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Reversible tumorigenesis induced by deficiency of vasodilator-stimulated phosphoprotein
K Liu1, L Li, P E Nisson
1Departments of Genetics, Stanford University School of Medicine, Stanford, California 94305-5120, USA.
Abstract:
Random homozygous knockout (RHKO) is an antisense RNA strategy capable of identifying genes whose homozygous functional inactivation yields a selectable phenotype in cells growing in culture. Using this approach, we isolated NIH 3T3 fibroblast clones that showed the ability to form colonies on 0.5% agar and tumors in nude mice. The gene inactivated in one of these clones was found to encode VASP (vasodilator-stimulated phosphoprotein), a previously identified protein that binds to components of the cadherin-catenin junctional complex and has been implicated in cell-cell interactions, the formation of actin filaments, and the transmission of signals at the cytoskeleton-membrane interface. Fibroblasts made deficient in VASP by RHKO showed loss of contact inhibition, and consequently, continued cell division past confluence. Restoration of VASP function by reversal of RHKO yielded cells that had lost the neoplastic capabilities acquired during RHKO. Overproduction of VASP mRNA in the sense or antisense orientation from expression constructs introduced by transfection into naive NIH 3T3 fibroblasts also resulted in neoplastic transformation, implying that normal cell growth may require the maintenance of VASP expression within a narrow range. Our results implicate VASP in tumorigenesis and/or cancer progression.
Insights
Researchers used antisense RNA to identify VASP (vasodilator-stimulated phosphoprotein) as a key factor in cell growth. Inactivating VASP led to neoplastic transformation, suggesting its role in tumor development.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- The vasodilator-stimulated phosphoprotein (VASP) is involved in cell-cell interactions and cytoskeletal dynamics.
- Understanding genes that regulate cell proliferation is crucial for cancer research.
Purpose of the Study:
- To identify genes whose inactivation leads to selectable phenotypes using antisense RNA technology.
- To investigate the role of VASP in cell transformation and tumorigenesis.
Main Methods:
- Utilized random homozygous knockout (RHKO) strategy with antisense RNA.
- Isolated and analyzed NIH 3T3 fibroblast clones with acquired neoplastic capabilities.
- Assessed VASP gene function and expression levels through genetic manipulation and transfection.
Main Results:
- Homozygous inactivation of the VASP gene resulted in NIH 3T3 fibroblasts forming colonies on agar and tumors in mice.
- VASP-deficient fibroblasts exhibited loss of contact inhibition and uncontrolled cell division.
- Altering VASP expression outside a narrow range, either by deficiency or overproduction, induced neoplastic transformation.
Conclusions:
- VASP plays a critical role in regulating normal cell growth and preventing neoplastic transformation.
- VASP deficiency or dysregulation is implicated in tumorigenesis and cancer progression.
- Maintaining VASP expression within a specific range is essential for normal cell proliferation.