新合成抗体抑制癌细胞生长和血管

Notch家族的4个受体是广泛表达的跨膜蛋白，哺乳动物细胞通过它们进行沟通，来调控细胞命运和生长。Notch信号作用的缺陷与很多癌症相关，包括急性淋巴细胞白血病。利用“噬菌体呈现技术”，“基因科技公司”一个多学科小组了合成抗体，它们是Notch1 和Notch2的强效和特异性拮抗剂。抗Notch1的抗体在临床前小鼠模型中表现出抗肿瘤活性，能抑制癌细胞生长和血管，并且在培养中也表现出针对人类癌细胞的活性。

Notch1和Notch2的同时抑制会引起小肠毒性，而只抑制其中一个能在很大程度上避免这一效应，这是相对“泛Notch”抑制药物来说的一个潜在治疗优势。

由来自Salamander Design Studios的Gregóire Vion提供的本期封面图片描绘了一个配体表达细胞（右）和一个相邻细胞之间的通信——前一个细胞刺激后一个中的Notch信号作用。受体-细胞膜表达Notches 1 和 2（红色和蓝色）；特异性拮抗剂的作用意味着，只有蓝色信号被传导到细胞核。

原文出处：

Nature doi:10.1038/nature08878

Therapeutic antibody targeting of individual Notch receptors
Yan Wu1,9, Carol Cain-Hom2,9, Lisa Choy2, Thijs J. Hagenbeek2, Gladys P. de Leon7, Yongmei Chen1, David Finkle4, Rayna Venook4, Xiumin Wu5, John Ridgway5, Dorreyah Schahin-Reed6, Graham J. Dow2,10, Amy Shelton2, Scott Stawicki1, Ryan J. Watts6, Jeff Zhang8, Robert Choy8, Peter Howard8, Lisa Kadyk8, Minhong Yan5, Jiping Zha3, Christopher A. Callahan3, Sarah G. Hymowitz7  &  Christian W. Siebel2

   1. Department of Antibody Engineering,
   2. Department of Molecular Biology,
   3. Department of Pathology,
   4. Department of Translational Oncology,
   5. Department of Tumor Biology and Angiogenesis,
   6. Department of Neurodegeneration,
   7. Department of Structural Biology, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, USA
   8. Exelixis Inc., 210 East Grand Avenue, PO Box 511, South San Francisco, California 94083-0511, USA
   9. These authors contributed equally to this work.
  10. Present address: Department of Biology, Stanford University, Stanford, California 94305, USA.

The four receptors of the Notch family are widely expressed transmembrane proteins that function as key conduits through which mammalian cells communicate to regulate cell fate and growth1, 2. Ligand binding triggers a conformational change in the receptor negative regulatory region （NRR） that enables ADAM protease cleavage3, 4  at a juxtamembrane site that otherwise lies buried within the quiescent NRR5, 6. Subsequent intramembrane proteolysis catalysed by the γ-secretase complex liberates the intracellular domain （ICD） to initiate the downstream Notch transcriptional program. Aberrant signalling through each receptor has been linked to numerous diseases, particularly cancer7, making the Notch pathway a compelling target for new drugs. Although γ-secretase inhibitors （GSIs） have progressed into the clinic8, GSIs fail to distinguish individual Notch receptors, inhibit other signalling pathways9  and cause intestinal toxicity10, attributed to dual inhibition of Notch1 and 2 （ref. 11）. To elucidate the discrete functions of Notch1 and Notch2 and develop clinically relevant inhibitors that reduce intestinal toxicity, we used phage display technology to generate highly specialized antibodies that specifically antagonize each receptor paralogue and yet cross-react with the human and mouse sequences, enabling the discrimination of Notch1 versus Notch2 function in human patients and rodent models. Our co-crystal structure shows that the inhibitory mechanism relies on stabilizing NRR quiescence. Selective blocking of Notch1 inhibits tumour growth in pre-clinical models through two mechanisms: inhibition of cancer cell growth and deregulation of angiogenesis. Whereas inhibition of Notch1 plus Notch2 causes severe intestinal toxicity, inhibition of either receptor alone reduces or avoids this effect, demonstrating a clear advantage over pan-Notch inhibitors. Our studies emphasize the value of paralogue-specific antagonists in dissecting the contributions of distinct Notch receptors to differentiation and disease and reveal the therapeutic promise in targeting Notch1 and Notch2 independently.