Cell Kinetics Analysis in Patients Affected by Squamous Cell Carcinoma of the Head and Neck Treated with Primary Surgery and Adjuvant Radiotherapy

BACKGROUND

The increasing complexity of management strategies for patients with head and neck squamous cell carcinoma (HN-SCC) calls for the investigation of new objective prognostic parameters to subdivide patients according to the tumor's biological aggressiveness.

METHODS

We evaluated in 35 HN-SCC patients the pretreatment cell kinetics parameters and DNA ploidy after in vivo infusion of bromodeoxyuridine and flow cytometric analysis. Patients were treated with radical surgery followed by conventional radiation therapy. Locoregional control data are available for follow-up times above five years.

RESULTS

We found that the likelihood of locoregional control for patients with rapidly proliferating HN-SCC characterized by a short potential doubling time (Tpot <5 days) was significantly smaller than for HN-SCC patients with slow tumor proliferation (Tpot >5 days). Moreover, when patients were stratified according to DNA ploidy and Tpot value, we found that the locoregional failure rate for rapidly proliferating tumors was significantly higher for diploid HN-SCCs than for aneuploid HN-SCCs.

CONCLUSION

The present data suggest that patients with resectable HN-SCC characterized by fast growth might have a worse prognosis after surgery and adjuvant conventional radiotherapy and might benefit from more aggressive radiotherapeutic modalities.

DNA-ploidy analysis within selected regions of colorectal adenomas containing carcinoma

In order to better understand the relationship of DNA ploidy, dysplasia, early cancer, and colorectal tumor progression, 11 colorectal adenomas containing carcinoma invading the submucosa were investigated using DNA flow cytometry. Multiple frozen samples were taken from the selected sectors corresponding to adenoma tissue with low-grade dysplasia, high grade dysplasia and early cancer. Sampling accuracy was performed under histologic examination by multiple cryostatic sections. Data were compared with previously reported results in non-cancerous adenomas and advanced carcinomas. Incidence of DNA aneuploidy among the dysplastic regions of the adenomas containing carcinomas resulted higher than that observed in non-cancerous adenomas (p=0.02). Furthermore, among the DNA aneuploid populations, the frequency of clones with high DNA Index (DI>1.3) was slightly higher in adenomas with cancer than in adenomas without cancer (p=0.07). We suggest that differences may exist in DNA aneuploidy evolution between these two types of lesions. In early cancer, the near-diploid clones were 57% with respect to 18% (p=0.01) in advanced cancer since in this latter case the majority of the DNA abnormal clones were in the near-hypertriploid region (82%). Thus, the acquisition of the invasive phenotype appears to be linked with the expansion and stabilization of high DNA aneuploid clones. Further analysis on a larger number of cases of adenomas containing carcinoma are necessary to validate these interpretations.

Evidence of cell kinetics as predictive factor of response to radiotherapy alone or chemoradiotherapy in patients with advanced head and neck cancer

PURPOSE

The aim of this study was to investigate the potential clinical relevance of cell kinetics parameters to the locoregional control (LRC) and overall survival of patients affected by head and neck squamous cell carcinoma (HN-SCC) treated by conventional radiotherapy, partly accelerated radiotherapy, or alternating chemoradiotherapy.

METHODS AND MATERIALS

Between January 1993 and June 1996,115 patients with HN-SCC at Stage III and IV entered the study. Multiple primary tumor biopsies were obtained 6 h after in vivo infusion of bromodeoxyuridine (BrdUrd), an analogue of thymidine that is incorporated in DNA-synthesizing cells. In vivo S-phase fraction labeling index (LI), duration of S-phase (Ts), and potential doubling time (Tpot) were obtained by analysis of the flow cytometric content of BrdUrd and DNA. Eighty-two patients were randomly assigned to receive either alternating chemoradiotherapy or partly accelerated radiotherapy, whereas 33 other matching patients received conventional radiotherapy.

RESULTS

Univariate LRC analysis showed that LI value was a prognostically significant factor, independent of type of therapy. Multivariate analysis failed to show cell kinetics parameters as statistically significant factors affecting LRC probability and overall survival. However, subgroup analysis showed that LRC probability at 4 years for fast proliferating tumors characterized by a LI >/= 8% was significantly better for patients treated either with alternating chemoradiotherapy or partly accelerated radiotherapy than it was for those treated with conventional radiotherapy. Conversely, LRC probability for slow proliferating tumors (LI < 8%) treated with the three treatment modalities was similar.

CONCLUSIONS

These results showed that, independent of type of treatment, pretreatment cell kinetics provided only a weak prognostic role of outcome in HN-SCC. However, this report raises the hypothesis that fast growing HN-SCC may be more likely to benefit from intensified therapy, as given in this series. Cell kinetics parameters studied by the in vivo BrdUrd/flow cytometry method might be considered predictive factors of response, providing information on which type of treatment may be selected according to tumor proliferation rate.

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.

Intratumor heterogeneity of k-ras and p53 mutations among human colorectal adenomas containing early cancer

The molecular pathways and the timing of genetic events during human colorectal carcinogenesis are still not fully understood. We have addressed the intratumor heterogeneity of the mutational status of the k-ras oncogene and of the p53 oncosuppressor gene during the adenoma-carcinoma sequence by investigating 26 human colorectal adenomas containing early cancer. An intratumor comparative analysis was obtained among the adenomatous and carcinomatous component pairs. Additionally, we have analyzed 17 adenomas having cancer in the near vicinity. The adenomatous components of the adenomas containing early cancer and the adenomas having cancer in the near vicinity had comparable frequencies for k-ras mutations (28 and 47%) but different for p53 mutations (52 and 7%, p-value = 0.01). Interestingly, the adenomatous and carcinomatous components of the adenomas containing early cancer were rarely heterogeneous for the k-ras mutational status (only in 13% of the cases) but were characterized by heterogeneity of the p53 status in 59% of the cases (p-value < 0.01). In addition, the mutations of p53 for the adenomatous components of the adenomas containing early cancer were statistically significantly associated with severe dysplasia (p-value = 0.01). Intratumor homogeneity of k-ras status during the human colorectal adenoma-carcinoma sequence suggests that the role of k-ras is more related to tumor initiation than to tumor progression. On the contrary, intratumor heterogeneity of p53 mutations indicates that the type of the p53 mutations may also be relevant for selection and expansion of new subclones leading to tumor progression.

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).

K-ras2 activation and genome instability increase proliferation and size of FAP adenomas

The possible role of K-ras2 mutations and aneuploidy toward increase of proliferation and adenoma size in Familial Adenomatous Polyposis (FAP) adenomas is not known. The present study addresses these issues by investigating 147 colorectal adenomas obtained from four FAP patients. The majority of adenomas had size lower than or equal to 10 mm (86%), low grade dysplasia (63%), and were preferentially located in the right colon (60%). Normal mucosa samples were obtained from 19 healthy donors. Three synchronous adenocarcinomas were also investigated. K-ras2 mutation spectrum was analysed by PCR and Sequence Specific Oligonucleotide (SSO) hybridization, while flow cytometry (FCM) was used for evaluating degree of DNA ploidy and S-phase fraction. Overall, incidences of K-ras2 mutations, DNA aneuploidy and high S-phase values (>7.2%) were 6.6%, 5.4% and 10.5%, respectively. In particular, among the adenomas with size lower than 5 mm, K-ras2 mutation and DNA aneuploidy frequencies were only slightly above 1%. Statistically significant correlations were found between K-ras2 and size, DNA ploidy and size and K-ras2 and S-phase (p < 0.001). In particular, among the wild type K-ras2 adenomas, high S-phase values were detected in 8% of the cases versus 57% among the K-ras2 mutated adenomas (p = 0.0005). The present series of FAP adenomas indicates that K-ras2 activation and gross genomic changes play a role toward a proliferative gain and tumour growth in size.

Specific K-ras2 mutations in human sporadic colorectal adenomas are associated with DNA near-diploid aneuploidy and inhibition of proliferation

Recent studies indicate that p21ras proteins mediate their multiple cell functions through interactions with multiple effectors and that the number of new effectors is growing. We recently reported that K-ras2 mutations in human colorectal adenomas were associated with chromosome instability and proliferation changes. In the present study, we extend these previous observations. Hereditary and multiple (n > or = 5) adenomas and adenomas with early cancer were excluded. Dysplasia was moderate in 91 cases and high in 25, and the median adenoma size was 1.5 cm. K-ras2 spectrum analysis was done by sequence-specific oligonucleotide hybridization using nuclear suspensions provided by analysis and sorting of multiparameter flow cytometry. In particular, tissue inflammatory cells were separated for DNA diploid tumors, whereas DNA aneuploid epithelial subclones were analyzed separately. K-ras2 mutations and DNA aneuploidy were both detected in 29 of 116 (25%) cases. DNA aneuploid index was in the near-diploid region in the majority of cases. DNA aneuploidy was strongly associated with G-->C/T transversions. An association was also found between low S-phase values and G-->A transitions. These findings were confirmed using multivariate logistic regression analysis to account for the effects of size, dysplasia, site, type, age, and sex. These data suggest that specific K-ras2 mutations in a subgroup of human sporadic colorectal adenomas play a role in chromosome instability and, contrary to expectations, are associated with inhibition of proliferation.

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.

p53 mutations and DNA ploidy in colorectal adenocarcinomas

The p53 tumour suppressor gene has an important role in the the maintenance of genome stability and its mutational inactivation may be at the origin of aneuploidy in cancer cells. The aim of this study was to determine whether p53 mutations were associated to DNA aneuploidy, as assessed by flow cytometry, in colorectal adenocarcinomas. Analysis of p53 mutations spectrum of the sorted nuclei was done by Denaturing Gradient Gel Electrophoresis (DGGE) and DNA sequencing. Overall, we studied 20 adenocarcinomas, the corresponding control mucosa, and 7 lymph node metastases. Five tumours (25%) were DNA diploid, while 15 tumours (75%) were composed of DNA aneuploid and diploid subpopulations. DNA diploid control mucosa and adenocarcinomas showed no p53 mutations, while 60% of the tumours with DNA aneuploidy had p53 mutations. Therefore, p53 mutations occurred significantly more often in DNA aneuploid than in DNA diploid tumours (p < 0.04, Fisher's exact test). Incidences of DNA aneuploidy and p53 mutations in lymph node metastases were 60 and 86%, respectively. In all tumours showing a p53 mutation, the wild-type allele was not or only bearly visible in DNA aneuploid cells suggesting that, in such cells, aneuploidy is accompanied by complete p53 functional inactivation. The present observations suggest that p53 mutations may have a role in the origin of aneuploidy at late stages of colorectal carcinogenesis.

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.

Chemoradiotherapy as an alternative to radiotherapy alone in fast proliferating head and neck squamous cell carcinomas

The aim of this pilot study was to explore the prognostic relevance of cell kinetics parameters on the local control of patients affected by head and neck squamous cell carcinoma (HN-SCC), randomly assigned to receive either alternating chemoradiotherapy or partly accelerated radiotherapy. Between 1992 and 1995, 40 patients with HN-SCC at stages III and IV entered the study. Multiple primary tumor biopsies were obtained 6 h after in vivo infusion of bromodeoxyuridine, an analogue of thymidine that is incorporated in DNA-synthesizing cells. In vivo S-phase fraction labeling index (LI), duration of S-phase (TS), and potential doubling time (Tpot) were obtained by analysis of the flow cytometric content of bromodeoxyuridine and DNA. Twenty patients were treated by alternating chemotherapy and conventional radiotherapy (arm A), whereas 20 other matching patients received partly accelerated radiotherapy alone (arm B). Univariate local control analysis showed that LI, TS, and Tpot were not prognostically significant in either arm. However, local control probability at 2 years for fast growing tumors, characterized by a LI of 9%, was higher for patients treated with alternating chemoradiotherapy than it was for those treated with partly accelerated radiotherapy alone (68 versus 39%). Conversely, local control probabilities for slow proliferating tumors (LI, <9%) treated in the two arms were similar. These results suggest a potential role for alternating chemotherapy and radiotherapy in HN-SCC patients with fast growing tumors.

Evidence of apoptosis in neuroblastoma at onset and relapse. An analysis of a large series of tumors

Neuroblastoma (NB) is a tumor of pediatric age that is associated with high mortality in metastatic stages, although stage IVS patients undergo frequent spontaneous regression. Since apoptosis has been proposed as a possible cause of remission among cancer patients, we tested this hypothesis among both localized and metastatic NB and, in particular, NB metastatic stage IVS. We have assayed 36 localized and 117 metastatic neuroblastomas for evidence of internucleosomal DNA degradation and confirmed DNA fragmentation by the flow cytometric Terminal deoxynucleotidyl Transferase method, which also allowed us to measure DNA content and cell cycle phases. These techniques provided evidence of apoptosis in 18 out of 153 samples (11.8%), that were equally distributed among all stages except IVS, i.e. 11.1% in stage I (2/18), 11.1% in stage II (2/18), 13.2% in stage III (5/38), 13.4% in stage IV (9/67), and 0% in stage IVS (0/12). Tumor tissue samples collected at onset and also at relapse for the same patients showed that apoptosis may occur at relapse. In addition, cells appear to undergo apoptosis independently from N-myc amplification, cell cycle phase and DNA ploidy. In conclusion, apoptosis seems to take place with about an equal frequency for both favourable and unfavourable stages with an exception for IVS. Since DNA fragmentation remained undetected in stage IVS, we suggest that apoptosis is not a mechanism of spontaneous regression for these patients. A better basic understanding of the complex molecular mechanisms and biochemical pathways that control apoptosis in neuroblastoma appears to be necessary.

Cell kinetics and tumor regression during radiotherapy in head and neck squamous-cell carcinomas

Head and neck squamous-cell carcinoma (HN-SCC) patient management is mainly based on TNM classification and needs be improved by considering other potentially useful prognostic factors. We examined the pre-radiotherapy tumor potential doubling time (Tpot) evaluated after in vivo infusion of bromodeoxyuridine and flow-cytometric analysis and the early clinical tumor regression after 40 Gy (40 Gy-TR). Tpot values and clinical 40 Gy-TR classes (minor and major) were available for 82 HN-SCC patients. Radiation therapy completion was done either with 1 dose per day (conventional regimen) or 2 doses per day (accelerated regimen). Local control was also available for follow-up times above 4 years. We found that major 40 Gy-TR was strongly correlated with fast tumor growth, characterized by Tpot values below 5 days, and that patients with major 40 Gy-TR showed better local control than those with minor 40 Gy-TR, independently from the radiotherapy regimen type. We also found that treatment completion with accelerated radiotherapy gave better local control for patients with major 40 Gy-TR and fast tumor growth than conventional radiotherapy. Multivariate analysis, performed on all patients, assigned an independent prognostic value to Tpot, tumor classification and 40 Gy-TR.

Transfection of human mutated K-ras in mouse NIH-3T3 cells is associated with increased cloning efficiency and DNA aneuploidization

The aim of the study was to test the hypothesis that a human mutated K-ras protein induces abnormalities in mitosis and development of sub-clones characterized by changes in DNA ploidy and proliferation. For this purpose, we used control and NIH-3T3 mouse cells transfected with the human codon 12 G-C-mutated K-ras oncogene. We found that abnormal mitoses, mainly characterized by lagging chromosomes in prometaphase or anaphase, had a significantly higher frequency in transfected cells than in control cells. The generation of sub-clones was screened by limiting-dilution experiments followed by cell expansion. Cloning efficiency was much higher for the K-ras transfected cells with 858/2112 (41%) successful sub-clones than for control, which provided 564/2592 (22%) sub-clones. DNA flow cytometry of 4.6-diamidino-2-phenilindole-2-hydrochloride-stained nuclei from randomly selected sub-clones was performed in order to evaluate DNA index and S-phase fraction values. We found 9 out of 100 DNA aneuploid sub-clones generated by the K-ras-transfected cells vs. 1 out of 100 for the controls. Overall, our data indicate that high expression of the mutationally activated human K-ras product in NIH-3T3 cells was associated with abnormal mitoses, increase of cloning efficiency and DNA aneuploidization.

Intratumor heterogeneity of K-ras2 mutations in colorectal adenocarcinomas: association with degree of DNA aneuploidy

Detailed information about intratumor K-ras2 mutations in colorectal adenocarcinomas and a possible association with DNA content heterogeneity is still lacking. DNA diploid and aneuploid subclones, detected among multiple histologically selected primary sectors (57 superficial and 40 deep) and 9 lymph node metastases, were flow cytometrically sorted and separately submitted to codons 12-13 K-ras2 mutation spectrum analysis. DNA aneuploidy was absent among 20 near and 20 distant mucosa sites and present in 7/9 lymph node metastases and in 17/19 primary tumors (90%). Primary intratumor DNA multiclonality was approximately 50%. Degree of DNA aneuploidy (DNA Index) distribution was nonrandom and showed peaks at approximate mean DNA Index values 1.2, 1.5, and 1.8. K-ras2 mutations were detected in 0/20 mucosa cases, in 2/9 lymph node metastases, and in 9/19 adenocarcinomas (47%). No more than one mutation type per tumor was detected. Intratumor distribution of K-ras2 mutations was homogeneous in 6 and heterogeneous in 3 cases. Homogeneous distribution was associated with DNA near-diploid aneuploidy. K-ras2 mutations were strongly associated with DNA Index in the near-diploid region (83%) and almost absent (5%) among DNA near-triploid subclones (P = 0.0001). K-ras2 mutation intratumor heterogeneity indicates that sampling of the tumor may be a critical step and suggests that K-ras2 activation may be a late event in a subgroup of tumors. Our data also suggest the existence of an early process of the colorectal carcinogenesis that favors both K-ras2 mutations and DNA near-diploid aneuploidy. Onset of DNA near-triploid subclones appears, instead, to be independent from K-ras2 activation.

N-(4-hydroxyphenyl)retinamide induces apoptosis in human leukemia hl-60 cells and mediates vimentin down-regulation

N-(4-Hydroxyphenyl)retinamide (HPR) is a synthetic retinoid with anticancer properties and lower toxicity than all-trans retinoic acid (RA). We have studied the effects of HPR on apoptosis and differentiation in the human promyelocytic leukemia HL-60 cell line. In addition, we have tested the hypothesis that vimentin expression after HPR and RA, taken as indirect evidence of the mechanisms of action of the two retinoids, may be different. Quantitative evaluation of the percentage of apoptotic cells was carried out on a cell by cell basis by the flow cytometric DNA-content in situ-terminal-deoxynucleotydil-transferase (TdT assay). HPR was found to clearly induce apoptosis, while RA: instead, induced differentiation without apoptosis. These data confirm previous observations. Vimentin protein content was evaluated by flow cytometry with use of monoclonal antibodies simultaneously with DNA content. We found that HPR treated apoptotic cells were characterized by negative vimentin expression, while the HPR treated non apoptotic cells had about the same level of vimentin as the RA treated cells. These latter findings suggest that HPR may induce a functional effect (apoptosis) by a mechanism of action different from that of RA. Further work is necessary to clarify this finding.

In vivo cell kinetics in head and neck squamous cell carcinomas predicts local control and helps guide radiotherapy regimen

PURPOSE

To determine whether pretherapy cell kinetics can predict local control for patients affected by head and neck squamous cell carcinomas (HN-SCCs) to be treated by primary radiotherapy and, moreover, guide to a choice between conventional and accelerated radiotherapy.

PATIENTS AND METHODS

Between 1989 and 1993, 83 patients with stage II to IV HN-SCC entered the study. Multiple primary tumor biopsies were obtained 6 hours after in vivo infusion of bromodeoxyuridine (BrdUrd). In vivo S-phase fraction labeling index (LI), duration of S phase (Ts), and potential doubling time (Tpot) were obtained by analysis of multivariate flow-cytometric data. Between April 1989 and January 1991, 49 patients were treated by conventional radiotherapy (70 Gy in 35 fractions over 7 weeks), whereas, afterwards, 34 patients entered an accelerated radiotherapy regimen with the concomitant boost technique (75 Gy in 40 fractions over 6 weeks).

RESULTS

Univariate analysis showed that, among patients treated by conventional radiotherapy, local control probability was affected by tumor stage (P = .02), Tpot (P < .001), and LI (P = .04). Similarly, among patients treated with accelerated radiotherapy, we found that local control probability was related to tumor stage (P = .03) and primary tumor site (P = .05). For the subgroup of patients with tumors characterized by fast growth (Tpot < or = 5 days), accelerated radiotherapy gave a better local control rate than conventional radiotherapy (P = .02). Cox multivariate analysis of the total number of patients showed that the only significant independent prognostic factors related to local control were tumor stage (P = .002) and Tpot (P = .004). Moreover, when the Cox analysis was restricted to the subgroup of patients treated with conventional radiotherapy, Tpot was the most significant factor to predict local outcome (P < .01).

CONCLUSION

Pretreatment tumor Tpot appears to be an important independent prognostic factor for local control of HN-SCC treated by primary radiotherapy.

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.

Potential doubling time in head and neck tumors treated by primary radiotherapy: preliminary evidence for a prognostic significance in local control

PURPOSE

The aim of the study was to determine preliminarily whether cell kinetic parameters evaluated using in vivo infusion of bromodeoxyuridine (BrdUrd) and flow cytometry, play a role as prognostic factors of loco-regional control in squamous cell head and neck carcinoma treated with radiotherapy.

METHODS AND MATERIALS

Between April 1989 and December 1991, 42 patients with unresectable Stage II-IV squamous cell carcinoma of the oral cavity, pharynx or larynx were given an infusion of BrdUrd solution prior to primary tumor biopsy sampling at 4-6 hr later. The simultaneous labeling S-phase fraction (LI) and duration (Ts) as well as the estimated potential doubling time (Tpot) were measured using flow cytometric analysis of BrdUrd and DNA content. Twenty-six patients received standard radiotherapy (70 Gy/35 fractions/7 weeks) whereas 15 patients were treated with the concomitant boost technique (75 Gy/40 fractions/6 weeks).

RESULTS

A complete set of flow cytometric data was available for 31 patients. The median value of LI, Ts, and Tpot were 9%, 9 hr and 5 days, respectively. Univariate analysis among the patients treated homogeneously by standard radiotherapy, indicated that local control was affected by Tpot value (p = 0.02). When the same analysis was performed for the patients treated with either standard radiotherapy or concomitant boost regimen, we found a p = 0.04. Thus, patients with a tumor Tpot value < or = 5 days had a significantly lower three-year local control than patients with Tpot > 5 days. Log-rank test univariate analysis showed, in addition, that nodal status was the strongest prognostic factor of local control (p = 0.005). Age, tumor stage, tumor site, performance status, grading, radiotherapy regimen, DNA ploidy and LI value were, instead, not significantly related to loco-regional control. Finally, when comparing the type of radiotherapy for tumors with Tpot < or = 5 days, we found a trend toward a better local control after concomitant boost regimen, with respect to standard regimen (p = 0.06).

CONCLUSION

The present preliminary results suggest that Tpot could play a role as additional prognostic factor influencing the disease outcome in head and neck carcinoma treated by radiotherapy.

DNA content analysis of Barrett's esophagus by flow cytometry

The purpose of this study was to investigate the correlation of flow cytometric (FCM) DNA content and cell cycle characteristics of Barrett's Esophagus (BE) with age and sex of the patients, length, histologic type and dysplasia of BE. Forty-one patients affected by histologically confirmed BE had multiple biopsies taken from the metaplastic epithelium and one biopsy taken from the gastric fundus, as control. The samples were either stored at -80 degrees C or immediately measured. Nuclei suspensions were obtained, stained with DAPI, measured with a high resolution flow cytometer (ICP22A, Ortho Instruments) and analyzed for the evaluation of the relative DNA content and the S- and G2 + M phases of the cell cycle. DNA histograms having two distinct G0/G1 peaks were classified as DNA aneuploid. The degree of DNA aneuploidy (DNA Index, DI), defined as the ratio of abnormal to normal DNA content, was obtained from the mixture of each BE sample with its control sample and trout erythrocytes. We found six patients with DNA aneuploid populations (14.6%), whose DNA Index values were 1.05 (in two), 1.8 (in one), and 2.0 (in three cases). DNA ploidy did not correlate with age and sex of the patients, length, histologic type, and dysplasia of BE. Among the 13 patients with dysplasia (6 indefinite, 4 low grade and 2 high grade with intramucous adenocarcinoma) only two (one indefinite and one low grade) showed DNA aneuploidy (15.4%). In addition, we found that the S-phase and the G2 + M-phase fractions in BE samples were both significantly higher than those of the controls (respectively, p = 0.01 and p = 0.0008).(ABSTRACT TRUNCATED AT 250 WORDS)

DNA aneuploidy is an independent factor of poor prognosis in pancreatic and peripancreatic cancer

The purpose of this study was to investigate the clinical significance of DNA ploidy, as assessed by flow cytometry, for pancreatic and peripancreatic cancers. Between 1988 and 1990, we examined fresh/frozen samples from 49 patients who had histologically confirmed adenocarcinomas of the bilio-pancreatic carrefour: They had 23 cancers of the pancreas, 21 of the Vater's papilla, and 5 of the common bile duct. All patients were selected among a cohort of subjects who underwent Endoscopic Retrograde Cholangio Pancreatography (ERCP) and/or surgery. No prognostic impact of age, sex, stage, and surgical treatment on survival was observed by univariate analysis. When the affected organ was considered, a statistically significant difference in survival was observed: At 88 wk, survival was 0% for pancreatic and common bile duct cancer patients, and 18.2% at 175 wk for Vater's papilla cancer patients (p = 0.04). In addition, we found, irrespective of affected organ, that the patients with DNA diploid tumors had a statistically significant survival advantage as compared to those with DNA aneuploidy (p = 0.02). Furthermore, the statistically significant prognostic power of DNA ploidy was confirmed when patients with tumors of the pancreas and those with tumors of the Vater's papilla were separately analyzed.(ABSTRACT TRUNCATED AT 250 WORDS)

[The prognostic role of the parameters of cellular kinetics in head and neck tumors treated solely by radiotherapy]

Cell cycle and cell population characteristics, as obtained for head and neck cancers by flow-cytometry analysis of a single tumor sample, after in vivo bromodeoxyuridine (Burd) infusion, were proposed for their prognostic value and for their potentials for radiotherapy planning (conventional vs accelerated) and monitoring. DNA ploidy, the S phase fraction labeling index (LI), and duration (Ts) as well as cell population potential doubling time (Tpot) were measured in 42 head and neck squamous cell carcinoma patients and analyzed along with histopathological and clinical data. Twenty-seven patients received standard radiotherapy (70 Gy/35 fractions/7 weeks) whereas 15 patients were treated with the concomitant boost technique (75 Gy/40 fr/6 weeks). The univariate analysis of 31 patients, for whom all the cell kinetic parameters were available, indicated that local control probability was strongly affected by lymph node status (p = 0.05) and by potential doubling time (p = 0.04). Patients having tumor Tpot < 5 days had markedly lower two-year local control rate (13%) than patients with Tpot > 5 days (68%). Furthermore, tumors with Tpot < or = 5 days exhibited a trend toward better local control after concomitant boost regimen compared with the patients treated with standard regimen (p = 0.06). These preliminary results point out that Tpot could play a role as additional prognostic factor influencing disease outcome in head and neck carcinomas treated by radiotherapy. In patients with fast growth-rate tumors (Tpot < or = 5 days) a more aggressive radiotherapy combination or chemo-radiotherapy should be suggested.

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.

[Cell kinetic analysis and treatment planning in epidermoid tumors of the head and neck]

Cell kinetic parameters were evaluated using the method based on in vivo incorporation of Bromodeoxyuridine (BrdU) and flow cytometric (FCM) analysis in 30 human epidermoid head and neck tumors from oropharynx, oral cavity, rhinopharynx, larynx and lips. BrdU was injected four/six hours before the obtainment of multiple bioptic samples from the tumor tissues. The flow cytometric method was carried out on 70% ethanol fixed cell suspensions based on established protocol for the simultaneous evaluation of DNA content and BrdU uptake using anti-BrdU monoclonal antibodies. We have evaluated the following FCM parameters: DNA ploidy, the degree of DNA aneuploidy (DNA index), Labelling Index (LI), duration of s-phase (Ts) and tumor potential doubling time (Tpot). LI values ranged from 1.5 to 20% with a median value of 10%. The median LI of DNA diploid tumors was 5.4% compared to 14% in DNA aneuploid tumors. Ts values ranged from 8 to 11, the median value being 10 hours. Tpot values ranged from 2 days to 16 days, the median Tpot being 5 days. The large heterogeneity of all these parameters indicates that these tumors may have a different degree of biologic aggressiveness (9). Tpot values did not correlate with DNA ploidy nor with lymph node metastasis status. Tpot values did not correlate in a statistically significant manner with degree of differentiation although shorter Tpot were more frequently observed in moderate or poorly differentiated tumors. Our study shows that the FCM-BrdU technique in vivo is feasible in a clinical setting to evaluate the proliferative behaviour of head and neck tumors, before any specific therapeutic decision is taken after surgery is performed. It is likely that tumors with more aggressive biological behavior, as indicated by LI > 15%, DNA aneuploidy and Tpot < 5 days, may benefit from more aggressive therapies such as accelerated regimeus of radiotherapy and/or other multimodal therapies in respect to tumors with slow growth rate (LI < 15%), DNA diploidy and Tpot > 5 days. So far, however, it still remains to be demonstrated from randomized clinical trials if the knowledge of such individualized cell Kinetic parameters really can help to choose the most effective therapy for every individual patient.

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.

Activity of 4-HPR in superficial bladder cancer using DNA flow cytometry as an intermediate endpoint

The ability of the synthetic retinoid N-(4-hydroxyphenyl)retinamide (4-HPR) to affect the outcome of previously resected superficial bladder cancer was investigated in a pilot study using DNA content flow cytometry and conventional cytology as intermediate endpoints. Twelve patients were treated with oral 4-HPR (200 mg daily) and compared with 17 non-randomized, untreated controls. The median interval between transurethral resection and 4-HPR administration was 5.5 months (range 0-36). The median follow-up period was 12 months (range 3-31) in the 4-HPR group and 9 months (range 2-22) in the control group. The proportion of patients with DNA aneuploid stemlines in bladder-washed cells decreased from 7/12 (58%) to 5/11 (45%) in the 4-HPR group, but increased from 7/17 (41%) to 10/17 (59%) in the control group. In patients with stable diploid profiles, mean (+/- SE) S-phase and G2+M-phase fractions decreased in the course of retinoid treatment from basal levels of 15.2 +/- 4.1% to 7.5 +/- 3.3% and 10.3 +/- 2.2% to 5.2 +/- 0.4%, respectively. The same parameters in the control group changed from basal levels of 14.6 +/- 3.4% to 12.4 +/- 2.7% and 9.8 +/- 1.6% to 12.6 +/- 1.6%, respectively. Positive or suspicious cytologic examinations were present in 3/12 (25%) treated cases prior to 4-HPR administration and all subsequently reverted to normal. The same parameter in the control group increased from 4/17 (24%) to 6/17 (35%) during follow-up. Impaired adaptation to darkness was recorded in 4 patients, and transient dermatologic alterations were observed in one-third of the patients, requiring dose reduction in one case.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Flow cytometric DNA index in the prognosis of colorectal cancer

The authors investigated the relationship between flow cytometric DNA index (DI, defined as the ratio of the DNA content of malignant cells to that of normal cells) and other prognostic factors (grade and stage, anatomical site, age and sex) with the survival of 115 patients with colorectal cancer. Multiple biopsy specimens from 62 patients were taken during colonoscopy before surgery. Additional samples from 53 patients were obtained from paraffin-embedded material. All patients were treated with surgery only. Fresh-frozen material gave higher incidence of DNA aneuploidy than paraffin-embedded material (79% versus 41%). The patients with DNA diploid tumors (DI = 1) had a better overall survival than those with DNA aneuploid tumors (DI = 1). Among DNA aneuploid tumors, those with DI greater than 1.2 (excluding DI = 2) were worse than those with DI = 1.2 (excluding DI = 1) and DI = 2. Cox's regression analysis showed that pathologic stage was more important for prognosis than DNA index, whereas age, sex, histologic grade, and anatomic site were removed from the analysis as not relevant for prognosis. Relative risk of death (RR), in reference to patients with DI = 1 and Stages A + B (RR = 1), were RR = 1.8 for patients with carcinomas with Stage C. RR = 2.7 for patients with carcinomas with DNA near-diploid and DNA tetraploid tumors. RR = 3.5 for those with DI greater than 1.2 (excluding DI = 2), and RR = 8.0 for those with Stage D. These data indicate that flow cytometrically evaluated DI values have a relevant independent power for predicting the clinical outcome of colorectal cancer patients.

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.

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.