Pathological and molecular characteristics distinguishing contralateral metastatic from new primary breast cancer

BACKGROUND

Breast cancer patients have a cumulative lifetime risk of 2%-15% of developing a contralateral metastatic or ex novo primary cancer. From prognostic and therapeutic viewpoints, it is important to differentiate metastatic from second primary. To distinguish these entities, we investigated whether the pattern of X chromosome inactivation could determine whether the two tumors derived from different progenitor cells.

MATERIALS AND METHODS

The clonality of bilateral breast cancer was evaluated through the X-inactivation analysis using the human androgen receptor gene (HUMARA) polymorphism and the histopathologic and molecular results were compared. A different or an identical pattern of X inactivation was considered as indicator of a second primary cancer or not informative, respectively. We considered morphological indicators of a new primary cancer the absence of concordance in the histological type or a better histological differentiation.

RESULTS

Ten patients with bilateral breast cancer were evaluated. Morphological criteria indicated that eight were second primary, a conclusion confirmed by the X-inactivation analysis. Two cases classified as recurrence according to morphological criteria were classified as second tumor by molecular analysis.

CONCLUSION

Our results show that the HUMARA clonality assay can improve the histological parameters in differentiating metastatic cancer from second primary cancer.

Ki-ras activation in vitro affects G1 and G2M cell-cycle transit times and apoptosis

Mutant ras genes occur frequently in human neoplasia and, in particular, in pancreatic, colorectal, and lung adenocarcinomas. Recent evidence suggests that G-->T and G-->C transversions of the Ki-ras gene in codon 12 may lead to biological effects in vitro and in vivo that may be associated with an abnormal cell cycle and increased tumour aggressiveness. The role of Ki-ras activation (a G-->C transversion in codon 12, arginine for glycine) in the cell cycle and apoptosis was investigated using control and permanently transfected NIH3T3 mouse fibroblasts. Flow cytometry was used to evaluate the G1-, S- and G2M-phase transit times, the potential doubling time, the growth fraction, and the cell loss factor during asynchronous exponential growth. Apoptosis was induced in both cell lines by absence of growth factors for an extended period of time (72 h) and quantitatively evaluated using the TUNEL method coupled with flow cytometry. It was found that codon 12 G-->C Ki-ras transfected cells compared with controls, had a significant prolongation of G1 by about 50%, a reduction of the G2M transit time by 30%, and a decrease of the cell loss factor by about 90%. Apoptotic cells were about 10% in control and less than 0.5% in Ki-ras transfected cells after 72 h starvation-confluency. These data suggest that codon 12 G-->C Ki-ras activation in mouse NIH3T3 fibroblasts is associated with deregulation of checkpoint controls in the G1 and G2M phases of the cell cycle and inhibition of apoptosis. It appears plausible that these cell mechanisms are related to a proliferative advantage and that they may also be important in the progression of human tumours characterized by specific Ki-ras mutations.

Analysis of erythrocyte glycophorin-A variants by flow cytometry in lung disease patients detects the effect of tobacco smoke

The glycophoryn A (GPA) assay evaluates somatic in vivo mutations. It is considered a cumulative biodosimeter for genotoxic exposures and is under evaluation in cancer risk assessment. GPA, a polymorphic membrane protein of the erythrocytes, determines the MN blood groups. The NO and NN variant frequencies (VF) may be detected in MN subjects (about 50% of the population) by flow cytometry using two differently labelled antibodies. We explored if GPA NO and NN VF might be relevant to the assessment of individual lung cancer risk and susceptibility, in a small population with a high prevalence of heavy tobacco smokers: 8 lung cancer patients and 16 subjects with non-malignant lung diseases associated with increased risk of lung cancer. There was a wide interindividual variability and complete overlap between non-neoplastic and neoplastic patients. A significant positive correlation was seen with smoking duration in NO VF (p = 0.04, age-adjusted). Current smokers (n = 12) displayed higher NO values than never (n = 1) or ex-smokers (n = 11), 36.3 +/- 18.2 and 21.0 +/- 13.2, respectively (p < 0.01). No association was shown with occupational exposure. The present exploratory study suggests that assessment of individual lung cancer risk and susceptibility by the GPA assay does not seem to be feasible. The assay appears to provide a biomarker of longterm exposure to tobacco smoke.

Cell cycle variations in azoxymethane-induced rat colorectal carcinogenesis studied by flow cytometry

Cell cycle variations and DNA aneuploidy, were investigated in different phases of azoxymethane (AOM)-induced colon carcinogenesis in rats by flow cytometry. K-ras gene mutations (transitions Gright curved arrow A) were frequently detected in aberrant crypt foci (ACF) initial pre-neoplastic lesions. The fraction of cells in the G2M-phase of the cell cycle was higher in ACF compared to the normal mucosa of control rats. A similar modification of the cell cycle was found in adenomas and adenocarcinomas but, unexpectedly, also in morphologically normal mucosa from AOM-treated animals indicating that AOM treatment permanently modifies cell cycle control in rat colon mucosa. These alterations, however, were not associated with DNA aneuploidy as reported in human sporadic colorectal cancer, suggesting that tumour development in AOM-treated rats is less dependent on aneuploidy.

Intratumor heterogeneity of chromosome 1, 7, 17, and 18 aneusomies obtained by FISH and association with flow cytometric DNA index in human colorectal adenocarcinomas

BACKGROUND

The origin and evolution of somatic chromosome aberrations in colorectal cancer is still poorly understood. The data in the literature suggest that some specific chromosome aberrations are more common. It is not known, however, if there is a correlation of these with near-diploid and high aneuploidy previously proposed to be a characteristic of the adenoma-carcinoma sequence.

METHODS

Chromosome 1, 7, 17 and 18 numerical aberrations and 1p deletions were evaluated by fluorescence in situ hybridization analysis for 20 human sporadic colorectal adenocarcinomas in 70 distinct tumor sectors and correlated with flow cytometric DNA index (DI) values.

RESULTS

Aneusomy for at least one of the investigated chromosomes was observed in 60 of 70 tumor sectors corresponding to 19 of 20 adenocarcinomas (95%). Deletions at 1p, observed in 8 of 18 adenocarcinomas (44%), were intratumor homogeneous in 7 of 8 tumors. In contrast, the other aberrations were intratumor heterogeneous. Aneusomies of chromosomes 1, 7, and 17 were strongly associated with DNA high aneuploidy (DI > or = 1.4), whereas aneusomy of chromosome 18 and 1p deletions were equally common among DNA diploid and near-diploid tumors (DI < 1.4 and DI not equal to 1).

CONCLUSIONS

Overall, these data suggest the existence of different aneuploidization routes correlated with specific chromosome aberrations. In addition, intratumor homogeneity of 1p deletions appears to be an indication of early occurrence or strong selection. We also suggest that tumors with monosomies and in particular monosomies-trisomies for the same chromosomes support a model of aneuploidization and chromosome instability during the colorectal tumor progression based on loss of symmetry during chromosome segregation (Giaretti: Lab Invest 71:904-910, 1994).

Intratumor distribution of 1p deletions in human colorectal adenocarcinoma is commonly homogeneous: indirect evidence of early involvement in colorectal tumorigenesis

BACKGROUND

Cytogenetics and molecular biology studies have indicated that a large subset of human colorectal adenocarcinomas have distal 1p chromosome arm deletions. The aim of this study was to evaluate the intratumor distribution of 1p deletions under the assumption that homogeneity is an indication of early occurrence.

METHODS

Seventy-nine histologically selected primary sectors (40 superficial and 39 deep) and 3 lymph node metastases obtained from 20 human sporadic adenocarcinomas were analyzed. Interphase two-color fluorescence in situ hybridization (FISH) was applied to cytocentrifuged nuclei using a centromeric probe for chromosome 1 and a telomeric probe mapping to the 1p36 band.

RESULTS

Deletions at 1p were observed in 35 of 82 tumor samples corresponding to 9 of 20 adenocarcinomas analyzed (45%). Seven of the 9 adenocarcinomas with 1p deletions showed an intratumor presence of these aberrations in all the different tumor sectors.

CONCLUSIONS

These data, acquired by FISH interphase cytogenetics, confirm that 1p deletions in colorectal adenocarcinoma are common and suggest that this structural chromosomal aberration occurs mainly as an early event in colorectal tumorigenesis.

Correlation between 1p deletions and aneusomy in human colorectal adenomas

Human sporadic colorectal adenomas are characterized by a relatively high occurrence of aneuploidy. Similarly, 1p deletions have been reported to be an early event in colorectal tumorigenesis, while chromosome 7, 17 and 18 gain/losses were also found. The present study investigated 1p deletions, the numerical aberrations of chromosomes 1, 7, 17 and 18, and the nuclear DNA content as obtained by flow cytometry in a series of 34 human sporadic colorectal adenomas. From these adenomas, 51 intra-adenoma regions were microdissected according to 2 degrees of dysplasia and presence of foci of early cancer. Isolated epithelial nuclei were analyzed by fluorescence in situ hybridization interphase cytogenetics using centromeric probes for chromosomes 7, 17 and 18 and, in a double-target analysis, a centromeric probe for chromosome 1 simultaneously with a telomeric probe mapping to the 1p36 band. Aneuploidy incidence due to presence of numerical aberrations for at least one among the investigated chromosomes and/or abnormal flow-cytometric DNA content was 35%, while 1p deletion incidence was 38%. The correlation of 1p deletions with aneuploidy was statistically highly significant (p = 0.003), suggesting that loss of genes in this region may be implicated in chromosome instability.

Preliminary characterization of a monoclonal antibody (AS-2) against cell cycle related proteins

A monoclonal antibody (AS-2) raised by using isolated nuclei from a human erythroleukemia cell line as immunogen is described. AS-2 was of IgM type and recognized proteins present in both isolated cytoplasms and nuclei. The molecular weight of the AS-2 recognized proteins in the cytoplasm was 200 kDa and 70 and 60 kDa in the nucleus. The relative amount of these proteins were measured simultaneously with DNA content by flow cytometry. We found the highest protein content (or stainability) for both cells and nuclei in late-G1, S and G2, at approximately the same level, and the lowest content in M and early-G1. Sorting based on DNA content and AS-2 associated fluorescence helped identifying the staining pattern of cells and nuclei. Interphase isolated nuclei and cell cytoplasms were characterized by interdispersed staining over the entire surfaces while mitoses showed two dots only. The present preliminary data indicate that the proteins recognized by the AS-2 monoclonal are cell cycle related and suggest that in mitoses they are associated with the centrosomes.

Deletions at chromosome 1p by fluorescence in situ hybridization are an early event in human colorectal tumorigenesis

BACKGROUND & AIMS

Deletions at chromosome 1p have been observed frequently in human colorectal adenocarcinomas, suggesting that loss of genes in this chromosome arm is relevant for tumorigenesis. The aim of this study was to investigate whether 1p deletions are already present in adenomas within selected foci of dysplasia and early cancer using two-color fluorescence in situ hybridization.

METHODS

Fifty-one sectors characterized by low- and high-grade dysplasia and early cancer were microdissected from 34 adenomas, and isolated epithelial nuclei were subjected to hybridization with probes to the telomeric and centromeric regions of chromosome 1.

RESULTS

Deletions of 1p were detected in 13 of 34 adenomas (38%). In particular, low/moderate and high dysplasia and foci of early cancer had 1p deletion frequencies of 31%, 44%, and 50%, respectively.

CONCLUSIONS

Compared with classic cytogenetics, fluorescence in situ hybridization seems to be a particularly useful methodology to detect 1p deletions in human colorectal adenomas. The present findings indicate that loss of genes from the 1p chromosome arm may play an important role during the early steps of the colorectal carcinogenesis.

K-ras-2 G-C and G-T transversions correlate with DNA aneuploidy in colorectal adenomas

BACKGROUND/AIMS

K-ras-2 mutations and DNA content heterogeneity represent early events of human colorectal tumor progression. The aim of the study was to investigate if specific K-ras-2 mutations in 58 human sporadic adenomas were correlated with DNA aneuploidization and cell proliferation.

METHODS

Multiparameter flow cytometry, based on scatter parameters and DNA content, was performed using 4,6-diamidino-2-phenilindole-2-hydrochloride-stained nuclei obtained from adenoma fragments with either mild-moderate or severe dysplasia. K-ras-2 polymerase chain reaction and spectrum analysis were performed using sorted DNA specific epithelial subclones.

RESULTS

We detected six G-A transitions, and four G-C and two G-T transversions. The DNA aneuploid subclones were 25 with DNA index values in the near diploid region (DNA index < 1.3) for the vast majority of cases (80%). DNA aneuploidy among the mutated adenomas with G-A transitions was 1 of 6 (17%) and 6 of 6 (100%) among G-C and G-T transversions. Although DNA aneuploidy and high S-phase values were also present among K-ras-2 wild-type adenomas, their statistical associations with K-ras-2 status were P < 0.005 and P < 0.05, respectively.

CONCLUSIONS

The present series of sporadic colorectal adenomas indicates that codon 12 G-C and G-T K-ras-2 transversion mutations and DNA aneuploidy are correlated. The underlying mechanisms that explain such association remain to be investigated.

Neuroblastoma cell apoptosis induced by the synthetic retinoid N-(4-hydroxyphenyl)retinamide

N-(4-hydroxyphenyl)retinamide (HPR) is a synthetic retinoid with anti-cancer properties and lower toxicity than all-trans retinoic acid (RA). Neuroblastoma cells treated with HPR and observed by fluorescence microscopy showed clear signs of apoptosis, such as chromatin condensation and margination, nuclear fragmentation and the presence of "apoptotic bodies". Moreover, measurements on a cell-by-cell basis by the flow-cytometric DNA-content in situ-terminal-deoxinucleotidyl-transferase(TDT) assay showed that apoptosis induced by HPR was dose- and time-dependent and that the fraction of apoptotic cells increased from approximately 15% at 1.25 microM at 2 days after treatment up to approximately 90% at 5 microM and 8 days of continuous treatment. Additionally, we found that cells were induced into apoptosis independently from the cell-cycle phase. In contrast, equimolar or higher doses of RA, from 5 microM to 80 microM, were able to inhibit growth by differentiation, but failed to induce apoptosis. We conclude that the functional effects of HPR and RA in LA-N-5 neuroblastoma cells are mediated by apoptosis and differentiation respectively, suggesting a potential clinical use of HPR in the management of neuroblastoma patients.

Quantitative analysis of mitotic and early-G1 cells using monoclonal antibodies against the AF-2 protein

We have recently described a novel protein (AF-2), conserved between fission yeast and man, and we have shown by flow cytometry (FCM) that AF-2 is highly accessible to specific monoclonal antibodies (MoAbs) in mitotic and postmitotic early-G1 phase cells. The aim of the present study was to optimize the FCM methodology using MoAbs against AF-2 and to show that the evaluation of the mitotic cells, using different cell lines, was quantitative and reproducible. We found that a method based on fixation with ethanol, instead of formalin, resulted in improved DNA histogram coefficients of variation and implemented separation of early-G1 cells from late-G1 cells. In addition, by eliminating several cell permeabilization and protein salt extraction steps, the method became straightforward, conserved a clear-cut separation of the green fluorescence of M- with respect to G2-phase cells, and did not significantly affect cellular integrity. The coefficient of correlation among the mitotic index values evaluated by this FCM method using MoAbs against AF-2 and by microscopic visual counting was R = 0.94. When the FCM/AF-2 method was tested against an independent FCM method, which allows clear separation of M- and G2-phase cells according to 90 degrees scattering, we found R = 0.93. We conclude that MoAbs against the AF-2 protein may be used in FCM for quantitative analysis and for isolation of M-phase cells, providing as well, the identification of the early-G1 cell subcompartment. The method may, in addition, be useful for the simultaneous detection of cytoplasmic cytokeratin and nuclear AF-2 antigen.

Interleukin-3 dependent c-myc protein expression during the cell cycle of murine mast cells

Aim of the study was to evaluate the relationship between the mitogenic stimulus interleukin-3 to normal murine mast cells and the cell cycle dependent expression of the nuclear c-myc protein. In order to do that on a cell by cell basis, we measured the nuclear c-myc protein simultaneously by flow cytometry, via specific monoclonal antibodies, and the DNA content via the intercalating dye propidium iodide. When cells were deprived from interleukin-3 (IL-3), proliferation was inhibited and the majority of cells arrested in early G1 (G1A, characterized by low c-myc content). Readdition of IL-3 resulted in a slow transition of cells from G1A to late G1 (G1B, at higher c-myc content) before DNA synthesis started. G1A cells with low c-myc content do not undertake DNA synthesis. Using a stathmokinetic methodology we confirmed that the G1A cells are early postmitotic G1 phase cells. The low content of c-myc within these cells appears a direct consequence of reduced c-myc levels during mitosis. Cumulatively, the data suggest that c-myc protein levels of murine mast cells fall at mitosis and that these levels must rise before cells can traverse the G1 phase. Our data are compatible with a model in which c-myc protein content of G1 phase cells has to reach a critical threshold before the cells can move further into the cell cycle.

Cell cycle dependent alterations of chromatin structure in situ as revealed by the accessibility of the nuclear protein AF-2 to monoclonal antibodies

We have recently described a novel nuclear antigen, AF-2, which is related to cell cycle dependent alterations of chromatin structure. We show by two parameter flow cytometry on a cell by cell basis that the antigen is accessible to specific monoclonal antibodies only in mitotic and postmitotic early G1-phase cells. The evaluation of nuclease susceptibility and AF-2 antigen accessibility reveals different subcompartments of the G1-phase of the cell cycle with distinct chromatin conformations. Digestion with DNase I seems to alter the chromatin structure according to concentration and this is reflected by an increase of the antigen accessibility. Chromatin in the more condensed early G1-phase is specifically digested by lower concentrations of the enzyme than chromatin in later stages of interphase. Chromatin from cells in the late-G1, S-, and G2-phases shows a higher relative resistance to DNase I and a reduced accessibility of the AF-2 antigen to monoclonal antibodies. Nuclease S1 has a similar effect on chromatin topology, as revealed by the reaction with anti-AF-2 antibodies, without digestion of detectable amounts of DNA. The antigen becomes available to the antibodies in almost all cells by digestion with high concentrations of DNase I or Nuclease S1.

Prognostic significance of nuclear DNA content in human neuroepithelial tumors

The relationship between survival and flow cytometric DNA-ploidy and other prognostic factors such as histological subtype, anatomical tumor site, patient sex and age was investigated in 153 patients with intracranial neuroepithelial tumors who underwent surgical treatment. We found a trend toward poorer survival from anaplastic astrocytomas and glioblastomas with respect to low-grade (I and II) astrocytomas (which did not differ significantly); accordingly, patients were grouped into these 3 histologic subgroups. Thirty-seven of the 153 tumors (24.2%) were aneuploid with a median DNA-index (DI) of 1.3 (range: 1.2-2.0). DNA-ploidy correlated with histology, since anaplastic astrocytomas and glioblastomas were significantly (p = 0.041) more frequently aneuploid (around 30%) than low-grade astrocytomas (around 10%). Patients with DNA-aneuploid tumors (i.e., with DI not equal to 1.00) survived for a shorter time (31.4 weeks) than patients with DNA diploid tumors (75.1 weeks) (p less than 0.001). This difference was confirmed by Cox's multivariate analysis. Aneuploid tumors were associated with a poorer survival (p = .0002) when compared with diploid tumors, resulting in a relative risk point estimate (RR) of 2.41, 95% confidence interval (Cl) = 1.55-3.74. Histological subtype was also significantly associated with survival (p less than 0.0001), with RRs of 2.09, 95% Cl = 1.13-3.86 and 3.59, 95% Cl = 1.96-6.59 for anaplastic astrocytomas and glioblastomas, respectively, compared to low-grade astrocytomas. We therefore suggest that the flow cytometric measurement of DNA-ploidy has relevant significance in predicting survival in patients treated for intracranial neuroepithelial tumors.

Measurement of c-myc protein content and cell cycle kinetics of normal and spontaneously transformed murine mastocytes by bivariate flow cytometry

Progressive in vitro culturing of interleukin-3 (IL-3) dependent normal murine mastocytes (PB-3) resulted in a variant cell line (PB-1) able to grow without exogenous IL-3 and which was tumorogenic in syngenic mice. Bivariate flow cytometry was used to evaluate the c-myc protein and DNA content of PB-3 and PB-1 cells. The c-myc protein was detected by specific monoclonal antibodies. Kinetic characteristics of PB-3 and PB-1 cell lines, namely, the duration of the G1, S and G2 + M cell cycle phases were also evaluated using the bromodeoxyuridine (BrdU) pulse-chase method and BrdU/DNA flow cytometry. Levels of c-myc protein in PB-1 cells were about two-fold higher than those of PB-3 cells in all cell cycle phases. Mean duration of the cell cycle (Tc) was 15.3 h for PB-3 cells and 12.4 h for PB-1 cells. Shortening in Tc for the transformed cells was due to a decrease of nearly 30% in mean duration of the G1 phase (from 8 h to 5.7 h). No significant differences were found in the duration of the S and G2 + M phases. These results indicate that acquired IL-3 independency in vitro and tumorogenicity of PB-1 cells were accompanied by a doubling of c-myc protein level and by a parallel shortening, or bypass, of the regulatory events within the G1 phase of the cell cycle.

Neurite outgrowth and cell cycle kinetic changes induced by cis-diamminedichloroplatinum II and retinoic acid in a human neuroblastoma cell line

The aim of this study was to analyze by flow cytometry the effect of cis-diamminedichloroplatinum II (CDDP) and retinoic acid (RA) on the cell cycle of a neuroblastoma cell line (SK-N-BE (2)C NB) and to correlate the kinetic data with cell morphology. CDDP at 1 microgram/ml induced a dramatic G2 + M cell cycle phases block (nearly 200% increase with respect to control) 2 days after treatment. The G2 + M block was spontaneously reversed starting from the 4th day. The cells treated with 10 microM RA were, instead, induced to irreversibly enter the G0 + G1 phase of the cell cycle (nearly 20% increase with respect to control) 48 h after treatment. Neurite-like structures were observed for both CDDP and RA treated cells. These data suggest different cell cycle dependent molecular mechanisms and different degrees of differentiation during CDDP or RA treatment of NB cells.

DNA flow cytometry of endoscopically examined colorectal adenocarcinomas

The purpose of the study was to evaluate the correlation of DNA-ploidy of colorectal adenocarcinomas (adk) with histological and clinical parameters including the survival of the patients. Multiple biopsies from 95 adk were taken during colonoscopy prior to surgery. The samples were used to obtain nuclei suspensions for specific staining of DNA content and high resolution flow cytometry. DNA-aneuploidy, i.e. the presence of more than one G0/G1 peak, was detected in 67/95 cases (71%). The individual-specific control mucosa was DNA-diploid in all cases. The mean fraction of S-phase cells was 7.2% in control mucosa and 13.6% in adk. DNA-ploidy did neither correlate with Dukes' stage nor with differentiation degree. Among the patients studied for the correlation of DNA ploidy with survival for a period extending to 30 months (n = 51), the DNA aneuploid group was estimated to be about 5 times as risky as the DNA diploid group with respect to the odds of dying. We conclude that DNA flow cytometry of colorectal adk may predict clinical outcome and be helpful in addition to histopathology.

A new method to discriminate G1, S, G2, M, and G1 postmitotic cells

A new flow cytometric method combining light scattering measurements, detection of bromodeoxyuridine (BrdU) incorporation via fluorescent antibody, and quantitation of cellular DNA content by propidium iodide (PI) allows identification of additional compartments in the cell cycle. Thus, while cell staining with BrdU-antibodies and PI reveals the G1, S, and G2 + M phases of the cell cycle, differences in light scattering allow separation of G2 phase cells from M phase cells and subdivision of G1 phase into two compartments, i.e., G1A representing postmitotic cells which mature to G1B cells ready to initiate DNA synthesis. The method involves fixation of cells in 70% ethanol, extraction of histones with HC1, and thermal denaturation of DNA. This treatment appears to enhance the differences in chromatin structure of cells in the various phases of the cell cycle to the extent that cells could be separated on the basis of the 90 degrees scatter. Mitotic cells show much lower scatter than G2 phase cells, and G1 postmitotic cells (G1A) show lower scatter than G1 cells about to enter the S phase (G1B). Light scattering is correlated with chromatin condensation, as judged by microscopic evaluation of cells sorted on the basis of light scatter. The method has the advantage over the parental BrdU/DNA bivariate analysis in allowing the G2 and M phases of the cell cycle to be separated and the G1 phase to be analyzed in more detail. The method may also allow separation of unlabeled S phase cells from mitotic cells and distinguish between labeled and unlabeled mitotic cells.

Flow cytometric detection of mitotic cells using the bromodeoxyuridine/DNA technique in combination with 90 degrees and forward scatter measurements

Mitotic cells could be well discriminated from the cells in the G1-, S- and G2-phases of the cell cycle using pulse labeling of S-phase cells with bromodeoxy-uridine (BrdUrd) and staining of the cells for incorporated BrdUrd and total DNA content. Unlabeled G2- and M-phase cells could be measured as two separate peaks according to propidium iodide fluorescence. M-phase cells showed lower propidium iodide fluorescence emission compared to G2-phase cells. The fluorescence difference of M- and G2-phase cells was caused by the different thermal denaturation of their DNA. Best separation of M- and G2-phase cells was obtained after 30-50 min heat treatment at 95 degrees C. Mitotic index could be measured if no unlabeled S-phase cells were present in the cell culture. With additional measurements of 90 degree scatter and/or forward scatter signals, mitotic cells could be clearly discriminated from both unlabeled G2- and S-phase cells. The correct discrimination (about 99%) of mitotic cells from interphase cells was verified by visual analysis of the nuclear morphology after selective sorting. Unlabeled and labeled mitotic cells could be observed as pulse-labeled cells progressed through the cell cycle. We conclude that this modified BrdUrd/DNA technique using prolonged thermal denaturation and the simultaneous measurement of scatter signals may offer additional information especially in the presence of BrdUrd-unlabeled S-phase cells.

Cell cycle synchronization induced by tamoxifen and 17 beta-estradiol on MCF-7 cells using flow cytometry and a monoclonal antibody against bromodeoxyuridine

Cell cycle synchronization of MCF-7 hormone-sensitive human breast cancer cells has been evaluated after sequential treatment with tamoxifen and 17 beta-estradiol. The analysis was performed by flow cytometry. Two methods were used, one for single-parameter DNA content analysis, and one for bivariate analysis of DNA content and amount of incorporated bromodeoxyuridine (BrdUrd) into DNA using a specific monoclonal antibody. According to the BrdUrd method, tamoxifen was found (over a 30h period) to decrease (with respect to cells grown in control medium) the fraction of cells in S phase from 45% to 20%, to increase cells in G0 + G1 from 47% to 68%, and to induce a slight build-up of cells in G2 + M. Subsequent addition of estradiol resulted in partial synchronous recruitment of the cells from G0 + G1 to progress through the S phase; after 6-8 h delay time, the percentage of cells in G0 + G1 decreased by 50% and cells in S increased by 175%. The bivariate BrdUrd technique offered more reliable and detailed information than the single-parameter DNA analysis for differentiating and measuring the time course of estrogen-recruited cells as they progressed through early and late S phase, and has the potential for a very detailed cell kinetic analysis of both in vitro and in vivo hormone-sensitive cells.

Flow cytometric evaluation of cell cycle characteristics during in vitro differentiation of chick embryo chondrocytes

The cell cycle kinetic characteristics of chick endochondral chondrocytes differentiating in vitro were studied by flow cytometry. In addition, the synthesis of type I and type X collagens of the same cells was evaluated by immunoprecipitation. Dedifferentiated cells, derived from chick embryo tibiae and grown attached to a substratum, were characterized by type I collagen synthesis, a high growth fraction (GF = 0.94), minimal cell loss factor (phi = 0.02), and a total cell cycle time of the proliferating cells of about 17 h (tG1 = 8 h, tS = 5 h, and tG2 + M = 4 h). Transfer of dedifferentiated cells to suspension culture on agarose-coated dishes induced differentiation to hypertrophic chondrocytes. These were characterized by type X collagen synthesis, a low growth fraction (GF = 0.52), maximal cell loss factor (phi = 1.0), and a total cell cycle time of the proliferating cells of about 73 h (tG1 = 53 h, tS = 12 h, and tG2 + M = 8 h). The transition from dedifferentiated chondrocytes to hypertrophic chondrocytes was accompanied by large increases of the duration of all the cell cycle phases and of the number of quiescent and degenerating cells. Associated with these alterations in cell cycle kinetics was a switch from type I to type X collagen synthesis. Further preliminary data suggest that the population of differentiating chondrocytes (a state between dedifferentiated and hypertrophic chondrocytes) comprises a heterogeneous population of fast and slow growing cells.

DNA flow cytometry of endoscopically examined colorectal adenomas and adenocarcinomas

DNA ploidy of 64 colorectal adenomas and 49 adenocarcinomas, examined endoscopically, was studied by flow cytometry. We found DNA aneuploidy in none of the 105 normal mucosa samples (0%), in 20 adenomas (31%), and in 36 adenocarcinomas (74%). DNA ploidy of adenomas correlated with size (P = 0.02) and degree of dysplasia (P less than 0.01) but not with histologic type. Adenomas had a 45% incidence of DNA aneuploid stem lines in the DNA index range of 0.80-1.20, compared with 8% in the case of adenocarcinomas. The distribution of the DNA index values of adenocarcinomas was approximately normal, with a mean value 1.63 +/- 0.28. The mean DNA index for the three cases of "carcinoma in adenoma" with invasion of the stalk of the adenoma was 1.52 +/- 0.18. These results, using DNA flow cytometry, provide evidence for the progression of colorectal adenoma to adenocarcinoma. The classification of adenomas according to DNA ploidy may be information of considerable practical value to the clinician in predicting risk of further adenomas and/or risk of cancer.

Flow cytometric DNA ploidy in colorectal adenomas and family history of colorectal cancer

Flow cytometric DNA ploidy of colorectal adenomas resected from 34 patients and the corresponding patient family history in first-degree relatives were evaluated. The samples with at least two separate G0-G1 peaks were defined as DNA aneuploid. The correlation between DNA ploidy and family history was evaluated using two-by-two contingency tables. This correlation was highly statistically significant: seven of nine patients (78%) with positive family histories, and five of 25 (20%) with negative family history had adenomas with DNA aneuploid stemlines (P = 0.0068). The overall DNA aneuploidy incidence was 12 in 34 cases (35.2%). The combined information of DNA aneuploidy and positive family history of colorectal cancer in patients with colorectal adenomas may help to better understand the process of colon carcinogenesis and to identify patients who have a higher risk for developing a malignancy.

Structural differences in the cell binding region of human fibronectin molecules isolated from cultured normal and tumor-derived human cells

Fibronectins isolated from human plasma (pFN) and from the conditioned media of normal (N-cFN) and tumor (T-cFN) human cells were compared by cathepsin D digestion followed by immunostaining of released fragments with the monoclonal antibody 3E3, specific for the cell binding site. Two different staining patterns were obtained, one specific for pFN and N-cFN, the second common to fibronectins from the 3 different kinds of tumors studied. This indicates structural differences between N-cFN and T-cFN in the cell binding region of the fibronectin molecule.