LIN28B is a post-transcriptional regulator of Wnt signalling in myeloid leukemia cells and dual targeting promotes cytotoxicity

Abstract

Wnt/{beta}-catenin signalling is dysregulated across hematological malignancies but lacks effective targeting agents. Previously, we discovered that {beta}-catenin interacts with RNA-binding proteins (RBP) and RNAs, indicating putative post-transcriptional roles in leukemia cells. The most frequent RBP-binding motif amongst {beta}-catenin-bound mRNAs was the GGAG motif targeted by the oncofetal miRNA-regulating RBP; LIN28B. LIN28B is a critical regulator of fetal hematopoiesis often reactivated in rare myeloid neoplasms including juvenile myelomonocytic leukemia (JMML). In this study we investigated the molecular crosstalk between LIN28B and {beta}-catenin in hematopoietic cells for the first time and examined dual targeting capacity. {beta}-Catenin:LIN28B interaction was detected in both myeloid and lymphoid cell lines, and in primary human CD34 fetal-liver derived HSCs. LIN28B regulated Wnt/{beta}-catenin signalling through post-transcriptional modulation of LEF1 via a let7 miRNA-mediated mechanism. Single cell RNA sequencing data revealed LIN28B and LEF1 correlation within abnormal JMML HSPCs enriched in high-risk hypermethylated subgroups characterised by oncofetal gene expression. miRNA sequencing of {beta}-catenin- and LIN28B-depleted myeloid cells revealed shared miRNA targets, and dual pharmacological targeting preferentially reduced myeloid cell line viability. This study reveals Wnt/LIN28B molecular crosstalk in leukaemia cells which could represent a novel therapeutic axis in rare myeloid neoplasms harbouring {beta}-catenin dysregulation and reactivation of LIN28B