miR-21 signaling in tumor response to radiation treatment

描述（由申请人提供）：克服放射耐药是改善放射治疗的必要条件。最近，我们发现miR-21作为一种onco-miR通过促进DNA双链修复参与细胞的辐射抵抗。这些结果表明，靶向miR-21是使肿瘤细胞对辐射敏感的良好策略；然而，由于辐射可诱导miR-21上调，miR-21的上调可反过来降低单独靶向miR-21对放射致敏的影响。此外，肿瘤微环境是影响肿瘤状况的重要因素，肿瘤周围组织中miR-21的状态可能会影响肿瘤对电离辐射治疗的反应。因此，为了有效阻断miR-21在肿瘤放射抵抗中的作用，我们需要在体外和体内了解辐照肿瘤细胞中miR-21信号转导的全貌。为此，我们设计了两个目标

DESCRIPTION (provided by applicant): Overcoming radioresistance is essential for improving radiotherapy. Recently, we found that miR-21 as an onco-miR involved cell radioresistance through promoting DNA double strand repair. These results suggest that targeting miR-21 is a good strategy for sensitizing tumor cells to radiation; however, since radiation could induce miR-21 up-regulation, the up-regulated miR- 21 could in turn reduce the effects of targeting miR-21 alone on radiosensitization. In addition, the miR-21 status in the surrounding tumor tissue may affect tumor response to ionizing radiation treatment since the tumor microenvironment is an important factor that affects the tumor situation. Therefore, in order to efficiently block the function of miR-21 in tumor radioresistance, we need to know the whole picture of miR-21 signaling in irradiated tumor cells in vitro and in vivo. For this purpose, we designed two aims in this proposal. Aim 1: Determine how IR stimulates miR-21 up-regulation. We will elucidate IR-promoted upstream regulation of miR-21 with the methods and approaches of molecular and cellular biology by answering the following four questions: 1) Whether the IR-activated ATR stimulates miR-21 expression through phosphorylating STAT3 at S694. 2) Whether STAT3 as a transcription factor could directly stimulate the EGFR expression to respond to IR. 3) Whether EGFR inhibits miR-21 maturation through phosphorylating AGO2 at Y393 to respond to IR. 4) Whether miR-21 could directly target p53 that negatively regulates EGFR expression through inhibiting YY1 and SP1 (the transcription factors of EGFR). Aim 2: Determine whether and how miR-21 in the tumor microenvironment affects the tumor response to IR treatment. We will use two mouse models: 1) miR-21 knock-in or knockout mouse model: we will use tumor cells that can grow tumors in these immune efficient mice. 2) nude mouse model: we will use the human tumor cells that can grow xenograft tumors in the immune deficient mice. These tumor cell lines (mouse or human) will be down-regulated with miR-21 or its upstream regulators, subcutaneously inoculated into the hind legs of the mice. We will observe the tumor size and examine the level/activity of miR- 21/its relevant regulators in the tumor tissue and the surrounding tissues after the tumor areas are irradiated. The results from this proposal are expected to help us better understand the role of miR-21 in mediating tumor radioresistance in vitro and in vivo, thus, providing an efficient way to block the miR-21 pathway for improving radiotherapy in the near future.