Effect of Ionizing Radiation on AP-1 Binding Activity and Basic Fibroblast Growth Factor Gene Expression in Drug-sensitive Human Breast Carcinoma MCF-7 and Multidrug-resistant MCF-7/ADR Cells

Yong J Lee,Sandra S Galoforo,Christine M Berns,Geza Erdos,Anjali K Gupta,D Kirk Ways,Peter M Corry

doi:10.1074/jbc.270.48.28790

Yong J Lee, Sandra S Galoforo + Show 5 more

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https://doi.org/10.1074/jbc.270.48.28790

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Abstract

We studied the effect of ionizing radiation on the activation of the AP-1 transcription factors and the regulation of basic fibroblast growth factor (bFGF) gene expression in drug-sensitive human breast carcinoma (MCF-7) cells and its drug-resistant variant (MCF-7/ADR) cells. Northern blot and gel mobility shift assays showed that 135 cGy of ionizing radiation induced c-jun and c-fos gene expression, AP-1 binding activity, as well as bFGF gene expression in MCF-7/ADR cells. In MCF-7 cells, however, we observed little/no induction of bFGF gene expression and AP-1 binding activity after the stress. Nevertheless, MCF-7 cells transfected with plasmids containing c-jun gene contain high levels of bFGF protein. H-7 (60 micrograms/ml), a potent protein kinase C (PKC) inhibitor, inhibited the stress-induced AP-1 binding activity and bFGF gene expression in MCF-7/ADR cells. Corroborating this observation, overexpression of PKC alpha induced bFGF gene expression in MCF-7 cells. Taken together, these results suggest that stress-induced bFGF gene expression is mediated through the activation of PKC and AP-1 transcription factors. Differences in the levels of PKC activity and AP-1 binding factors may be responsible for differential expression of bFGF among breast cancer cell lines. Although there are large differences in response to ionizing radiation between MCF-7 and MCF-7/ADR cell lines, we observed no significant differences in radiocytotoxicity between them.

Highlights

We studied the effect of ionizing radiation on the activation of the AP-1 transcription factors and the regulation of basic fibroblast growth factor gene expression in drug-sensitive human breast carcinoma (MCF-7) cells and its drug-resistant variant (MCF-7/ ADR) cells
Several researchers have reported that UV radiation or H2O2 treatment stimulates the expression of both c-jun and c-fos, as well as AP-1 binding activity in HeLa S3 cells (Devary et al, 1991)
Studies from Datta et al (1992) suggest that x-ray-induced transcriptional activation of the c-jun gene is mediated through the formation of reactive oxygen intermediates and protein kinase C (PKC) is involved in the signal pathway

Summary

Introduction

We studied the effect of ionizing radiation on the activation of the AP-1 transcription factors and the regulation of basic fibroblast growth factor (bFGF) gene expression in drug-sensitive human breast carcinoma (MCF-7) cells and its drug-resistant variant (MCF-7/ ADR) cells. H-7 (60 ␮g/ml), a potent protein kinase C (PKC) inhibitor, inhibited the stress-induced AP-1 binding activity and bFGF gene expression in MCF-7/ADR cells Corroborating this observation, overexpression of PKC␣ induced bFGF gene expression in MCF-7 cells. Several researchers have reported that c-jun and c-fos genes are expressed in response to a wide range of stresses including heat shock exposure (Andrews et al, 1987; Bukh et al, 1990), UV irradiation (Angel et al, 1985; Hollander and Fornace, 1989; Stein et al, 1992), ionizing radiation exposure (Sherman et al, 1990; Hallahan et al, 1991a), and treatment with chemical agents (Andrews et al, 1987; Hollander and Fornace, 1989; Shibanuma et al, 1990) in mammalian cells These stresses increase AP-1 binding activity (Piette et al, 1988; Hallahan et al, 1993). There was no significant differences in the cytotoxic effects of ionizing radiation between these two cell lines

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