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Characterization of the interface between normal and transformed epithelial cells


In most cancers, transformation begins in a single cell in an epithelial cell sheet1,2,3. 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 (RasV12) 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, RasV12 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 RasV12 cells are surrounded by other RasV12 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 RasV12 cells reduces the frequency of apical extrusion, while promoting basal protrusion formation and invasion. These results indicate that RasV12-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.

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Figure 1: Epithelial cells expressing RasV12 are apically extruded from surrounding normal epithelium in a non-cell-autonomous manner.
Figure 2: Molecular mechanism for apical extrusion of RasV12-expressing cells from a monolayer of normal cells.
Figure 3: Non-extruded GFP–RasV12 cells produce dynamic basal protrusions beneath the neighbouring MDCK cells.
Figure 4: Molecular mechanisms for apical extrusion and basal protrusion formation of RasV12 cells in a monolayer of normal cells.
Figure 5: E-cadherin-based intercellular adhesions of surrounding normal cells can influence the fate of RasV12 cells.


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We thank G. K. Ojakian for the anti-gp135 antibody, A. Hall, A. Lloyd, R. Y. Tsien, S. Lowe and E. Sahai for constructs, and A. Vaughan for technical assistance with microscopes. We also thank Y. Morishita for discussion on physical forces at cell–cell adhesions. S.D-C. was supported by a FEBS Long Term Fellowship. A.E.P. acknowledges the Interdisciplinary Research Collaboration (IRC) in Nanotechnology (Cambridge, EPSRC UK) and the Dr Mortimer and Theresa Sackler Trust for financial support. This work is supported by MRC funding of the Cell Biology Unit.

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C.H. designed the experiments and generated most of the data; S.D-C. established stable MDCK cell lines and performed statistical analyses (Fig. 1d); M.N. analysed clonal expression of RasV12, RasN17 and RasWT in Drosophila wing imaginal discs (Fig. 1e and Supplementary Information, Fig. S3); M.K. performed western blot analyses (Supplementary Information, Fig. S1b), immunofluorescence studies (Supplementary Information, Fig. S4a) and established stable MDCK cell lines; C.Z. performed western blot and time-lapse analyses (Supplementary Information, Figs S2a, d and S5e), and established stable MDCK cell lines; A.E.P. performed AFM experiments and analyses (Supplementary Information, Fig. S9); E.P., L.A.B-L. and J-P.V. analysed clonal expression of RasV12, RasN17 and RasWT in Drosophila wing imaginal discs (Fig. 1e and Supplementary Information, Fig. S3); Y.I. provided technical expertise on use of collagen; H.H. provided technical expertise on myosin-II; F.P. assisted with Drosophila experiments; Y.F. conceived and designed the study and acted as principal investigator.

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Correspondence to Yasuyuki Fujita.

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Hogan, C., Dupré-Crochet, S., Norman, M. et al. Characterization of the interface between normal and transformed epithelial cells. Nat Cell Biol 11, 460–467 (2009).

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