PDF(Pubmed)
Abstract：
Background: Cellular senescence in response to ionizing radiation (IR) limits the replication of damaged cells by causing permanent cell cycle arrest. However, IR can induce pro-survival signaling pathways that reduce the extent of radiation-induced cytotoxicity and promote the development of radioresistance. The differential incorporation of histone variant H2A.J has profound effects on higher-order chromatin organization and on establishing the epigenetic state of radiation-induced senescence. However, the precise epigenetic mechanism and function of H2A.J overexpression in response to IR exposure still needs to be elucidated. Methods: Primary (no target, NT) and genetically modified fibroblasts overexpressing H2A.J (H2A.J-OE) were exposed to 20 Gy and analyzed 2 weeks post-IR for radiation-induced senescence by immunohistochemistry and immunofluorescence microscopy. Transcriptome signatures were analyzed in (non-)irradiated NT and H2A.J-OE fibroblasts by RNA sequencing. Since H2A.J plays an important role in the epidermal homeostasis of human skin, the oncogenic potential of H2A.J was investigated in cutaneous squamous cell carcinoma (cSCC). The tissue microarrays of cSCC were analyzed for H2A.J protein expression pattern by automated image analysis. Results: In response to radiation-induced DNA damage, the overexpression of H2A.J impairs the formation of senescence-associated heterochromatin foci (SAHF), thereby inhibiting the SAHF-mediated silencing of proliferation-promoting genes. The dysregulated activation of cyclins and cyclin-dependent kinases disturbs cell cycle arrest in irradiated H2A.J-OE fibroblasts, thereby overcoming radiation-induced senescence. Comparative transcriptome analysis revealed significantly increased WNT16 signaling in H2A.J OE fibroblasts after IR exposure, promoting the fundamental mechanisms of tumor development and progression, including the activation of the epithelial-mesenchymal transition. The quantitative analysis of cSCCs revealed that undifferentiated tumors are associated with high nuclear H2A.J expression, related with greater oncogenic potential. Conclusion: H2A.J overexpression induces radioresistance and promotes oncogenic transformation through the activation of WNT16 signaling pathway functions. H2A.J-associated signatures may improve risk stratification by identifying patients with more aggressive cSCC who may require radiotherapy with increased doses.
摘要：
背景：响应电离辐射（IR）的细胞衰老通过引起永久性细胞周期停滞来限制受损细胞的复制。然而,IR可以诱导促存活信号通路，从而降低辐射诱导的细胞毒性程度并促进辐射抗性的发展。组蛋白变体H2A的差异掺入。J对高阶染色质组织和建立辐射诱导衰老的表观遗传状态具有深远的影响。然而,H2A的确切表观遗传机制和功能。仍然需要阐明响应于IR暴露的J过表达。方法：主要(无目标，NT）和过表达H2A的基因修饰成纤维细胞。J（H2A。J-OE）暴露于20Gy，并在IR后2周通过免疫组织化学和免疫荧光显微镜分析辐射诱导的衰老。在(未)照射的NT和H2A中分析转录组特征。通过RNA测序的J-OE成纤维细胞。自从H2A。J在人类皮肤的表皮稳态中起着重要作用，H2A的致癌潜力。J在皮肤鳞状细胞癌（cSCC）中进行了研究。分析cSCC的组织微阵列的H2A。通过自动图像分析的J蛋白表达模式。结果：对辐射引起的DNA损伤，H2A的过表达。J损害衰老相关异染色质灶（SAHF）的形成，从而抑制SAHF介导的增殖促进基因的沉默。细胞周期蛋白和细胞周期蛋白依赖性激酶的激活失调会干扰辐照的H2A中的细胞周期停滞。J-OE成纤维细胞,从而克服辐射诱导的衰老。比较转录组分析显示H2A中WNT16信号传导显著增加。红外暴露后的JOE成纤维细胞，促进肿瘤发展和进展的基本机制，包括上皮-间质转化的激活。cSCC的定量分析显示未分化肿瘤与高核H2A相关。J表达式,与更大的致癌潜力有关。结论：H2A。J过表达通过激活WNT16信号通路功能诱导放射抗性并促进致癌转化。H2A.J相关的特征可以通过识别具有更积极的cSCC的患者来改善风险分层，这些患者可能需要增加剂量的放疗。
