中文摘要：

肿瘤的发生和发展是一个多因素、多步骤的过程。越来越多的证据表明，肿瘤的发生发展与表观遗传学机制所致的癌基因激活和抑癌基因失活有关。表观遗传学尤其是miRNA调控异常导致的癌基因和抑癌基因表达异常研究越来越深入，miRNA调控异常介导的肿瘤放化疗抗拒是目前成功治疗大多数肿瘤的主要阻碍。虽然表观遗传学中miRNA研究越来越多，但是miRNA介导放化疗抗拒的相关文献较少，本综述希望结合目前miRNA在肿瘤中的作用以及其放化疗耐受的机制作进一步的探讨，深入了解miRNA在肿瘤中的作用能有望为我们治疗肿瘤提供新思路。

英文摘要：

The tumorigenesis and progression of cancers are a multi-step and multi-factor process. More and more evidence has suggested that several factors, including gene regulatory mechanisms and epigenetic regulations, are involved in carcinogenesis and progression. Recent studies have focused on the epigenetic changes especially ofmiRNA which can lead to dysfunctions of oncogenes and tumor suppressor genes. However, the underlying mechanism of miRNAs on chemo- and radio- resistance of tumors remains unclear and the related researches are very few. This review discusses new insights into the role of miRNAs in regulating genes or proteins and explains how miRNAs influence treatment efficacy in cancer chemotherapy and radiotherapy through miRNAs regulation.