Competitive Inhibitors of Ras Effector Binding

Abstract

The small GTPases H, K and NRas are molecular switches that are indispensable for the correct regulation of cellular proliferation and growth. Mutations in Ras are associated with cancer and result in unwanted activation of signaling processes caused by aberrant recruitment of downstream effector proteins. In this study, we have engineered variants of the Ras-binding domain (RBD) of CRAF kinase that bind with highly improved affinity the effector binding site of Ras. Structural characterization demonstrates how the engineered RBD variants outcompete effector binding and inhibit Ras signaling in cells leading to apoptosis, growth arrest and senescence. The optimized RBD variants provide new insights in Ras biology and enabled the functional stratification of Ras dependency in patient-derived colorectal cancer organoids. One sentence summary:Inhibition of effector kinase binding to Ras induces senescence in non-tumorigenic cells and reveals Ras dependency in patient-derived cancer organoids.

The Multi-Level Mechanism of Action of a Pan-Ras Inhibitor Explains its Antiproliferative Activity on Cetuximab-Resistant Cancer Cells

“…The aberrant mitogenic signaling in Ras-driven cancer cells largely depends on the increased recruitment of the downstream effectors Raf1, from the constitutively active Ras oncoproteins ( Metcalfe et al, 1993 ; Warne et al, 1993 ). Accordingly, molecules disrupting Ras/Raf1 association block KRas downstream signaling and impair Ras-mediated tumorigenic proliferation ( Waldmann et al, 2004 ; Athuluri-Divakar et al, 2016 ; Trinh et al, 2016 ; Liu et al, 2017 ; McGee et al, 2018 ; Wiechmann et al, 2019 ). To assess the ability of cmp4 to affect Ras-GTP/Raf1 binding, we performed an ELISA assay with increasing concentrations of cmp4 (from 0 to 500 µM).…”