Induction of Potent Antitumor Immunity by Sustained Release of Cationic Antigen from a DNA‐Based Hydrogel with Adjuvant Activity

Abstract

Previous studies indicate that immunostimulatory DNA‐based injectable hydrogels harboring unmethylated cytosine‐phosphate‐guanine (CpG) dinucleotides meet the requirements of an effective antigen delivery system, including safety, biodegradability, ease of administration, and stimulation of the innate immune system. However, rapid release of the model antigen ovalbumin (OVA) from the hydrogel limits its potential. Here, the aim is to achieve sustained OVA release from a DNA hydrogel through cationization of the antigen. Ethylenediamine (ED)‐conjugated cationized OVA (ED‐OVA), but not OVA, forms a complex with hexapod‐like structured DNA, a component of the DNA hydrogel. The release of ED‐OVA from the hydrogel is significantly slower than that of OVA. ED‐OVA mixed with CpG DNA hydrogel efficiently binds to mouse dendritic DC2.4 cells and results in high antigen presentation. Intratumoral injections of ED‐OVA/CpG DNA hydrogel significantly delays tumor growth of OVA‐expressing EG7‐OVA cells in mice. Then, a cationic OVA peptide antigen (R8‐L2‐pepI) consisting of an OVA MHC class I epitope, octaarginine, and a linker is designed. Intratumoral injections of R8‐L2‐pepI/CpG DNA hydrogel eradicate tumors in five out of six mice. Thus, it is concluded that a vaccine consisting of immunostimulatory CpG DNA hydrogel and cationized antigens can be effective for cancer immunotherapy.

Tailoring Biomaterials for Cancer Immunotherapy: Emerging Trends and Future Outlook

“…[80,81] Besides cancer cells, the TME includes blood vessels, tumor-infiltrating immune cells, [8,[82][83][84] fibroblasts, [85] tumor-associated macrophages (TAMs), [86] myeloid-derived suppressor cells (MDSCs), [87] signaling molecules, and the extracellular matrix (ECM). [90][91][92][93][94][95][96][97][98] For example, Liao et al [92] developed tumor-targeting liposome nanoparticles loaded with a signal transducer and an activator of transcription 3 (STAT3) inhibition. [88,89] Modulation of the TME by cytokines and inhibitory molecules can significantly enhance anti-cancer immunity.…”

“…[104] However, the rapid loss of CpG ODNs from the injection site (intratumoral/peritumoral) resulted in limited antitumor effects. [94] Cationized OVA, or cationic OVA peptide antigen (R8-L2-pepI), was electrostatically encapsulated into the CpG-encoded DNA hydrogel. After intratumoral injection of such CpG ODN, the researchers measured a higher local concentration of CpG ODN within the TME over a prolonged period of time with improved anti-tumor activity.…”

“…To prolong CpG ODN retention at tumor sites, CpG was modified with a diacyl lipid that could be inserted into cell membranes for in vivo anchoring to tumor cells. [94] CD137 is another co-stimulatory immune molecule expressed by activated T cells. [91] In another study, PEGylated liposomes bearing CpG in combination with APC-stimulating anti-CD40 were injected intratumorally into the B16F10 melanoma-bearing murine model.…”

Nucleic Acid Drugs and DNA-based Delivery Systems

“…Keywords: Nucleic acid drug, DNA-based delivery system (5,6). The physicochemical and biological properties of this DNA hydrogel can be modulated through the use of chemically modified nucleotides, which would greatly increase its therapeutic potency and, inevitably, the cost of its synthesis.…”

Biomaterials for enhancing anti-cancer immunity

“…This produced an increase in median survival in a B16-F10 model (45 days with anti-CD40/CpG liposomes vs 35 days with soluble anti-CD40/CpG vs 19 days with PBS treatment), while diminishing systemic dissemination of these immunostimulants and reducing toxicity compared to soluble formulations. Recently, cationized protein or peptide antigens was electrostatically associated with a DNA hydrogel containing CpG sequences and delivered to the TME [48]. The intrinsic adjuvant activity of the CpG sequences in the hydrogel and controlled release of cationic peptide antigen at the site of ovalbumin-expressing EG.7 lymphoma tumors resulted in an increased fraction of surviving mice (~65% with cationized peptide/CpG-gel vs. ~15% with native peptide/CpG-gel vs. 0% with cationized peptide/ G p C -gel).…”