Pharmacological Activation of cGAS for Cancer Immunotherapy

Abstract

When compartmentally mislocalized within cells, nucleic acids can be exceptionally immunostimulatory and can even trigger the immune-mediated elimination of cancer. Specifically, the accumulation of double-stranded DNA in the cytosol can efficiently promote antitumor immunity by activating the cGAMP synthase (cGAS) / stimulator of interferon genes (STING) cellular signaling pathway. Targeting this cytosolic DNA sensing pathway with interferon stimulatory DNA (ISD) is therefore an attractive immunotherapeutic strategy for the treatment of cancer. However, the therapeutic activity of ISD is limited by several drug delivery barriers, including susceptibility to deoxyribonuclease degradation, poor cellular uptake, and inefficient cytosolic delivery. Here, we describe the development of a nucleic acid immunotherapeutic, NanoISD, which overcomes critical delivery barriers that limit the activity of ISD and thereby promotes antitumor immunity through the pharmacological activation of cGAS at the forefront of the STING pathway. NanoISD is a nanoparticle formulation that has been engineered to confer deoxyribonuclease resistance, enhance cellular uptake, and promote endosomal escape of ISD into the cytosol, resulting in potent activation of the STING pathway via cGAS. NanoISD mediates the local production of proinflammatory cytokines via STING signaling. Accordingly, the intratumoral administration of NanoISD induces the infiltration of natural killer cells and T lymphocytes into murine tumors. The therapeutic efficacy of NanoISD is demonstrated in preclinical tumor models by attenuated tumor growth, prolonged survival, and an improved response to immune checkpoint blockade therapy.

Multifunctional nanoparticle potentiates the in situ vaccination effect of radiation therapy and enhances response to immune checkpoint blockade

“…2 , 3 ). PIC may also contribute to additional mechanisms that lead to the activation of IFN-I response, such as capturing the cell-free DNA released from RT-treated cells and facilitating its internalization in immune cells to stimulate an IFN-I response 57 . This will be an important topic for further investigation on the interactions between PIC with RT in future studies.…”

Chemical and Biomolecular Strategies for STING Pathway Activation in Cancer Immunotherapy

“…In addition to Mn 2+ -encompassing therapies, DNA-based cGAS agonists that employ delivery technologies to achieve cytosolic accumulation of exogenous dsDNA can also facilitate the pharmacological activation of cGAS. Indeed, targeting cGAS activation via intracellular delivery of dsDNA has now been explored by several research teams including our group. − Notably, Garland et al developed NanoISD, a DNA-based cGAS agonist designed for use as an intratumoral immunotherapy . NanoISD is a nanoparticle formation that is assembled by complexing an exonuclease-resistant cGAS ligand ( i.e.…”

“…351−355 Notably, Garland et al developed NanoISD, a DNA-based cGAS agonist designed for use as an intratumoral immunotherapy. 355 NanoISD is a nanoparticle formation that is assembled by complexing an exonuclease-resistant cGAS ligand (i.e., 95 bp phosphorothioate-capped dsDNA) with endosomolytic polymer micelles that can simultaneously enable cytosolic delivery of nucleic acids and inhibit endonuclease degradation of loaded nucleic acids via steric interference. The resultant DNA/polymer nanoparticle complexes are ∼60−90 nm in diameter and have a positive surface charge of +14.87 mV.…”

Engineering endosomolytic nanocarriers of diverse morphologies using confined impingement jet mixing

“…[3][4][5] Many of these advances utilize pH-responsive polymers to facilitate the endosomal escape and cytosolic delivery of their therapeutic payloads. [6][7][8][9][10][11][12][13] These systems typically exploit the pH drop from 7.4 to 5.8 that occurs during endolysosomal acidification to protonate amino groups within the polymer backbone and/or side chains. As the amines become protonated, the polymer develops a netpositive charge, stimulating interaction with the negatively charged endosomal membrane.…”