# Gold-incorporated hyaluronic acid nanoparticles enhance ablative radiotherapy efficacy in lung cancer

## TL;DR

Gold-containing hyaluronic acid nanoparticles improve lung cancer radiotherapy by boosting tumor control and immune response.

## Contribution

Au/HA nanoparticles enhance ablative radiotherapy by inducing immunogenic cell death and modulating the tumor microenvironment.

## Key findings

- Au/HA NPs increased radiation-induced DNA damage and G2/M phase arrest in lung cancer cells.
- Combination therapy induced immunogenic cell death and increased infiltration of immune cells like NK and CD8+ T cells.
- Au/HA NPs accumulated specifically in tumors with no observed toxicity.

## Abstract

We aimed to investigate the utility of Au-incorporated hyaluronic acid nanoparticles (Au/HA NPs) for improving the therapeutic efficacy of ablative radiotherapy (RT) for tumor control and microenvironment remodeling. HA-functionalized NPs exhibited uniform size, stability, and efficient SN38 encapsulation. Au incorporation increased NP diameter and reduced surface charge while remaining stable. HA and Au/HA NPs were efficiently internalized by lung cancer cells, with free HA pretreatment suppressing internalization. Moreover, Au/HA NP internalization strongly downregulated CD44 expression in lung cancer cells, confirming CD44-mediated internalization. In vitro, Au/HA NPs enhanced radiation-induced G2/M phase arrest and γH2AX foci formation with increased DNA double-strand breaks. Au/HA NPs and RT induced immunogenic cell death (ICD) in lung cancer cells, characterized by elevated reactive oxygen species, increased calreticulin surface expression, and extracellular adenosine triphosphate release. Tumor control, survival, immune infiltration, and systemic effects were investigated in vivo using A549 xenografts and Lewis lung carcinoma synchronous flank-lung tumor models. Au/HA NPs and ablative RT decreased tumor growth, reduced lung tumor burden in non-irradiated areas, and prolonged survival. This therapeutic combination led to increased infiltration of natural killer (NK), NK T, CD8+ T, and dendritic cells and decreased regulatory T cells, suggesting robust immunological activation. Biodistribution studies confirmed CD44-targeted tumor-specific NP accumulation. No substantial toxicity was observed. In conclusion, Au/HA NPs and ablative RT induced ICD in vivo. Au/HA NPs enhanced local and systemic immunity via radiosensitization and ICD. This NP-assisted approach may improve RT efficacy in lung cancer.

Schematic overview of the synergistic effects of gold (Au)-incorporated hyaluronic acid (HA) nanoparticle (Au/HA NPs) combined with ablative ionizing radiation in enhancing antitumor immunity. Au/HA NPs are synthesized using a lyophilization–rehydration approach. Upon intravenous administration, these NPs preferentially accumulate in tumors. When combined with ablative ionizing irradiation, Au/HA NPs enhance local cytotoxicity and increase the generation of reactive oxygen species (ROS), thereby promoting immunogenic cell death (ICD). This process triggers the release of damage-associated molecular patterns (DAMPs), including calreticulin (CRT) and ATP, which activate immature dendritic cells (iDCs) and drive their maturation into antigen-presenting mature dendritic cells (mDCs). The resulting presentation of tumor-associated antigens facilitates the recruitment and activation of tumor-infiltrating immune cells (TIIs), including T cells, NK cells, and NKT cells, both at the primary tumor site and in distant tumors, thereby augmenting systemic antitumor immune responses.

Abbreviations: HSA, human serum albumin; HA, hyaluronic acid; NK, natural killer cell; NKT, natural killer T cellUnlabelled Image

•Au/HA NPs demonstrate radiotherapy-enhanced tumor control and immune response.•Au incorporation altered the NP size and charge while maintaining stability.•CD44-mediated uptake is confirmed by downregulated CD44 expression.•Combination therapy induced ICD and boosted local/systemic immunity.•Biodistribution showed tumor-specific NP accumulation with no toxicity.

Au/HA NPs demonstrate radiotherapy-enhanced tumor control and immune response.

Au incorporation altered the NP size and charge while maintaining stability.

CD44-mediated uptake is confirmed by downregulated CD44 expression.

Combination therapy induced ICD and boosted local/systemic immunity.

Biodistribution showed tumor-specific NP accumulation with no toxicity.