Hydroxyethyl Starch Nanoparticles Disrupt Redox Homeostasis Of Cancer Stem Cells For Cancer Therapy

Triple-negative breast cancer(TNBC)remains a great clinical challenge with its heterogeneous,aggressive nature and lack of effective receptor molecules(such as estrogen receptors)for targeted therapy.Although the prognosis of chemotherapy is often accompanied by drug resistance,metastasis and recurrence,chemotherapy remains the main treatment modality for TNBC patients at present.Cancer stem cells(CSCs)are thought to be responsible for the progression,recurrence and metastasis of many malignancies due to their high tumorigenicity,aggressiveness and resistance to conventional chemotherapy and radiotherapy.Therefore,the eradication of CSCs is the key to treat TNBC and improve the prognosis and survival rate of TNBC patients.CSCs only contain low levels of ROS,which mainly maintains the ability of CSCs to self-renew,initiate tumor and resist chemotherapy and radiotherapy.Therefore,increasing the intracellular ROS level by disrupting the redox balance to regulate the self-renewal of CSCs is a very promising approach for cancer therapy.In this study,a hydroxyethyl starch(HES)nanodrug delivery system is prepared to codeliver the redox regulator erastin with the chemotherapeutic drug Doxorubicin(Dox)for investigating the effect of combined therapy on the clearance of breast CSCs.Furthermore,the effect of erastin on the antitumor activity of Dox was also investigated.The main studies and results are as follows:(1)Dox-erastin@PCL-HES nanoparticles(DEPH,NPs)were prepared and charactered.The study of the interaction between the redox regulator erastin and the chemotherapeutic drug Dox revealed a significant synergistic effect of Dox and erastin in killing cancer cells as well as CSCs.The synergistic mechanism between Dox and erastin was elucidated for the first time.Erastin not only increased the intracellular Dox accumulation by inhibiting Dox efflux,but also promoted the oxidative stress induced by Dox.The optimal synergistic ratio of Dox to erastin was calculated to be 2/1,and this ratio was selected for the preparation of nanoparticles.HES coupled with PCL was used to codeliver Dox and erastin and DEPH NPs were prepared.DEPH NPs were spherical in shape with homogeneous particle size and good stability.The optimal synergistic ratio of Dox to erastin was maintained during delivery and after durgs release.(2)In vitro,DPEH NPs not only increased the amount of Dox accumulation in tumor cells and CSCs,but also enhanced intracellular oxidative stress.With the enhancement of intracellular oxidative stress,DEPH NPs induced cancer cells apoptosis.DEPH NPs also induced large amouts of ROS accumulated in CSCs,and the high levels of ROS inhibited the self-renewal of CSCs by suppressing Hedgehog(Hh)pathways and downregulating the expression of stemness-related genes Sox2,Nanog,Oct4,and Bmi1.Furthermore,high levels of ROS not only directly induced a small fraction of CSCs apoptosis,but also induced most of CSCs differentiation firstly and then induced differentiated CSCs apoptosis.DEPH NPs restrained self-renewal of CSCs,induced CSCs and cancer cells apoptosis by disrupting intracellular redox homeostasis.(3)The effects of DEPH NPs on CSCs in 4T1 cancer cells were examined using flow cytometry,soft 3D fibrin gel technique,and a mouse lung metastasis model.It was found that DEPH NPs weakened the ability of CSCs to form 3D tumor spheroids as well as reduced the number of metastasis nodules in mouse lungs by decreasing the percentage of CSCs.(4)More DEPH NPs were accumulated at the tumor compared to Dox-erastin,and DEPH NPs also significantly reduced the side effects induced by Dox-erastin.In the 4T1 subcutaneous tumor mouse model and lung metastasis model,DEPH NPs not only inhibited tumor growth and prolonged the survival of mice,but also significantly reduced the number of metastatic nodules in the lung.Flow cytometry revealed that DEPH NPs reduced the amount of CSCs in tumor tissues and peripheral blood by increasing the oxidative stress of CSCs.Reduction of CSCs enhanced the anti-tumor activity of DEPH NPs and inhibited the formation of pulmonary metastatic nodules.In conclusion,the strategy of disrupting the redox homeostasis of CSCs by co-delivery redox regulators and chemotherapeutic agents can effectively eliminate CSCs and cancer cells and enhance antitumor efficacy.This stategy provides a promising therapeutic approach for the treatment of CSCs-rich solid tumors including TNBC.