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 phenomenon and of interest with regard to subpopulations with differences in clonality, metastatic potential, and response to therapy under different treatment 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 antigens and DNA content. METHODS: In the present study, six different malignant tumors grown as xenografts in nude mice were characterized by five-parameter flow cytometry. Immunophenotyping was performed using a variety of direct fluorescence-conjugated antibodies. In all cases, simultaneous detection of DNA content was done after staining with 7-aminoactinomycin D. RESULTS: Tumor cells were characterized by light scatter properties, antigen expression, and DNA content. Tumor cell heterogeneity, subpopulations, and DNA content-dependent antigen expression were identified. CONCLUSIONS: This method offers the possibility of characterizing solid tumors according to their immunophenotype and DNA content. The results obtained can be used to identify changes in immunophenotypic and DNA profiles of tumor cell populations before and after therapy and might be useful to define parameters predictive for response to therapy.