A major problem with flow cytometric analysis of clinical solid
tumor specimens is that of non-malignant cell contamination which contributes to inaccurate results.
Monoclonal antibody to
cytokeratin, a marker for epithelial
tumor (
carcinoma) cells, was successfully used in conjunction with
a DNA-specific
dye to dually
stain specimens so as to obtain
DNA profiles exclusively for marker-positive
tumor cells. This gating procedure was used also for analysis of the cell marker distribution for those cells having
a DNA content consistent with
aneuploidy. After successful verification in model systems, clinical
carcinoma specimens were studied. The
aneuploid population increased from a mean of 61% without gating to a mean of 81% with gating for
cytokeratin. The
cytokeratin-positive cell fraction increased from a mean of 55% without gating to a mean of 96% with gating for
aneuploid DNA content. This gating procedure makes it possible to associate cell markers confidently with
tumor cell populations, thus providing objective verification of the tissue of origin for these
tumors. It can be performed simultaneously with standard gating for
DNA analysis; and both procedures used together, cross-gating, are invaluable for more precise analysis of human
tumor DNA and cell markers.