FADD 基因扩增在乳腺癌中的作用与靶向治疗研究

Deregulation of cell apoptosis is a hallmark of cancer. FADD gene plays a key role in extrinsic apoptosis pathway by forming Death-inducing signaling complex (DISC) with other factors, which proceeds to induce apoptosis of cells. By analyzing the genomic profiling data of breast cancer, we found that chromosome 11q13.3 locus is highly amplified in some breast cancer tissues, leading to increased copy number of FADD. In addition, amplification of FADD correlates with higher gene expression and poorer prognosis of patients. This observation contradicts with the pro-apoptosis role of FADD in cells, suggesting FADD-associated cell apoptosis signaling is blocked. Previous studies found that FADD also has pro-proliferation functions, which is related to its phosphorylation and nuclear translocation. Our preliminary data also demonstrated that an inhibitor of FADD kinase CKIα can block the proliferation of FADD amplified cells, whereas little effects were observed in non-amplified cells. Based on those data, we propose that FADD amplification in breast cancer leads to higher FADD expression, which is then phosphorylated by CKIα and undergoes functional switch from pro-apoptosis to pro-proliferation. Inhibition of FADD phosphorylation may reverse its function and induce apoptosis of cancer cells. So, in this study, we are going to investigate the effect of FADD gene amplification on the apoptosis and proliferation of breast cancer cells, and study the mechanisms underlying the tolerance of cancer cells to FADD induced apoptosis. We will also explore the strategies to inhibit this process. This study may reveal the mechanisms underlying apoptosis tolerance of FADD amplified breast cancer, and may suggest new targets for breast cancer treatment.

凋亡调控异常是肿瘤典型特征之一。FADD 是外源性凋亡通路的核心，能够参与凋亡复合体形成并诱发凋亡。我们分析多个乳腺癌基因组数据发现，染色体 11q13.3发生明显扩增，导致 FADD基因拷贝数增加，且患者预后不良。同时，免疫组化染色显示FADD在乳腺癌中表达升高。这些现象与FADD的凋亡调控功能相左。既往研究表明FADD同时具有促进增殖作用，且与其磷酸化和细胞核转位密切相关。我们发现抑制FADD激酶CKIα能够抑制FADD扩增细胞的生长，而对非扩增细胞无影响。据此我们提出假设：乳腺癌中FADD扩增并高表达，产物被CKIα磷酸化导致促凋亡功能受抑制而促增殖功能被激活；阻断FADD磷酸化能够逆转其功能并重启凋亡。本项目拟通过体内外实验研究 FADD基因扩增对乳腺癌凋亡和增殖的作用，发现肿瘤细胞凋亡耐受的分子机制，并寻找重启细胞凋亡的措施。本研究有望揭示FADD 扩增乳腺癌的新型治疗靶点。

FADD基因在调控细胞凋亡在肿瘤生长，进展，转移中发生重要作用。在研究中，我们发现FADD是一个潜在的乳腺癌治疗靶点，并且揭示其在乳腺癌进展中发挥重要作用，并进一步揭示其机制。FADD在乳腺正常细胞以及正常组织低表达,而在乳腺癌细胞以及乳腺癌组织中表达增高。本研究中我们发现通过使用siRNA沉默FADD的表达可以抑制乳腺癌细胞的生长，促进乳腺癌细胞的凋亡，抑制乳腺癌癌细胞转移，而这些现象涉及的分子通路改变包括敲低FADD可以抑制AKT/ ERK 通路，抑制BAX/LC3,激活ATM相关凋亡通路，而对经典凋亡通路Caspase 3/Caspase 8相关凋亡通路无明显影响。我们还发现FADD与凋亡通路的表达存在负相关. 进一步研究表明，裸鼠移植瘤的实验结果进一步证实抑制FADD的表达可减轻乳腺癌移植瘤的体积和重量。我们同时发现乳腺癌病人的临床标本中FADD高表达患者的预后更差，总生存率较FADD低表达者低。综上所述，我们的研究证明，在乳腺癌中敲低FADD通过影响一系列信号通路抑制肿瘤细胞的生长，有望成为乳腺癌治疗的可能的靶点。