MYL9高表达的肿瘤相关成纤维细胞在宫颈癌放疗抵抗中的功能和机制研究

Radiation resistance is a significant challenge to the therapy of advanced cervical carcinoma (CC). Tumor radiosensitivity is determined by both the intrinsic characteristics and the extrinsic stromal components of cancer cells. As the most abundant stromal cells in tumor microenvironment, cancer-associated fibroblasts (CAFs) are heterogeneous and contain different subpopulations with distinct molecular features and functions, which are critically involved in the radiation resistance of cancer cells. In previous study, we found that MYL9 was overexpressed in CC CAFs than in the normal cervical fibroblasts. In addition, the density of CAFs with high MYL9 expression in CC tissues of the radioresistant patients was markedly higher than that of radiosensitive ones. More importantly, knockdown of MYL9 reduced the radioprotective function of CAFs and inhibited the stemness in CC cells. On this basis, we intend to carry out the following researches: examine the clinical correlations between the expression of MYL9 in CAFs and the clinicopathologic characteristics, recurrence free survival and overall survival of CC patients treated with radiation therapy; study the function of CAFs with high MYL9 expression in CC radioresistance both in vitro and in vivo; clarify the regulation mechanism how MYL9 overexpressing CAFs mediate CC cells radiation resistance. This research will provide new targets and compelling evidence to apply radiation sensitization therapy as a promising strategy for accurate therapy, to further improve survival in CC patients.

放疗抵抗是局部晚期宫颈癌治疗面临的巨大难题。肿瘤放射敏感性不仅是癌细胞的内在属性，并与肿瘤间质密切相关。肿瘤相关成纤维细胞CAFs是肿瘤微环境中数量最丰富的间质成分，具有丰富的分子特征及功能，在肿瘤放疗抵抗中发挥重要作用。我们前期研究发现：①宫颈癌CAFs较正常宫颈成纤维细胞高表达MYL9分子；②放疗抵抗型宫颈癌CAFs中MYL9表达显著高于放疗敏感型；③敲降MYL9能削弱CAFs对宫颈癌细胞的放射保护作用，抑制癌细胞的干性。在此基础上，本项目将继续开展：①检测300例宫颈癌组织中MYL9的表达，揭示CAFs中MYL9表达与患者临床病理因素、放疗后无复发生存及总生存的关系；②通过细胞实验和动物实验进一步明确MYL9高表达CAFs在宫颈癌中放疗抵抗中的功能；③阐明CAFs高表达MYL9促进宫颈癌细胞放疗抵抗的机制。通过本项目的实施，有望为宫颈癌放射增敏提供新的靶点并最终提高肿瘤治疗效果。

宫颈癌是最常见的妇科系统恶性肿瘤，放射治疗是适用于各期宫颈癌的重要治疗手段，放疗抵抗是局部晚期宫颈癌复发及患者死亡的关键原因。随着对肿瘤微环境认识的加深，肿瘤相关成纤维细胞CAFs促进肿瘤发展的机制不断被揭示，靶向CAFs成为克服放疗抵抗的新手段。既往研究提示CAFs具有高度异质性，发现并鉴定宫颈癌与放疗抵抗相关的CAFs成为关注的重点。.我们通过宫颈癌CAFs和邻近正常成纤维细胞NFs的测序分析，发现肌球蛋白调节轻链9（MYL9）分子在CAFs高表达。免疫组化检测178例接受根治性放疗的宫颈癌组织样本，发现MYL9主要表达于肿瘤间质的成纤维细胞，MYL9高表达患者的无进展生存及总生存时间明显低于低表达患者，MYL9高表达是宫颈癌患者的不良预后因素，与宫颈癌的放疗抵抗可能相关。CAFs与宫颈癌细胞的共培养实验发现，敲降CAFs中MYL9表达能够减少照射后肿瘤细胞的存活，动物实验证实敲降CAFs中MYL9能够削弱照射后残余瘤的生长，说明CAFs表达MYL9在体外及体内均对肿瘤细胞具有放射保护作用。进一步研究发现MYL9在成纤维细胞中的高表达与肿瘤间质活化相关，MYL9下调能够抑制胶原回缩、下调细胞骨架蛋白表达。流式细胞术分选与CAFs共培养的宫颈癌细胞，发现多个介导放疗抵抗作用的分子在MYL9敲降组发生下调。我们的研究表明，MYL9是一个潜在的靶向宫颈癌肿瘤间质的治疗靶点。