Radiation oncology in vitro: trends to improve radiotherapy through molecular targets

Cyclin D1 promotes radioresistance through regulation of RAD51 in melanoma

Melanoma is a notoriously radioresistant type of skin cancer. Elucidation of the specific mechanisms underlying radioresistance is necessary to improve the clinical efficacy of radiation therapy. To identify the key factors contributing to radioresistance, five melanoma cell lines were selected for study and genes that were upregulated in relatively radioresistant melanomas compared with radiosensitive melanoma cells determined via RNA sequencing technology. In particular, we focused on cyclin D1 (CCND1), a well known cell cycle regulatory molecule. In radiosensitive melanoma, overexpression of cyclin D1 reduced apoptosis. In radioresistant melanoma cell lines, suppression of cyclin D1 with a specific inhibitor or siRNA increased apoptosis and decreased cell proliferation in 2D and 3D spheroid cultures. In addition, we observed increased expression of γ-H2AX, a molecular marker of DNA damage, even at a later time after γ-irradiation, under conditions of inhibition of cyclin D1, with a response pattern similar to that of radiosensitive SK-Mel5. In the same context, expression and nuclear foci formation of RAD51, a key enzyme for homologous recombination (HR), were reduced upon inhibition of cyclin D1. Downregulation of RAD51 also reduced cell survival to irradiation. Overall, suppression of cyclin D1 expression or function led to reduced radiation-induced DNA damage response (DDR) and triggered cell death. Our collective findings indicate that the presence of increased cyclin D1 potentially contributes to the development of radioresistance through effects on RAD51 in melanoma and could therefore serve as a therapeutic target for improving the efficacy of radiation therapy.

Insights into Gold Nanoparticles Possibilities for Diagnosis and Treatment of the Head and Neck Upper Aerodigestive Tract Cancers

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer affecting people and accounts for more than 300,000 deaths worldwide. Improvements in treatment modalities, including immunotherapy, have demonstrated promising prognoses for eligible patients. Nevertheless, the five-year overall survival rate has not increased significantly, and the tumor recurrence ratio remains at 50% or higher, except for patients with HPV-positive HNSCC. Over the last decades, nanotechnology has provided promising tools, especially for biomedical applications, due to some remarkable physicochemical properties of numerous nanomaterials, particularly gold nanoparticles. This review addresses the features and some applications of gold nanoparticles reported in the literature over the last five years regarding the diagnosis and treatment of head and neck cancer, highlighting the exciting possibilities of this nanomaterial in oncology.

METHODS

The scientific papers selected for this review were obtained from the PubMed Advanced, Web of Science, Scopus, ClinicalTrials.gov, and Google Scholar platforms.

CONCLUSIONS

Results from papers applying gold nanoparticles have suggested that their application is a feasible approach to diagnostics, prognostics, and the treatment of HNC. Moreover, phase I clinical trials suggest that gold nanoparticles are safe and can potentially become theranostic agents for humans.

Variation of 4 MV X-ray dose rate in fractionated irradiation strongly impacts biological endothelial cell response in vitro

PURPOSE

Even though X-ray beams are widely used in medical diagnosis or radiotherapy, the comparisons of their dose rates are scarce. We have recently demonstrated in vitro (clonogenic assay, cell viability, cell cycle, senescence) and in vivo (weight follow-up of animals and bordering epithelium staining of lesion), that for a single dose of irradiation, the relative biological effectiveness (RBE) deviates from 1 (up to twofold greater severe damage at the highest dose rate depending on the assay) when increasing the dose rate of high energy X-ray beams.

MATERIAL AND METHODS

To further investigate the impact of the dose rate on RBE, in this study, we performed in vitro fractionated irradiations by using the same two dose rates (0.63 and 2.5 Gy.min^-1) of high-energy X-rays (both at 4 MV) on normal endothelial cells (HUVECs). We investigated the viability/mortality, characterized radiation-induced senescence by using flow cytometry and measured gene analysis deregulations on custom arrays.

RESULTS

The overall results enlighten that, in fractionated irradiations when varying the dose rate of high-energy X-rays, the RBE of photons deviates from 1 (up to 2.86 for viability/mortality experiments performed 21 days postirradiation).

CONCLUSION

These results strengthen the interest of multiparametric analysis approaches in providing an accurate evaluation of the outcomes of irradiated cells in support of clonogenic assays, especially when such assays are not feasible.

Gold nanoparticles enhance fluorescence signals by flow cytometry at low antibody concentrations

Flow cytometry is a universally applied technique in many biological and clinical assays to evaluate cells, bacteria, parasites, and particles at a micrometre scale. More advanced flow cytometers can detect small molecules down to the nanometre scale that may identify intracellular nanostructures. Advancements in the field of nanobiotechnology have led to techniques that allow the study of cellular behaviour after exposure to nanomaterials, particularly, metal nanoparticles. The optical properties of gold nanoparticles regarding surface plasmon resonance (SPR) are established to increase the fluorescence quantum yields of several dyes working as optical antennas, enabling the enhancement of light emission in fluorescent emitters. In this work we constructed a nanoprobe using gold nanoparticles coated with primary antibody Cetuximab. Then, we investigated whether this nanoprobe labelled with secondary fluorescent antibody Alexa Fluor 488, at low concentrations, could promote fluorescent signal enhancement, associated with SPR, and detected by the flow cytometry technique. Our results showed an enhanced fluorescent signal likely due to the proximity between the extinction coefficient of gold nanoparticles and the emission peak of Alexa Fluor 488, at exceptionally low concentrations, occurring within a high level of specificity. Moreover, the nanoprobe did not alter the cellular viability suggesting gold nanoparticles as a feasible approach for cell labelling using low concentrations of secondary antibodies for routine flow cytometry applications.

Effects of radiotherapy and short-term starvation combination on metastatic and non-tumor cell lines

BACKGROUND

Since its discovery in the late 19^th century, radiotherapy has been one of the most important medical treatments in oncology. Recently, fasting or short-term starvation (STS) in cancer patients undergoing chemotherapy has been studied to determine its potential for enhancing the therapeutic index and for preventing side- effects, but no data are available in the radiotherapy setting. We thus decided to investigate the effects in vitro of STS in combination with radiotherapy in metastatic cancer cells and non-cancer cells.

METHODS

Cells were incubated in short-term starvation medium (STS medium, 0·5 g/L glucose + 1% FBS) or in control medium (CM medium, 1 g/L glucose + 10 % FBS) for 24 h and then treated with single high-dose radiation. A plexiglass custom-built phantom was used to irradiate cells. DNA damage was evaluated using alkaline comet assay and theCometAnalyser software. The cell surviving fraction was assessed by clonogenic assay.

FINDING

STS followed by single high-dose radiation significantly increased DNA damage in metastatic cancer cell lines but not in normal cells. Furthermore, STS reduced the surviving fraction of irradiated tumor cells, indicating a good radio-sensitizing effect on metastatic cell lines. This effect was not observed in non-tumor cells.

INTERPRETATION

Our results suggest that STS may alter cellular processes, enhancing the efficacy of radiotherapy in metastatic cancer cellsin vitro. Interestingly, STS has radioprotective effect on the survival of healthy cells.

The physicochemical and biological characterization of a 24-month-stored nanocomplex based on gold nanoparticles conjugated with cetuximab demonstrated long-term stability, EGFR affinity and cancer cell death due to apoptosis

Nanotechnology is one of the most promising tools for future diagnosis and therapy. Thus, we have produced gold nanoparticles coated with cetuximab at a dose-range from 5 μg up to 200 μg, and prolonged stable nanocomplexes were obtained. The nanocomplexes were characterized by UV-Vis, zeta potential, TEM, fluorometry, infrared regions, XPS and atomic absorption spectrometry. For biological characterization the A431 cell line was used. Cellular uptake, target affinity and cell death were assessed using ICP-OES, immunocytochemistry and flow cytometry, respectively. The immobilization of cetuximab on the AuNPs surfaces was confirmed. The nanocomplex with 24 months of manufacturing promoted efficient EGFR binding and induced tumour cell death due to apoptosis. Significant (p < 0.05) cell death was achieved using relatively low cetuximab concentration for AuNPs coating compared to the antibody alone. Therefore, our results provided robust physicochemical and biological characterization data corroborating the cetuximab-bioconjugate AuNPs as a feasible nanocomplex for biomedical applications.

Inhibiting pulmonary metastasis of breast cancer based on dual-targeting graphene oxide with high stability and drug loading capacity

In this study, heparin and polyethyleneimine-folic acid modified graphene oxide was designed and synthesized as a dual-targeting biomaterial to load doxorubicin (DOX@GPFH) with high loading capacity for enhanced cellular uptake. GDC0941, a phosphatidylinositide 3-kinase/Akt phosphorylation inhibitor, was selected to enhance anti-metastasis effect of DOX@GPFH via down-regulating expression of matrix metalloproteinase. Modified with heparin, the stability of DOX@GPFH was significantly enhanced and the drug loading ratio increased largely from 64.4% to 125.1%. The inhibition rates of the mixture of DOX@GPFH and GDC0941 in vitro by wound healing, cell migration and invasion assays were 61.2%±13.9%, 81.0%±3.6% and 76.8%±5.2%, respectively, while the tumor and the pulmonary anti-metastasis rates tested in vivo were 77.0%±7.6% and 73.7%±9.6%, respectively. Our findings illustrated an effective approach for developing dual-targeting graphene oxide with high drug loading for pulmonary anti-metastasis of breast cancer.

DANGER is involved in high glucose-induced radioresistance through inhibiting DAPK-mediated anoikis in non-small cell lung cancer

¹⁸F-labeled fluorodeoxyglucose (FDG) uptake during FDG positron emission tomography seems to reflect increased radioresistance. However, the exact molecular mechanism underlying high glucose (HG)-induced radioresistance is unclear. In the current study, we showed that ionizing radiation-induced activation of the MEK-ERK-DAPK-p53 signaling axis is required for anoikis (anchorage-dependent apoptosis) of non-small cell lung cancer (NSCLC) cells in normal glucose media. Phosphorylation of DAPK at Ser734 by ERK was essential for p53 transcriptional activity and radiosensitization. In HG media, overexpressed DANGER directly bound to the death domain of DAPK, thus inhibiting the catalytic activity of DAPK. In addition, inhibition of the DAPK-p53 signaling axis by DANGER promoted anoikis-resistance and epithelial-mesenchymal transition (EMT), resulting in radioresistance of HG-treated NSCLC cells. Notably, knockdown of DANGER enhanced anoikis, EMT inhibition, and radiosensitization in a mouse xenograft model of lung cancer. Taken together, our findings offered evidence that overexpression of DANGER and the subsequent inhibitory effect on DAPK kinase activity are critical responses that account for HG-induced radioresistance of NSCLC.

Gold nanoparticles and their applications in biomedicine

Although used in medical applications for centuries, the development of nanotechnology has shed new light in the plethora of possible medical and biological applications using gold-based nanostructures. Gold nanostructures are stable and relatively inert in biological systems, leading to low reatogenicity, biocompatibility and general lack of toxicity. Allied to that, gold nanoparticles present optical and electronic properties that have been exploited in a range of biomedical applications. In this review we discuss biologically relevant properties of gold nanoparticles and how they are used in some biomedicine fields, especially those involving biosensing of biological analytes – including viruses and antibodies against them, cancer therapies, and antigen delivery, including viral antigens – as part of nonclassic vaccine strategies.

Targeting irradiation-induced mitogen-activated protein kinase activation in vitro and in an ex vivo model for human head and neck cancer

BACKGROUND

Despite new radiotherapeutic strategies, radioresistance in head and neck squamous cell carcinoma (HNSCC) remains a major problem. Preclinical model systems are needed to identify resistance mechanisms in this heterogeneous entity.

METHODS

We elucidated the interplay among mitogen-activated protein kinase (MAPK)-inhibition, radiation, and p53 mutations in vitro and in a novel ex vivo model derived from vital human HNSCC samples. HNSCC cell lines (p53WT/mut) were treated with the mitogen-activated protein kinase (MEK)-inhibitor PD-0325901 and subsequently irradiated. Radiosensitization was functionally assessed and evaluated in the ex vivo model.

RESULTS

We observed a pronounced irradiation-induced extracellular signal-regulated kinase (ERK) phosphorylation in 2 cell lines, which was independent of their p53 mutation status and associated with PD-0325901-related radiosensitization in a clonogenic assay. Heterogeneity in irradiation-induced ERK phosphorylation and in radiosensitization after MEK-inhibition was also reflected in the ex vivo model.

CONCLUSION

We provide experimental evidence for radiosensitizing effects of PD-0325901 in HNSCC. The ex vivo culture technology might offer a promising tool for individualized drug efficacy testing. © 2016 Wiley Periodicals, Inc. Head Neck 38: E2049-E2061, 2016.