Downregulation of A2AR by siRNA loaded PEG-chitosan-lactate nanoparticles restores the T cell mediated anti-tumor responses through blockage of PKA/CREB signaling pathway

Adenosine and its receptors are novel promising targets for cancer immunotherapy. In here, we aimed to evaluate the efficacy of Polyethylene glycol (PEG)-chitosan-lactate (PCL) nanoparticles (NPs) loaded with A2AR-specific siRNA for interfering with differentiation and function of T cells derived from the 4T1 breast tumor-bearing Balb/C mice, ex vivo. The size of synthesized NPs was about 100 nm in association with low polydispersive index (pdi < 0.3) and a zeta potential of 11 mV. In association with good physicochemical characteristics, NPs exhibited high transfection efficiency in T cells and low toxicity on the various cell lines. T cells were treated with A2AR siRNA-loaded NPs demonstrated suppressed expression of A2AR which was associated with increased proliferation, reduced apoptosis, increased production of inflammatory and reduced secretion of inhibitory cytokines compared to untreated T cells. Moreover, differentiation of conventional T cells purified from tumor-bearing mice to regulatory T cells (Treg) was blocked using A2AR-specific siRNA-loaded NPs. These immune-stimulatory effects were in part through downregulation of protein kinase A/cAMP-response element binding protein (PKA/CREB) axis and upregulation of nuclear factor-κB (NF-κB).