Jamary 19, 1953
Dear Dr. Duran-Reynals:

Thank you for your letter of the 16th. I am sorry if my comment was
confusing—~ perhaps because I am not entirely clear ayself. I have gotten
the impression from conversations with various people that you had found
fowl pox virus to be closely asscelated with tumor viruses under special,
obscure ciroumstances. I have not been able to follow your work as cloesly
ae I would like, and for just this reason am locking forward to your pro-
mised reprints.

The suggestion that I was trying to put forward was that. in certain
situations, latent viruses having no special relationship to tumors might
acquire a tumor-inducing capacity by the very fact of their grorvth in
neoplastic celis. Gn this basis, the taincor change would te intrinsic to the
cell, but might also be transakitted by viruses growing in these cells. This
would be comparable in its way to genetic transduction In bacteria. Its only
virwue is that it would possibly help tc unify the somatic mutation and virus
induction faote and theories of oarcinogenseis. I do not know whether any
existing data would justify this notion. If the tumor viruses can be grown
in indifferent host celle (e.g. embrycnic tissues) and retéén their carcino~
genetic putency, thin would tend against the theory. On the other hand, it
@ight be worth vile to try growing various viruses cn tumor cells from which
a transcissible agent cannot ordinarily be extracted. /
Yours sincerely, A
: f

‘Joehua Lederberg

Dr. F. Duran-Reynals ,.
Department of Mierobi@logy
Yale University %

New Haven 11, Conn.