Ror2 Signaling and Its Relevance in Breast Cancer Progression.

Michaela Bayerlová,Kerstin Menck,Tim Beißbarth,Florian Klemm,Tobias Pukrop,Alexander Wolff,Annalen Bleckmann,Claudia Binder

doi:10.3389/fonc.2017.00135

Abstract

Breast cancer is a heterogeneous disease and has been classified into five molecular subtypes based on gene expression profiles. Signaling processes linked to different breast cancer molecular subtypes and different clinical outcomes are still poorly understood. Aberrant regulation of Wnt signaling has been implicated in breast cancer progression. In particular Ror1/2 receptors and several other members of the non-canonical Wnt signaling pathway were associated with aggressive breast cancer behavior. However, Wnt signals are mediated via multiple complex pathways, and it is clinically important to determine which particular Wnt cascades, including their domains and targets, are deregulated in poor prognosis breast cancer. To investigate activation and outcome of the Ror2-dependent non-canonical Wnt signaling pathway, we overexpressed the Ror2 receptor in MCF-7 and MDA-MB231 breast cancer cells, stimulated the cells with its ligand Wnt5a, and we knocked-down Ror1 in MDA-MB231 cells. We measured the invasive capacity of perturbed cells to assess phenotypic changes, and mRNA was profiled to quantify gene expression changes. Differentially expressed genes were integrated into a literature-based non-canonical Wnt signaling network. The results were further used in the analysis of an independent dataset of breast cancer patients with metastasis-free survival annotation. Overexpression of the Ror2 receptor, stimulation with Wnt5a, as well as the combination of both perturbations enhanced invasiveness of MCF-7 cells. The expression–responsive targets of Ror2 overexpression in MCF-7 induced a Ror2/Wnt module of the non-canonical Wnt signaling pathway. These targets alter regulation of other pathways involved in cell remodeling processing and cell metabolism. Furthermore, the genes of the Ror2/Wnt module were assessed as a gene signature in patient gene expression data and showed an association with clinical outcome. In summary, results of this study indicate a role of a newly defined Ror2/Wnt module in breast cancer progression and present a link between Ror2 expression and increased cell invasiveness.

Highlights

Breast cancer is a heterogeneous disease with respect to pathological characteristics, molecular profiles, and prognoses
Aberrant regulation of Wnt signaling has been implicated in breast cancer progression [4] and expression of a number of important Wnt pathway members has been shown to be altered in different molecular subtypes [5]
To investigate the effect of non-canonical Wnt signaling on cancer progression and downstream signaling, the Wnt5a ligand and the membrane receptor Ror2 were chosen as non-canonical Wnt pathway members to be perturbed

Summary

Introduction

Breast cancer is a heterogeneous disease with respect to pathological characteristics, molecular profiles, and prognoses. Gene signatures derived from gene expression profiles proved to be useful to separate breast cancers into distinct molecular subtypes. Ror2/Wnt Signaling in Breast Cancer five subtypes have been defined: Basal-like (Basal), ERBB2overexpressing (Her2), luminal A (LumA), luminal B (LumB), and normal-breast-like breast cancer [1, 2]. They have been associated with significant differences in clinical outcome in terms of developing distant metastasis and overall survival [3]. These subtypes vary in activation states of multiple signaling pathways, among them the Wnt signaling pathway. Aberrant regulation of Wnt signaling has been implicated in breast cancer progression [4] and expression of a number of important Wnt pathway members has been shown to be altered in different molecular subtypes [5]

Objectives

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Conclusion