Isolated Oncogenes for Transfection Assay
Viral infection is not really necessary for tumour formation. We can actually assay for transformation by directly transfecting normal recipient cells (3T3 fibroblast line is often used) with either the DNA isolated from animal tumours, (Fig. 45.3) or with the isolated and cloned genes (cloned genes have greater efficiency for transformation). When a cell in 3T3 line or other cell line is transformed, its descendants pile up into a focus, whose appearance, is a measure of transforming ability of DNA preparation used. A highly transforming gene may give > 100 foci/ng DNA/10⁶ cells as against < 10 foci/ng DNA/10⁶ cells obtained with a weakly transforming gene. A number of isolated genes used for transformation are listed in Table 45.5.