EphA2 Drives the Segregation of Ras-Transformed Epithelial Cells from Normal Neighbors

© 2016 Elsevier Ltd In epithelial tissues, cells expressing oncogenic Ras (hereafter RasV12 cells) are detected by normal neighbors and as a result are often extruded from the tissue [1–6]. RasV12 cells are eliminated apically, suggesting that extrusion may be a tumor-suppressive process. Extrusion depends on E-cadherin-based cell-cell adhesions and signaling to the actin-myosin cytoskeleton [2, 6]. However, the signals underlying detection of the RasV12 cell and triggering extrusion are poorly understood. Here we identify differential EphA2 signaling as the mechanism by which RasV12 cells are detected in epithelial cell sheets. Cell-cell interactions between normal cells and RasV12 cells trigger ephrin-A-EphA2 signaling, which induces a cell repulsion response in RasV12 cells. Concomitantly, RasV12 cell contractility increases in an EphA2-dependent manner. Together, these responses drive the separation of RasV12 cells from normal cells. In the absence of ephrin-A-EphA2 signals, RasV12 cells integrate with normal cells and adopt a pro-invasive morphology. We also show that Drosophila Eph (DEph) is detected in segregating clones of RasV12 cells and is functionally required to drive segregation of RasV12 cells invivo, suggesting that our invitro findings are conserved in evolution. We propose that expression of RasV12 in single or small clusters of cells within a healthy epithelium creates ectopic EphA2 boundaries, which drive the segregation and elimination of the transformed cell from the tissue. Thus, deregulation of Eph/ephrin would allow RasV12 cells to go undetected and expand within an epithelium

Relatório de estágio em farmácia comunitária

Relatório de estágio realizado no âmbito do Mestrado Integrado em Ciências Farmacêuticas, apresentado à Faculdade de Farmácia da Universidade de Coimbr

ADAM-like Decysin-1 (ADAMDEC1) is a positive regulator of Epithelial Defense Against Cancer (EDAC) that promotes apical extrusion of RasV12-transformed cells

Recent studies have revealed that newly emerging transformed cells are often eliminated from epithelia via cell competition with the surrounding normal epithelial cells. However, it remains unknown whether and how soluble factors are involved in this cancer preventive phenomenon. By performing stable isotope labeling with amino acids in cell culture (SILAC)-based quantitative mass spectrometric analyses, we have identified ADAM-like Decysin-1(ADAMDEC1) as a soluble protein whose expression is upregulated in the mix culture of normal and RasV12-transformed epithelial cells. Expression of ADAMDEC1 is elevated in normal epithelial cells co-cultured with RasV12 cells. Knockdown of ADAMDEC1 in the surrounding normal cells substantially suppresses apical extrusion of RasV12 cells, suggesting that ADAMDEC1 secreted by normal cells positively regulate the elimination of the neighboring transformed cells. In addition, we show that the metalloproteinase activity of ADAMDEC1 is dispensable for the regulation of apical extrusion. Furthermore, ADAMDEC1 facilitates the accumulation of filamin, a crucial regulator of Epithelial Defense Against Cancer (EDAC), in normal cells at the interface with RasV12 cells. This is the first report demonstrating that an epithelial intrinsic soluble factor is involved in cell competition in mammals

A role of the sphingosine-1-phosphate (S1P)-S1P receptor 2 pathway in epithelial defense against cancer (EDAC)

At the initial step of carcinogenesis, transformation occurs in single cells within epithelia, where the newly emerging transformed cells are surrounded by normal epithelial cells. A recent study revealed that normal epithelial cells have an ability to sense and actively eliminate the neighboring transformed cells, a process named epithelial defense against cancer (EDAC). However, the molecular mechanism of this tumor-suppressive activity is largely unknown. In this study, we investigated a role for the sphingosine-1-phosphate (S1P)-S1P receptor 2 (S1PR2) pathway in EDAC. First, we show that addition of the S1PR2 inhibitor significantly suppresses apical extrusion of RasV12-transformed cells that are surrounded by normal cells. In addition, knockdown of S1PR2 in normal cells induces the same effect, indicating that S1PR2 in the surrounding normal cells plays a positive role in the apical elimination of the transformed cells. Of importance, not endogenous S1P but exogenous S1P is involved in this process. By using FRET analyses, we demonstrate that S1PR2 mediates Rho activation in normal cells neighboring RasV12-transformed cells, thereby promoting accumulation of filamin, a crucial regulator of EDAC. Collectively these data indicate that S1P is a key extrinsic factor that affects the outcome of cell competition between normal and transformed epithelial cells

The COX-2/PGE(2) pathway suppresses apical elimination of RasV12-transformed cells from epithelia

At the initial stage of carcinogenesis, when RasV12-transformed cells are surrounded by normal epithelial cells, RasV12 cells are apically extruded from epithelia through cell competition with the surrounding normal cells. In this study, we demonstrate that expression of cyclooxygenase (COX)-2 is upregulated in normal cells surrounding RasV12-transformed cells. Addition of COX inhibitor or COX-2-knockout promotes apical extrusion of RasV12 cells. Furthermore, production of Prostaglandin (PG) E-2, a downstream prostanoid of COX-2, is elevated in normal cells surrounding RasV12 cells, and addition of PGE(2) suppresses apical extrusion of RasV12 cells. In a cell competition mouse model, expression of COX-2 is elevated in pancreatic epithelia harbouring RasV12-exressing cells, and the COX inhibitor ibuprofen promotes apical extrusion of RasV12 cells. Moreover, caerulein-induced chronic inflammation substantially suppresses apical elimination of RasV12 cells. These results indicate that intrinsically or extrinsically mediated inflammation can promote tumour initiation by diminishing cell competition between normal and transformed cells. Sato et al find that in an epithelial cell sheet containing some RasV12-transformed cells, expression of cyclooxygenase-2 and production of its downstream product prostaglandin E2 are increased in normal cells surrounding transformed cells, and suppress extrusion of the latter. This study sheds light on how transformed cells are eliminated from epithelia

Filamin acts as a key regulator in epithelial defence against transformed cells

Recent studies have shown that certain types of transformed cells are extruded from an epithelial monolayer. However, it is not known whether and how neighbouring normal cells play an active role in this process. In this study, we demonstrate that filamin A and vimentin accumulate in normal cells specifically at the interface with Src- or RasV12-transformed cells. Knockdown of filamin A or vimentin in normal cells profoundly suppresses apical extrusion of the neighbouring transformed cells. In addition, we show in zebrafish embryos that filamin plays a positive role in the elimination of the transformed cells. Furthermore, the Rho/Rho kinase pathway regulates filamin accumulation and filamin acts upstream of vimentin in the apical extrusion. This is the first report demonstrating that normal epithelial cells recognize and actively eliminate neighbouring transformed cells and that filamin is a key mediator in the interaction between normal and transformed epithelial cells