EPHA2-dependent outcompetition of KRASG12D mutant cells by wild-type neighbors in the adult pancreas

William Hill,Andreas Zaragkoulias,Beatriz Salvador-Barbero,Geraint J Parfitt,Markella Alatsatianos,Ana Padilha,Sean Porazinski,Thomas E Woolley,Jennifer P Morton,Owen J Sansom,Catherine Hogan

doi:10.1016/j.cub.2021.03.094

William Hill, Andreas Zaragkoulias + Show 9 more

Open Access

https://doi.org/10.1016/j.cub.2021.03.094

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Abstract

SummaryAs we age, our tissues are repeatedly challenged by mutational insult, yet cancer occurrence is a relatively rare event. Cells carrying cancer-causing genetic mutations compete with normal neighbors for space and survival in tissues. However, the mechanisms underlying mutant-normal competition in adult tissues and the relevance of this process to cancer remain incompletely understood. Here, we investigate how the adult pancreas maintains tissue health in vivo following sporadic expression of oncogenic Kras (KrasG12D), the key driver mutation in human pancreatic cancer. We find that when present in tissues in low numbers, KrasG12D mutant cells are outcompeted and cleared from exocrine and endocrine compartments in vivo. Using quantitative 3D tissue imaging, we show that before being cleared, KrasG12D cells lose cell volume, pack into round clusters, and E-cadherin-based cell-cell adhesions decrease at boundaries with normal neighbors. We identify EphA2 receptor as an essential signal in the clearance of KrasG12D cells from exocrine and endocrine tissues in vivo. In the absence of functional EphA2, KrasG12D cells do not alter cell volume or shape, E-cadherin-based cell-cell adhesions increase and KrasG12D cells are retained in tissues. The retention of KRasG12D cells leads to the early appearance of premalignant pancreatic intraepithelial neoplasia (PanINs) in tissues. Our data show that adult pancreas tissues remodel to clear KrasG12D cells and maintain tissue health. This study provides evidence to support a conserved functional role of EphA2 in Ras-driven cell competition in epithelial tissues and suggests that EphA2 is a novel tumor suppressor in pancreatic cancer.

Highlights

Epithelial homeostasis is fundamental to survival and is required to balance the number and fitness of cells that contribute to tissue function
Using fluorescence imaging of murine pancreas tissues and quantitative image analysis platforms, we demonstrate that KrasG12D cells are actively cleared from the adult pancreas over time and in an EphA2dependent manner
Sparse KrasG12D mutant cells are lost from adult pancreas tissues over time We used the pancreas-specific Pdx1-CreERT LSL-KrasG12D/+; Rosa26LSL-tdRFP (KC; red fluorescent protein [RFP]) mouse and administered a single low dose of tamoxifen to induce Pdx1Cre recombinase in a low number of cells in an otherwise normal epithelium

Summary

Introduction

Epithelial homeostasis is fundamental to survival and is required to balance the number and fitness of cells that contribute to tissue function. Homeostasis is maintained through distinct processes that dynamically maintain this equilibrium in response to tissue crowding,[1] damage,[2] or mutational insult.[3,4,5,6,7,8,9,10] Retention of excess, mutant, or aberrant cells would impair tissue integrity and promote disease.[11,12,13] The mechanisms underlying these processes are multifaceted and involve cell competition,[14] mechanical cues,[15] and cell plasticity.[16] Epithelial cells expressing oncogenes compete for space and survival in tissues and are often eliminated via processes that require the presence of normal cells; the mechanisms underlying how normal cells sense and eliminate mutant cells remain incompletely understood. Whether EphA2 is a general regulator of mammalian tissue homeostasis in vivo is currently unknown

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