The influence of ionising radiation on intracellular pathways of the mitogen activated protein kinase (MAPK) family

对于放射治疗师来说，众所周知，不同类型的肿瘤具有不同的放射敏感性。据信，肿瘤和内皮细胞之间的串扰对实体瘤的放射敏感性有影响。电离辐射调节肿瘤细胞的信号通路。在这种情况下，丝裂原活化蛋白激酶（MAPK）途径发挥了主要作用。肿瘤细胞中有两个MAPK通路的关键参与者，它们被已知影响肿瘤细胞存活或凋亡的电离辐射激活。此外，这些通路的激活可导致血管内皮生长因子（VEGF）的过度表达。然后，VEGF从肿瘤细胞中释放出来，保护内皮细胞免受辐射诱导的凋亡。本研究的目的是首先研究电离辐射对肿瘤细胞中VEGF释放的影响，其次分析VEGF对内皮细胞内MAPK信号通路的影响，第三，通过特异性VEGF受体酪氨酸激酶抑制剂（PTK787）阻断VEGF的信号转导，评估电离辐射对MAPK信号通路的直接影响。细胞系研究已经在进行中。本研究的一部分将是肿瘤异种移植模型。这些小鼠将接受单独或联合PTK787的分次放射治疗。同时，犬自发性口腔SCC、FSA患者也将被纳入研究。为了检测活性和非活性信号蛋白，将使用免疫荧光和免疫印迹。这项研究将通过在体外和体内显示活跃和不活跃的MAPK信号通路之间的比例，为肿瘤的辐射抗性机制提供更多的见解。本研究将证明放射治疗和特异性阻断生存途径联合治疗的有效性。

For radiotherapists, it is well known that different tumour types have different radiosensitivities. It is believed that a cross talk between tumour and endothelial cells have an impact on the radiosensitivity of solid tumours. Ionising radiation modulates signaling pathways in tumour cells. In this context, the mitogen activated protein kinase (MAPK) pathways play a major role. There are two key players of MAPK pathways in tumour cells that are activated by ionising radiation known to influence survival or apoptosis of tumour cells. In addition, the activation of these pathways can lead to overexpression of the vascular endothelial growth factor (VEGF). VEGF is then released from tumour cells and it protects endothelial cells from radiation induced apoptosis. The aim of this study is to first investigate the influence of ionising radiation on VEGF release from tumour cells, second, to analyse the influence of VEGF on intracellular MAPK signalling pathways in endothelial cells and third, to evaluate the direct influence of ionising radiation on MAPK pathways by blocking the signal transduction of VEGF with a specific VEGF receptor tyrosin kinase inhibitor (PTK787). Cell line studies are already under investigation. Part of this study will be a tumour xenograft model. The mice will be treated with fractionated radiation therapy alone or in combination with PTK787. At the same time canine patients with spontaneous oral SCC, FSA will be included in the study. For detection of active and inactive signalling proteins immunofluorescence and immunoblotting will be used. This study will give more insights in the mechanisms of radioresistance in tumours by showing a ratio between active and inactive MAPK signalling pathways in vitro and in vivo. This study will prove the efficacy of combined treatment of radiation therapy and specific blockage of survival pathways.