HI! your question is very vague and hard to address with so little information; tumor suppressors' signal transduction pathways can be so different depending on the suppressor gene.

Nevertheless, I would suggest a simple western blot to make sure you are in fact re-expressing your tumor suppressor protein. If you'd like to take this further, you can perform co-immunoprecipitations and detect interactions of known proteins to your newly expressed tumor suppressor. Also, it might help if you introduce a small tag onto your re-expressed tumor suppressor gene (flag, hemagglutinin, myc, for example); this will allow you easier western blots and co-IPs.

You might also want to consider expression analysis of downstream genes induced/mediated by your tumor suppressor. RT-PCR (ideally qPCR) techiniques are very powerful and will allow you to compare "before/after" re-expression at a more functional way.

Good Luck!

Thanks a lot. That confirms my expectations. 

Put cancer cells deleted with your genes of interest in mice and check effect on tumor growth and at the same time implant cancer cells with your genes of interest expressed. You will get your answer.

First, you will need western blots to confirm the expression of your tumor suppressor gene. Re-expression of tumor suppressors in cancer cells will probably inhibit the growth of those cells by inducing apoptosis or senescence, for example. If using a cell line in vitro (without and with your gene of interest), you can use growth curves, colony formation assays, SA-B-Galactosidase assays (for senescence), or many of the apoptosis assays (FACS, apoptosis markers etc). You can also perform a tumorigenic assay in vivo by injecting the cells in nude mice. The possibilities are infinite... Good luck :)

Thanks Jacqui, awesome answer. Have a wonderful day!