p330d, also known as CENP-F, is a newly characterized cell cycle specific nuclear autoantigen which is associated both with the centromeres and the nuclear matrix. It is expressed in low amounts in GO/Gl-cells and accumulates in the nuclear matrix during S-phase with a maximum expression in G2/M-cells. In the present study we have investigated ifp330d/CENP-F could be used as a marker for proliferation in Werent human malignancies. A flow cytometric method was developed by which p330d/CENP-F expression and DNA-content could be assessed on hematopoietic and solid tumors. Twenty-four different human hematopoietic malignancies, 12 breast cancers, and several cell lines were analyzed and the number of p330d/CENP-F positive cells and the S-phase fraction were determined. The percentage of p330dlCENP-F positive cells correlated with the fraction of S-phase cells in a l l human malignancies tested. Various cell lines revealed a similar cell cycle specific distribution. The association of p330d/CENP-F with the nuclear matrix Eacilitated the flow cytometric analysis of this protein due to its resistance to dmerent preparation and fixation procedures. In summary, p330dl CENP-P seems to be a potentially valuable proliferation marker which can be applied to different tumors. o 1996 wilq-~iss, I ~C .