Department of Radiation Oncology, Changzhou No. 4 People's Hospital, Soochow University, Changzhou, China.
Department of Oncology, The Affiliated Changzhou No. 2 People's Hospital of Nanjing Medical University, Changzhou, China.
Cancer Sci. 2019 Mar;110(3):962-972. doi: 10.1111/cas.13946. Epub 2019 Feb 8.
Radiotherapy has been widely used for the clinical management of esophageal squamous cell carcinoma. However, radioresistance remains a serious concern that prevents the efficacy of esophageal squamous cell carcinoma (ESCC) radiotherapy. REV7, the structural subunit of eukaryotic DNA polymerase ζ, has multiple functions in bypassing DNA damage and modulating mitotic arrest in human cell lines. However, the expression and molecular function of REV7 in ESCC progression remains unclear. In this study, we first examined the expression of REV7 in clinical ESCC samples, and we found higher expression of REV7 in ESCC tissues compared to matched adjacent or normal tissues. Knockdown of REV7 resulted in decreased colony formation and increased apoptosis in irradiated Eca-109 and TE-1 cells coupled with decreased tumor weight in a xenograft nude mouse model postirradiation. Conversely, overexpression of REV7 resulted in radioresistance in vitro and in vivo. Moreover, silencing of REV7 induced increased reactive oxygen species levels postirradiation. Proteomic analysis of REV7-interacting proteins revealed that REV7 interacted with peroxiredoxin 2 (PRDX2), a well-known antioxidant protein. Existence of REV7-PRDX2 complex and its augmentation postirradiation were further validated by immunoprecipitation and immunofluorescence assays. REV7 knockdown significantly disrupted the presence of nuclear PRDX2 postirradiation, which resulted in oxidative stress. REV7-PRDX2 complex also assembled onto DNA double-strand breaks, whereas REV7 knockdown evidently increased double-strand breaks that were unmerged by PRDX2. Taken together, the present study sheds light on REV7-modulated radiosensitivity through interacting with PRDX2, which provides a novel target for ESCC radiotherapy.
放射治疗已广泛用于食管鳞癌的临床治疗。然而，放射抵抗仍然是一个严重的问题，它会影响食管鳞癌（ESCC）放射治疗的疗效。REV7 是真核 DNA 聚合酶 ζ 的结构亚基，在人细胞系中具有多种功能，包括绕过 DNA 损伤和调节有丝分裂停滞。然而，REV7 在 ESCC 进展中的表达和分子功能仍不清楚。在本研究中，我们首先检测了临床 ESCC 样本中 REV7 的表达，发现 ESCC 组织中 REV7 的表达高于匹配的相邻或正常组织。REV7 敲低可降低照射后 Eca-109 和 TE-1 细胞的集落形成和增加细胞凋亡，并在照射后裸鼠异种移植模型中降低肿瘤重量。相反，REV7 的过表达导致体外和体内的放射抵抗。此外，REV7 沉默照射后可增加活性氧水平。REV7 相互作用蛋白的蛋白质组学分析表明，REV7 与过氧化物酶 2（PRDX2）相互作用，PRDX2 是一种众所周知的抗氧化蛋白。REV7-PRDX2 复合物的存在及其在照射后的增加通过免疫沉淀和免疫荧光检测得到进一步验证。REV7 敲低显著破坏了照射后核 PRDX2 的存在，从而导致氧化应激。REV7-PRDX2 复合物也组装到 DNA 双链断裂处，而 REV7 敲低明显增加了 PRDX2 未合并的双链断裂。综上所述，本研究表明，REV7 通过与 PRDX2 相互作用调节放射敏感性，为 ESCC 放射治疗提供了一个新的靶点。
