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Replication and 5-Iodo-2'-deoxyuridine-³H Incorporation by Tumor and Normal Cells¹

New York University Research Service, Goldwater Memorial Hospital, Welfare Island, New York, New York

The replication patterns and times of an experimentally induced breast tumor and of coexistent ileal epithelium were studied in the female rat in vivo. The data show that the normal ileal cells replicate 4 times as rapidly as do the tumor cells. In addition, many more ileal cells are engaged in multiplication.

The incorporation of 5-iodo-2'-deoxyuridine-³H (5-IUDR-³H) is greater by the more rapidly replicating ileal cells than by the tumor cells.

A review of the available data on the replication in vivo of specific autochthonous tumor and normal cell lines in patients and in experimental animals indicates that tumor cells, as a group, replicate relatively slowly. It is suggested that the competitive incorporation of antitumor cytotoxins depends upon the comparative rates of the metabolic processes involved.

The observed greater vulnerability of bone marrow and intestinal cells to cytotoxins is probably due to their more rapid replication and these relationships may effectively limit the usefulness of the antitumor agents.

Finally, tumors differ from each other in their replication times and nuclear DNA contents and may not be treated as a single biologic entity, in relation to normal cell lines.

¹ Presented in part at the Fifty-seventh Annual Meeting of the American Society for Clinical Investigation in Atlantic City, New Jersey, May 3, 1965. Supported in part by USPHS Grant Nos. CA 03917-07 and HD 00672-08, in part by the Atomic Energy Commission under NYO-Contract No. 2778—Report No. 2, and by the Health Research Council of the City of New York under Contract Nos. U-1089 and U-1579.

Received 9/22/65.