THE INSTITUTE FOR CANCER RESEARCH 
IfOl BUHHOLME AVENUE 
FOX CHASE • PHILADELPHIA, PENNSYLVANIA I© 111 
|S1S| 348-lOOO CABLI address: can s sabc h 
December 17, 1979 
Dr. Donald S. Fredrickson 
Director 
National Institutes of Health 
Bethesda, MD 20014 
Dear Dr. Fredrickson: 
I am writing this letter to let you know that I fully support 
your position that all recombinant DNA research performed with 
E coli strain K12 should be classified P1/EK1. I feel that 
the potential risks of such research have been carefully evaluated 
by well-informed specialists and that this classification is a 
proper one. 
I stress that I am not working with recombinant DNA in my bio- 
medical research, and have no self-promoting or vested interest 
in this decision. 
Sam Sorof, Ph 
Senior Member 
SS/bh 
[521] 
THE FOX CHASE CANCER CENTER 
