gene down-regulated in cancer cell line but no proliferation inhibit ability - (May/03/2008 )

we cloned a novel gene which down-regulated in cancer cell line, in order to clarify whether this gene is tumor suppressor gene or not, this gene was transfected into cancer cell line which have no expression of this gene ,and stablely over-expression cell line were used to proliferation ability and growth ability assay, surpprisingly, over-expression this gene have no inhibition on the cell growth and proliferation. why?

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Could it be that the gene has another function rather than suppressing growth and proliferation?? Or if you assume that the gene has a tumor suppressor function, maybe overexpression of this gene alone is not enough to excert its function?? Any idea of other proteins interacting with your ptotein of interest?? Or this gene is specific to your cell line??

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i performed two-hybrid screening and found several inteacting protein, one is a microtubule associated protein and another is a subunit of a enzyme which play role in energy metabolism. this gene is a relatively tissue specific gene which high expressed in bronchia and have lower expression in nasopharynx ,this gene is down-regulated in nasopharyngeal carcinoma(NPC) tissues and cell lines ,so wo assume this gene has a tumor suppressor function in NPC,

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cancer cells and paternal epithelial cells differ in many aspects; beside increased proliferation and partial loss of apoptosis, other physiological functions of paternal cells are altered or down-regulated in cancer cells which means that not all down-regulations must be associated with cell cycle or apoptosis;

what are the facts to think of a tumor suppressor? down-regulation alone is an only weak hint...

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