Desai Sejal, Srambikkal Nishad, Yadav Hansa D, Shetake Neena, Balla Murali M S, Kumar Amit, Ray Pritha, Ghosh Anu, Pandey B N
Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India.
Homi Bhabha National Institute, Mumbai, Maharashtra, India.
PLoS One. 2016 Aug 25;11(8):e0161662. doi: 10.1371/journal.pone.0161662. eCollection 2016.
Even though bystander effects pertaining to radiation risk assessment has been extensively studied, the molecular players of radiation induced bystander effect (RIBE) in the context of cancer radiotherapy are poorly known. In this regard, the present study is aimed to investigate the effect of irradiated tumor cells on the bystander counterparts in mouse fibrosarcoma (WEHI 164 cells) tumor model. Mice co-implanted with WEHI 164 cells γ-irradiated with a lethal dose of 15 Gy and unirradiated (bystander) WEHI 164 cells showed inhibited tumor growth, which was measured in terms of tumor volume and Luc+WEHI 164 cells based bioluminescence in vivo imaging. Histopathological analysis and other assays revealed decreased mitotic index, increased apoptosis and senescence in these tumor tissues. In addition, poor angiogenesis was observed in these tumor tissues, which was further confirmed by fluorescence imaging of tumor vascularisation and CD31 expression by immuno-histochemistry. Interestingly, the growth inhibitory bystander effect was exerted more prominently by soluble factors obtained from the irradiated tumor cells than the cellular fraction. Cytokine profiling of the supernatants obtained from the irradiated tumor cells showed increased levels of VEGF, Rantes, PDGF, GMCSF and IL-2 and decreased levels of IL-6 and SCF. Comparative proteomic analysis of the supernatants from the irradiated tumor cells showed differential expression of total 24 protein spots (21 up- and 3 down-regulated) when compared with the supernatant from the unirradiated control cells. The proteins which showed substantially higher level in the supernatant from the irradiated cells included diphosphate kinase B, heat shock cognate, annexin A1, angiopoietin-2, actin (cytoplasmic 1/2) and stress induced phosphoprotein 1. However, the levels of proteins like annexin A2, protein S100 A4 and cofilin was found to be lower in this supernatant. In conclusion, our results provided deeper insight about the damaging RIBE in an in vivo tumor model, which may have significant implication in improvement of cancer radiotherapy.
尽管与辐射风险评估相关的旁观者效应已得到广泛研究，但在癌症放射治疗背景下，辐射诱导旁观者效应（RIBE）的分子机制却鲜为人知。在这方面，本研究旨在探讨受照射肿瘤细胞对小鼠纤维肉瘤（WEHI 164细胞）肿瘤模型中旁观者细胞的影响。将接受15 Gy致死剂量γ射线照射的WEHI 164细胞与未照射（旁观者）的WEHI 164细胞共同植入小鼠体内，结果显示肿瘤生长受到抑制，这通过肿瘤体积以及基于体内生物发光成像的Luc+WEHI 164细胞数量来衡量。组织病理学分析和其他检测表明，这些肿瘤组织的有丝分裂指数降低、凋亡和衰老增加。此外，在这些肿瘤组织中观察到血管生成不良，通过肿瘤血管荧光成像和免疫组织化学检测CD31表达进一步证实了这一点。有趣的是，与细胞成分相比，来自受照射肿瘤细胞的可溶性因子对旁观者效应的生长抑制作用更为显著。对受照射肿瘤细胞获得的上清液进行细胞因子分析显示，VEGF、RANTES、PDGF、GMCSF和IL-2水平升高，而IL-6和SCF水平降低。与未照射对照细胞的上清液相比，对受照射肿瘤细胞的上清液进行比较蛋白质组学分析显示，共有24个蛋白点表达差异（21个上调和3个下调）。在受照射细胞上清液中水平显著升高的蛋白质包括二磷酸激酶B、热休克同源蛋白、膜联蛋白A1、血管生成素-２、肌动蛋白（细胞质1/2）和应激诱导磷蛋白1。然而，发现膜联蛋白A2、蛋白S100 A4和丝切蛋白等蛋白质在该上清液中的水平较低。总之，我们的结果为体内肿瘤模型中具有损伤性的RIBE提供了更深入的见解，这可能对改善癌症放射治疗具有重要意义。
