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pp60(cSrc) is a caspase-3 substrate and Is essential for the transformed phenotype of A431 cells
1Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Jerusalem, 91904, Israel.
Abstract:
The protein tyrosine kinase c-Src is a major signal transduction element in many growth factor receptor signals for proliferation and transformation. We showed recently that c-Src is a mediator of antiapoptotic signals through regulation of the antiapoptotic gene Bcl-X(L). A431 cells overexpress the EGF receptor (EGFR) and possess high Src activity. In A431 cells, Src is activated by the EGFR, and inhibition of the EGF receptor results in c-Src inhibition. In this study we show that (i) inhibition of the EGFR kinase or Src kinase by specific inhibitors results in growth inhibition and inhibition of colony formation in soft agar. The relative efficacies of the EGFR kinase inhibitor and of the Src kinase inhibitor are similar suggesting the major role src plays in the oncogenic signaling of EGFR in A431 cells. (ii) The Src kinase inhibitor PP1 sensitizes A431 cells to CDDP-induced apoptosis. (iii) CDDP induces caspase-3-dependent cleavage of the c-Src C-terminal portion and a concomitant reduction in Bcl-X(L) levels. We conclude that c-Src is an important antiapoptotic signaling molecule downstream of the EGF receptor that contributes to the transformed phenotype of A431 cells.
Insights
The protein tyrosine kinase c-Src is crucial for cancer cell growth and survival. Inhibiting c-Src or the EGF receptor (EGFR) halts cancer cell proliferation and sensitizes cells to chemotherapy, highlighting c-Src as a key therapeutic target.
Area of Science:
- Oncology
- Molecular Biology
- Cell Signaling
Background:
- c-Src is a protein tyrosine kinase involved in cell proliferation and transformation.
- c-Src regulates antiapoptotic signals, including the Bcl-X(L) gene.
- A431 cells exhibit high Src activity due to EGFR overexpression and EGFR-mediated Src activation.
Purpose of the Study:
- To investigate the role of c-Src in EGFR-driven oncogenic signaling in A431 cells.
- To determine the impact of EGFR and c-Src inhibition on cancer cell growth and apoptosis.
- To elucidate the mechanism by which c-Src contributes to the transformed phenotype.
Main Methods:
- Utilized specific kinase inhibitors for EGFR and c-Src.
- Assessed cell proliferation and colony formation in soft agar.
- Evaluated apoptosis induction by CDDP (cisplatin) and measured caspase-3 activity.
- Analyzed c-Src cleavage and Bcl-X(L) levels.
Main Results:
- Inhibition of EGFR or c-Src kinase activity similarly reduced cancer cell growth and colony formation.
- The c-Src inhibitor PP1 enhanced CDDP-induced apoptosis in A431 cells.
- CDDP treatment led to caspase-3-dependent cleavage of c-Src and decreased Bcl-X(L) levels.
Conclusions:
- c-Src is a critical downstream signaling molecule of EGFR, contributing to the transformed phenotype.
- c-Src acts as an antiapoptotic factor, promoting cancer cell survival.
- Targeting c-Src may enhance chemotherapy efficacy and represents a potential therapeutic strategy.