Department of Medicine, Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center-Shreveport, Shreveport, Louisiana 71130, USA.
J Cell Biochem. 2011 Sep;112(9):2340-51. doi: 10.1002/jcb.23157.
The Notch receptor pathway provides a paradigm for juxtacrine signaling pathways and controls stem cell function, developmental cell fate decisions, and cellular differentiation. The Notch pathway is constitutively activated in human cancers by chromosomal rearrangements, activating point mutations, or altered expression patterns. Therefore, the Notch pathway is the subject of chemotherapeutic intervention in a variety of human cancers. Notch receptor activation results in the gamma-secretase dependent proteolytic cleavage of the receptor to liberate the Notch intracellular domain that acts to mediate co-activator recruitment to the DNA binding transcription factor, CSL (CBF-1/RBP-Jκ, Su(H), Lag-1). Therapeutic targeting of the Notch pathway by gamma-secretase inhibitors prevents NICD production and regulates CSL-dependent transcriptional activity. To interrogate the loss of CSL activity in breast and prostate cancer cells, we used lentiviral-based shRNA knockdown of CSL. Knockdown of CSL expression was assessed by decreased DNA binding activity and resulted in decreased cell proliferation. In contrast, gamma-secretase inhibitor (GSI) treatment of these prostate and breast cancer cell lines resulted in minimal growth effects. PCR profiling of Notch pathway genes identified expression changes in few genes (Delta-like-1, Deltex-1, LMO2, and SH2D1A) after CSL knockdown. Consistent with differential effects of GSI on cell survival, GSI treatment failed to recapitulate the gene expression changes observed after CSL knockdown. Thus, CSL inhibition may provide a more effective mechanism to inhibit Notch-pathway dependent cancer cell proliferation as compared to GSI treatment.
Notch 受体途径为旁分泌信号通路提供了范例，控制着干细胞功能、发育细胞命运决定和细胞分化。 Notch 途径在人类癌症中通过染色体重排、激活点突变或改变表达模式而被持续激活。因此， Notch 途径是各种人类癌症化疗干预的对象。 Notch 受体的激活导致 Notch 细胞内结构域的 γ-分泌酶依赖性蛋白水解切割，从而介导共激活因子募集到 DNA 结合转录因子 CSL（CBF-1/RBP-Jκ、Su（H）、Lag-1）。通过 γ-分泌酶抑制剂对 Notch 途径进行治疗性靶向，可防止 NICD 的产生并调节 CSL 依赖性转录活性。为了研究 CSL 活性在乳腺癌和前列腺癌细胞中的缺失，我们使用基于慢病毒的 shRNA 敲低 CSL。CSL 表达的敲低通过降低 DNA 结合活性来评估，并导致细胞增殖减少。相比之下，γ-分泌酶抑制剂（GSI）处理这些前列腺和乳腺癌细胞系仅导致最小的生长效应。Notch 途径基因的 PCR 谱分析表明，CSL 敲低后少数基因（Delta-like-1、Deltex-1、LMO2 和 SH2D1A）的表达发生变化。与 GSI 对细胞存活的不同影响一致，GSI 处理未能重现 CSL 敲低后观察到的基因表达变化。因此，与 GSI 治疗相比，CSL 抑制可能为抑制 Notch 途径依赖性癌细胞增殖提供更有效的机制。
