Main Approaches to Enhance Radiosensitization in Cancer Cells by Nanoparticles: A Systematic Review

Understanding the molecular mechanism responsible for developing therapeutic radiation-induced radioresistance of rectal cancer and improving the clinical outcomes of radiotherapy - A review

Rectal cancer accounts for the second highest cancer-related mortality, which is predominant in Western civilizations. The treatment for rectal cancers includes surgery, radiotherapy, chemotherapy, and immunotherapy. Radiotherapy, specifically external beam radiation therapy, is the most common way to treat rectal cancer because radiation not only limits cancer progression but also significantly reduces the risk of local recurrence. However, therapeutic radiation-induced radioresistance to rectal cancer cells and toxicity to normal tissues are major drawbacks. Therefore, understanding the mechanistic basis of developing radioresistance during and after radiation therapy would provide crucial insight to improve clinical outcomes of radiation therapy for rectal cancer patients. Studies by various groups have shown that radiotherapy-mediated changes in the tumor microenvironment play a crucial role in developing radioresistance. Therapeutic radiation-induced hypoxia and functional alterations in the stromal cells, specifically tumor-associated macrophage (TAM) and cancer-associated fibroblasts (CAF), play a crucial role in developing radioresistance. In addition, signaling pathways, such as - the PI3K/AKT pathway, Wnt/β-catenin signaling, and the hippo pathway, modulate the radiation responsiveness of cancer cells. Different radiosensitizers, such as small molecules, microRNA, nanomaterials, and natural and chemical sensitizers, are being used to increase the effectiveness of radiotherapy. This review highlights the mechanism responsible for developing radioresistance of rectal cancer following radiotherapy and potential strategies to enhance the effectiveness of radiotherapy for better management of rectal cancer.

Critical appraisal tools used in systematic reviews of in vitro cell culture studies: A methodological study

Systematic reviews (SRs) of preclinical studies are marked with poor methodological quality. In vitro studies lack assessment tools to improve the quality of preclinical research. This methodological study aimed to identify, collect, and analyze SRs based on cell culture studies to highlight the current appraisal tools utilized to support the development of a validated critical appraisal tool for cell culture in vitro research. SRs, scoping reviews, and meta-analyses that included cell culture studies and used any type of critical appraisal tool were included. Electronic search, study selection, data collection and methodological quality (MQ) assessment tool were realized. Further, statistical analyses regarding possible associations and correlations between MQ and collected data were performed. After the screening process, 82 studies remained for subsequent analysis. A total of 32 different appraisal tools were identified. Approximately 60% of studies adopted pre-structured tools not designed for cell culture studies. The most frequent instruments were SYRCLE (n = 14), OHAT (n = 9), Cochrane Collaboration's tool (n = 7), GRADE (n = 6), CONSORT (n = 5), and ToxRTool (n = 5). The studies were divided into subgroups to perform statistical analyses. A significant association (OR = 5.00, 95% CI = 1.54-16.20, p = 0.008) was found between low MQ and chronic degenerative disorders as topic of SR. Several challenges in collecting information from the included studies led to some modifications related to the previously registered protocol. These results may serve as a basis for further development of a critical appraisal tool for cell culture studies capable of capturing all the essential factors related to preclinical research, therefore enhancing the practice of evidence-based.

Synthesis and characterization of actively HER-2 Targeted Fe3O4@Au nanoparticles for molecular radiosensitization of breast cancer

Introduction: The present study was done to assess the effect of molecularly-targeted core/shell of iron oxide/gold nanoparticles (Fe₃O₄@AuNPs) on tumor radiosensitization of SKBr-3 breast cancer cells. Methods: Human epidermal growth factor receptor-2 (HER-2)-targeted Fe₃O₄@AuNPs were synthesized by conjugating trastuzumab (TZ, Herceptin) to PEGylated (PEG)-Fe₃O₄@AuNPs (41.5 nm). First, the Fe₃O₄@Au core-shell NPs were decorated with PEG-SH to synthesize PEG-Fe₃O₄@AuNPs. Then, the TZ was reacted to OPSS-PEG-SVA to conjugate with the PEG-Fe₃O₄@AuNPs. As a result, structure, size and morphology of the developed NPs were assessed using Fourier-transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy. The SKBr-3 cells were treated with different concentrations of TZ, Fe₃O₄@Au_, and TZ-PEG-Fe₃O₄@AuNPs for irradiation at doses of 2, 4, and 8 Gy (from X-ray energy of 6 and 18 MV). Cytotoxicity was assessed by MTT assay, BrdU assay, and flow cytometry. Results: Results showed that the targeted TZ-PEG-Fe₃O₄@AuNPs significantly improved cell uptake. The cytotoxic effects of all the studied groups were increased in a higher concentration, radiation dose and energy-dependent manner. A combination of TZ, Fe₃O₄@Au, and TZ-PEG-Fe₃O₄@AuNPs with radiation reduced cell viability by 1.35 (P=0.021), 1.95 (P=0.024), and 1.15 (P=0.013) in comparison with 8 Gy dose of 18 MV radiation alone, respectively. These amounts were obtained as 1.27, 1.58, and 1.10 for 8 Gy dose of 6 MV irradiation, respectively. Conclusion: Radiosensitization of breast cancer to mega-voltage radiation therapy with TZ-PEG-Fe₃O₄@AuNPs was successfully obtained through an optimized therapeutic approach for molecular targeting of HER-2.

Nanostructures as Radionuclide Carriers in Auger Electron Therapy

The concept of nanoparticle-mediated radionuclide delivery in the cancer treatment has been widely discussed in the past decade. In particular, the use of inorganic and organic nanostructures in the development of radiopharmaceuticals enables the delivery of medically important radioisotopes for radionuclide therapy. In this review, we present the development of nanostructures for cancer therapy with Auger electron radionuclides. Following that, different types of nanoconstructs that can be used as carriers for Auger electron emitters, design principles, nanoparticle materials, and target vectors that overcame the main difficulties are described. In addition, systems in which high-Z element nanoparticles are used as radionuclide carriers, causing the emission of photoelectrons from the nanoparticle surface, are presented. Finally, future research opportunities in the field are discussed as well as issues that must be addressed before nanoparticle-based Auger electron radionuclide therapy can be transferred to clinical use.

Monte Carlo Simulations Reveal New Design Principles for Efficient Nanoradiosensitizers Based on Nanoscale Metal-Organic Frameworks

Nanoscale metal-organic frameworks (nMOFs) have recently been shown to provide better radiosensitization than solid nanoparticles (NPs) when excited with X-rays. Here, a Monte Carlo simulation of different radiosensitization effects by NPs and nMOFs using a lattice model consisting of 3D arrays of nanoscale secondary building units (SBUs) is reported. The simulation results reveal that lattices outperform solid NPs regardless of radiation sources or particle sizes via enhanced scatterings of photons and electrons within the lattices. Optimum dose enhancement can be achieved by tuning SBU size and inter-SBU distance.