Abstract

Purpose

Agents that increase tumor radiosensitivity are of interest in improving outcomes in radiotherapy (XRT). DNA-PK inhibitors radiosensitize and alter cell adhesion proteins. We investigated combination radiation and a DNA-PK inhibitor in monolayers vs spheroids.

Materials and methods

Using HER2 positive mammary carcinoma cells, we investigated the impact of NU7441, a DNA-PK inhibitor, on irradiated monolayer and spheroid cultures. Colony formation assays were performed with monolayer culture cells and spheroids after irradiation with/without NU7441 (5 μM).

Results

In monolayer culture cells, α/β increased from 3.0 ± 0.2 Gy (XRT alone) to 6.9 ± 0.2 Gy (XRT+NU7441). Corresponding α/β values for cells obtained by disaggregating treated spheroids were 3.6 ± 0.7 Gy (XRT alone) and 3.5 ± 0.2 Gy (XRT+NU7441). However, spheroid survival was highly sensitive to NU7441 incubation. After 4 Gy XRT alone 75% of the irradiated spheroids remained intact; when NU7441 treatment was involved, 13% remained intact. No spheroids survived to 3 weeks at 6 Gy or more. The discrepancy between the minimal change in α/β from cells derived from spheroids and the spheroid growth response was not related to poor penetration of NU7441.

Conclusions

DNA-PK inhibitor NU7441 radiosensitized monolayer cells but not cells obtained from spheroids. NU7441 and radiation increased spheroid fragmentation.

摘要

目的

提高肿瘤放射敏感性的药物对改善放射治疗（XRT）的结果很重要。DNA-PK抑制剂导致放射致敏作用，并导致细胞粘附蛋白发生改变。我们在单层与球形培养细胞中研究了辐射和DNA-PK抑制剂的组合。材料和方法：使用HER2阳性乳腺癌细胞系NT2.5，我们研究了NU7441（一种有效的，选择性的DNA-PK抑制剂）与外部射线束在2D单层和3D球形细胞培养系统中的影响。在不同剂量的外部束辐照后或在辐照后与NU7441（5 µM）孵育24小时后，对单层培养细胞和球体中的细胞进行集落形成测定。结果：在单层培养细胞中，α/β从3.0±0.2 Gy（仅XRT）增加到6.9±0。2 Gy（XRT + NU7441）。通过分解处理过的球体得到的细胞的相应α/β值为3.6±0.7 Gy（仅XRT）和3.5±0.2 Gy（XRT + NU7441）。与α/β的最小变化相反，球状体的存活对NU7441孵育高度敏感。分别在0、2、4、6、8或10 Gy XRT照射21天后，分别有100％，83％，75％，63％，56％和31％的辐照球体完好无损；当使用NU7441治疗时，在2 Gy时完整的保持56％，在4 Gy时完整的保持13％，在6 Gy或以上时，没有球体存活到3周。我们还发现仅暴露于NU7441的球体的碎片逐渐增加。球状体细胞的α/β最小变化与球状体生长反应之间的差异与NU7441的渗透性差无关，因为用4 Gy处理不同大小的球状体（180至400 µm）的菌落形成试验结果是否使用NU7441没有显着差异。结论：DNA-PK抑制剂NU7441对2D培养的NT2.5单层细胞进行放射增敏，但对3D培养的球体获得的细胞无效。与仅用辐射处理的球体相比，NU7441和放射线的结合导致球体碎片的增加。