# of tumor suppressor genes

[spate]

Out of curiousity, do you know approxiately how many tumor suppressor genes have been identified? I read an article in Nature Review and apparently there's almost 300 oncogenes (that have been identified) but didn't mention anything about tumor suppressor genes.......

[Poison]

I like to read about cancer but I haven't came across with an info like that. I will look again for you.

[weesper]

I got an answer to tour question but you might not be content with it; the answer is that it all depends on your definition of what constitutes a tumor suppressor gene (TSG). back in the day when the concept was launched TSGs were defined as genes that were biallelicly inactivated, affect cell-cycle progression and show somatic point-mutations in sporadic cancers. Over time it has become clear that a lot of TSGs don't dit this definition; take for example the haplo-insufficient TSGs, these are not necessarily biallelicly inactivated yet their gene dosage influences tumor initiation and or progression(say p27Kip1 as an example) other genes do not influence cell cyle progression yet they are clear tumor supressors (see TSGs in the angiogenic pathway such as VHL), lastly genes can become inactivated without point mutations but by promoter methylation (see Rassf1a). Thus the actual number depends on how strict your definition is. Hope this suffices as an answer to your question. take care

[spate]

Hi Poison and Weesper,

Thanks for the reply. Yeah, I think it is difficult to state how many tumor suppressor genes there are out there.......what you said, Weesper, makes a lot of sense, it really does depend on what the definition of TSG is. I will look into it some more, hopefully I will find out more about it and I'll share it with you guys. Wish me luck!!