p66(Shc) restrains Ras hyperactivation and suppresses metastatic behavior
1Department of Internal Medicine, Division of Pulmonary and Critical Care, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Oncogene
|August 3, 2010
Summary
Loss of p66(Shc) and retinoblastoma (pRB) in cancer cells enables metastasis by preventing anoikis. Restoring p66(Shc) inhibits metastasis and restores anoikis, highlighting its role in cancer progression.
Area of Science:
- Cell Biology
- Cancer Research
- Molecular Oncology
Background:
- Normal cells require substrate attachment for survival and proliferation (anchorage dependence).
- Cancer cells often evade this requirement, surviving and proliferating after detachment (anoikis resistance), a key step in metastasis.
- p66(Shc) is a focal adhesion protein involved in sensing cell attachment via RhoA signaling.
Purpose of the Study:
- To investigate the role of p66(Shc) and retinoblastoma (pRB) in anoikis resistance and metastasis of small cell lung cancer (SCLC) and Lewis lung carcinoma (LLC) cells.
- To determine if p66(Shc) re-expression can restore anoikis and inhibit metastasis.
- To elucidate the interplay between p66(Shc), Ras signaling, RhoA, and pRB in regulating proliferation and anoikis.
Main Methods:
- Analysis of p66(Shc) and pRB expression in SCLC and LLC cells.
- Experimental re-expression of p66(Shc) in cancer cells.
- Knockdown of p66(Shc) in normal epithelial cells.
- Assessment of anoikis and metastasis in vivo (using LLC cells).
- Investigation of Ras, RhoA, and pRB activation states.
Main Results:
- Aggressive SCLC and LLC cells lack both p66(Shc) and pRB, exhibiting anoikis resistance and metastatic potential.
- Re-expression of p66(Shc) in these cancer cells restored anoikis and significantly reduced metastasis in vivo.
- p66(Shc) knockdown in normal cells caused Ras activation, suppressed RhoA, blocked proliferation via pRB, mimicking oncogenic Ras.
- LLC and SCLC cells showed constitutive Ras activation, essential for anoikis bypass, which was reversed by p66(Shc) re-expression.
Conclusions:
- p66(Shc) is crucial for coordinating Ras-dependent proliferation and anchorage sensing.
- Loss of both p66(Shc) and pRB contributes to the evolution of highly metastatic tumors by enabling anoikis evasion.
- p66(Shc) represents a potential therapeutic target for inhibiting cancer metastasis.
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