Cancer: steroids of the future!
No, that's not how it works. If cancer cells had any of those controls, they would be normal cells. Cancer cells also don't differentiate. So your new hand that you'd try to grow with cancer cells would wind up being-- you guessed it-- a tumor.
You're onto something though... and that has everything to do with the wonderful field of stem cells.
And cancers don't actually "attack" anything. They basically just grow and take up everything for themselves. I'm not entirely sure how venom works although I know some are deadly because they clot up your blood rather than being cell-killing toxins. But there is work being done with killer bee toxin among other things to see if they can be delivered to cancers to kill them.
The big problem is that cancer is pretty easy to kill but the specificity of the treatment often isn't limited to the cancer alone. Chemo kills anything that rapidly divides, for example. You can jump into an incinerator and your cancer will be long gone. Doesn't really solve the problem without creating a larger one though.
