NRAS mRNA-Degrading Bifunctional Small Molecules Induce Diverse Cellular Morphological Changes in Cancer Cells

Therapeutic targeting of the oncogenic NRAS protein, which is constitutively activated in human cancers, with small molecules is a promising yet challenging anticancer strategy. Therefore, targeting the NRAS mRNA poses a feasible alternative that will likely yield new biological consequences due to the new mechanism of regulation at the post-transcriptional level. We report herein the first examples of a reversely regulating NRAS mRNA-degrading ribonuclease targeting chimeric small molecules (NRAS-RIBOTAC), which were assembled by conjugating a reported 4-aminoquinazoline G4-NRAS binder with a biphenyl RNase L binder. Among the obtained NRAS-RIBOTACs, 5 impacted G4-containing NRAS mRNA expression while it did not significantly impact the expression of NRAS protein in MD-MB-231 cells, which could be explained by the fact that the G4-containing NRAS transcript only accounts for a trace amount in comparison with the dominant G4-lacking NRAS mRNA. Furthermore, we report here for the first time the phenotypic evaluation of RIBOTACs in the unbiased phenotypic profiling method, cell painting assay. In comparison with the monovalent ribonuclease recruiter and G4-NRAS mRNA binder, selected RIBOTACs showed significant activities in inducing cellular morphological changes and demonstrated a new biological performance that is reflected by the diverse cellular morphological changes in cancer cells.