Doxorubicin is widely used in chemotherapy of breast cancer and many other cancers.How ever,doxorubicin resistance restricts its use to some extent.The mechanisms of doxorubicin resistance may involve transport protein,apoptosis protein,DNA repair function,enzyme and other factors.Researches about reversing doxorubicin resistance are ongoing and provide some effective therapeutic regimens to overcome doxorubicin resistance clinically.But the specific mechanism of doxorubicin resistance is yet to be elucidated.It is expected that more reasonable and effective counter-measures will be put forward to improve the theraputical effect of doxorubicin.

Immunotherapy has become a highly promising paradigm for cancer treatment. Herein, a chemo-immunotherapy was developed by encapsulating chemotherapeutic drug doxorubicin (DOX) and Toll-like receptor 7 agonist imiquimod (IMQ) in low molecular weight heparin (LMWH)-d--tocopheryl succinate (TOS) micelles (LT). In this process, LMWH and TOS were conjugated by ester bond and they were not only served as the hydrophilic and hydrophobic segments of the carrier, but also exhibited strong anti-metastasis effect. The direct killing of tumor cells mediated by DOX-loaded micelles (LT-DOX) generated tumor-associated antigens, initiating tumor-specific immune responses in combination with IMQ-loaded micelles (LT-IMQ). Furthermore, the blockade of immune checkpoint with programmed cell death ligand 1 (PD-L1) antibody further elevated the immune responses by up-regulating the maturation of DCs as well as the ratios of CD8 CTLs/T and CD4 T/T. Therefore, such a multifunctional strategy exhibited great potential for inhibiting the growth of orthotopic and metastatic breast cancer.