Molecular Pharmacology, Vol 2, 363-367, Copyright © 1966 by the American Society for Pharmacology and Experimental Therapeutics

Absence of DNA Synthesis in One-Half of a Population of Mammalian Tumor Cells Inhibited in Culture by 5-Iodo-2'-Deoxyuridine

¹ Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06519

After a single doubling in culture with 5-iodo-2'-deoxyuridine (2 x 10^-4 M), about one-half of a population of murine mast tumor cells (P815Y) fails to carry out DNA synthesis, as evidenced by the lack of grain formation in radioautographs of the cells after incubation in medium with ³H-thymidine. These findings support the conclusion that only about one-half of the hybrid DNA of such a culture can replicate.

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ACKNOWLEDGMENT We are greatly indebted to Professor Arnold D. Welch for valuable experimental suggestions and for help in the preparation of the manuscript; our grateful appreciation is extended to Mrs. Loretta Duer, Miss Katja Hahn, and Mrs. Donna Reno for their excellent technical assistance. The work of N.R.M., American Cancer Society Scholar in Cancer Research, was supported by a grant (P333) of the American Cancer Society. The work of J.W.C. was supported by a grant. (CA-02817-09) of the National Cancer Institute, Public Health Service.