Augmentation of Radiotherapy Using a Novel Loco-regional Hydrogel Based Radiosensitizer Delivery Platform for Head and Neck Squamous Cell Carcinoma

Abstract

Head and neck cancers are one of the major causes of morbidity and mortality globally. Concurrent chemoradiation is a definitive treatment for majority of locoregionally advanced head and neck squamous cell carcinomas (HNSCC). However, it is associated with dose dependent side effects on normal tissues due to systemic absorption. Though numerous radiosensitizers are being used clinically to lower the therapeutic dose of radiotherapy, their dose associated toxicities, low circulation half-life and bioaccumulation at target site limits the use. Hence, we developed a novel low cost mucoadhesive nanoparticle-in-hydrogel platform for the loco-regional delivery of synergistically acting dual radiosensitizers for the treatment of HNSCC. Dual nanoparticles containing hydrogel (DN-H) was characterized in terms of size, surface charge, encapsulation efficiency, release profile and visco-elastic behavior. Biocompatibility and immunogenicity studies were performed on mouse fibroblast L929 and human THP-1 cells respectively. In vitro efficacy of the formulation was evaluated on malignant AW8507 sublingual squamous cells using cell viability assay, Annexin-V apoptosis assay, Gamma H2AX assay and cell cycle analysis. In vivo biodistribution, efficacy and survival studies were performed on subcutaneous oral cancer xenograft bearing NOD-SCID mice. Dual nanoparticles of size 150-220 nm exhibiting sustained release profile of respectively loaded radiosensitizers were encapsulated into an injectable, viscoelastic and sheer thinning hydrogel. Blank DN-H was found to be biocompatible and non-immunogenic with no elicitation of IFN-ɣ and IL-6 cytokine. In vitro efficacy study showed ∼57-fold reduction in the IC50 when cells were treated with DN-H along with radiation as compared to free drug combination. Effect of DN-H on AW8507 cell cycle revealed the enhanced progression of cells previously arrested in S-G2 phase into early and late apoptotic phase due to increased generation of double stranded DNA nicks upon irradiation as compared to single radiosensitizer containing formulation and non-irradiated controls. In vivo biodistribution of both the radiosensitizers showed a preferential accumulation at the tumor site over a period of 72 hours as compared to other organs reflecting the improvement in mice survival. In vivo efficacy study revealed ∼11-fold, ∼5-fold, and ∼3-fold enhanced tumor inhibition in mice treated with DN-H along with radiation as compared to untreated control, only radiation treated control, and marketed systemic formulation treated controls respectively. Based on profound preclinical evaluations, developed nanoparticle-in-hydrogel system exhibits a promising and efficacious strategy over conventional chemoradiotherapy of HNSCC.