DNA content in colorectal carcinoma: a flow cytometric study of the epithelial fraction

The aim of this study was to estimate the proliferative activity of the epithelial fraction in human colorectal carcinomas. Cell suspensions from 27 human colorectal carcinomas were simultaneously selected for epithelial cells and analyzed for DNA content. The staining procedure we employed, after dispersing the tumour sample into a single-cell suspension, included propidium iodide and a monoclonal antibody to the intermediate filament cytokeratin specific for secretory epithelia of normal human tissue and cells of epithelial origin in adenocarcinomas. This technique made it possible to distinguish the epithelial cell population from non-epithelial cells in the tumour. Flow cytometry was used for DNA analysis and the results obtained after epithelial selection were compared with conventional DNA analysis of crude tumour tissue. No difference in S-phase values of diploid and aneuploid cytokeratin positive cells were seen, whereas analysis of crude tumour cell suspensions showed lower S-phase values in diploid tumours compared to aneuploid ones. When cytokeratin-positive cells in the tumour were selected, we found presence of diploid tumour cells in almost all aneuploid tumours.