Cytotoxic effects of hyperthermia, chemotherapy (Navelbine) and radiation on glioma spheroids

Efficient Heat Shock Response Affects Hyperthermia-Induced Radiosensitization in a Tumor Spheroid Control Probability Assay

Hyperthermia (HT) combined with irradiation is a well-known concept to improve the curative potential of radiotherapy. Technological progress has opened new avenues for thermoradiotherapy, even for recurrent head and neck squamous cell carcinomas (HNSCC). Preclinical evaluation of the curative radiosensitizing potential of various HT regimens remains ethically, economically, and technically challenging. One key objective of our study was to refine an advanced 3-D assay setup for HT + RT research and treatment testing. For the first time, HT-induced radiosensitization was systematically examined in two differently radioresponsive HNSCC spheroid models using the unique in vitro "curative" analytical endpoint of spheroid control probability. We further investigated the cellular stress response mechanisms underlying the HT-related radiosensitization process with the aim to unravel the impact of HT-induced proteotoxic stress on the overall radioresponse. HT disrupted the proteome's thermal stability, causing severe proteotoxic stress. It strongly enhanced radiation efficacy and affected paramount survival and stress response signaling networks. Transcriptomics, q-PCR, and western blotting data revealed that HT + RT co-treatment critically triggers the heat shock response (HSR). Pre-treatment with chemical chaperones intensified the radiosensitizing effect, thereby suppressing HT-induced Hsp27 expression. Our data suggest that HT-induced radiosensitization is adversely affected by the proteotoxic stress response. Hence, we propose the inhibition of particular heat shock proteins as a targeting strategy to improve the outcome of combinatorial HT + RT.

A cellular automaton model for spheroid response to radiation and hyperthermia treatments

Thermo-radiosensitisation is a promising approach for treatment of radio-resistant tumours such as those containing hypoxic subregions. Response prediction and treatment planning should account for tumour response heterogeneity, e.g. due to microenvironmental factors, and quantification of the biological effects induced. 3D tumour spheroids provide a physiological in vitro model of tumour response and a systems oncology framework for simulating spheroid response to radiation and hyperthermia is presented. Using a cellular automaton model, 3D oxygen diffusion, delivery of radiation and/or hyperthermia were simulated for many ([Formula: see text]) individual cells forming a spheroid. The iterative oxygen diffusion model was compared to an analytical oxygenation model and simulations were calibrated and validated against experimental data for irradiated (0-10 Gy) and/or heated (0-240 CEM43) HCT116 spheroids. Despite comparable clonogenic survival, spheroid growth differed significantly following radiation or hyperthermia. This dynamic response was described well by the simulation ([Formula: see text] > 0.85). Heat-induced cell death was implemented as a fast, proliferation-independent process, allowing reoxygenation and repopulation, whereas radiation was modelled as proliferation-dependent mitotic catastrophe. This framework stands out both through its experimental validation and its novel ability to predict spheroid response to multimodality treatment. It provides a good description of response where biological dose-weighting based on clonogenic survival alone was insufficient.

Gold-coated iron oxide nanoparticles trigger apoptosis in the process of thermo-radiotherapy of U87-MG human glioma cells

Recently, gold-coated iron oxide nanoparticles (Au@IONPs) have received a great deal of attention in cancer therapy. In this in vitro study we aimed to investigate the anti-cancer effects of Au@IONPs core-shell nanoparticles when applied in thermo-radiotherapy. Moreover, we investigated the level of apoptosis induced in U87-MG human glioma cells after receiving a combinatorial treatment regimen (Au@IONPs + hyperthermia + radiotherapy). Firstly, the Au@IONPs nanocomplex was prepared and characterized. Cytotoxicity of the nanoparticles (various concentrations; 4 h incubation time) was investigated on U87-MG cells and finally the concentrations of 10 and 15 µg/mL were selected for further studies. After incubation of the cells with nanoparticles, they received hyperthermia (43 °C; 1 h) and then were immediately exposed to 6 MV X-ray (2 and 4 Gy). Following the treatments, MTT assay was used to analyze cell viability and flow cytometry was used to determine the level of apoptosis in each treatment group. The results revealed that nanoparticles have no significant cytotoxicity at concentrations lower than 10 µg/mL. Also, we observed that nanoparticles are able to enhance the cytotoxic effect of hyperthermia and radiation. The major mode of cell death was apoptosis when nanoparticles, hyperthermia and radiation were concomitantly applied to cancer cells. In conclusion, Au@IONP nanoparticle can be considered as a good thermo-radio-sensitizer which triggers significant levels of apoptosis in cancer therapy. In this in vitro study, we report the anti-cancer effects of gold-coated iron oxide nanoparticles (Au@IONPs) when applied in thermo-radiotherapy.

Multimodal cancer cell therapy using Au@Fe2O3 core-shell nanoparticles in combination with photo-thermo-radiotherapy

In this study, gold coated iron oxide nanoparticle (Au@Fe₂O₃ NP) was synthesized in a core-shell structure. Photothermal and radiosensitization effects of Au@Fe₂O₃ NPs were investigated on KB human mouth epidermal carcinoma cell line. Cell death and apoptosis were measured to study the effects of nanoparticles in combination with both radiotherapy (RT) and photothermal therapy (PTT). The KB cells were treated with Au@Fe₂O₃ NPs (20 μg/ml; 4 h) and then received different treatment regimens of PTT and/or RT using laser (808 nm, 6 W/cm², 10 min) and/or 6 MV X-ray (single dose of 2 Gy). Following the various treatments, MTT assay was performed to evaluate the cell survival rate. Also, the mode of cell death was determined by flow cytometry using an annexinV-fluorescein isothiocyanate/propidium iodide apoptosis detection kit. No significant cell death was observed due to laser irradiation. The viability of the cells firstly incubated with NPs and then exposed to the laser was significantly decreased. Additionally, our results demonstrated that Au@Fe₂O₃ NP is a good radiosensitizer at megavoltage energies of X-ray. When nanoparticles loaded KB cells were received both laser and X-ray, the cell viability substantially decreased. Following such a combinatorial treatment, flow cytometry determined that the majority of cell death relates to apoptosis. In conclusion, Au@Fe₂O₃ NP has a great potential to be applied as a photo-thermo-radiotherapy sensitizer for treatment of head and neck tumors.