Heparanase-Responsive Biomimetic Drug Delivery System For Anti-Lung Metastasis Of Breast Cancer

Breast cancer is the threat of women's health and metastasis is the major cause of death in breast cancer patients.Currently,chemotherapy is still the main clinical choice to combat metastatic breast cancer.Unfortunately,chemotherapeutic agents always lack the targeting ability toward tumor tissues and cancerous cells,which leads to inefficient therapy and severe systemic side effects.The different microenvironment between tumor tissues and the normal ones has been exploited.The microenvironment of tumor provides multiple biological stimulus,including low pH,redox gradient,hypoxia,overexpression of enzymes,etc.,basing on which numerous bio-responsive drug delivery systems have been developed.It has been reported that the heparanase(Hpa)was the only endoglycosidase which cleaves heparan sulfate(HS)in mammalian.The expression of Hpa is elevated in most advanced cancer cells but not the normal cells around the tumor tissues.Therefore,HS can be an ideal modulator to form the prodrugs with the chemotherapeutic drugs for tumor cell-specific release of parent drugs.However,HS is composed of repeating disaccharide unities of uronic acid and highly negatively charged,which makes it prone to clearance by mononuclear-phagocyte system.The red blood cell membrane owns unique advantage of being biocompatible and non-immunogenic.In addition,the rich“self-markers”of red blood cell membrane contain the proteins that assist the nanoparticles to escape from mononuclear-phagocyte system capturing and immune attack.Herein,we first constructed red blood cell membrane coated biomimetic nanoparticles delivering chemotherapeutic agent docetaxel(DTX)for metastatic breast cancer therapy.The DTX was conjugated to HS for synthesizing Hpa-responsive prodrug HS-DTX.The HS-DTX could self-assemble into the micelles in the aqueous medium.Then red blood cell membrane coated HS-DTX by an extrusion method.The red blood cell membrane coated HS-DTX micelles forming nanoparticles,termed as rHS-DTX.The rHS-DTX maintained the long circulating property of red blood cell and could passive-targeting deliver HS-DTX to both primary tumor and the metastasis foci.After rHS-DTX entered the tumor cells,HS-DTX was released into the cytoplasm where Hpa was highly expressed.Once HS was degraded by Hpa,the free DTX was released to kill the tumor cells.While in normal cells,the HS-DTX linked together and showed low cytotoxicity.The results showed that compared with free DTX,rHS-DTX increased the concentration of DTX in tumor and lung by 5.35-fold and 8.68-fold,respectively.Meanwhile,rHS-DTX presented in situ tumor inhibition rate over 98%and reduced the formation of lung metastasis by 99.6%.In contrast with the highly toxic DTX,rHS-DTX displayed good biocompatibility.For constructing biomimetic drug delivery system that combining chemotherapy and immunotherapy,the indoleamine-2,3-dioxygenase(IDO)inhibitor NLG919 was conjugated to heparan sulfate to form Hpa-responsive prodrug HS-NLG and then encapsulated PD-1/PD-L1 inhibitor HY19991(HY)with HS-DTX to construct HDNH micelles.We chose monocytes with tumor homing and internalization capacity as the micelles carrier for enhancing the active tumor targeting ability.As a result,the Hpa-responsive micelle/monocytes biomimetic drug delivery system,termed as HDNH@MC was developed.Since monocytes were capable of homing to tumor sites,HDNH@MC could accumulated actively in the tumor tissues.DTX,NLG919 and HY were released in tumor cells since the high Hpa concentration triggered the dissociation of HS domain.Firstly,the DTX caused death of tumor cells directly and induced the tumor-associated antigen(TAA)release which stimulated immune response.Then the NLG919 inhibited the activity of IDO and reduced the concentration ratio of kynurenine(Kyn)to tryptophan(Trp).It also decreased the regulatory T cells(Tregs)amount to modulate immunosuppressive microenvironment.In addition,the HY inhibited the PD-1/PD-L1 interaction and strengthened the immune system killing to tumor cells.Assisted by the DTX,the NLG919 and HY cooperated to induce the anti-tumor immune responses in different mechanisms for improving the immunotherapy.The results showed that HDNH@MC targeted actively to the in situ tumor and lung metastatic foci.The biomimetic system destroyed tumor cells and reduced the concentration ratio of Kyn to Trp in tumor tissue.Also,the CD8~+T cell infiltration and the ratio of CD8~+T cells/Tregs in the tumor of mice treated with HDNH@MC were14.95-fold and 37.22-fold of that in the mixed free drug group,respectively.Meanwhile,the number of lung metastatic nodule in the tumor-bearing mice of HDNH@MC group decreased by 98.2%.Finally,chemotherapy/immunotherapy based on HDNH@MC effectively extended the life span of tumor-bearing animals.Focusing on the prodrug strategy,biomimetic technology and nanotechnology,we constructed heparanase-responsive prodrug micelles based on heparan sulfate.To enhance the stability and targeting delivery ability,red blood cell membrane and monocytes were utilized to encapsulate of micelles,developing biomimetic drug delivery system.Biomimetic drug delivery system could deliver drugs to tumor tissues actively or passively and cause enzyme-responsive drug release.Through the synergistic effect of chemotherapy and immunotherapy,the system could effectively inhibit the in situ growth and pulmonary metastasis of breast cancer.The biomimetic drug delivery system also presented the application potential in the treatment of metastatic breast cancer.