Poleszczuk Jan, Krzywon Aleksandra, Forys Urszula, Widel Maria
a College of Inter-faculty Individual Studies in Mathematics and Natural Sciences, University of Warsaw, Warsaw, Poland.
Radiat Res. 2015 May;183(5):571-7. doi: 10.1667/RR13907.1. Epub 2015 Apr 6.
For the last two decades radiation-induced bystander effects (RIBEs) have attracted significant attention due to their possible implications for radiotherapy. However, despite extensive research, the molecular pathways associated with RIBEs are still not completely known. In the current study we investigated the role of senescence in the bystander response. Irradiated (2, 4, 6 and 8 Gy) human colorectal carcinoma cells (HCT116) with p53(+/+) (wild-type) or p53(-/-) (knockout) gene were co-incubated with nonirradiated cells of the same type. Clonogenic and senescence assays were used for both irradiated and co-incubated bystander cell populations. We also performed additional measurements on the number of remaining cells after the whole co-incubation period. For radiation doses larger than 2 Gy we observed much larger fractions of senescent cells in p53-positive populations compared to their p53-negative counterparts (15.81% vs. 3.63% in the irradiated population; 2.89% vs. 1.05% in the bystander population; 8 Gy; P < 0.05). Statistically significant differences between cell lines in the clonogenic cell surviving fraction were observed for doses higher than 4 Gy (1.61% for p53(+/+) vs. 0.19% for p53(-/-) in irradiated population; 3.57% for +/+ vs. 50.39% for -/- in bystander population; 8 Gy; P < 0.05). Our main finding was that the number of senescent cells in the irradiated population correlated strongly with the clonogenic cell surviving fraction (R = -0.98, P < 0.001) and the number of senescent cells (R = 0.97, P < 0.001) in the bystander population. We also extended the standard linear-quadratic radiation response model by incorporating the influence of the signals released by the senescent cells, which accurately described the radiation response in the bystander population. Our findings suggest that radiation-induced senescence might be a key player in RIBE, i.e., the strength of RIBE depends on the amount of radiation-induced senescence.
在过去二十年中，辐射诱导的旁观者效应（RIBE）因其对放射治疗的潜在影响而备受关注。然而，尽管进行了广泛研究，但与RIBE相关的分子途径仍未完全明确。在本研究中，我们调查了衰老在旁观者反应中的作用。将经2、4、6和8 Gy照射的具有p53（+/+）（野生型）或p53（-/-）（敲除）基因的人结肠癌细胞（HCT116）与未照射的同类型细胞共同孵育。对照射的和共同孵育的旁观者细胞群体进行克隆形成和衰老测定。我们还对整个共同孵育期后的剩余细胞数量进行了额外测量。对于大于2 Gy的辐射剂量，我们观察到p53阳性群体中的衰老细胞比例远高于其p53阴性对应群体（照射群体中分别为15.81%和3.63%；旁观者群体中分别为2.89%和1.05%；8 Gy；P < 0.05）。对于高于4 Gy的剂量，观察到细胞系在克隆形成细胞存活分数上存在统计学显著差异（照射群体中p53（+/+）为1.61%，p53（-/-）为0.19%；旁观者群体中+/+为3.57%，-/-为50.39%；8 Gy；P < 0.05）。我们的主要发现是，照射群体中的衰老细胞数量与克隆形成细胞存活分数（R = -0.98，P < 0.001）以及旁观者群体中的衰老细胞数量（R = 0.97，P < 0.001）密切相关。我们还通过纳入衰老细胞释放信号的影响扩展了标准的线性二次辐射反应模型，该模型准确描述了旁观者群体中的辐射反应。我们的研究结果表明，辐射诱导的衰老可能是RIBE中的关键因素，即RIBE的强度取决于辐射诱导衰老的程度。
