CELLULAR DNA OF HUMAN NEOPLASTIC B-CELLS MEASURED BY FLOW-CYTOMETRY

  • 1 January 1984
    • journal article
    • research article
    • Vol. 44  (11) , 5010-5016
Abstract
Flow cytometric analysis of DNA of tumor cells rapidly provides information on cell kinetics and tumor ploidy. Human B cell lymphomas, however, often contain high numbers of nonneoplastic cells, mainly T lymphocytes, which may hamper the accurate measurement of cell cycle phases and ploidy level of these tumors. The neoplastic cells in each B cell lymphoma express a single Ig L chain. Surface Ig L chains were labeled to discriminate between predominantly neoplastic B cells and nonneoplastic cells in the same tissues. Using this label as well as antibodies against nonneoplastic T cells, multiparameter correlated flow cytometric analysis of 52 human B cell lymphomas was performed measuring cellular DNA in neoplastic and nonneoplastic populations from the same tissues without physical separation of cells. Comparison of celluar DNA of Ig L chain-bearing neoplastic cells with that of nonneoplastic cells from the same tumor enabled us to detect DNA changes (aneuploidy) in almost 80% of the lymphomas, an incidence higher than observed previously by conventional DNA analysis of unseparated cells. These ploidy changes were confirmed by comparing in the same tumor the DNA of normal T cells with that of predominantly neoplastic cells. The proportion of neoplastic cells in the synthetic phase of the cell cycle (S-fraction) varied widely from tumor to tumor. Lymphomas with high neoplastic S-fractions (> 10%) were mostly hyperdiploid tumors and histologically corresponded to intermediate- and high-grade unfavorable lymphomas. Tumors with low neoplastic S-fractions (< 5%) were predominantly diploid and near diploid, histologically low-grade lymphomas. Six lymphomas showed 2 discrete cell populations bearing the same Ig L chain but containing different amounts of DNA, suggesting the presence of 2 neoplastic clones in the same tumor (biploidy). In 2 patients in whom the lymphoma relapsed at 17 and 34 mo., respectively, after the initial biopsies, repeat tumor samples were obtained. Despite an increase in the neoplastic S-fraction, no change in ploidy level was observed in either case. Light scatter analysis suggested a relationship between cell size and genomic size; large cells in these tumors were mostly presynthetic aneuploid cells. The ability to measure DNA, antigens and cell size in individual cells in a rapid, correlated manner is a unique attribute of flow cytometry. The approach utilized in this study enabled analysis of cell cycle fractions and ploidy changes in lymphomas with a precision and resolution that is extremely difficult to attain by any other method.