When is it suitable for using NIH3T3 cells to validate cancer genes? - (Jan/12/2015 )

I have read some papers which use over-expression of cancer genes in  3T3 cells to investigate the function of the gene. 3T3 cells is mouse cell line. How can it be? 

The reasoning is the same as for using mice as a model for human disease. Humans and mice share a quite high sequence identity in their genomes, and if you find a gene in a human, there is a good chance you will find a mouse homologue.