Automated flow-cytometric identification of colo-rectal tumour cells by simultaneous DNA, CEA-antibody and cell volume measurements.

A new method for the automated flow-cytometric identification of colo-rectal tumour cells was developed. Fresh tissue is cut mechanically to obtain single cell suspensions. The cells are then incubated with antibodies in an indirect immunofluorescence assay for CEA (carcino-embryonic antigen) on the cell surface, and counterstained with the DNA stain propidium iodide. Monosized latex particles are added as internal standard, then cell volume, antibody fluorescence and DNA are measured simultaneously in a FLUVO-METRICELL flow cytometer. A FORTRAN IV computer program was used to determine whether aneuploid cells or cells with high density of CEA on their surface were present in the sample. All relevant data were stored automatically in a self updating data base, which is important for quality control and automated thresholding. The samples were taken from 120 different patients. A tumour sample and a sample of healthy adjacent mucosa of the same patient were available in 88 patients. 97.5% of all tumours and 88.6% of the normal mucosa samples were correctly identified. This shows for the first time that the majority of colo-rectal tumour samples can be identified by a flow cytometric measurement with automated data evaluation. The identification of tumour samples was substantially better when based on the measurement of the three parameters, compared with identification by aneuploidy (59%) or by the CEA antibody alone (91%). It will be possible to automate the measurement of the samples.