A Strategy of Killing Three Birds with One Stone for Cancer Therapy through Regulating the Tumor Microenvironment by H₂O₂-Responsive Gene Delivery System

Abstract

Constructing an efficient in vivo gene delivery system has always been extremely challenging. Herein, a highly efficient H₂O₂-responsive in vivo polycationic gene delivery system is developed for the first time. The efficient vector PLL-RT (i.e., polylysine grafted with <i>p</i>-tosyl-l-arginine) is used to mediate plasmid DNA (pDNA) delivery, and H₂O₂-responsive thioketal dipropanedioic acid-modified dextran (TDPAD) is used as a shielding system for effectively coating vector/pDNA polyplexes. The constructed gene delivery system exhibits a prolonged circulatory half-life in vivo and accelerates the accumulation of vector/DNA polyplexes in tumor tissue by the enhanced permeability and retention (EPR) effect. Moreover, this gene delivery system exhibits highly efficient and synergistic antitumor effects through a strategy of killing three birds with one stone. First, upon the arrival of TDPAD/PLL-RT/pDNA [abbreviated as T(PD)] at the tumor site by the EPR effect, TDPAD reacts with excess H₂O₂ in tumor tissue, contributing to the detachment of TDPAD, and PLL-RT then mediates the enhanced endocytosis of pDNA encoding shVEGF and significantly downregulates the expression of vascular endothelial growth factor (VEGF) in tumor tissue, exhibiting an outstanding antitumor effect. Second, the H₂O₂ consumption by TDPAD significantly decreases the H₂O₂ level in tumor tissue, which synergistically suppresses tumor growth. Third, small-molecule product mercaptopropionic acid, generated by the reaction of TDPAD with H₂O₂, can induce cancer cell apoptosis and exert pronounced antitumor efficacy. This polycationic gene delivery system shows negligible toxicity in vitro and in vivo. This strategy provides an ideal platform for constructing an efficient in vivo gene delivery system and has bright prospects for cancer therapy.