Ozone-loaded Pt(IV) prodrug self-assembled micelles with high bioavailability, low toxicity as a novel irradiation-controlled release treatment and the immune microenvironment editor for triple-negative breast cancer.

Abstract

e12575 Background: A considerable part of TNBC shows poor response to the immune checkpoint blockades (ICBs) due to the immunosuppressive microenvironment. Chemotherapy performs well in synergizing with ICBs by improving tumor immunogenicity or eliminating the immunosuppressive tumor microenvironment. However, limited bioavailability, significant systematic toxicity and immunosuppressive metastatic niche induced by chemotherapy restrict its systematic application. Methods: We constructed the Pt(IV)-prodrug self-assembled micelles of O3_PFD@PtF with an ozone-loaded perfluorodecalin as the core (O3_PFD), and Pt(IV)-fluorocarbon chains assembled micelle as the shell (PtF). Results: The particle sizes of the prodrug were about 130.5 nm of PFD@PtF and 174.7 nm of O3_PFD@PtF, and both of the two showed good stability in the environment of different pH value and temperature. The Pt(IV) in the prodrug can be reduced and released in the sodium citrate solution. In addition, ozone was well stabilized by the PFD@PtF as the ROS donor and decomposed rapidly upon the irradiation excitation. O3_PFD@PtF boosted the level of GSH by promoting the intracellular redox balance with ROS and then the Pt(IV) was reduced to Pt(II) to release only within tumor. The prodrug was efficiently endocytosed into TNBC cells. Compared to cisplatin, a higher amount of Pt(II) was detected inserted into DNA in the O3_PFD@PtF combining irradiation treating group, which was released through depleting GSH donated by ROS. Accordingly, a remarkable reduction in IC50 was recorded in TNBC cells when O3_PFD@PtF was applied synergizing with irradiation. Furthermore, a relatively low IC50 was detected in non-ozone loaded prodrug-treated TNBC cells, which was attributed to the high concentration of background GSH, whereas the IC50 of PtF in Hacat was significantly higher than in other treating groups due to the low concentration of background GSH. Excellent inhibiting rates of the TNBC cells proliferation were observed in O3_PFD@PtF plus irradiation group 96 hours after treating, outperforming the conventional cisplatin plus irradiation group. We also observed a medium proliferation rate of TNBC cells in O3_PFD@PtF treating group in the absence of irradiation, which may be attributed to the Pt(II) released by the automatic decomposition of ozone. More importantly, cisplatin was reported to induced immunogenic cell death when synergizing with irradiation, but not alone. The dual potential to enhance TNBC proliferation inhibition and edit its immune microenvironment are now continuously detected. Conclusions: As a novel nano-prodrug with high efficiency and safty, O3_PFD@PtF plus irradiation is expected to improve the response of TNBC to ICBs by editing the tumor immune microenvironment.