TIM-3 signaling hijacks the canonical Wnt/β-catenin pathway to maintain cancer stemness in acute myeloid leukemia

Abstract

The activation of β-catenin plays critical roles in normal stem cell function, and when aberrantly activated, maintenance and enhancement of cancer stemness in many solid cancers. The aberrant β-catenin activation is also observed in acute myeloid leukemia (AML), and crucially contributes to self-renewal and propagation of leukemic stem cells (LSCs) regardless of mutations in contrast to such solid tumors. In this study, we showed that the AML-specific autocrine loop constituted of T-cell immunoglobulin mucin-3 (TIM-3) and its ligand, galectin-9 (Gal-9), drives the canonical Wnt pathway to stimulate self-renewal and propagation of leukemic stem cells (LSCs), independent of Wnt ligands. Gal-9 ligation activates the cytoplasmic Src homology 2 (SH2) domain of TIM-3 to recruit hematopoietic cell kinase (HCK), an Src family kinase highly expressed in LSCs but not in HSCs, and HCK phosphorylates p120-catenin to promote formation of the LDL-receptor related protein 6 (LRP6) signalosome, hijacking the canonical Wnt pathway. This TIM-3/HCK/p120-catenin axis is principally employed in immature LSCs compared to TIM-3-expressed differentiated AML blasts and exhausted T-cells. These data suggest that human AML LSCs constitutively activates β-catenin through utilizing the autocrine TIM-3/HCK/p120-catenin signaling, and that molecules related to this signaling axis should be critical targets for selective eradication of LSCs without impairing normal HSCs.

Attenuated cell cycle and DNA damage response transcriptome signatures and overrepresented cell adhesion processes imply accelerated progression in patients with lower‐risk myelodysplastic neoplasms

“…To confirm that we dichotomized the patients based purely on MDS progression without other unrecognized causes of disease severity, we evaluated expression of two components of WNT signaling, known to be associated with differential outcome in MDS/AML. We observed significant downregulation of LEF1 , a marker of poor outcome in MDS, 10 and significant upregulation of LRP6 , a marker of AML leukemia stem cells (LSCs) activity 11 in prMDS vs stMDS (Figure S3). The differential expression analysis (DEA) showed 378 significantly (ІlogFCІ > 1, FDR < 0.01) upregulated and 467 significantly downregulated genes in stMDS (Figure 1A).…”

“…Such coregulation may have functional implications similar to the ZEB1 role in tumor stromal endothelial cells. 53 The expression of the LSC phenotype in prMDS, characterized by LRP6 gene, 11 could result from Wnt/β-catenin/ZEB1 corregulation.…”

“…27 Other PCGs, such as RPAP2 and LRP6 belong to the key molecules of AML LSCs. 11,28 We further investigated the commitment to specific hematopoietic lineages as previously described, 4 where a decrease in the expression of genes specifically expressed in erythroblasts and megakaryocyte/ erythrocyte progenitors and upregulation of genes related to immature progenitor cells was associated with shorter survival and leukemic transformation in myelodysplasia samples. Indeed, prMDS had significantly reduced expression of genes of more mature hematopoietic lineages (Figures 4B and S13, Table S6).…”

“…LRP6, encoding the coreceptor of Wnt/β-catenin signaling, 11 is a ZEB1 target according to publicly available (ChIP)-seq datasets from the ENCODE project.…”

Multiomic single-cell analysis identifies von Willebrand factor and TIM3-expressingBCR-ABL1+CML stem cells

“…We also identified significant cell surface overexpression of TIM3 when comparing CML LSC with normal HSC, which is in line with a previous report showing upregulated TIM3 gene expression ( HAVCR2 ) in CML LSC based on mining of publicly available RNA-seq datasets 29 . In addition, TIM3 is reportedly overexpressed and critical for self-renewal of LSC in acute myeloid leukemia (AML) 23,24,30 . Collectively, these results point to the targeting of TIM3 as a possible strategy to reduce stem cell renewal in CML.…”