Showing papers by "Stephen W. Fesik published in 2012"
TL;DR: K-Ras inhibition represents an attractive therapeutic strategy for many cancers, however, Ras activation and signaling is accomplished primarily through protein-protein interactions that typically lack well-defined binding pockets and have been difficult to target with small molecules.
Abstract: K-Ras is a small GTPase that functions as a molecular switch cycling between inactive (GDP-bound) and active (GTP-bound) states. The conversion of K-Ras-GDP to K-Ras-GTP is the rate-limiting step in the activation of K-Ras and is catalyzed by guanine nucleotide exchange factors such as the son of sevenless (Sos). Mutations in K-Ras fix the protein in the active state and endow cells with capabilities that represent the hallmarks of cancer.[1] These include the ability to proliferate, evade apoptosis, reprogram cell metabolism, induce angiogenesis, activate invasion and metastasis, and escape immune destruction.[2] Indeed, aberrant K-Ras signaling plays a role in 30% of all human cancers, with the highest incidence of activating mutations found in pancreatic (70-90%), colon (30-50%), and lung (20-30%) carcinomas.[3] Downregulation of activated Ras reverses the transformed phenotype of cells and results in the dramatic regression of tumors in murine xenograft models.[4] Thus, K-Ras inhibition represents an attractive therapeutic strategy for many cancers. However, Ras activation and signaling is accomplished primarily through protein-protein interactions. Such protein interfaces typically lack well-defined binding pockets and have been difficult to target with small molecules.[5]
459 citations
TL;DR: A homogeneous, high-throughput fluorescence polarization assay for identifying compounds that block the critical protein-protein interaction site in the basic cleft of the 70N domain of RPA (RPA70N).
37 citations
TL;DR: The data disputes the proposed synthetic lethal relationship of oncogenic K-Ras and TBK1 and does not support development ofTBK1 inhibitors for treatment of K- Ras driven tumors.
Abstract: TBK1 (TANK-binding kinase 1) is a serine/threonine kinase best known for its role in mediating the innate immune response through modulation of the interferon and NF-kB pathways. TBK1 has also been implicated in supporting cancer cell survival and transformation as the downstream effector of the small GTPase RalB, and is overexpressed in lung, breast and colon tumors. Recently, a high-throughput RNAi screen identified TBK1 as a synthetic lethal partner of oncogenic K-Ras, suggesting that small molecule inhibition of TBK1 may provide a novel therapeutic strategy for K-Ras mutant tumors. Given the high tractability of kinases as drug targets, we sought to confirm that kinase inhibition recapitulated the synthetic lethal effects observed with shRNA silencing. We examined two small molecule inhibitors of TBK1, BX795 (6 nM) and GSK2292978A (4 nM), in a panel of lung, pancreas and colon cancer cell lines. We found only a small subset of lines that were sensitive to TBK1 inhibition and this sensitivity did not correlate with K-Ras dependence. We then used K-Ras and TBK1 siRNA in a similar panel of cell lines. As anticipated, knockdown of K-Ras using siRNA produced significant growth and signaling defects in K-Ras dependent cell lines. In contrast, knockdown of TBK1 did not result in a significant alteration of growth in any of our cell lines. Neither TBK1 siRNA nor TBK1 inhibitors revealed a sensitivity that correlated with K-Ras dependence in our lung, pancreatic, or colorectal cancer cell lines. Our data disputes the proposed synthetic lethal relationship of oncogenic K-Ras and TBK1 and does not support development of TBK1 inhibitors for treatment of K-Ras driven tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1813. doi:1538-7445.AM2012-1813
3 citations