INST. FOR CELLFORSKNING OCH GENETIK

MEDICINSKA NOBELINSTITUTET -
KAROLINSKA INSTITUTET / /
STOCKHOLM 60

Telefon 23 54.80

INST. FOR CELI. RESEARCH AND GENETICS

April 12, 1957

 

CIR Wy 6
ae Professor Joshua Lederberg

Department of Genetics

The University -of Wisconsin
Madison 5, Wisconsin

U.S.A.

Dear dosh:

Thank you very much for your letter of April
7. I can see that you will have a busy time next year
but I hope very much indeed that you will find it pos-
sible to come to the Congress of Microbiology. I have
forwarded your letter to the organisation comritee and
they will contact you about the financial arransenents
in the near future,

Thank you very tuch for your willingness to
help us to put adequate selection pressure on the DO-
pulation of transformists. Perhaps it will be wisest
if we wait until the registration# forms have been
returned which is due to hanpen shortly. After we have
gone through them we shall take the liberty to ask your
advice about how to arrange the suitable sessions and
whom to invite particularly,

Thank you for your comments about the H-2
system. It is very difficult to make good chromosome
preparations from solid tumors an4d we have as yet not
made any serious attempts in this direction, It is
ouite apparent that there is 4 rood deal of variation
in the behavior of different sarcomas, induced by the
Same carcinogen in the same zenotyve (F ay sad of
two isogenic resistent sublines, genotype H-2°H-2 }
and having roughly the same histological structure,
Some of these tumors are very strictly svecific and have
so far resisted attempts to select out variants that
would grow in one of the parental strains. One sarcoma
has readily yielged yariants <oing in one iireetion
(towards the H-2"H-2° parent) but never in the other,
Still others are appearently “non-specific” from the
very beginning and grow readily in bothevarental and
also in a number of foreign strains.It is not possible,
or rather hag not been possible until present to select
precise variants from these tumors that would have a
sélective compatibility for Only one genotype. This
variability in behavior probably reflects differences
in the cytogenetig makeup of the different tumors, It
would be a beaut ful task to try to vin th@se iifferen-
ces down and I hope that we shall be able to tackle
this. In the meantime, it is quite tempting to svecu-
- 2.
Professor Joshua Lederberg April 12, 1957
Madison 5,Wisconsin

late that such differences in the cytocenetic etruc-
ture of Jifferent primary tumors, induced in the sare
fashion and in the same genotype, may verhaps be re-
flections o* the *®act that neovlastic transformation

may oroceed along several alternative voathways in the
cell. Alternatively, it would be possible that all these
differences have occurred durins the secondary evolu-
tion of the established tumors. There are some reasons,
however, which make this second possibility somewhat
less probable,

I have received an offer from Hilary Koprow-
ski but have so far been unacle to give a definite ansgs-
wer, My professorship is still on @ a orovogal that
hag recently reached Parliament. Such thines take an
enormus amount of time in this country. If it goes through,
I think I should be very hesitating to leave it. If
it does not, however, I would feel nyself quite free.
The trouble is that it may take quite some time before
a final decision will be reached.

I shall be in New England in June and nothing
would please me more than a trip to Madison anda dis-
cussion with you and Esther. However, both tive and
funds are rather limited on this occasion. Since you
have kindly mentioned it, I would indeed like to corte
but I could stay only a very few days and I could only
make it if there were sore funds available for the trip
between the East Soast and Madison. I should hardly
think that it would be worth while for yov to go into
trouble to secure such funds, voarticularly since the
profit from such a trip would be @ntirely on my side.
If you would nevertheless want to maze guch an arrange-
ment, nowever, I should be most JjJelizhted to come,

“To. yours,

George Flein

With kindest regards,