J. Wang1, F. Zhang2, S. Liu1, M. Cai1, C. Ji1, J. Chen1, and J. Ma1; 1Department of Radiation Oncology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Jiaotong University, Xian, China, 2Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Jiaotong University, Xian, China
Purpose/Objective(s): Radiation resistance is one of the biggest challenges in radiotherapy for a long time. Traditional studies predominantly centered on biochemical approaches to conquer this obstacle, but faced multiple difficulties to increase radiosensitivity further. Recently, with the advent of nano-technologies and functional biomaterials, the physical traits of tumors have emerged as a promising target for cancer treatment. However, there is a lack of studies for improving radiosensitivity by targeting these physical cues. In this study, we hypothesized that targeting solid stress, one of the pivotal physical traits of tumors, could improve the efficacy of radiotherapy. Materials/
Methods: The human cervical cancer cell line, SiHa, was cultured in Dulbecco’s Modified Eagle Medium (DMEM) with 10% fetal bovine serum (FBS) and 1% penicillin-streptomycin. To simulate the high solid stress environment, the isotonic culture medium was mixed with either 0.5% or 1% PEG-300 to create a high osmolality medium. The solid stress-induced radiosensitivity was evaluated by colony formation assay and live-dead staining, whereas alternations in chromatin distribution and state were examined using western blotting and immunofluorescence staining. Fluorescent images were taken by a confocal laser scanning microscope with a 100× objective. Imaris and ImageJ were used to process the fluorescence and microscope images. RNA-sequencing was conducted and analyzed in R to compare the expression differentiation between normal and high solid-stress environments. Statistical analysis was conducted employing one-way ANOVA and unpaired t-tests. Results: The solid stress led to multiple mechanical property alterations in tumor cells, including changes in cell volume, cellular sphericity, nuclear volume, nuclear stiffness, nuclear envelope wrinkling, and nuclear envelope tension. These mechanical changes caused heterochromatin to detach from the nuclear envelope and unfold, mediated by H3K9me3 and H3K27me3 reduction. It resulted in increased accessibility of previously protected chromatin regions to radiation, consequently more DNA damage accumulated in the tumor cells, which in turn induced cell death and enhanced the radiosensitivity. Conclusion: Our research provides a novel strategy for improving radiosensitivity through the manipulation of solid stress, mediated by the change of chromatin state and distribution. Our finding exhibits the great potential of integrating physical cues of tumors into radiotherapy and provides new avenues for cancer treatment.