Gradient tumor microenvironment-promoted penetrating micelles for hypoxia relief and immunosuppression reversion in pancreatic cancer treatment.

The tumor microenvironment of pancreatic ductal adenocarcinoma (PDAC) is the main block for the penetration of chemotherapy. In the tumor microenvironment, a dense matrix composed of fibrin is formed on the exterior, while the interior is featured by high reduction, hypoxia and low pH. How to match the special microenvironment to on-demand drug release is the key to improve chemotherapeutic efficacy. Herein, a microenvironment-responsive micellar system is developed to deepen tumoral penetration. Briefly, the conjugation of a fibrin-targeting peptide to PEG-poly amino acid has been utilized to achieve accumulation of micelles in the tumor stroma. By modification of micelles with hypoxia-reducible nitroimidazole which becomes protonated under acidic conditions, their surface charge is more positive, facilitating deeper penetration into tumors. Paclitaxel was loaded onto the micelles via a disulfide bond to enable glutathione (GSH)-responsive release. Therefore, the immunosuppressive microenvironment is relived through the alleviation of hypoxia and depletion of GSH. Hopefully, this work could establish paradigms by designing sophisticated drug-delivery systems to tactfully employ and retroact the tamed tumoral microenvironment to improve the therapeutic efficacy based on understanding the multiple hallmarks and learning the mutual regulation. STATEMENT OF SIGNIFICANCE: Tumor microenvironment(TME) is an unique pathological feature of pancreatic cancer and an inherent barrier to chemotherapy. Numerous studies regard TME as the targets for drug delivery. In this work, we propose a hypoxia-responsive nanomicellar drug delivery system that aiming hypoxia TME of pancreatic cancer. The nanodrug delivery system could respond to the hypoxic microenvironment and enhance the penetration of the inner tumor at the same time preserving the outer tumor stroma, thus achieving targeted treatment of PDAC by preserving the integrity of the outer stroma. Simultaneously, the responsive group can reverse the degree of hypoxia in TME by disrupting the redox balance in the tumor region, thus achieving precise treatment of PDAC by matching the pathological characteristics of TME. We believe our article would provide new design ideas for the future treatments for pancreatic cancer.