Biological Response of Human Cancer Cells to Ionizing Radiation in Combination with Gold Nanoparticles

Abstract

In the context of improving radiation therapy, high-atomic number (Z) metallic nanoparticles and, more importantly, gold-based nanostructures are developed as radiation enhancers/radiosensitizers. Due to the diversity of cell lines, nanoparticles, as well as radiation types or doses, the resulting biological effects may differ and remain obscure. In this multiparameter study, we aim to shed light on these effects and investigate them further by employing X-irradiation and three human cancer cell lines (PC3, A549, and U2OS cells) treated by multiple techniques. TEM experiments on PC3 cells showed that citrate-capped AuNPs were found to be located mostly in membranous structures/vesicles or autophagosomes, but also, in the case of PEG-capped AuNPs, inside the nucleus as well. The colony-forming capability of cancer cells radiosensitized by AuNPs decreased significantly and the DNA damage detected by cytogenetics, γH2AX immunostaining, and by single (γH2AX) or double (γH2AX and OGG1) immunolocalization via transmission electron microscopy (TEM) was in many cases higher and/or persistent after combination with AuNPs than upon individual exposure to ionizing radiation (IR). Moreover, different cell cycle distribution was evident in PC3 but not A549 cells after treatment with AuNPs and/or irradiation. Finally, cellular senescence was investigated by using a newly established staining procedure for lipofuscin, based on a Sudan Black-B analogue (GL13) which showed that based on the AuNPs’ concentration, an increased number of senescent cells might be observed after exposure to IR. Even though different cell lines or different types and concentrations of AuNPs may alter the levels of radiosensitization, our results imply that the complexity of damage might also be an important factor of AuNP-induced radiosensitization.

Application of nano‐radiosensitizers in combination cancer therapy

“…Primary antibodies target specific repair proteins that are conjugated by gold secondary antibodies similar to immunocytochemistry 184 . Although TEM has not been used to study DNA damage caused by radiation sensitivity, it was used to monitor cell uptake and distribution of NPs 185 . Furthermore, recently the technical use of TEM has been thoroughly described as a tool to study NP‐induced radiosensitivity in vitro 179,185 …”

“…185 Furthermore, recently the technical use of TEM has been thoroughly described as a tool to study NP-induced radiosensitivity in vitro. 179,185 Furthermore, flow cytometry could be used to detect DNA damage and analyze the cell cycle. 186 Propidium iodide is the most commonly used dye for quantitative assessment of DNA content and is a very useful technique for studying various checkpoints during the cell cycle.…”

“… 185 Furthermore, recently the technical use of TEM has been thoroughly described as a tool to study NP‐induced radiosensitivity in vitro. 179 , 185 …”

Albumin-Modified Gold Nanoparticles as Novel Radiosensitizers for Enhancing Lung Cancer Radiotherapy

“…However, the biological mechanism is influenced by various factors, such as the cell characteristic, the uptake of NPs, and differences between different cell lines. 27 Moreover, a strong and positive correlation can be expected between the tumor local concentration of GNPs and the radiosensitization effect. Regarding GNPs delivery, relying solely on the EPR effect is inadequate to reach an effective concentration.…”