N-Biphenyl Pyrrolinones and Dibenzofurans as RNA-Binding Protein LIN28 Inhibitors Disrupting the LIN28–Let-7 Interaction

Abstract

The RNA-binding protein LIN28 is a regulator of miRNA let-7 biogenesis. Inhibitors of LIN28 are highly sought after given the central role that LIN28 plays in tumorigenesis and development of cancer stem cells as well as LIN28's association with poor clinical prognosis. Although LIN28 inhibitors of different scaffolds have been reported, the potential of most LIN28 inhibiting small molecules was not fully explored since very limited structure−activity relationship (SAR) studies have been performed. We previously identified trisubstituted pyrrolinones as a new class of LIN28 inhibitors disrupting the LIN28−let-7 interaction. Here, we performed extensive SAR by evaluating 95 small molecules and identified new trisubstituted pyrrolinones featuring either an N-biphenyl or Ndibenzofuran substituent, overthrowing the existing conclusion that a salicylic acid moiety is indispensable for activity. Exchange of the negatively charged salicylic acid moiety in LIN28 inhibitors with a heterocyclic substituent is beneficial for membrane permeability, leading to increased activity in a cellular assay, and will potentially reduce toxicity.

Targeting MicroRNAs with Small Molecules

“…The Lin28 protein plays a pivotal role by binding to let-7 miR precursors, inhibiting their maturation, and consequently impairing their tumor-suppressive functions [ 171 , 172 ]. Inhibiting Lin28 protein using small molecules leads to elevated levels of let-7 miR, consequently inducing tumor-suppressive functions [ 173 ]. This highlights the potential for small molecule intervention in depleted miRs, offering promising results in tumor suppression.…”