MTp53-FOXM1-HMGB2轴促进浆液性卵巢癌恶性行为的机制研究

Serous ovarian carcinoma (SOC) is the most common subtype of ovarian cancer. The Cancer Genome Atlas (TCGA) project showed that FOXM1 signaling pathway is over-activated in 87% SOC patients. The mechanism of FOXM1 overexpression and its downstream target genes haven't been systematically illustrated. FOXM1 was found to be overexpressed and associated with poor clinical prognosis of SOC in our preliminary study. HMGB2 was identified as the candidate downstream target gene of FOXM1 through ChIP-seq in our previous work. We put forward the hypothesis that TP53 mutation leads to over-activation of FOXM1, then FOXM1 transcriptionally activates HMGB2 and mutant p53-FOXM1-HMGB2 axis promotes the malignancy of SOC. This study aims to determine the biological functions of FOXM1 by in vitro and in vivo assays and illustrate the transcriptional activation mechanism of HMGB2 by FOXM1 through ChIP and luciferase assays. We will interpret the upstream regulatory mechanism of FOXM1 in SOC. The immunohistochemistry staining analysis will be applied to characterize the expression and prognostic value of MTp53-FOXM1-HMGB2 axis. This study contributes to revealing the application value of FOXM1 for molecular classification and molecularly-targeted therapy of SOC.

浆液性卵巢癌（serous ovarian carcinoma, SOC）是最常见的卵巢恶性肿瘤。TCGA计划对SOC测序分析发现，FOXM1信号通路在87%样本中存在异常活化，但其高表达机制及调控的靶基因尚未系统阐明。课题组前期发现FOXM1在SOC中普遍高表达并与患者不良预后相关，ChIP-seq筛选出候选靶基因HMGB2。课题组提出假说：SOC中TP53突变导致FOXM1过度激活，FOXM1又转录激活HMGB2，MTp53-FOXM1-HMGB2轴促进SOC的恶性行为。为验证该假说，课题组将利用体内外实验明确FOXM1在SOC中生物学功能；ChIP和luciferase实验阐明FOXM1转录激活HMGB2的机制；阐释FOXM1上游调控机制；免疫组化分析MTp53-FOXM1-HMGB2表达相关性及与预后关系。本研究有助于揭示FOXM1在分子分型和靶向治疗中的应用价值。

卵巢癌的TCGA数据发现87%高级别浆液性卵巢癌中存在FOXM1异常激活，但其高表达机制及调控的靶基因尚未系统阐明。课题组发现FOXM1在新鲜冰冻卵巢癌组织中的表达明显高于正常输卵管伞组织。基于课题组构建的高级别浆液性卵巢癌组织芯片的免疫组化证实FOXM1在卵巢中高表达，并与患者不良预后密切相关。生物学功能证实FOXM1促进卵巢癌细胞增殖和转移。p53突变和DDX23转录调控是卵巢癌中FOXM1异常高表达的重要原因。ChIP-seq以及RNA-seq联合分析发现了FOXM1在卵巢癌中的关键下游靶基因HMGB2，FOXM1干扰后HMGB2的mRNA及蛋白表达均下调，双荧光素酶报告基因实验确认FOXM1可以直接结合到HMGB2启动子上转录激活其表达。HMGB2是卵巢癌中异常高表达的染色质重塑分子，基于卵巢癌组织芯片免疫组化染色发现HMGB2高表达与患者总生存期以及无进展生存期呈负相关。生物学功能实验发现HMGB2干扰抑制卵巢癌细胞的增殖和转移。干扰HMGB2表达后RNA-seq分析发现下调基因主要富集在转录调控、细胞增殖、细胞黏附等功能。ATAC-seq分析了HMGB2干扰前后对卵巢癌细胞染色质开放性的影响，发现HMGB2干扰后PTK2/FAK的mRNA及蛋白表达均下调，拯救实验证实FAK是HMGB2在卵巢癌中执行促癌功能的关键靶基因。此外，通过ChIP-seq以及RNA-seq筛选鉴定出HMGB2在卵巢癌中潜在结合并转录调控下游关键靶基因RALBP1。