TY - JOUR
T1 - Shortage of mitogen-activated protein kinase is responsible for resistance to AP-1 transactivation and transformation in mouse JB6 cells
AU - Huang, Chuanshu
AU - Ma, Wei-Ya
AU - Yound, Matthew R.
AU - Colburn, Nancy
AU - Dong, Zigang
PY - 1998/1/6
Y1 - 1998/1/6
N2 - The JB6 mouse epidermal cell system, which includes tumor promotion- sensitive (P+) and tumor promotion-resistant (P-) cells, is a well- established and extensively used cell culture model for studying the mechanism of late-stage tumor promotion. Tumor promoters, such as 12-O- tetradecanoylphorbol 13-acetate (TPA) or epidermal growth factor (EGF), induce high levels of activator protein 1 (AP-1) activity and large, tumorigenic, anchorage-independent colonies in soft agar at a high frequency in JB6 P+ cells, but not in JB6 P- cells. We report here a molecular explanation for the defect in the AP-1 activation and promotion-resistant phenotype of P- cells. We demonstrate that the lack of AP-1 activation and cell transformation responses to TPA and EGF in P- cells appears attributable to the low level of mitogen-activated protein kinase (MAPK) (extracellular signal-regulated protein kinase, Erk) in these cells. TPA and EGF induce transactivation of AP-1 activity in P+ cells but not in P- cells. Nonphosphorylated forms and TPA- or EGF-induced phosphorylated forms of Erks (Erk1 and Erk2) in P- cells were much lower than those in P+ cells. Stable transfection of wild-type MAPK (Erk2) into P- cells restored its response to TPA and EGF for both AP-1 activation and cell transformation. These results suggest that the shortage of MAPK (Erk1 and Erk2) appears to be an important contributor to the tumor promotion-resistant phenotype in JB6 cells.
AB - The JB6 mouse epidermal cell system, which includes tumor promotion- sensitive (P+) and tumor promotion-resistant (P-) cells, is a well- established and extensively used cell culture model for studying the mechanism of late-stage tumor promotion. Tumor promoters, such as 12-O- tetradecanoylphorbol 13-acetate (TPA) or epidermal growth factor (EGF), induce high levels of activator protein 1 (AP-1) activity and large, tumorigenic, anchorage-independent colonies in soft agar at a high frequency in JB6 P+ cells, but not in JB6 P- cells. We report here a molecular explanation for the defect in the AP-1 activation and promotion-resistant phenotype of P- cells. We demonstrate that the lack of AP-1 activation and cell transformation responses to TPA and EGF in P- cells appears attributable to the low level of mitogen-activated protein kinase (MAPK) (extracellular signal-regulated protein kinase, Erk) in these cells. TPA and EGF induce transactivation of AP-1 activity in P+ cells but not in P- cells. Nonphosphorylated forms and TPA- or EGF-induced phosphorylated forms of Erks (Erk1 and Erk2) in P- cells were much lower than those in P+ cells. Stable transfection of wild-type MAPK (Erk2) into P- cells restored its response to TPA and EGF for both AP-1 activation and cell transformation. These results suggest that the shortage of MAPK (Erk1 and Erk2) appears to be an important contributor to the tumor promotion-resistant phenotype in JB6 cells.
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U2 - 10.1073/pnas.95.1.156
DO - 10.1073/pnas.95.1.156
M3 - Article
C2 - 9419345
AN - SCOPUS:0031913814
SN - 0027-8424
VL - 95
SP - 156
EP - 161
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 1
ER -