The proliferative patterns of human breast cancer cellsin vivo

Abstract

The cell proliferation pattern in human breast cancer was studied in 8 patients in vivo using i.v. administered 3HTdR [3H-thymidine] as a pulse and continuous label. Two to 4% of the tumor cells were engaged in DNA synthesis in 6 patients, and 7 and 11%, respectively, in 2 others. From the composite percent labeled mitosis curve the estimated time for G2 + (M[mitosis]/2) was .apprx. 4 h and for DNA synthesis about 24 h. Many cells which entered the cycle spent longer intervals in DNA synthesis and in the post-DNA synthetic phase before entering M. There was a wide range of intermitotic times among the tumor cells. These findings are of significance in the planning of drug therapy.