Cell heterogeneity and subpopulations in solid tumors characterized by simultaneous immunophenotyping and DNA content analysis

Background: Heterogeneity in human malignant tumors is a well-described phe nomenon and of interest with regard to subpopulations with differences in c lonality, metastatic potential, and response to therapy under different tre atment regimes. The aim of this study was the simultaneous characterization of surface markers and DNA content of solid tumors to identify tumor cell subpopulations and to study the association between the expression of antig ens and DNA content. Methods: In the present study, six different malignant tumors grown as xeno grafts in nude mice were characterized by five-parameter flow cytometry. Im munophenotyping was performed using a variety of direct fluorescence-conjug ated antibodies. In all cases, simultaneous detection of DNA content was do ne after staining with 7-aminoactinomycin D. Results: Tumor cells were characterized bg light scatter properties, antige n expression, and DNA content. Tumor cell heterogeneity, subpopulations, an d DNA content-dependent antigen expression were identified. Conclusions: This method offers the possibility of characterizing solid tum ors according to their immunophenotype and DNA content. The results obtaine d can be used to identify changes in immunophenotypic and DNA profiles of t umor cell populations before and after therapy and might be useful to defin e parameters predictive for response to therapy. (C) 2000 Wiley-Liss, Inc.