Monoclonal antibodies (MoAbs) against proliferating cell nuclear antigen (PCNA) represent a potentially useful tool for cell kinetic analysis of tumours. Because in paraffin-embedded tissue the relationship between PCNA immunoreactivity and tumour cell proliferation is not well characterized, we have compared PCNA positivity as detected by the PC10 MoAb with the bromodeoxyuridine labelling index (BrdUrd-LI) in two different transplantable hormone-dependent rat mammary tumours. Together, these two tumour models (MCR-83 and EMR-86) cover a wide range of S-phase fractions. Evaluating 31 methacarn-fixed tumours, a strong but non-linear relationship (r = 0.98) was obtained. PCNA-positive fractions were invariably higher than corresponding BrdUrd-LIs and also higher than the estimated growth faction: growth fractions as determined by continuous BrdUrd labelling of the tumour and stromal cell population in EMR-86 carcinomas were 12 and 26 per cent lower than PCNA-positive fractions, implying that a certain fraction of non-cycling cells can also express PCNA. A dramatic disturbance in the relationship of PCNA positivity and the BrdUrd-LI was observed in the EMR-86 model after growth arrest induced by hormonal ablation: PCNA immunoreactivity remained detectable for at least 3 days, whereas the BrdUrd-LI decreased almost immediately. In comparison, PCNA immunoreactivity persisted for a much shorter period in small intestinal cells that had stopped DNA replication when moving from the crypt towards the villus. It is concluded that although differences in PCNA expression exist between various tissues, PCNA as detected by the PC10 MoAb may be used in tumours as an operational marker for the growth fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

These data provide evidence for the involvement of mitochondria in the hepatotoxicity of the HStk/ganciclovir combination. This may explain the toxicity of the HSVtk/gancilovir combination in some metabolically active but non-proliferating cells, such as liver cells. This toxicity limits the applicability of this enzyme/prodrug combination.

Single-laser flow cytometry has been used to study the feasibility of flow karyotyping of human solid tumors. As a model, seven human melanoma cell lines have been used with varying numerical chromosome composition as verified by FCM DNA content measurements and chromosome countings. For all seven cell lines, flow karyotypes that showed a variety of consistent deviations from the normal diploid flow karyotype could be obtained although the resolution of the flow system and varying debris continuum limited the number of resolvable peaks. The predominant changes observed involved the regions normally representing chromosomes 3-8, 9-12, and 13-16. It is concluded that at present the preparation procedure is the main limiting factor for exploring the full potential of flow karyotyping for cytogenetic analysis of solid-tumor cell lines.Key terms: Chromosomes, flow cytometry Flow cytometry is widely used for studying the diagnostic and prognostic significance of DNA content differences in human tumors. The advantage of this technique is that rapid ploidy determinations can be made on large numbers of cells. However, the information provided by measuring total DNA content gives only a rather crude estimate for numerical chromosome abnormalities. Potentially, more detailed information can be obtained by flow cytometric measurement of the DNA content of isolated chromosomes. The evolution of this technique during the last 5 years has now made it possible to identify a variety of chromosomal polymorphisms and abnormalities and to sort individual chromosomes for gene mapping and cloning experiments (13,201. So far, only few reports on the application of flow cytometry for karyotyping of solid tumors have appeared (11,141.The purpose of the present study was to explore the possibility of using flow karyotyping for characterizing genetic differences between seven different human melanoma cell lines. We chose this neoplasm because melanoma shows a high degree of genetic instability, and cell lines from this tumor can be relatively easily maintained in tissue culture. The variation in ploidy level of the melanoma cell lines was determined by chromosome Table 1. Human foreskin fibroblasts (VH-25, 10th passage) were kindly provided by Dr. P. Abraham, Department of Medical Biochemistry, University Medical Center, Leiden. The cell lines were maintained in continuous cultures in 75-cm3 plastic culture flasks on Ham's F-12 medium supplemented with 10% foetal calf serum and antibiotics and passaged twice a week.Chromosome Isolation Confluent cultures were trypsinized and plated out in a 140-4 ratio into new culture flasks. After reaching 75% confluency (usually in about 48 h) colchicin (Colcemid, Gibco, Madison, WI) was added to the culture medium to a final concentration of 0.05 hg/ml. Mitotic cells were harvested 15-18 h later by gently tapping the side of the culture flask. Next the cells were centrifuged at 175g for 5 min at room temperature, and the pellet was washed once with hypotonic KC1 solution (0.075 M). After that, the c...

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