Cell-cell contacts prevent anoikis in primary human colonic epithelial cells.
OBJECTIVE
Colonic epithelial cells (CECs) receive important survival signals from the extracellular matrix and undergo detachment-induced apoptosis (anoikis) as soon as they lose their cell-matrix anchorage. In contrast to the established role of cell-matrix contact, the role of cell-cell contacts as a physiologic survival factor for CECs is less clear.


METHODS
Intact CEC crypts gently centrifuged to form a cell aggregate in which cell-cell contacts were maintained. Induction of apoptosis was assessed by Western Blot analysis, colorimetric assays, DNA electrophoresis, 4',6-diamidino-2-phenylindole staining, and flow cytometry. Activation of survival pathways was analyzed by Western blot. The role of mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (Erk)1/2, epidermal growth factor receptor, phosphatidylinositol 3-kinase (PI3-K), and Src signaling was investigated using specific inhibitors.


RESULTS
Despite a complete loss of cell-matrix adhesion after CEC isolation, activation of caspases was blocked and anoikis was prevented when cell-cell contacts were preserved. CECs with preserved cell-cell contacts exhibited a rapid dephosphorylation of focal adhesion kinase. Aggregated CECs had stable levels of active beta-catenin and phosphorylated Akt, Erk1/2, and epidermal growth factor receptor, but CECs undergoing anoikis rapidly degraded beta-catenin and dephosphorylated Akt. Inhibition of Src- and PI3-K-dependent signaling reversed the antiapoptotic effect of cell-cell contact preservation, while inhibition of the MEK pathway had no effect.


CONCLUSIONS
Integrity of cell-cell contacts compensates for the loss of cell-matrix contact-mediated survival signals in CECs and prevents apoptosis. Cell-cell contact-triggered CEC survival involves antiapoptotic signaling through beta-catenin-, Src-, and PI3-K/Akt- but not through MEK- and focal adhesion kinase-dependent pathways.
Hofmann
Claudia
C
Department of Internal Medicine I, University of Regensburg, Regensburg, Germany.
Obermeier
Florian
F
Artinger
Monika
M
Hausmann
Martin
M
Falk
Werner
W
Schoelmerich
Juergen
J
Rogler
Gerhard
G
Grossmann
Johannes
J
D023102:Anoikis; D015820:Cadherins / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D002449:Cell Aggregation; D002450:Cell Communication; D048430:Cell Shape; D002470:Cell Survival; D053938:DNA Fragmentation; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D066246:ErbB Receptors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D051176:beta Catenin / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
D015820:Cadherins; D051176:beta Catenin; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D020169:Caspases