Low level expression of basic FGF upregulates Bcl-2 and delays apoptosis, but high intracellular levels are required to induce transformation in NIH 3T3 cells.
We investigated the roles of basic fibroblast growth factor (bFGF) in the transformation and survival of NIH 3T3 cells. We constructed NIH 3T3-derived cell lines expressing human bFGF using retroviral gene transfer with an N2-based vector. Clonally derived cell lines containing a single copy of the vector overexpress bFGF mRNA and produce more immunoreactive protein (0.407 +/- 0.010-3.028 +/- 0.087 ng bFGF/10(6) cells) which is biologically active than nontransduced (0.151 +/- 0.013 ng bFGF/10(6) cells) or N2-transduced (0.211 +/- 0.029 ng bFGF/10(6) cells) NIH 3T3 cells. All cells producing excess amounts of bFGF achieve greater density at confluence, show delayed apoptosis and increased survival and have elevated intracellular levels of Bcl-2. However, only cells expressing from 8-15 times background levels of bFGF are phenotypically transformed. The transformed cells form dense foci at confluence, have decreased adherence to tissue culture plates and grow colonies in soft agar. Exogenous bFGF induces higher Bcl-2 levels in a dose dependent manner and recapitulates the antiapoptotic effects of the overexpressed species but fails to induce changes associated with the transformed phenotype. In this study, we demonstrate a dissociation between phenotypic transformation secondary to bFGF overexpression and upregulation of cellular Bcl-2 that correlates with a delay in programmed cell death. Although low level expression of bFGF or exogenous bFGF is sufficient to upregulate Bcl-2 and delay apoptosis, high intracellular levels are required for cellular transformation. These data suggest that overexpression of bFGF modulates cellular transformation and Bcl-2-mediated inhibition of apoptosis through alternate molecular mechanisms.
Wieder
R
R
Department of Medicine, UMDNJ-New Jersey Medical School, Newark 07103, USA.
Wang
H
H
Shirke
S
S
Wang
Q
Q
Menzel
T
T
Feirt
N
N
Jakubowski
A A
AA
Gabrilove
J L
JL
D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis; D002455:Cell Division; D002470:Cell Survival / Q000187:drug effects; D002471:Cell Transformation, Neoplastic; D002999:Clone Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000032:analysis; D016222:Fibroblast Growth Factor 2 / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein
D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; D016222:Fibroblast Growth Factor 2; D004247:DNA