release of multiple factors associated with tumor proliferation and invasion, creating a microenvironment conducive to local recurrence and metastasis, and promoting tumor progression and drug resistance. This review assessed studies on the resistance of several tumor cells to commonly utilized anticancer treatments induced by TLR-4 to better comprehend the phenomena and mechanism of TLR-4-dependent resistance, as well as to put forward suggestions and insights for overcoming tumor resistance.