Matrix-independent survival of human keratinocytes through an EGF receptor/MAPK-kinase-dependent pathway.
Normal epithelial cells undergo apoptosis when they are denied contact with the extracellular matrix, in a process termed "anoikis." Conversely, malignant epithelial cells typically acquire anchorage independence, i.e., the capacity to survive and grow in the absence of matrix interaction. Here we asked the question whether anoikis is affected by signaling through the EGF receptor (EGFR). We focused on the EGFR because EGFR signaling is frequently deregulated in malignant epithelial cells. We demonstrate that EGFR activation markedly alleviated the requirement of matrix engagement for survival of primary and immortalized human keratinocytes in suspension culture. Protection of epithelial cells through EGFR activation against anoikis was associated with and required sustained MAPK phosphorylation during the early phase of suspension culture. Interestingly, high levels of MAPK phosphorylation were not only required for EGFR-mediated protection against anoikis but also occurred as a consequence of caspase activation at later stages of suspension culture. These results demonstrate that EGFR activation contributes to anchorage-independent epithelial cell survival and identify MAPK activation as an important mechanism in this process.
Jost
M
M
Department of Dermatology and Cutaneous Biology and the Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Huggett
T M
TM
Kari
C
C
Rodeck
U
U
D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism*; D005109:Extracellular Matrix / Q000502:physiology*; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D020287:In Situ Nick-End Labeling; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011799:Quinazolines; D020032:Tyrphostins / Q000494:pharmacology; D051020:bcl-X Protein
C494811:BCL2L1 protein, human; D061945:Caspase Inhibitors; D002867:Chromones; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009025:Morpholines; D009842:Oligopeptides; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D011799:Quinazolines; D020032:Tyrphostins; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; D051020:bcl-X Protein; C101044:RTKI cpd; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D017027:Protein Tyrosine Phosphatases; D020169:Caspases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one