Activating mutations in β-catenin in colon cancer cells alter their interaction with macrophages; the role of snail.

Pawan Kaler,Leonard Augenlicht,Lidija Klampfer,Masaru Katoh

doi:10.1371/journal.pone.0045462

Pawan Kaler, Leonard Augenlicht + Show 2 more

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https://doi.org/10.1371/journal.pone.0045462

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Abstract

BackgroundTumor cells become addicted to both activated oncogenes and to proliferative and pro-survival signals provided by the abnormal tumor microenvironment. Although numerous soluble factors have been identified that shape the crosstalk between tumor cells and stroma, it has not been established how oncogenic mutations in the tumor cells alter their interaction with normal cells in the tumor microenvironment.Principal FindingsWe showed that the isogenic HCT116 and Hke-3 cells, which differ only by the presence of the mutant kRas allele, both stimulate macrophages to produce IL1β. In turn, macrophages enhanced Wnt signaling, proliferation and survival in both HCT116 and Hke-3 cells, demonstrating that signaling by oncogenic kRas in tumor cells does not impact their interaction with macrophages. HCT116 cells are heterozygous for β-catenin (HCT116WT/MT), harboring one wild type (WT) and one mutant (MT) allele, but isogenic lines that carry only the WT (HCT116WT) or MT β-catenin allele (HCT116MT) have been generated. We showed that macrophages promoted Wnt signaling in cells that carry the MT β-catenin allele, but not in HCT116WT cells. Consistent with this observation, macrophages and IL1β failed to stabilize Snail in HCT116WT cells, and to protect these cells from TRAIL-induced apoptosis. Finally, we demonstrated that HCT116 cells expressing dominant negative TCF4 (dnTCF4) or HCT116 cells with silenced Snail failed to stimulate IL1β production in macrophages, demonstrating that tumor cells activate macrophages via a Wnt-dependent factor.SignificanceOur data demonstrate that oncogenic β-catenin mutations in tumor cells, and subsequent activation of Wnt signaling, not only trigger cell-intrinsic alterations, but also have a significant impact on the crosstalk of tumor cells with the tumor associated macrophages.

Highlights

Beta catenin (b-catenin) is an E-cadherin binding protein and plays an important role in cell-cell adhesion [1]
We reported that colon cancer cells, via a soluble factor, activate macrophages to secrete IL1b, which in turn promotes b-catenin/ TCF4 transcriptional activity in the cancer cells and stimulates their growth [10]
Macrophages and IL1b stimulated Wnt signaling (Fig. 1B), promoted growth (Fig. 1C) and protected HCT116 and Hke-3 cells from TRAIL-induced apoptosis (Fig. 1D). These studies demonstrated that the presence of oncogenic kRas in tumor cells does not have a significant impact on their interaction with tumor associated macrophages

Summary

Introduction

Beta catenin (b-catenin) is an E-cadherin binding protein and plays an important role in cell-cell adhesion [1]. It acts as an effector of Wnt signaling [2]. In the absence of Wnt signaling b-catenin is phosphorylated by GSK3b, resulting in its ubiquitination and subsequent degradation in the proteasome [3]. The activity of b-catenin is controlled by the tumor suppressor Adenomatous Polyposis Coli (Apc) and inactivating mutations in the Apc gene, which prevent b-catenin degradation, are found in the large majority of sporadic colorectal cancers [4,5]. Approximately 10% of colorectal cancers carry mutations in the GSK3b phosphorylation site located in the N-terminus of bcatenin [6]. Numerous soluble factors have been identified that shape the crosstalk between tumor cells and stroma, it has not been established how oncogenic mutations in the tumor cells alter their interaction with normal cells in the tumor microenvironment

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