title: Epidermal growth factor induces cell cycle arrest and apoptosis of squamous carcinoma cells through reduction of cell adhesion.
abstract: Most squamous epithelial cells are strictly anchorage-dependent cell types. We observed that epidermal growth factor (EGF) promoted the growth of A431 squamous carcinoma cells in suspension cultures but suppressed cell growth and induced apoptosis in monolayer cultures, suggesting that loss of adhesion is responsible for the effects observed in monolayer culture, before cell death. Consistent with this finding, we demonstrated that EGF reduced cell attachment, cell-cell interaction, and cell spreading. Treatment with EGF increased cell adhesion-regulated expression of p21 but suppressed expressions of cyclin A, D1, cdk2, and retinoblastoma protein (pRb), leading to cell cycle arrest and adhesion-regulated programmed cell death. To test directly whether promoting cell adhesion could reduce the effects of EGF, we grew cultures on plates coated with type II collagen. On these plates, cell adhesion was enhanced and EGF treatment had little effect on cell adhesion and apoptosis when cells were attached to the collagen. The collagen effects were dose dependent, and cell cycle and cell cycle-associated proteins were altered accordingly. Finally, when cultures were plated on bacterial Petri dishes, which completely disrupted cell attachment to substratum, the level of apoptosis was greatly higher and cell cycle was arrested as compared with monolayer cultures. Taken together, our results strongly suggest that the EGF-induced cell cycle arrest and apoptosis in monolayer cultures was the result of a decline in cell adhesion.
authors.affiliation: Sunnybrook and Women's College Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Cao
authors.forename: Y
authors.initials: Y
authors.lastname: Yao
authors.forename: V
authors.initials: V
authors.lastname: Lee
authors.forename: C
authors.initials: C
authors.lastname: Kiani
authors.forename: D
authors.initials: D
authors.lastname: Spaner
authors.forename: Z
authors.initials: Z
authors.lastname: Lin
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: M E
authors.initials: ME
authors.lastname: Adams
authors.forename: B B
authors.initials: BB
authors.lastname: Yang
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D042846:CDC2-CDC28 Kinases; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology; D002448:Cell Adhesion / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D003094:Collagen / Q000378:metabolism; D019925:Cyclin A / Q000096:biosynthesis; D019938:Cyclin D1 / Q000096:biosynthesis; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000096:biosynthesis; D016213:Cyclins / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D009375:Neoplasms, Glandular and Epithelial / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis; D016160:Retinoblastoma Protein / Q000096:biosynthesis; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: C493956:CDKN1A protein, human; D019925:Cyclin A; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016160:Retinoblastoma Protein; D019938:Cyclin D1; D004815:Epidermal Growth Factor; D003094:Collagen; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases