Casteloes Nicholas, House Carrie D, Tambasco Mauro
Department of Physics, San Diego State University, San Diego, CA 92182, USA.
Biology Department, San Diego State University, San Diego, CA 92182, USA.
Int J Mol Sci. 2025 May 7;26(9):4436. doi: 10.3390/ijms26094436.
Spatially fractionated radiotherapy (SFRT) offers a promising approach for debulking large tumors by delivering high-dose radiation to a fraction of the tumor volume. However, the complex tumor microenvironment necessitates models beyond traditional 2D cultures and resource-intensive animal studies for SFRT investigations. Three-dimensional (3D) scaffold-based models with an adequate cross-sectional area have emerged as uniquely suited platforms to bridge this gap, by providing a more realistic platform for GRID-based SFRT research. In this study, we employed a 3D co-culture scaffold model to dissect the contributions of the radiation-induced bystander effect, abscopal effect, and immune system response on clonogenic survival following GRID irradiation. MDA-MB-231 breast cancer cells were seeded on commercial 3D scaffolds and irradiated at a 20 Gy peak dose using lead grids with three- and six-hole patterns, exposing ~12.8% and 25.7% of the scaffold area, respectively. An assessment of reproductive cell survival revealed a significant bystander effect, as the survival was notably lower than predicted based solely on the directly irradiated fraction. Evidence of an abscopal effect was observed by culturing non-irradiated cells in media exposed to GRID irradiation. Furthermore, a co-culture with allogeneic peripheral blood mononuclear cells (PBMCs) modulated clonogenic survival, with an additive effect observed when combined with SFRT. These findings underscore the presence of a bystander effect in GRID radiotherapy and indicate an abscopal immune component, particularly with the three-hole GRID configuration. This study established the utility of in vitro 3D co-culture scaffolds as an effective model system for elucidating complex SFRT-mediated biological responses.
空间分割放疗（SFRT）通过向部分肿瘤体积输送高剂量辐射，为缩小大肿瘤提供了一种有前景的方法。然而，复杂的肿瘤微环境需要超越传统二维培养和资源密集型动物研究的模型来进行SFRT研究。具有足够横截面积的三维（3D）支架模型已成为填补这一空白的独特合适平台，为基于格栅的SFRT研究提供了更现实的平台。在本研究中，我们采用3D共培养支架模型来剖析辐射诱导的旁观者效应、远隔效应和免疫系统反应对格栅照射后克隆形成存活的影响。将MDA-MB-231乳腺癌细胞接种在商用3D支架上，并使用具有三孔和六孔图案的铅格栅以20 Gy的峰值剂量进行照射，分别使支架面积的约12.8%和25.7%暴露。对生殖细胞存活的评估显示出显著的旁观者效应，因为存活率明显低于仅基于直接照射部分所预测的存活率。通过在暴露于格栅照射的培养基中培养未照射的细胞，观察到了远隔效应的证据。此外，与同种异体外周血单个核细胞（PBMCs）共培养可调节克隆形成存活，与SFRT联合使用时观察到相加效应。这些发现强调了格栅放疗中旁观者效应的存在，并表明存在远隔免疫成分，特别是在三孔格栅配置中。本研究确立了体外3D共培养支架作为阐明复杂的SFRT介导的生物学反应的有效模型系统的实用性。
