The tubes in the CABAL bunkers are the Biological part of CABAL- Computer Assisted Biological Artificial Lifeform, IIRC. That Kane was a part of that is up for debate.
What is known is that Kane is somehow unnatural, or that he has a great many stand-ins to die in his place. The Brotherhood goes back to the biblical story of Cain(sp?) killing his brother Abel- there's a coffin in Renegade with Abel written in Hebrew, to boot, and his InterPol file is GENsomething), and that KAne was banished to the Land of Nod, which means that he was to be an eternal wanderer, as Nod is Hebrew for nothing IIRC. And he was cursed to live until the proverbial judgment day, and that no man could slay him to end his exile.
Now, you can divulge many different theories about Kane's roots from that, but since none of them are verifiable, I don't think it's a worthwhile endeavor.