EVIDENCE FOR QUIESCENT S-PHASE AND G(2)-PHASE CELLS IN HUMAN COLORECTAL CARCINOMAS - A FLOW CYTOMETRIC STUDY WITH THE KI-67 ANTIBODY

The expression of certain antigens specific for proliferating cells ca n be determined simultaneously with cell cycle distribution by means o f two-dimensional flow cytometry. In this way, a tumour's growth poten tial is characterized more precisely than with any one parameter alone . Here we describe such simultaneous measurements of DNA content and l abelling with the Ki-67 antibody that distinguishes between cycling an d non-cycling cells. Having overcome a number of technical problems we were able to analyse material from 29 biopsies of human colorectal tu mours. In a number of cases, Ki-67 negative cells were found with a DN A-content of G(0/1) only, whereas all cells with an S- or G(2)-phase D NA-content were Ki-67 positive. There were other cases in which cells with an S- and G(2)-phase DNA-content had obviously become quiescent ( Ki-67 negative), sometimes even outnumbering the proliferating (Ki-67 positive) cells in the respective compartments of the cycle. Generally , however, when Ki-67 negative and positive subpopulations were analys ed separately It was found that the former had a significantly lower ( S + G(2))-phase fraction than the latter. There was evidence for a cor relation between Ki-67 index and (S + G(2))-phase fraction at least in the subgroup of aneuploid tumours. Neither of the two parameters was correlated with stage according to Duke's classification or tumour siz e, However, a positive correlation was found between the fraction of u nlabelled S- and G(2)-phase cells and tumour size as reflected in the T category.