Enhanced drug release from a pH-responsive nanocarrier can augment colon cancer treatment by blocking PD-L1 checkpoint and consuming tumor glucose
Kai Guo, Yixuan Liu, Min Ding, Qi Sun, Quazi T.H. Shubhra
Abstract
In this study, it was aimed to exploit no chemical drug to treat cancer by starvation-immunotherapy combination. We used PD-L1 siRNA to down-regulate checkpoint protein PD-L1 on cancer cell surfaces, and IFN-γ was used as an immunomodulatory agent to activate the innate immune system. When PD-L1 siRNA, IFN-γ, and glucose oxidase (GOx) were co-delivered to the tumor microenvironment (TME) by a pH-sensitive drug delivery system (DDS), starvation-immunotherapy combinedly resulted in significant tumor volume reduction in a mouse model. The DDS was prepared by using PLGA polymer whose surface was coated with chitosan. IFN-γ, siRNA, and GOx entrapment efficiencies were 93.5 ± 3.1%, 65.1 ± 2.6%, and 66.2 ± 3.3%, respectively. Moreover, the size of the DDS was well below 200 nm, allowing easy sterilization and tumor accumulation by the enhanced permeability and retention (EPR) effect. In vitro pH-dependent release study indicated that in acidic pH, the developed DDS can show accelerated drug release. In a mouse model and in acidic TME, the DDS resulted in the best therapeutic effect due to pH-dependent drug release compared to unmodified DDS and free drug. Our findings reflect that high efficiency in colon cancer treatment is achieved by combination therapy over the studied monotherapies.