Flow cytometric DNA analysis using cytokeratin labeling for identificationof tumor cells in carcinomas of the breast and the female genital tract

Flow cytometric assessment of DNA-ploidy and S-phase fraction in malignant tumors is compromised by the heterogeneity of cell subpopulations derived f rom the malignant and surrounding connective tissue, e.g., tumor, stromal a nd inflammatory cells. To evaluate the effect on quality of DNA cell cycle analysis and determination of DNA ploidy, cytokeratin labeling of epithelia l cells was used for tumor cell enrichment in breast, ovarian, cervical and endometrial cancer prior to DNA analysis. In a prospective study, tumor ce ll subpopulations of 620 malignant tumors were labeled by a FITC-conjugated cytokeratin antibody (CK 5, 6, CK18 and CK 5, 6, 8 and CK 17, respectively ) prior to flow cytometric cell cycle analysis. Compared to total cell anal ysis, detection rate of DNA-aneuploid tumors following cytokeratin labeling was increased from 62% to 76.5% in breast cancer, from 68% to 77% in ovari an cancer, from 60% to 80% in cervical cancer and from 30% to 53% in endome trial cancer. Predominantly in DNA-diploid tumors, a significantly improved detection of S-phase fraction of the tumor cells was shown due to the elim ination of contaminating nonproliferating "normal cells". S-phase fraction following tumor cell enrichment was increased by 10% (mean) following cytok eratin staining in ovarian and endometrial cancer, by 30% in breast cancer and even by 70% in cervical cancer compared to total cell analysis. Thus, d iagnostic accuracy of DNA-analysis was enhanced by cytokeratin labeling of tumor cells for all tumor entities investigated.