The HIPPO pathway plays a critical role in contact inhibition, a pathway that is commonly dysregulated in many human cancers (including liver, colon, ovarian, and lung) and which relies on the intranuclear interaction of the transcriptional coactivator YAP and the transcription factor TEAD(1-4). This pathway also plays a crucial role in recovery from injury; for example, its regulated repression allows hepatocytes to divide and replace tissue lost to a partial hepatectomy, after which its activation suppresses cell growth and prevents tissue overgrowth. While small molecule enzyme inhibitors have proven to be a revelation in cancer therapy, cell growth signaling via protein-protein interactions has proven much more difficult to drug. While Antibodies can be effective in targeting extracellular or cell surface epitopes, intracellular targets, such as the interaction between YAP and TEAD, are not amenable to antibody-based therapeutics. Optides are small disulfide-knotted peptides (knottins) and serve to bridge these capabilities; they are large enough to interfere with protein-protein interactions, but small enough to penetrate into the cytosol. Examples include imperatoxin, an activator of mitochondrial ryanodine receptors, and Tumor Paint, which contains an optimized variant of chlorotoxin conjugated to a fluorescent probe and is capable of accumulating in a wide range of tumor types.

To test whether Optides can abrogate oncogenic signaling mediated by protein-protein interactions, we created libraries of computationally designed candidates to target the TEAD/YAP interface. The library is expressed on the surface of mammalian cells, chosen for the improved fidelity of disulfide bridge connectivity observed in the mammalian secretory pathway as compared to that found in yeast. By repetitive screening against soluble TEAD protein, we are optimizing the pool of candidates for targeting TEAD. The lead Optides will be characterized for their ability to reduce YAP-TEAD interaction, and to impair YAP-mediated cell growth. Owing to the wide variety of knottin scaffolds, both natural and in silico designed, this flexible technology could be applied to other targets in order to impair oncogenic protein-protein interactions.

Citation Format: Zachary R. Crook, Philip Bradley, Chris King, Andrew J. Mhyre, David Baker, James M. Olson. Optides (optimized knottin peptides) computationally designed to target the oncogenic HIPPO pathway. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2971.