Center of Imaging Sciences, University Medical Center Utrecht, Utrecht, the Netherlands.
Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands.
PLoS One. 2018 Sep 18;13(9):e0204063. doi: 10.1371/journal.pone.0204063. eCollection 2018.
To increase the efficacy of chemoradiation and decrease its toxicity in normal tissue, a new concept is proposed, local radiosensitizer delivery, which combines triggered release of a radiosensitizer from thermosensitive liposomes with local hyperthermia and radiotherapy. Here, key aspects of this concept were investigated in vitro I) the effect of hyperthermia on the enhancement of radiotherapy by ThermoDox (thermosensitive liposome containing doxorubicin), II) the concentration dependence of the radiosensitizing effect of doxorubicin and III) the sequence of doxorubicin, hyperthermia and radiotherapy maximizing the radiosensitizing effect.
Survival of HT1080 (human fibrosarcoma) cells was measured after exposure to ThermoDox or doxorubicin for 60 minutes, at 37 or 43°C, with or without irradiation. Furthermore, cell survival was measured for cells exposed to different doxorubicin concentrations and radiation doses. Finally, cell survival was measured after applying doxorubicin and/or hyperthermia before or after irradiation. Cell survival was measured by clonogenic assay. In addition, DNA damage was assessed by γH2AX staining.
Exposure of cells to doxorubicin at 37°C resulted in cell death, but exposure to ThermoDox at 37°C did not. In contrast, ThermoDox and doxorubicin at 43°C resulted in similar cytotoxicity, and in combination with irradiation caused a similar enhancement of cell kill due to radiation. Doxorubicin enhanced the radiation effect in a small, but significant, concentration-dependent manner. Hyperthermia showed the strongest enhancement of radiation effect when applied after irradiation. In contrast, doxorubicin enhanced radiation effect only when applied before irradiation. Concurrent doxorubicin and hyperthermia immediately before or after irradiation showed equal enhancement of radiation effect.
In vitro, ThermoDox resulted in cytotoxicity and enhancement of irradiation effect only in combination with hyperthermia. Therefore hyperthermia-triggered radiosensitizer release from thermosensitive liposomes may ultimately serve to limit toxicities due to the radiosensitizer in unheated normal tissue and result in enhanced efficacy in the heated tumor.
为了提高放化疗的疗效，降低正常组织的毒性，提出了一种新的概念，即局部放射增敏剂的传递，它将热敏脂质体中放射增敏剂的触发释放与局部热疗和放疗相结合。在这里，我们在体外研究了这个概念的关键方面：i）热疗对ThermoDox（含有阿霉素的热敏脂质体）增强放疗的影响，ii）阿霉素放射增敏作用的浓度依赖性，iii）最大程度提高放射增敏作用的 doxorubicin、hyperthermia 和 radiotherapy 的顺序。
HT1080（人纤维肉瘤）细胞在 37°C 或 43°C 下暴露于 ThermoDox 或阿霉素 60 分钟后，测量其存活情况，是否进行照射。此外，还测量了暴露于不同阿霉素浓度和辐射剂量的细胞的存活情况。最后，测量了先应用 doxorubicin 和/或 hyperthermia 然后再进行照射，或者先照射然后再应用 doxorubicin 和/或 hyperthermia 的细胞的存活情况。细胞存活情况通过集落形成试验进行测量。此外，通过 γH2AX 染色评估 DNA 损伤。
细胞在 37°C 下暴露于阿霉素会导致细胞死亡，但在 37°C 下暴露于 ThermoDox 则不会。相反，ThermoDox 和 43°C 下的阿霉素导致类似的细胞毒性，并且与照射结合导致由于辐射导致的细胞杀伤增强相似。阿霉素以小但显著的浓度依赖性方式增强了辐射效应。热疗在照射后应用时显示出最强的辐射增强效果。相反，阿霉素仅在照射前应用时增强辐射效果。照射前或照射后立即应用 doxorubicin 和 hyperthermia 表现出相等的增强辐射效果。
在体外，ThermoDox 仅在与热疗结合时才会导致细胞毒性和增强照射效果。因此，热敏脂质体中放射增敏剂的热触发释放最终可能有助于限制未加热的正常组织中放射增敏剂的毒性，并在加热的肿瘤中提高疗效。
