6th ESACP Congress, Heidelberg, April 7-11, 1999

A116
BIVARIATE ANALYSIS OF CYTOKERATIN AND DNA IN COLORECTAL CANCER BY FLOW CYTOMETRY ON FINE-NEEDLE ASPIRATES FROM FROZEN TISSUE
Post C, Christensen IJ, Flyger H *, Christiansen J, Larsen JK

Finsen Laboratory, Rigshospitalet, Copenhagen, * Dept. of Surgery, Hillerod Hospital, Denmark

The aim was to investigate a method for simultaneous measurement of cytokeratin and DNA content in colorectal cancer, in order to improve the estimation of the S-phase fraction (SPF) of DNA aneuploid subpopulations. From 162 colorectal tumors fine-needle aspirates of 744 frozen biopsies were analyzed. Cytokeratin/DNA measurements were based on staining in PBS with 0.3% saponin, propidium iodide, RNase, and FITC-conjugated anti-cytokeratin antibody "(DAKO MNF-116)". Fluorescence was compensated after measurement. DNA histograms of cytokeratin-positive cells "(CG)" were found by gating of the cytokeratin/DNA measurement (CT) based on an isotype control. These results were compared to univariate DNA measurements (Vi) (method of Vindel°v et al.). For the initial analysis, good quality DNA histograms with low CV, debris and a sufficient number of counts in the region of interest were selected, representing 406 biopsies from 129 patients. The median G1 peak CV was 2.3% for Vi and 3.2% for CG/CT. The SPF was higher in CG than in CT histograms (mean difference 3.1%, p<0.0001), and higher in CT than in Vi (1.3%, p=0.0005). The correlation coefficient between SPF for CG and Vi was 0.56 (p<0.0001). Comparison of the DNA ploidy patterns between Vi and CT, including only a DNA subpopulation if the G1 fraction was 10% or more of the region of interest, showed complete accordance both ways in 346 (85%) biopsies. We conclude that this method yields the same ploidy pattern as Vi and that SPF is significantly different for CG, suggesting that additional information may be obtained using this measure.