Mechanical Property Measurement Of Cancer Cells And Biomechanics Of Cell Damage Induced By Irradiation

Cancer treatment mainly includes radiotherapy, surgery, chemotherapy and other biophysical methods. And radiation therapy has certain advantages in patients who are not suitable for surgery and chemotherapy. Heavy ions represent the best tool for external radiotherapy(RT) of inoperable tumors. Heavy ion RT has been used in the treatment of various tumors. Carbon ion beam is as a approch of the heavy-ion cancer therapy, one of the most commonly of radiation method has been used in all kinds of oncotherapy, especially for radioresistant tumors mediated by hypoxia, localized near organs at risk. Currently, most of these treatments are concentrated in deep-seated tumor cases such as those of the brain, head, lung, liver, rectum and urogenital organs, and treatment of skin carcinomas, showing more remarkably curative effect than conventional radiation. Because the apoptotic mechanisms induced by the radiation is served as the key effects of tumortherapy. Therefore, how effectively evaluate the curative effects of heavy-ion cancer therapy, the cell-killing mechanism and the side effects, is the necessary condition to improve the advanced treatment. In fact, the apoptosis process is not only accompanied by the change in the phenotype of cell morphology, but also inherent mechanical properties of cells(mechanical cues) inevitably and continuously participated in regulating mechanical evolution, and how the coupling relationship with the molecular pathways of apoptosis is a still unresolved important scientific problems. In this context, based on the induction effect of cell apoptosis by heavy ion RT, this study established a canonical cell apoptosis model in vitro and cell damage model in vivo. By means of molecular biology methods, such as MTT assay, and western blotting technique and combining with single cell mechanics technique based on atomic force microscopy(AFM) and clinical cytology analysis, we investigate how the change of cell mechanical properties would be brought into to the research system to assess cancer killing mechanism, therapeutic effect and adverse effects of radiation.Obtained innovative research results as follows:(1) Based on the change of mechanical properties to characterize the differences between cancer cells and normal cells, we found that hepatocellular carcinoma cell(HCC) lines showed the smaller value of cell elasticity compared with normal hepatocyte(NH) line(more softer), with the increasing of the HCC invasiveness, which exhibited a lower cell elasticity value. Meawhile, cell adhesion force and surface adhesion energy increased with the enhancing of invasive potential in the HCCs. Therefore, we propose that mechanical signatures(such as cell elasticity, stiffness) in a specific biological process maybe used to evaluate the biological events, or based on mechanics indicators to identify the differences in cell evolution process from normal cells to cancer cells, it has a remarkable value of clinical application.(2) Based on the cancer cell-killing effects by carbon ion irradiation, five HCCs and one NHs were treated with CII technique to establish a canonical cell apoptosis model by regualting the molecular pathways in vitro. We confirmed that key apoptotic molecules derived from the mitochondrial and death receptor pathways were verified to be activated, and the results indicated that CII could trigger apoptosis in HCCs by activating of the mitochondrial and death receptor pathways to regualte cell apoptosis, ultimately executing the killing role of cell death modalities as part of the radiation effects. From the perspective of the mechanical signatures to characterize, we found a close relationship during the apoptotic process that appears to exist among the cell microstructure, cell mechanical properties, actin cytoskeletal organization, and expression of apoptotic signaling molecules. These findings imply that the cell mechanical properties, morphological remodeling and molecular pathways are tightly coupled interaction to regulate the progression of apoptosis. Furthermore, based on the classical morphological features during the the onset of apoptosis, for the first time, we proposed a theoretical model of apoptosis which revealed that the characteristic change in cellular budding of apoptotic bodies was mainly dominated by the mechanical mechanism. Ultimately, the coupled mechanism during the onset of apoptosis can be used to clarify the biomechanical mechanism of cell apoptosis. Thus, we also put forward the change of the mechanical parameters as indicators to assess the cancer-killing mechanism and curative effects of heavy ions RT.(3) Based on the viewpoint of irradiation-induced damage-effect evaluation of erythrocytes in the Syrian hamsters, the results showed that dynamic changes were evident in erythrocytes exposed to different doses of carbon ion beams compared with X-rays and the control. The magnitude of impairment of the cell number and cellular morphology manifested the subtle variation according to the irradiation dose. In particular, the differences in the size, shape and mechanical properties of the erythrocytes and the expression of the cytoskeletal protein spectrin-α1 was reduced after irradiation, and there was a common pattern among its substantive characteristics in the irradiated group. This clarify the biomechanical mechanism of ionizing radiation induction to erythrocytes damage from two aspects between mechanical properties and configuration changes. As well, we for the first time put forward the change of erythrocyte rigidity to evaluate the ionizing radiation damage classification of erythrocytes and the influence of adverse effects.Based on these acquired findings, this study provides important clues not only regarding the role of apoptosis by carbon ion irradiation as the conservative molecular pathway of the cellular mechanism that regulates tumor cell death, and also importantly supporting the existence of a tight coupling interpaly mechanism of ongoing apoptosis associated with morphological and mechanical remodeling, which may mediate a novel interactive pathway in determining the fate of cell induced by carbon ion irradiation. This strategy based on a novel biomechanical scenario should help us to gain profound insight into the cancer-killing mechanism in the context of carbon ion irradiation and to provide experimental support and theoretical basis in clinical carbon ion radiotherapy. In parallel, the research on the biomechanical mechanism of the radiation damage in erythrocytes also concluded that carbon ion irradiation could induce a change in mechanical properties. We deduce that changes in cytomorphology and mechanical properties can be measured to evaluate the adverse effects generated by tumor radiotherapy, and the current study will provide a new strategy for enhancing the assessment of the curative effects and safety of clinical radiotherapy, as well as reducing adverse effects.