Carcinoma cells induce lumen filling and EMT in epithelial cells by soluble E-cadherin-mediated activation of EGFR

Abstract

In epithelial cancers, carcinoma cells coexist with normal cells. Although it is known that the tumor microenvironment (TME) plays a pivotal role in cancer progression, it is not completely understood how the tumor influences adjacent normal epithelial cells. In this study, a three-dimensional co-culture system comprising non-transformed epithelial cells (MDCK) and transformed carcinoma cells (MSV-MDCK) was used to demonstrate that carcinoma cells sequentially induce preneoplastic lumen filling and epithelial-mesenchymal transition (EMT) in epithelial cysts. MMP-9 secreted by carcinoma cells cleaves cellular E-cadherin (encoded by CDH1) from epithelial cells to generate soluble E-cadherin (sE-cad), a pro-oncogenic protein. We show that sE-cad induces EGFR activation, resulting in lumen filling in MDCK cysts. Long-term sE-cad treatment induced EMT. sE-cad caused lumen filling by induction of the ERK signaling pathway and triggered EMT through the sustained activation of the AKT pathway. Although it is known that sE-cad induces MMP-9 release and consequent EGFR activation in tumor cells, our results, for the first time, demonstrate that carcinoma cells can induce sE-cad shedding in adjacent epithelial cells, which leads to EGFR activation and the eventual transdifferentiation of the normal epithelial cells.

Beyond a tumor suppressor: Soluble E‐cadherin promotes the progression of cancer

“…More interestingly, this feedback loop also participates in the oncogenic transformation of normal epithelial cells: MMPs derived from cancer cells cleave the extracellular domain of E‐cad between normal epithelial cells to release sE‐cad to bind to the EGFRs located at the surface of normal epithelial cells. The EGFR signaling pathway is thus activated to promote the malignant transformation of these cells …”

Aquaporins differentially regulate cell‐cell adhesion in MDCK cells

“…Like AQP5, the lumens of the cysts formed by AQP5 S156A were also filled with cells, but to a lesser extent than the AQP5 cysts, indicating that serine 156, probably through Ras-signaling activation, contributes to cell migration into cyst lumens. Presence of cells within the cyst lumens has been described in cases of perturbed cell polarity or dysregulation of major signaling pathways, which are features often displayed by cancer cells (7,12,46). Together, these data show that AQP5 expression causes lower cell adhesiveness and promotes cell detachment and dissemination from the migrating sheet or migration into the cyst lumens.…”

Oncogenic transformation of normal breast epithelial cells co-cultured with cancer cells

“…However, the mechanisms of luminal filling initiation are poorly understood. Recent studies have reported that carcinoma cells directly contact normal epithelial cells through filopodia-like projections in the 3D co-culture system, or they secrete MMP-9 that cleaves E-cadherin disrupting the luminal architecture [28], or alternatively they use exosomes to induce oncogenic transformation of adjacent normal epithelial cells [29]. Our results were consistent with previous reports, and we went a step further and compared the properties of C2 and C3 cancer cells and found that the transmitted cancer cells (C2 cells) were more malignant than the original cancer cells (C3 cells), which could explain how cancer heterogeneity is formed.…”