Fibroblast growth factor 2 restrains Ras-driven proliferation of malignant cells by triggering RhoA-mediated senescence.
Fibroblast growth factor 2 (FGF2) is considered to be a bona fide oncogenic factor, although results from our group and others call this into question. Here, we report that exogenous recombinant FGF2 irreversibly inhibits proliferation by inducing senescence in Ras-dependent malignant mouse cells, but not in immortalized nontumorigenic cell lines. We report the following findings in K-Ras-dependent malignant Y1 adrenocortical cells and H-Ras V12-transformed BALB-3T3 fibroblasts: (a) FGF2 inhibits clonal growth and tumor onset in nude and immunocompetent BALB/c mice, (b) FGF2 irreversibly blocks the cell cycle, and (c) FGF2 induces the senescence-associated beta-galactosidase with no accompanying signs of apoptosis or necrosis. The tyrosine kinase inhibitor PD173074 completely protected malignant cells from FGF2. In Y1 adrenal cells, reducing the constitutively high levels of K-Ras-GTP using the dominant-negative RasN17 mutant made cells resistant to FGF2 cytotoxicity. In addition, transfection of the dominant-negative RhoA-N19 into either Y1 or 3T3-B61 malignant cell lines yielded stable clonal transfectants that were unable to activate RhoA and were resistant to the FGF2 stress response. We conclude that in Ras-dependent malignant cells, FGF2 interacts with its cognate receptors to trigger a senescence-like process involving RhoA-GTP. Surprisingly, attempts to select FGF2-resistant cells from the Y1 and 3T3-B61 cell lines yielded only rare clones that (a) had lost the overexpressed ras oncogene, (b) were dependent on FGF2 for proliferation, and (c) were poorly tumorigenic. Thus, FGF2 exerted a strong negative selection that Ras-dependent malignant cells could rarely overcome.
Costa
Erico T
ET
Departmento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
Forti
Fábio L
FL
Matos
Tatiana G F
TG
Dermargos
Alexandre
A
Nakano
Fábio
F
Salotti
Jacqueline
J
Rocha
Kátia M
KM
Asprino
Paula F
PF
Yoshihara
Celina K
CK
Koga
Marianna M
MM
Armelin
Hugo A
HA
D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D016922:Cellular Senescence / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D016222:Fibroblast Growth Factor 2 / Q000502:physiology*; D005434:Flow Cytometry; D051379:Mice; D008807:Mice, Inbred BALB C; D015689:Oncogene Protein p21(ras) / Q000502:physiology*; D020742:rhoA GTP-Binding Protein / Q000502:physiology*
D016222:Fibroblast Growth Factor 2; D015689:Oncogene Protein p21(ras); D020742:rhoA GTP-Binding Protein