SOX4在去势抵抗性前列腺癌中的作用及其机制研究

Castration-resistant prostate cancer (CRPC) has an extremely poor prognosis and remains a significant clinical challenge as the underlying mechanisms are largely unknown. The SOX4 transcription factor is involved in the development, maintenance of stem cell and cell fate decision. Overexpression of SOX4 has been identified in multiple cancers. Previously, our group has reported that SOX4 may collaborate with other oncogenes to promote PCa invasion and metastasis. Most recently, we found that the expression levels of SOX4 increases significantly in both CRPC tissues and PCa cells when placed under long-term androgen-deprivation condition. Furthermore, SOX4 expression was also up-regulated in the induced PCa stem cells. These data suggest that SOX4 may promote CRPC progression through androgen receptor (AR) dependent as well as AR independent ways (induction/maintenance of tumor stem cell). To define the roles of SOX4 in CRPC, our project is intended to: 1) characterize the clinico-pathological features of SOX4+ subtype PCa and mechanisms of SOX4 overexpression in CRPC. 2) determine the biological functions of SOX4 in CRPC and interactions between SOX4 and androgen-AR signaling pathway in vitro and in vivo. 3) evaluate the role of SOX4 in the induction, maintenance and self-renewal of PCa stem cells in CRPC. 4) systematically screen and identify the potentially targeted genes and miRNAs of SOX4. 5) establish transcription program and individualized regulation network of SOX4 expressions in CRPC.

去势抵抗性前列腺癌（CRPC）是前列腺癌（PCa）治疗领域的难点，患者预后差。SOX4基因是参与胚胎发育和干细胞维持的转录因子，在多种恶性肿瘤中过表达。本课题组前期报道了SOX4可与其它癌基因协同促进PCa的侵袭和转移。最近我们发现，SOX4在CRPC组织、长期雄激素剥夺条件下的PCa细胞和其诱导生成的肿瘤干细胞中表达水平均显著升高,提示SOX4可能通过雄激素受体(AR)依赖和AR非依赖（涉及肿瘤干细胞形成/维持）途径参与CRPC的发生和发展。为阐明SOX4在CRPC中的作用和机制，本课题拟分析SOX4在CRPC中过表达的病理学特征和分子机制；体内外实验观察SOX4在CRPC发生发展中的生物学功能及与雄激素-AR通路的关系；研究SOX4对PCa肿瘤干细胞形成、维持及自我更新的作用；系统筛选SOX4调控的靶基因和miRNA；整合并建立CRPC中SOX4表达相关的转录程序及"个性化"调控网络。

去势抵抗性前列腺癌（CRPC）是前列腺癌（PCa）治疗领域的难点，患者预后差。本研究运用免疫组化及生物学信息学数据库分析，miRNAseq、染色质免疫沉积（ChIP），荧光素酶报告实验、western-blot及裸鼠成瘤模型等体内外实验方法，发现：（1）与雄激素依赖性前列腺癌（HDPC）相比较，SOX4在CRPC中高表达。与LNCaP细胞相比，SOX4在LNCaP-AI细胞中高表达。（2）SOX4是雄激素抑制性基因且雄激素剥夺可诱导SOX4表达，SOX4促进CRPC细胞增殖、迁移和侵袭。（3）SOX4可通过调控HOXA9、STK33、EZH2表达促进前列腺癌进展。（4）CUL4B和SOX4在PCa组织均表达上调，并与恶性进展高度相关，即CUL4B及SOX4过表达与高Gleason评分（Gleason>7）及远处转移呈显著相关。（5）体内外实验表明CUL4B及SOX4均可促进PCa细胞增殖、浸润和转移。（6）CUL4B可通过表观遗传抑制miR-204表达正向调控SOX4表达。反之，SOX4可通过转录激活机制上调SOX4的表达，形成正反馈环路。此环路可进一步激活Wnt通路，进而促进PCa恶性进展。（7）Wnt通路抑制剂LGK974可显著抑制CUL4B介导的PCa细胞增殖及转移。临床样本也进一步证实，与CUL4B-/SOX4-（CUL4B和SOX4均低表达）组相比，CUL4B+/SOX4+组（CUL4B和SOX4均高表达）PCa患者预后更差。（8）SOX4可以正向调节miR-17-92的表达， SOX4过表达可以促进CRPC细胞LNCaP-AI增殖与迁移。（9）RB1是SOX4的下游靶基因，miR-17-92中的miR-17，miR-20a可以结合到RB1的3’UTR区并调控RB1的表达。（10）SOX4蛋白水平与miR-19a和miR-20a的表达水平呈正相关，与RB1蛋白的表达成负相关。因RB1的缺失在CRPC和NEPC的发生和发展中发挥重要作用，提示SOX4可能在上述转型中发挥重要作用。上述结果以SOX4研究为核心，探讨了其在CRPC发生发展和演进过程中的病理学特征及分子机制，从而为前列腺癌特异性诊断标志物及预后标志物的识别，分子分型的建立和治疗新靶点的筛选提供了重要实验依据。