Qvarnström Fredrik, Simonsson Martin, Nyman Jan, Hermansson Ingegerd, Book Majlis, Johansson Karl-Axel, Turesson Ingela
Section of Oncology, Department of Radiology, Oncology and Radiation Science, Uppsala University, Sweden.
Department of Oncology, Göteborg University, Sahlgrenska University Hospital, Sweden.
Radiother Oncol. 2017 Jan;122(1):163-169. doi: 10.1016/j.radonc.2016.12.004. Epub 2016 Dec 22.
Previously we reported that hyper-radiosensitivity (HRS) was evidenced by quantifying DNA double strand break (DSB) foci in epidermis biopsies collected after delivering radiotherapeutic one and five dose fractions. The aim of this study was to determine whether HRS was preserved throughout a 7-week radiotherapy treatment, and also to examine the rate of foci decline and foci persistence between dose fractions.
42 patients with prostate cancer received 7-week fractionated radiotherapy treatment (RT) with daily dose fractions of 0.05-1.10Gy to the skin. Before RT, and at several times throughout treatment, skin biopsies (n=452) were collected at 30min, and 2, 3, 24, and 72h after dose fractions. DSB-foci markers, γH2AX and 53BP1, were labelled in epidermal keratinocytes with immunofluorescence and immunohistochemical staining. Foci were counted both with digital image analysis and manually.
HRS in keratinocytes was evidenced by the dose-response relationships of DSB foci, observed throughout the treatment course, independent of sampling time and quantification method. Foci observed at 24h after dose fractions indicated considerable DSB persistence. Accordingly, foci significantly accumulated after 5 consecutive dose fractions. For doses below 0.3Gy, persistent foci could be observed even at 72h after damage induction. A comparison of γH2AX and 53BP1 quantifications in double-stained biopsies showed similar HRS dose-response relationships.
These results represented the first evidence of preserved HRS, assessed by γH2AX- and 53BP1-labelled DSB foci, throughout a 7-week treatment course with daily repeated subtherapeutic dose fractions.
此前我们报道，通过对放射治疗1次和5次剂量分割后采集的表皮活检组织中的DNA双链断裂（DSB）灶进行定量分析，证实了超放射敏感性（HRS）。本研究的目的是确定在为期7周的放射治疗过程中HRS是否持续存在，并研究剂量分割之间灶的下降率和灶的持续性。
42例前列腺癌患者接受为期7周的分次放射治疗（RT），皮肤每日剂量分割为0.05 - 1.10Gy。在放疗前以及治疗过程中的多个时间点，在剂量分割后30分钟、2小时、3小时、24小时和72小时采集皮肤活检组织（n = 452）。用免疫荧光和免疫组织化学染色在表皮角质形成细胞中标记DSB灶标志物γH2AX和53BP1。通过数字图像分析和手动计数灶的数量。
在整个治疗过程中观察到，DSB灶的剂量反应关系证明了角质形成细胞中的HRS，与采样时间和定量方法无关。在剂量分割后24小时观察到的灶表明有相当数量的DSB持续存在。因此，连续5次剂量分割后灶显著积累。对于低于0.3Gy的剂量，即使在损伤诱导后72小时也能观察到持续存在的灶。对双重染色活检组织中γH2AX和53BP1定量的比较显示了相似的HRS剂量反应关系。
这些结果首次证明，在为期7周的每日重复亚治疗剂量分割治疗过程中，通过γH2AX和53BP1标记的DSB灶评估，HRS持续存在。
