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.

Inhibition of NF-κB Sensitizes A431 Cells to Epidermal Growth Factor-induced Apoptosis, whereas Its Activation by Ectopic Expression of RelA Confers Resistance

“…The dual effect of EGF on the proliferation of A431 cells is also attributed to differential activation of p42 MAP kinase at low and high concentrations of EGF (11,46). Another hypothesis proposes that EGF-induced apoptosis is the result of a decline in cell adhesion (47), and detachment of cells because of anoikis is said to be responsible for the paradoxical anti-proliferative effects of EGF (16,48). Our results do not support the view that EGF-induced apoptosis results from the loss of cell-substratum attachment and many other workers also have not observed EGF-induced anoikis of A431 or other EGFR-overexpressing cells (8,11,49,50).…”

Mature MiR-17-5p and passenger miR-17-3p induce hepatocellular carcinoma by targeting PTEN, GalNT7, and vimentin in different signal pathways

“…Protein lysates containing vimentin, PTEN, and GalNT7 were subjected to SDS-PAGE-western blot assays using the method described previously (Cao et al, 2000).…”

EGF receptor: which way to go?

“…Its mechanism is poorly understood. EGFinduced attenuation of cell adhesion [15], EGF acting as a dedi¡erentiation factor for some cells [16] and down-regulation of EGFR in response to EGF [17] have all been suggested as possible mechanisms.…”