Characterization of the interface between normal and transformed epithelial cells

Abstract

In most cancers, transformation begins in a single cell in an epithelial cell sheet. However, it is not known what happens at the interface between non-transformed (normal) and transformed cells once the initial transformation has occurred. Using Madin-Darby canine kidney (MDCK) epithelial cells that express constitutively active, oncogenic Ras (Ras(V12)) in a tetracycline-inducible system, we investigated the cellular processes arising at the interface between normal and transformed cells. We show that two independent phenomena occur in a non-cell-autonomous manner: when surrounded by normal cells, Ras(V12) cells are either apically extruded from the monolayer, or form dynamic basal protrusions and invade the basal matrix. Neither apical extrusion nor basal protrusion formation is observed when Ras(V12) cells are surrounded by other Ras(V12) cells. We show that Cdc42 and ROCK (also known as Rho kinase) have vital roles in these processes. We also demonstrate that E-cadherin knockdown in normal cells surrounding Ras(V12) cells reduces the frequency of apical extrusion, while promoting basal protrusion formation and invasion. These results indicate that Ras(V12)-transformed cells are able to recognize differences between normal and transformed cells, and consequently leave epithelial sheets either apically or basally, in a cell-context-dependent manner.

Disruption of epithelial architecture caused by loss of PTEN or by oncogenic mutant p110α/PIK3CA but not by HER2 or mutant AKT1

“…This contrasts somewhat with recent work [47] showing lumenal translocation of single HER2/ERBB2 expressing MCF10A cells in pre-formed normal hollow acini. This would seem to imply that a key determinant of this luminal translocation is the recognition of differences between the transformed HER2 expressing cell and surrounding cells, consistent with existing models [48]. In our work, PTEN loss from established hollow NMuMG acini does not affect their morphology.…”

Competition between human cells by entosis

“…The observation that mammalian cells expressing activated Src or Kras are extruded when surrounded by normal cells in monolayer cultures has demonstrated one mode of competitive interactions between neighboring mammalian cells, which could influence tumorigenesis [9,10]. Similarly, knockdown of the polarity protein Scribble and the Lgl-binding protein Mahjong, whose loss induces cell competition in Drosophila, leads to death of mammalian cells only when knockdown cells are mixed with wild-type cells in culture [11,12].…”

Expulser les cellules suspectes

“…Dans une Nouvelle publiée en 2010 dans méde-cine/sciences, S. Dupré-Crochet et al [3] décrivait un exemple de ce processus d'exclusion chez les mammifères. Ainsi, l'induction, dans une couche confluente de cellules MDCK (Madin-Darby canine kidney) normales, de l'expression de Ras v12 -une forme mutée de Ras -, ou celle de v-Src dans des cellules isolées, entraîne l'expulsion rapide de ces cellules à la surface apicale de la monocouche [3,4]. L'expulsion ne se produit que si la cellule transformée reste entourée de cellules normales.…”

“…« Comment les cellules transformées et les cellules normales peuvent-elles reconnaître leurs différences ? » [3,4]. Malgré la caractérisation de quelques uns des acteurs moléculaires, cette extrusion reste mal expliquée.…”