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Focus Formation: A Cell-based Assay to Determine the Oncogenic Potential of a Gene
Published on: December 31, 2014
Focus formation: a cell-based assay to determine the oncogenic potential of a gene
Angel Alvarez1, Gustavo A Barisone1, Elva Diaz2
1Department of Pharmacology, University of California, Davis.
Abstract:
Malignant transformation of cells is typically associated with increased proliferation, loss of contact inhibition, acquisition of anchorage-independent growth potential, and the ability to form tumors in experimental animals(1). In NIH 3T3 cells, the Ras signal transduction pathway is known to trigger many of these events, what is known as Ras transformation. The introduction of an overexpressed gene in NIH 3T3 cells may promote morphological transformation and loss of contact inhibition, which can help determine the oncogenic potential of that gene of interest. An assay that provides a straightforward method to assess one aspect of the transforming potential of an oncogene is the Focus Formation Assay (FFA)(2). When NIH 3T3 cells divide normally in culture, they do so until they reach a confluent monolayer. However, in the presence of an overexpressed oncogene, these cells can begin to grow in dense, multilayered foci(1) that can be visualized and quantified by crystal violet or Hema 3 staining. In this article we describe the FFA protocol with retroviral transduction of the gene of interest into NIH 3T3 cells, and how to quantify the number of foci through staining. Retroviral transduction offers a more efficient method of gene delivery than transfection, and the use of an ecotropic murine retrovirus provides a biosafety control when working with potential human oncogenes.
Insights
The Focus Formation Assay (FFA) uses retroviral transduction to introduce genes into NIH 3T3 cells, enabling assessment of oncogenic potential by quantifying cell foci. This method efficiently determines cellular transformation and oncogene activity.
Area of Science:
- Cell Biology
- Molecular Oncology
- Cancer Research
Background:
- Cellular transformation involves hallmarks like increased proliferation and loss of contact inhibition.
- The Ras signaling pathway is crucial in triggering these transformation events.
- Assessing oncogenic potential requires reliable methods to detect cellular transformation.
Purpose of the Study:
- To describe the Focus Formation Assay (FFA) protocol for evaluating oncogene transforming potential.
- To detail the use of retroviral transduction for efficient gene delivery into NIH 3T3 cells.
- To explain the quantification of transformed foci via staining.
Main Methods:
- Utilizing NIH 3T3 cells for transformation assays.
- Employing retroviral transduction for introducing genes of interest.
- Visualizing and quantifying transformed foci using crystal violet or Hema 3 staining.
Main Results:
- Retroviral transduction proved more efficient for gene delivery compared to transfection.
- The FFA protocol allows for the visualization and quantification of multilayered cell foci.
- Ecotropic murine retrovirus provides a biosafety control for working with potential human oncogenes.
Conclusions:
- The Focus Formation Assay is a straightforward method to assess one aspect of oncogene transforming potential.
- Retroviral transduction is an effective and efficient gene delivery method for transformation studies.
- This protocol provides a standardized approach for evaluating oncogenes in NIH 3T3 cells.
