Department of Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark.
Int J Radiat Biol. 2012 Jun;88(6):457-65. doi: 10.3109/09553002.2012.683509. Epub 2012 May 8.
Resistance to radiation therapy remains a serious impediment to cancer therapy. We previously reported heterogeneity for clonogenic survival when testing in vitro radiation resistance among single-cell derived clones from a human mesenchymal cancer stem cell model (hMSC). Here we aimed to determine whether this heterogeneity persisted in tumours established from these clones, and whether the response to radiation treatment was principally governed by cell-intrinsic qualities or by factors pertaining to the tumour microenvironment, such as the degree of hypoxia and vascularization.
Immune-deficient female mice were implanted on the backs with cells from one of the clones. The subsequent tumours were subjected to either radiation treatment or had the tumour microenvironment assayed, when they reached 400 mm³. Radiation was given as a single fraction of 0-15 Gy and the degree of tumour control and time to three times the treatment volume were noted. Tumours used for the microenvironmental assay had intratumoral hypoxia measured by the Eppendorf oxygen electrode and pimonidazole staining, and the extent of vascularization determined by a microvasculature density assay using endothelial-specific staining.
All microenvironmental assays indicated a similar degree of hypoxia and vascularization for the selected clones. Nonetheless, the tumours responded differently to radiation treatment since the BB3 clone displayed tumour control at 5, 10 and 15 Gy, whereas tumour control was not seen below 15 Gy with the CE8 clone.
For tumours that displayed similar degrees of oxygenation and vascularization, the clone-specific in vitro radiation resistance could predict the in vivo response to radiation treatment. These results favor the hypothesis that intrinsic genetic factors can govern radiation resistance in this cancer stem cell model.
抵抗放射疗法仍然是癌症治疗的一个严重障碍。我们之前曾报道过，在测试来自人间质癌干细胞模型（hMSC）的单细胞衍生克隆的体外放射抗性时，克隆形成存活存在异质性。在这里，我们旨在确定这种异质性是否在这些克隆建立的肿瘤中仍然存在，以及对放射治疗的反应主要是由细胞内在特性决定，还是由肿瘤微环境中的因素决定，例如缺氧和血管化程度。
免疫缺陷雌性小鼠背部植入来自一个克隆的细胞。当随后的肿瘤达到 400mm³时，对其进行放射治疗或检测肿瘤微环境。给予 0-15Gy 的单次剂量，记录肿瘤控制程度和达到治疗体积三倍的时间。用于微环境测定的肿瘤通过 Eppendorf 氧电极和 pimonidazole 染色测量肿瘤内缺氧程度，并通过内皮特异性染色的微血管密度测定法确定血管化程度。
所有微环境测定均表明所选克隆具有相似程度的缺氧和血管化。尽管如此，肿瘤对放射治疗的反应不同，因为 BB3 克隆在 5、10 和 15Gy 时显示出肿瘤控制，而 CE8 克隆在低于 15Gy 时则没有看到肿瘤控制。
对于显示出相似程度的氧合和血管化的肿瘤，体外放射抗性的克隆特异性可以预测体内对放射治疗的反应。这些结果支持这样的假设，即内在遗传因素可以控制这种癌症干细胞模型中的放射抗性。
