TY - JOUR
T1 - Reversible G1 arrest induced by inhibition of the epidermal growth factor receptor tyrosine kinase requires up-regulation of p27(KIP1) independent of MAPK activity
AU - Busse, Dagmar
AU - Doughty, Rachel S.
AU - Ramsey, Timothy T.
AU - Russell, William E.
AU - Price, James O.
AU - Flanagan, W. Michael
AU - Shawver, Laura K.
AU - Arteaga, Carlos L.
PY - 2000/3/10
Y1 - 2000/3/10
N2 - We have used quinazoline inhibitors of the epidermal growth factor receptor (EGFR) tyrosine kinase to study the link between EGFR signaling and G1 to S traverse. Treatment of A431 and MDA-468 human tumor cells with 0.1- 10 μM AG-1478 inhibited basal and ligand-stimulated EGFR phosphorylation without a decrease in receptor content, EGF-binding sites, or binding affinity. Incubation of A431 cells with 0.1-1 μM AG-1517 abrogated 125I- EGF internalization. Both AG-1478 and AG-1517 markedly inhibited A431 and MDA-468 colony formation in soft agarose at concentrations between 0.01 and 1 μM. Daily injections of AG-1478 at 50 mg/kg delayed A431 tumor formation in athymic nude mice. A transient exposure of A431 cells to AG-1478 resulted in a dose-dependent up-regulation of the cyclin-dependent kinase inhibitor p27, down-regulation of cyclin D1 and of active MAPK, and hypophosphorylation of the retinoblastoma protein (Rb). These changes were temporally associated with recruitment of tumor cells in G1 phase and a marked reduction of the proportion of cells in S phase. Upon removal of the kinase inhibitor, EGFR and Rb phosphorylation and the levels of cyclin D1 protein were quickly restored, but the cells did not reenter S phase until p27 protein levels were decreased. Phosphorothioate p27 oligonucleotides decreased p27 protein in A431 cells and abrogated the quinazoline-mediated G1 arrest. Treatment of A431 cells with PD 098509, a synthetic inhibitor of MEK1, inhibited MAPK activity without inducing G1 arrest or increasing the levels of p27. However, treatment with LY 294002, an inhibitor of phosphatidylinositol 3- kinase (PI3K), inhibited basal Akt activity, up-regulated p27, and recruited cells in G1. These data suggest that p27 is required for the growth arrest that follows interruption of the EGFR kinase in receptor-overexpressing cells. In addition, the G1 arrest and up-regulation of p27 resulting from EGFR blockade are not due to the interruption of MAPK, but to the interruption of constitutively active PI3K function.
AB - We have used quinazoline inhibitors of the epidermal growth factor receptor (EGFR) tyrosine kinase to study the link between EGFR signaling and G1 to S traverse. Treatment of A431 and MDA-468 human tumor cells with 0.1- 10 μM AG-1478 inhibited basal and ligand-stimulated EGFR phosphorylation without a decrease in receptor content, EGF-binding sites, or binding affinity. Incubation of A431 cells with 0.1-1 μM AG-1517 abrogated 125I- EGF internalization. Both AG-1478 and AG-1517 markedly inhibited A431 and MDA-468 colony formation in soft agarose at concentrations between 0.01 and 1 μM. Daily injections of AG-1478 at 50 mg/kg delayed A431 tumor formation in athymic nude mice. A transient exposure of A431 cells to AG-1478 resulted in a dose-dependent up-regulation of the cyclin-dependent kinase inhibitor p27, down-regulation of cyclin D1 and of active MAPK, and hypophosphorylation of the retinoblastoma protein (Rb). These changes were temporally associated with recruitment of tumor cells in G1 phase and a marked reduction of the proportion of cells in S phase. Upon removal of the kinase inhibitor, EGFR and Rb phosphorylation and the levels of cyclin D1 protein were quickly restored, but the cells did not reenter S phase until p27 protein levels were decreased. Phosphorothioate p27 oligonucleotides decreased p27 protein in A431 cells and abrogated the quinazoline-mediated G1 arrest. Treatment of A431 cells with PD 098509, a synthetic inhibitor of MEK1, inhibited MAPK activity without inducing G1 arrest or increasing the levels of p27. However, treatment with LY 294002, an inhibitor of phosphatidylinositol 3- kinase (PI3K), inhibited basal Akt activity, up-regulated p27, and recruited cells in G1. These data suggest that p27 is required for the growth arrest that follows interruption of the EGFR kinase in receptor-overexpressing cells. In addition, the G1 arrest and up-regulation of p27 resulting from EGFR blockade are not due to the interruption of MAPK, but to the interruption of constitutively active PI3K function.
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U2 - 10.1074/jbc.275.10.6987
DO - 10.1074/jbc.275.10.6987
M3 - Article
C2 - 10702262
AN - SCOPUS:0034629485
SN - 0021-9258
VL - 275
SP - 6987
EP - 6995
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 10
ER -