Enhancing the radiosensitivity of Glioblastoma using Hedgehog (Hh) antagonising gold nanoparticles

Among these, the Hedgehog (Hh) signaling pathway plays a fundamental role in regulating cellular proliferation, differentiation, and tissue patterning during embryonic development. Although largely quiescent in normal adult tissue, aberrant reactivation of Hh signaling is linked to the initiation and progression of multiple malignancies, including GBM. Activation of the smoothened (SMO) receptor drives downstream transcriptional cascades that promote tumour growth and survival.

Consequently, inhibition of SMO represents a potential strategy for disrupting oncogenic Hh signaling in GBM.<br><br>In parallel, the development of high atomic number (high-Z) nanomaterials have emerged as a promising approach to enhance the efficacy of radiotherapy through radiosensitisation. Gold nanoparticles (AuNPs) have attracted considerable attention due to their favourable physicochemical properties, biocompatibility, and ability to amplify radiation-induced energy deposition within tumour cells.

This project proposes a dual-functional therapeutic strategy that integrates molecular pathway inhibition with nanomaterial-mediated radiosensitisation. Specifically, an antagonistic lipidated peptide (pepducin) targeting the SMO receptor was conjugated to the surface of AuNPs to generate a novel nanoparticle termed AuXSMO.<br><br>Initial studies demonstrated the ability of the pepducin (SMOi2-8) to inhibit the downstream regulators of Hh signaling, GLI-1 and GLI-2, at both mRNA level and protein levels using several GBM cancer cell models (U251 MG, U87 MG, T98G).

Additionally, we report that combined treatment of ionising radiation (IR) and SMOi2-8 inhibited tumoursphere growth in 3D GBM tumoursphere models. Subsequently, we successfully developed a novel AuNPs formulation (AuXSMO), demonstrated favourable characteristics in terms of size and homogeneity, and good stability. AuXSMO suppressed GLI-1/2 and cyclin D1 expression and enhanced GBM radiosensitivity.

Finally, we investigated the impact of combining AuXSMO with the currently standard treatment of GBM, demonstrating a slight synergistic radiosensitising effect in TMZ-sensitive GBM models.<br><br>In conclusion, this work demonstrates that targeting the SMO receptor with AuXSMO can enhance the effects of radiotherapy in GBM. The results indicate that AuXSMO functions as an effective radiosensitiser. Although these findings are promising, further optimisation of the formulation is required.

Collectively, this work provides a foundation for the development of targeted radiosensitisers for GBM treatment.<br><br><i>Thesis is embargoed until 31 July 2031.</i>