Full oncogenic activities of v-Src are mediated by multiple signaling pathways. Ras as an essential mediator for cell survival.
Tyrosine kinase oncoproteins cause simultaneous activation of multiple intracellular signaling pathways. However, the precise mechanisms by which individual pathways induce oncogenesis are not well understood. We have investigated the roles of individual signaling pathways in v-Src-dependent cell growth and survival by inhibiting one particular pathway. v-Src induced constitutive activation of signal transducers and activators of transcription 3 (STAT3), phosphatidylinositol 3-kinase, and Ras in murine Ba/F3 cells and led to factor-independent proliferation. Dominant-negative mutants of STAT3 (STAT3D) and phosphatidylinositol 3-kinase (Deltap85) inhibited v-Src-dependent growth by approximately 60 and approximately 40%, respectively. Moreover, dominant-negative Ras (N17) induced severe apoptosis, which was accompanied by down-regulation of Bcl-2 and activation of caspase-3. Although cells overexpressing Bcl-2 or caspase-3 inhibitors remained viable even when N17 was expressed, the growth was reduced by approximately 85%. During N17- and STAT3D-induced growth suppression, expression of cyclin D2, cyclin D3, c-myc, and c-fos was suppressed by N17, whereas that of cyclin D2, cyclin E, and c-myc was suppressed by STAT3D. Thus, v-Src-activated Ras and STAT3 are involved in distinct but partly overlapping transcriptional regulation of cell cycle regulatory molecules. These results suggest that the full oncogenic activity of v-Src requires simultaneous activation of multiple signalings, in which Ras is particularly required for survival.
Odajima
J
J
Department of Hematology/Oncology and Molecular Oncology, Biomedical Research Center, Osaka University Medical School, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
Matsumura
I
I
Sonoyama
J
J
Daino
H
H
Kawasaki
A
A
Tanaka
H
H
Inohara
N
N
Kitamura
T
T
Downward
J
J
Nakajima
K
K
Hirano
T
T
Kanakura
Y
Y
D000818:Animals; D017209:Apoptosis; D001402:B-Lymphocytes; D002455:Cell Division; D002470:Cell Survival; D002471:Cell Transformation, Neoplastic; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D007377:Interleukin-3 / Q000494:pharmacology; D051379:Mice; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D013234:Stem Cells; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D007377:Interleukin-3; D019253:Proto-Oncogene Proteins c-bcl-2; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D019869:Phosphatidylinositol 3-Kinases; D015688:Oncogene Protein pp60(v-src); D018631:ras Proteins