A method for simultaneous quantification of monoclonal antibody Ki-67 and DNA content by flow cytometry - Application to breast carcinomas

OBJECTIVE: To seek a method assessing Ki-67 immunostaining and DNA content by flow cytometry simultaneously. STUDY DESIGN: The murine monoclonal antibody Ki-67 (Ki) identifies a nuclea r protein complex expressed by all nonquiescent tumor cells. Since the anti gen detected by Ki is quite labile in most fixation and embedding protocols , a new method for simultaneous quantification of nuclear Ki immunofluoresc ence and DNA content by flow cytometry was developed. Unfixed, solid tumor cells are permeabilized only with saponin to preserve Ki antigen. The perce ntage of Ki-positive cell subpopulations calculated by subtraction of the r elated aspecific fixation histogram gives optimal results more rapidly than by cytogram analysis. Application to breast carcinoma shows the feasibilit y of the method. RESULTS: Significant correlations between Ki staining and the S-phase fract ion were observed. Mean Ki labelling rates of aneuploid tumors were signifi cantly higher than those of the diploid tumors, and significant differences between histologic types were found. CONCLUSION: This technique can be considered a fast, sensitive and optimal method to evaluate the proliferative activity of breast carcinomas and poss ibly of other solid tumors in a department of pathology.