colony formation assay - (May/20/2013 )

Hi,

I plan to do a colony foration assay (or foci formation assay) to observe the effect of my plant extract, of certain concentration, on cancer cell lines. I plan to seed about 300-500 cells per 60mm dish and observe the no. of colonies that form after about 2 weeks. In these two weeks, can I change medium (containing the right dosage of the extract)?

You can change the medium as this would be similar to giving repeated doses as a therapy, though it depends if you want this to be the case or not.