Interphase cell flow cytometry as a means of monitoring genomic size in normal and neoplastoid cell cultures.

The DNA specific fluorescence of mass cultures and clones derived from human skin and bladder tumor tissue was assayed by flow cytometry. In order to detect and quantitate small fluorescence intensity changes, cytogenetically defined triploid or diploid human fibroblast strains were cocultivated, harvested, and stained with the cell strain of unknown karyotype. The triploid standard (derived from human abortus tissue) proved chromosomally unstable at high passage level. Fifteen male, female, and 45,X strains displayed target-to-standard cell fluorescence ratios commensurate with their respective chromosome constitutions. Interstrain variation was highest among the 45,X strains, although mosaicism could not be detected by conventional cytogenetics. Interclonal fluorescence variation was two- to ten-fold higher among the tumor-derived clones tested. Chromosome counts and subcloning experiments indicate that this increased fluorescence variation is due to genome size variation. The clonal evolution of genome size differences was observed in subclones of chromosomally divergent parental clones. These observations suggest that well controlled flow cytometry can adequately resolve subtle degrees of genome size variation in cultivated human cells. The technique is especially suited for monitoring genome size changes in cultivated tumor cells.