Proliferative Activity of Human Solid Tumors Evaluated by Thymidine Labeling Index and Primer-Dependent α-DNA Polymerase

Abstract

Proliferating cells, independent of their position in the cell cycle, contain a primer-dependent .alpha.-DNA polymerase (PDP);we have, therefore, tested the feasibility of the PDP assay in breast, ovarian, and head and neck tumors. Experimental results demonstrate that the PDP labeling index (PDP-LI) is constantly superior to the thymidine labeling index (TLI), which indicates the percentage of S phase cells. The PDP-LI/TLI ratios observed were 5.0 in breast cancer, 3.6 in ovarian cancer, and 2.5 in head and neck tumors. Higher PDP-LI scores have been obtained in metastatic breast tumor samples (PDP-LI = 8.8) compared to nonmetastatic tumors (PDP-LI = 4.9).