Improved sensitivity and resolution in the flow cytometric DNA analysis of human solid tumor specimens : use of in vitro fine-needle aspiration and uniform staining reagents

Twenty-five unselected fresh colon or breast tumors were studied to identify specific components of sample preparation, sample staining, and flow cytometer operation affecting the sensitivity of DNA stemline analysis. Solid tumors were disaggregated using both a published method for mechanical/enzymatic whole cell (M/EWC) isolation and a fine-needle aspiration (FNA) technique. Staining FNA samples with CycleTEST propidium iodide reagents demonstrated improved sensitivity in the recognition of near diploid and near tetraploid aneuploid populations: 9 of 20 resolvable aneuploid DNA stemlines identified in FNA suspensions were not detected or clearly resolved in M/EWC preparations. These results suggest that previously reported discordances between flow and static image cytometry in the recognition of near tetraploid DNA stemlines may be related to inherent limitations of M/EWC. The in vitro FNA technique, when compared to M/EWC, may yield increased sensitivity and precision in clinical DNA stemline analysis when using fresh, unfixed, solid tumor specimens.