Flow cytometric DNA and 5′‐nucleotide phosphodiesterase in endometrium

One hundred endometrium specimens have been studied with flow cytometry for DNA analysis (FCDA) and a proliferative enzyme marker, 5′‐nucleotide phosphodiesterase (5′‐NPD). FCDA data showed that aneuploidy was present in only 5 of 40 cancer specimens. However, with corrected histograms, a higher DNA value was observed in the G₂/M (6%) of all cancer compared with noncancer specimens (4%). Thus, FCDA can be a useful diagnostic aid for endometrial cancer. The determination of 5′‐NPD was done with a quenching method based on the use of 5′‐(5‐iodo‐3‐indoxyl)‐thymidine phosphodiester as a substrate and 4′,6‐diamidino‐2‐phenylindole for DNA. This method could qualitatively define which population of the cell cycle had a higher enzyme level and also quantitatively gave the enzyme units per cell. It was found that 12.5% of all cancer specimens had 5′‐NPD activity in the G₀/G₁ cells and 87.5% in the S and/ or G₂/M cells, whereas in the noncancer specimens 5′‐NPD was found in 28.5% of the G₀/C₁ cells and 71.5% of the specimens had 5′‐NPD in the S and/or G₂/M cells. Furthermore, the concentration of 5′‐NPD was found to be five times higher in the G₂/M cells of the cancer specimens than that in the noncancer specimens. However, in the hyperplasia specimens, the activity was only two times higher in the same cell cycle fraction than in the normal specimens. The results of this investigation provided for the first time evidence that this exonuclease activity alters in the cell cycle fractions and that a decrease in the enzyme activity in G₀/G₁ cells and an increase in G₂/M cells may be a useful marker for neoplastic development in human endometrial cancer.