Heparin induces dimerization and confers proliferative activity onto the hepatocyte growth factor antagonists NK1 and NK2.

Hepatocyte growth factor (HGF) is a potent epithelial mitogen whose actions are mediated through its receptor, the proto-oncogene c-Met. Two truncated variants of HGF known as NK1 and NK2 have been reported to be competitive inhibitors of HGF binding to c-Met, and to function as HGF antagonists (Lokker, N.A., and P.J. Godowski. 1993. J. Biol. Chem. 268: 17145-17150; Chan, A.M., J.S. Rubin, D.P. Bottaro, D.W. Hirschfield, M. Chedid, and S.A. Aaronson. 1991. Science (Wash. DC). 254:1382-1387). We show here, however, that NK1 acts as a partial agonist in mink lung cells. Interestingly, NK1, which is an HGF antagonist in hepatocytes in normal conditions, was converted to a partial agonist by adding heparin to the culture medium. The interaction of NK1 and heparin was further studied in BaF3 cells, which express little or no cell surface heparan sulfate proteoglycans. In BaF3 cells transfected with a plasmid encoding human c-Met, heparin and NK1 synergized to stimulate DNA synthesis and cell proliferation. There was no effect of heparin on the IL-3 sensitivity of BaF3-hMet cells, and no effect of NK1 plus heparin in control BaF3 cells, indicating that the response was specific and mediated through c-Met. The naturally occurring HGF splice variant NK2 also stimulated DNA synthesis in mink lung cells and exerted a heparin-dependent effect on BaF3-hMet cells, but not on BaF3-neo cells. The activating effect of heparin was mimicked by a variety of sulfated glycosaminoglycans. Mechanistic studies revealed that heparin increased the binding of NK1 to BaF3-hMet cells, stabilized NK1, and induced dimerization of NK1. Based on these studies, we propose that the normal agonist activity of NK1 and NK2 in mink lung cells is due to an activating interaction with an endogenous glycosaminoglycan. Consistent with that model, a large portion of the NK1 binding to mink lung cells could be blocked by heparin. Moreover, a preparation of glycosaminoglycans from the surface of mink lung cells induced dimerization of NK1. These data show that the activity of NK1 and NK2 can be modulated by heparin and other related glycosaminoglycans to induce proliferation in cells expressing c-Met.

Activation of apoptosis by Apo-2 ligand is independent of FADD but blocked by CrmA.

A new member of the tumor necrosis factor (TNF) cytokine family, designated Apo-2 ligand (Apo-21) [1] or TRAIL [2], has been shown recently to induce apoptosis in various tumor cell lines; however, its biological role is unknown. Here, we show that Apo-21, activated apoptosis in T-cell-enriched cultures of peripheral blood lymphocytes stimulated by interleukin-2 (IL-2), but not in unstimulated cells. This finding suggests that, like Fas/Apo-1 ligand and TNF [3-5], Apo-2L may play a role in regulating post-stimulation apoptosis of mature lymphocytes. Studies on the mechanism of Apo-2L action demonstrated marked membrane blebbing, a hallmark of apoptosis, within a few minutes of the addition of Apo-2L to tumor cells. Ectopic expression of a dominant negative mutant of FADD, a cytoplasmic protein that mediates death signalling by Fas/Apo-1 and by TNF receptor type 1 (TNFR1) [6-9], inhibited the induction of apoptosis by anti-Fas/Apo-1 antibody, but had little effect on Apo-2L function. In contrast, expression of CrmA, a cowpox virus-derived inhibitor of the Ced-2-like proteases ICE [10] and CPP32/Yama [11,12], blocked the induction of apoptosis by either Apo-2L or anti-Fas/Apo-1 antibody. These results suggest that Apo-2L activates a rapid, FADD-independent pathway to trigger a cell-death programme that requires the function of cysteine proteases such as ICE or CPP32/Yama.

Apo-3, a new member of the tumor necrosis factor receptor family, contains a death domain and activates apoptosis and NF-kappa B.

BACKGROUND: Two receptors that contain the so-called "death domain' have been described to date: tumor necrosis factor receptor 1 (TNFR1) and Fas/Apo-1 (CD95); both belong to the TNFR gene family. The death domain of TNFR1 mediates the activation of programmed cell death (apoptosis) and of the transcription factor NF-kappa B, whereas the death domain of CD95 only appears to activate apoptosis. RESULTS: We have identified an additional member of the TNFR family, which we have named Apo-3. Apo-3 is a transmembrane protein of approximately 47 kDa that has similarity of members of the TNFR family in its extracellular, cysteine-rich domains. In addition, Apo-3 resembles TNFR1 and CD95 in that it contains a cytoplasmic death domain. The Apo-3 gene mapped to human chromosome 1p36.3, and Apo-3 mRNA was detected in several human tissues, including spleen, thymus, peripheral blood lymphocytes, small intestine and colon. Ectopic expression of Apo-3 in HEK293 or HeLa cells induced marked apoptosis. CrmA, a poxvirus inhibitor of Ced-3-like proteases which blocks death signaling by TNFR1 and CD95, inhibited Apo-3-induced apoptosis. Ectopic expression of Apo-3 also induced the activation of NF-kappa B. Apo-3 did not specifically bind to the Apo-2 ligand, suggesting the existence of a distinct ligand for Apo-3. CONCLUSIONS: These results identify Apo-3 as a third member of the TNFR family that activates apoptosis, and suggest that Apo-3, TNFR1 and CD95 engage a common apoptotic cell-death machinery. Apo-3 resembles TNFR1 because it can stimulate NF-kappa B activity and regulate apoptosis. Apo-3 mRNA is expressed in various tissues, consistent with the possibility that this receptor may regulate multiple signaling functions.

Isolation of quiescent cells from multicellular tumor spheroids using centrifugal elutriation.

A quiescent (nonproliferating) subpopulation was identified by flow cytometric analysis using two-step acridine orange staining in the EMT6/Rochester, N. Y. subline multicellular tumor spheroid, an in vitro culture system which provides a cellular microenvironment which mimics that of many of in vivo tumors. To isolate a viable quiescent cell subpopulation, centrifugal elutriation which allows for cell separation mainly on the basis of size was used. This technique provided single cells of relatively homogeneous cell volume which varied over a wide range (approximately 100 to 5000 cu microgram). Though the relatively small cell volume fractions were the most enriched (82%) in quiescent cells, such cells were also observed in significant numbers (congruent to 20%) even in the largest cell fractions. The cell clonogenicity of the various elutriation constant in fractions was also assessed and shown to be lowest (plating efficiency congruent to 20%) in the small spheroid cells but relatively constant in fractions containing intermediate and large cells (plating efficiency congruent to 50%). Continuous [3H]thymidine labeling indicated a slower rate of accumulation of labeled cells in the small spheroid cells, which may result from the transition of proliferating spheroid cells to the quiescent compartment during the course of labeling. These finding indicate the utility of centrifugal elutriation for quiescent cell characterization in in vitro tumor systems.

Genetic assessment of the strength of a cancer suppressor gene in hamster cells.

Tetraploid and near-tetraploid chemically transformed derivatives of the pseudodiploid hamster line BHK 21/clone 13 were prepared in four different ways and their ability to be suppressed for anchorage independence by fusion to the anchorage-dependent parental line was tested. In all cases the presence of a single normal genome, thought on genetic grounds to contain a single suppressor gene, was able to prevent the anchorage-independent growth of transformed lines whether they contained one or two complements of pseudodiploid chromosomes. Suppression of the single step in carcinogenesis that is registered by BHK cells as they transform to anchorage independence is thus unusually powerful and apparently independent of chromosome balance and of strict dosage effects.

Chromosomes 8, 12, and 17 copy number in Astler-Coller stage C colon cancer in relation to proliferative activity and DNA ploidy.

Fluorescence in situ hybridization using centromere-specific DNA probes to chromosomes 8, 12, and 17 was applied to 23 archival paraffin-embedded stage C colonic cancer specimens. Chromosome copy number was related to flow cytometric determinations of S-phase fraction and DNA ploidy. Three to eight copies of chromosomes 8, 12, and 17 were observed at mean frequencies of 28.7%, 37.8%, and 20.9%, respectively. The mean frequency of multiple copies of chromosome 12 was significantly greater than that for chromosome 17 (P < 0.0025). The mean frequency of single copies of chromosome 17 was significantly greater than that for chromosomes 8 and 12 (P < 0.0025 and P < 0.0005, respectively). Regarding the fourth quartile of cases, defined on the basis of the frequency of multiple chromosome copies, the proportion demonstrating moderate to high proliferative activity greatly exceeded the proportion displaying low proliferative activity. The same cases (most chromosomally aberrant) also generally demonstrated DNA aneuploidy. The results indicate a substantial degree of karyotypic instability in advanced colon cancer, particularly in cases with high proliferative activity and DNA aneuploidy.

Simultaneous nuclear antigen and DNA content quantitation using paraffin-embedded colonic tissue and multiparameter flow cytometry.

The simultaneous quantitation of nuclear antigens and DNA content is presented using monoclonal antibodies and flow cytometric analysis, with paraffin-embedded human colonic pathology specimens utilized as source material. The monoclonal antibodies evaluated were shown by immunogold electron microscopy to recognize nuclear proteins preferentially associated with interchromatin (p105) and heterochromatin (p34) regions. Indirect immunofluorescence analysis of p105 revealed two distinct G1-G0 cell subpopulations in cells from normal colonic epithelium and colonic adenocarcinomas. In addition, enhanced levels of both p105 and p34 were observed in aneuploid DNA content stemlines, relative to diploid cells. Cell-sorting experiments performed on cells sorted on the basis of p105 and DNA contents reveal the capability of this method for identifying morphologically heterogeneous cell subpopulations. Other data suggest that p105 is differentially expressed in well-differentiated versus poorly differentiated tumor regions. The potential utility of this approach for the retrospective study of proliferation-associated antigens and protooncogene protein products is discussed.

Prognostic implications of ploidy and proliferative activity in diffuse large cell lymphomas.

Paraffin-embedded surgical biopsies from 50 patients with newly diagnosed diffuse large cell lymphoma (DLCL) were examined for proliferative activity and DNA aneuploidy by flow cytometry. These results were correlated with the clinical characteristics of these patients and the course of their disease. High proliferative activity, defined as less than 80% of cells in G0 or G1, was found to be the single most important pretreatment adverse prognostic factor in these patients. This relationship remained significant after correcting for poor performance status and advanced Ann Arbor stage, the other factors found to be associated with a shortened survival. DLCLs with high proliferative activity were more probable to present with extranodal involvement than those with lower proliferative activity. The mitotic count as determined by light microscopy did not correlate with flow cytometry-defined proliferative activity and may be a less accurate method for assessing this important biological characteristic in DLCL. DNA aneuploidy was detected in 62% of cases but did not appear to have any prognostic significance. Biopsies from patients who presented with lymphomatous bone marrow involvement, however, invariably demonstrated an aneuploid stemline. These results suggest that differences in proliferative activity may be an important biological basis for the variable prognosis seen in DLCL.

Prognostic implications of proliferative activity and DNA aneuploidy in Astler-Coller Dukes stage C colonic adenocarcinomas.

Paraffin-embedded surgical specimens from 69 patients who underwent resections of otherwise untreated Dukes stage C adenocarcinoma of the colon were examined for proliferative activity, DNA aneuploidy, DNA index, and proportion of aneuploid cells by flow cytometry. Results were correlated to clinical characteristics of the patients and to overall survival times. DNA aneuploid tumors were identified in 60 cases (87%), diploid tumors in 9 cases (13%). The mean S-phase fraction for all cases was 17.6%, with a standard deviation (SD) of 7.8. In univariate statistical analysis, younger patient age, lower tumor proliferative activity, DNA index less than or equal to 1.2, and presence of only 1-4 lymph nodes with tumor involvement were found to be significant predictors of improved patient survival. In multivariate Cox regression analysis, low tumor proliferative activity, younger patient age, and location of the tumor in the right or transverse colon were found to be significant independent predictors of increased patient survival. When tumor proliferative activity was stratified into statistically defined subgroups, patients with tumors of low proliferative activity (S-phase less than mean - 0.5 SD) had significantly longer survival than patients with tumors of moderate proliferative activity (S-phase value greater than mean - 0.5 SD and less than mean +0.5 SD) or high proliferative activity (S-phase greater than mean +0.5 SD). These results suggest that tumor proliferative activity in Dukes C colon carcinoma may be an important biological factor in determining patient prognosis.

Growth regulation of human breast and ovarian tumor cells by heregulin: Evidence for the requirement of ErbB2 as a critical component in mediating heregulin responsiveness.

Alterations in the expression of the epidermal growth factor (EGF) receptor ErbB family are frequently encountered in a number of human cancers. Two of these receptors, ErbB3 and ErbB4, are known to bind a family of related proteins termed heregulins (HRGs) or neu differentiation factors. In biologically relevant systems, interaction of HRG with ErbB3 or ErbB4 results in the transactivation of ErbB2. In this report, we show that ErbB2 is a critical component in mediating HRG responsiveness in a panel of human breast and ovarian tumor cell lines. Because HRGs have been reported to elicit diverse biological effects on cultured cells, including growth stimulation, growth inhibition, and induction of differentiation, we systematically examined the effect of rHRG beta 1 on tumor cell proliferation. HRG binding studies were performed with a panel of breast and ovarian tumor cell lines expressing a range of levels of ErbB2. The biological responses to HRG were also compared to EGF and to the growth-inhibitory anti-ErbB2 antibody, 4D5. In most cases, HRG stimulation of DNA synthesis correlated with positive effects on cell cycle progression and cell number and with enhancement of colony formation in soft agar. On each cell line tested, the HRG effects were distinguishable from EGF and 4D5. Our findings indicate that HRG induces cell proliferation in a number of tumor cell lines. In addition, we show that methods for measuring cell proliferation, as well as experimental conditions, are critical for determining HRGs effect on tumor cell growth in vitro.

Human immunodeficiency virus-related lymphomas: a possible association between tumor proliferation, lack of ploidy anomalies, and immune deficiency.

In an attempt to identify a biologic basis for the aggressive clinical behavior of human immunodeficiency virus (HIV)-associated lymphomas (HAL), dual-parameter flow-cytometric analysis was performed on 22 paraffin-embedded biopsy specimens. Cases were analyzed for DNA ploidy, the percentage of cells in S-phase (proliferative activity), and content of a recently identified proliferation-associated nuclear antigen, p105. The DNA-content analysis of 22 HALs was compared with that of 109 cases of intermediate-grade non-Hodgkin's lymphoma (NHL) unrelated to the acquired immune deficiency syndrome (AIDS) studied previously in our laboratory and 125 cases of high-grade NHL reported in the literature. The proliferative activity was higher in intermediate-grade HAL relative to non-AIDS NHL (24.0% v 10.4%; P = .03), and in high-grade HAL in comparison with NHLs of similar histology unassociated with HIV infection (24.8% v 19%), although the latter did not reach statistical significance. The number of mitoses per 10 high-power fields was found to correlate with the percentage of cells in S-phase (r = .68; P = .0004). Although p105 content tended to be higher in HAL than in an AIDS-related complex (ARC)-associated hyperplastic lymph node control, no statistically significant associations were found between p105 content and proliferative activity or the number of mitoses per 10 high-power fields. When compared with non-AIDS NHLs of comparable grade, there was a trend toward a lower incidence of DNA aneuploidy in both intermediate- (25% v 56%) and high-grade (38.5% v 60%) HALs. The higher proliferative activity and lower incidence of DNA aneuploidy found in HAL relative to non-AIDS NHL of comparable histologic grade may represent differences in pathogenesis and may underlie the poor prognosis of HIV-associated NHL.

Reliable and sensitive analysis of occult bone marrow metastases using automated cellular imaging.

The presence of occult bone marrow metastases (OM) has been reported to represent an important prognostic indicator for patients with operable breast cancer and other malignancies. Assaying for OM most commonly involves labor-intensive manual microscopic analysis. The present report examines the performance of a recently developed automated cellular image analysis system (ACIS; ChromaVision Medical Systems, Inc.) for identifying and enumerating OM in human breast cancer specimens. OM analysis was performed after immunocytochemical staining. Specimens used in this study consisted of normal bone marrow (n = 10), bone marrow spiked with carcinoma cells (n = 20), and bone marrow obtained from breast cancer patients (n = 39). The reproducibility of ACIS-assisted analysis for tumor cell detection was examined by having a pathologist evaluate montage images generated from multiple ACIS runs of five specimens. Independent ACIS-assisted analysis resulted in the detection of an identical number of tumor cells for each specimen in all instrument runs. Additional studies were performed to analyze OM from 39 breast cancer patients with two pathologists performing parallel analysis using either manual microscopy or ACIS-assisted analysis. In 17 of the 39 cases (44%), specimens were classified by the pathologist as positive for tumor cells after ACIS-assisted analysis, whereas the same pathologist failed to identify tumor cells on the same slides after analysis by manual microscopy. These studies indicate that the ACIS-assisted analysis provides excellent sensitivity and reproducibility for OM detection, relative to manual microscopy. Such performance may enable an improved approach for disease staging and stratifying patients for therapeutic intervention.

Effects of omeprazole on cell kinetics of carcinogen-induced colon tumours in rats.

This study was designed to evaluate the effects of hypergastrinaemia induced via suppression of gastric acid by omeprazole on carcinogen-induced colon cancer in rats. The carcinogen methylazoxymethanol (MAM), 30 mg/kg, was administered intraperitoneally at 6-weekly intervals to Sprague-Dawley rats. Four weeks after the last MAM injection, the first daily dose of omeprazole, 40 mg/kg, was given by gastric gavage to one group of rats, and the rest were given buffered methylcellulose vehicle. After 10 weeks of daily omeprazole or vehicle, the rats were anaesthetized with ether, blood samples obtained, and animals sacrificed. Gastrin levels in serum from omeprazole-treated rats were elevated nearly six-fold. DNA and RNA levels in gastric mucosa were unchanged by omeprazole, but protein content was somewhat reduced. No biochemical or histological changes related to omeprazole treatment were observed in normal colon. The number of tumours, tumour volumes, and total tumour burden were not significantly different in colons of vehicle- or omeprazole-treated rats. Analysis by flow cytometry revealed that the S phase fraction was lower in tumour cells from omeprazole-treated animals; and that the frequency of DNA aneuploidy was also reduced. The results indicate that while omeprazole-induced suppression of stomach acid in rats elevates levels of gastrin in serum, it does not substantially alter the biochemical or cellular characteristics of carcinogen-induced colon tumours.

Changes in T and non-T lymphocyte subsets following seroconversion to HIV-1: stable CD3+ and declining CD3- populations suggest regulatory responses linked to loss of CD4 lymphocytes. The Multicenter AIDS Cohort Study.

We investigated changes in lymphocyte subsets (total, CD4+ and CD8+ T cells, as well as non-T cells) associated with human immunodeficiency virus type I (HIV-1) seroconversion in 321 homosexual or bisexual men in the Multicenter AIDS Cohort Study (MACS). These subjects had serial lymphocyte characterizations for up to 4 years before and 5 years after seroconversion. CD4+ lymphocyte levels declined rapidly in the first 18 months following seroconversion and less rapidly thereafter, while CD8 lymphocytes increased with similar kinetics. In contrast, total T (CD3+) lymphocytes declined only slightly in the first 18 months following seroconversion, and then remained stable. These results support the hypothesis of physiologic regulation of the total number of circulating T cells, such that lost CD4+ lymphocytes are replaced by newly generated CD4+ and CD8+ lymphocytes; over time, continued loss of CD4+ lymphocytes due to HIV-1 infection would result in net replacement of lost CD4+ lymphocytes with CD8+ lymphocytes. Non-T (CD3-) lymphocytes also declined after seroconversion, and this decline paralleled that of CD4+ lymphocytes. Thus, changes in both T and non-T lymphocytes after HIV-1 seroconversion may reflect the operation of homeostatic or regulatory mechanisms. Whether these mechanisms contribute to the development of immune deficiency requires further study.

Improved detection of rare CALLA-positive cells in peripheral blood using multiparameter flow cytometry.

A major limitation to the detection of rare cell types in the peripheral blood using monoclonal antibodies is nonspecific binding of the antibody reagent to normal cells. Detection of rare common acute lymphoblastic leukemia antigen (CALLA)-positive cells in peripheral blood is significantly improved by using multiple flow cytometric parameters to exclude a variety of mature blood cells which may nonspecifically bind the antibody reagent. Monocytes and granulocytes are excluded by gating out cells with high 90 degrees light scatter. By gating on red fluorescence, a variety of mature cell types binding to phycoerythrin (PE)-conjugated Leu 3, Leu 2, and M3 monoclonal antibodies are also excluded. CALLA-positive lymphoblasts from 6 consecutive patients were not excluded on the basis of these parameters. Gating on log 90 degrees light scatter and log red fluorescence in this fashion reduced the incidence of nonspecific binding to peripheral blood mononuclear cells of a fluorescein-conjugated irrelevant monoclonal antibody by 98% from 308 cells per million to 5 cells per million. One CALLA-positive lymphoblast per 100,000 peripheral blood mononuclear cells could be detected in mixture experiments using this method. The normal range of CALLA-positive cells in adults is less than 16 cells per million peripheral blood mononuclear cells. This low background of CALLA-positive peripheral blood cells may permit the detection of early leukemic relapse in acute lymphoblastic leukemia by analysis of the peripheral blood. This methodology can be applied to the detection of any rare cell type by using phycoerythrin-conjugated antibodies to markers that the cell type does not possess.

The effect in the KHT sarcoma of CCNU and MISO on cell cycle progression evaluated by flow-cytometry.

Previous studies using the KHT sarcoma have shown that misonidazole (MISO) enhances the cytotoxicity of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) by as much as a factor of 2.0. In the present study flow cytometry was used to monitor the changing DNA distributions of cells dissociated from solid tumors at successive times following treatment with CCNU, applied either alone or in combination with 0.5 mg/g MISO. The proportion of cells in late S and the G2M phases of the cell cycle increased gradually after CCNU treatment. MISO did not significantly change this block in cell progression, which persisted for at least 48 hr after treatment in all cases. CCNU shows marked carbamoylating activity, which has been associated with inhibition of RNA processing and with the degree of chemopotentiation achieved with MISO. Consequently, to evaluate whether MISO chemopotentiation was influencing the RNA distributions in tumors, RNA histograms were generated using acridine orange to differentially stain cellular DNA and RNA. By 24 hr after treatment, CCNU clearly altered the distribution of RNA, but no significant differences could be detected between results obtained from drug and drug plus sensitizer treated groups. These studies demonstrate the effect of CCNU on cell cycle progression in vivo. The addition of MISO did not result in further perturbation of the total tumor population, suggesting that cell cycle redistribution does not play a major role in chemopotentiation by MISO.

Total cellular RNA content: correlation between flow cytometry and ultraviolet spectroscopy.

Total RNA content in Chinese hamster ovary and HeLa-S3 cells determined by ultraviolet spectroscopy is compared with the red fluorescence distribution of acridine orange-stained cells observed by flow cytometry. A correlation coefficient of 0.93 is obtained when these methods of estimating RNA content are compared after various RNAse treatments. These data suggest that acridine orange staining effectively quantitates total cellular RNA content when analyzed by flow cytometry, although DNA is also shown to contribute a low but significant background of red fluorescence.

Assessment of cell cycle-associated antigen expression using multiparameter flow cytometry and antibody-acridine orange sequential staining.

A novel approach which enables direct assessment of the differential expression of cellular antigens in noncycling (G0) and cycling cell subpopulations is presented. The method involves flow cytometric analysis and sorting of cells stained by use of indirect immunofluorescence, followed by restaining using acid acridine orange, to relate the immunofluorescence of sorted lymphoid subpopulation(s) to cell proliferation status (i.e., G0 vs. G1 vs. S vs. G2 and M). In the present study, this technique successfully identifies the proliferation-associated modulation of a heterochromatin-associated antigen in pokeweed mitogen-stimulated human lymphoid cultures. The potential utility of this method for documenting early antigenic changes associated with the G0-G1 transition is discussed.

Neoplasms of endometrial stroma: histopathologic and flow cytometric analysis with clinical correlation.

Ten neoplasms of endometrial stroma (one stromal nodule, four endolymphatic stromal myoses, and five stromal sarcomas) were compared using clinical data as well as histopathologic and flow cytometric parameters. None of the patients with stromal nodules or endolymphatic stromal myosis had extrauterine disease at presentation or tumors displaying a mitotic rate greater than 10/10 hpf (high-power fields), nuclear pleomorphism, atypical mitotic figures, DNA aneuploidy, or a high proliferative index (greater than 10% S phase cells). The stromal nodules were circumscribed and behaved in a benign fashion. The patients with endolymphatic stromal myosis had infiltrative tumors that behaved as low-grade cancers with good responses to therapy. Four of the five patients with stromal sarcoma had extrauterine disease at presentation as well as tumors characterized by a mitotic rate much greater than 10 mitoses/10 hpf, nuclear pleomorphism, atypical mitotic figures, DNA aneuploidy, and a high proliferative index. These four patients had aggressive disease with poor response to therapy. The fifth of the stromal sarcomas had a high mitotic rate, but lacked the other features linked with aggressive behavior; this patient has responded well to treatment. The mitotic count may not be the most useful criterion for predicting biologic behavior in endometrial stromal tumors since it does not always reflect an increased rate of cell turnover as demonstrated by the percentage of cells in the S phase. DNA analysis by flow cytometry yields a more accurate picture of tumor behavior.

Cell cycle progression in irradiated endothelial cells cultured from bovine aorta.

Logarithmically growing endothelial cells from bovine aortas were exposed to single doses of 0-10 Gy of 60Co gamma rays, and cell cycle phase distribution and progression were examined by flow cytometry and autoradiography. In some experiments, cells were synchronized in the cell cycle with hydroxyurea (1 mM). Cell number in sham-irradiated control cultures doubled in approximately 24 h. Estimated cycle stage times for control cells were 14.4 h for G1 phase, 7.2 h for S phase, and 2.4 h for G2 + M phase. Irradiated cells demonstrated a reduced distribution at the G1/S phase border at 4 h, and an increased distribution in G2 + M phase at 24 h postirradiation. Autoradiographs of irradiated cells after continuous [3H]thymidine labeling indicated a block in G1 phase or at the G1/S-phase border. The duration of the block was dose dependent (2-3 min/cGy). Progression of the endothelial cells through S phase after removal of the hydroxyurea block also was retarded by irradiation, as demonstrated by increased distribution in early S phase and decreased distribution in late S phase. These results indicate that progression of asynchronous cultured bovine aortic endothelial cells through the DNA synthetic cycle is susceptible to radiation inhibition at specific sites in the cycle, resulting in redistribution and partial synchronization of the population. Thus aortic endothelial cells, diploid cells from a normal tissue, resemble many immortal cell types that have been examined in this regard in vitro.