Related Experiment Videos
v-Src generates a p53-independent apoptotic signal
B L Webb1, E Jimenez, G S Martin
1Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA.
Abstract:
Evasion of apoptosis appears to be a necessary event in tumor progression. Some oncogenes, such as c-myc and E1A, induce apoptosis in the absence of survival factors. However, others, such as bcl-2 and v-src, activate antiapoptotic pathways. For v-Src, these antiapoptotic pathways are dependent on the function of Ras, phosphatidylinositol (PI) 3-kinase, and Stat3. Here we asked whether v-Src can activate a proapoptotic signal when survival signaling is inhibited. We show that when the functions of Ras and PI 3-kinase are inhibited, v-src-transformed Rat-2 fibroblasts undergo apoptosis, evidenced by loss of adherence, nuclear fragmentation, and chromosomal DNA degradation. The apoptotic response is dependent on activation of caspase 3. Under similar conditions nontransformed Rat-2 cells undergo considerably lower levels of apoptosis. Apoptosis induced by v-Src is accompanied by a loss of mitochondrial membrane potential and release of cytochrome c and is blocked by overexpression of bcl-2, indicating that it is mediated by the mitochondrial pathway. However apoptosis induced by v-Src is not accompanied by an increase in the level of p53 and is not dependent on p53 function. Thus v-Src generates a p53-independent proapoptotic signal.
Insights
The v-Src oncogene can trigger programmed cell death (apoptosis) in cancer cells, even when survival signals are blocked. This occurs through a p53-independent pathway involving mitochondria.
Area of Science:
- Molecular Biology
- Oncology
- Cell Biology
Background:
- Tumor progression often involves evading apoptosis, the programmed cell death.
- Oncogenes like c-myc and E1A can induce apoptosis, while others like bcl-2 and v-Src promote survival.
- v-Src-mediated antiapoptotic pathways rely on Ras, phosphatidylinositol 3-kinase (PI3K), and Stat3 signaling.
Purpose of the Study:
- To investigate if v-Src can induce apoptosis when survival signaling is inhibited.
- To elucidate the specific pathways involved in v-Src-induced apoptosis.
Main Methods:
- Inhibition of Ras and PI3K signaling in v-Src-transformed Rat-2 fibroblasts.
- Assessment of apoptotic markers including loss of adherence, nuclear fragmentation, and DNA degradation.
- Analysis of caspase 3 activation, mitochondrial membrane potential, cytochrome c release, and p53 levels.
Main Results:
- v-Src-transformed cells underwent apoptosis upon Ras and PI3K inhibition, unlike normal cells.
- Apoptosis was dependent on caspase 3 activation and involved mitochondrial pathway activation (cytochrome c release).
- The v-Src-induced apoptosis was p53-independent and not blocked by p53 inhibition.
Conclusions:
- v-Src can generate a proapoptotic signal independently of p53 when survival pathways are suppressed.
- The mitochondrial pathway is crucial for v-Src-induced apoptosis under these conditions.
- This finding offers insights into targeting oncogene-driven apoptosis in cancer therapy.