A comparison of the changes induced in rat liver by feeding low levels of aflatoxin B1 or an azo dye.

(1) Rats have been given 6 weeks' feeding with low levels of the hepatocarcinogens aflatoxin B1 and 2-methyl dimethyl aminoazobenzene (2-Me-DAB). (2) It has been confirmed that 3 weeks' feeding with either toxin is sub-carcinogenic, whereas 6 weeks' feeding results in a high incidence of hepatocarcinoma. (3) The changes occurring in the liver during this feeding have been monitored by histological examination and zonal rotor centrifugation. (4) Marked similarities have been observed between the time courses of development of changes induced in the liver by the two carcinogens. Little change is observed after 2 weeks' feeding with the toxins. The greatest change occurs after 3 weeks' feeding, which results in tissue necrosis and the loss of a large proportion of the tetraploid hepatocyte nuclei. (5) A compensatory proliferation of predominantly diploid hepatocytes takes place in the presence of a continuing supply of either of the carcinogens. This indicates that not only does feeding each carcinogen induce the production of a population of hepatocytes resistant to the cytotoxicity of the inducing agent, but that the population is also resistant to the cytotoxicity of the other carcinogen.     

Estrogen receptor, epidermal growth factor receptor and cellular ploidy in elutriated subpopulations of hepatocytes during liver tumor promotion by 17 alpha-ethinylestradiol in rats.

17 alpha-Ethinylestradiol (EE2)-mediated promotion of diethylnitrosamine (DEN)-initiated liver tumors was evaluated in distinct hepatocyte subpopulations. Our initiation-promotion regime consisted of a single dose of DEN (200 mg/kg) to ovariectomized rats, followed by chronic exposure to EE2 (90 micrograms/kg/day for 30 weeks). We observed significant increases in liver and uterine organ wts which were associated with liver tumor formation. Isolated hepatocytes were separated by elutriation into seven subpopulations. The early eluting subpopulations consisted of a greater proportion of diploid cells and they exhibited a preferential uptake of acridine orange, which is characteristic of periportal cells. With the increasing order of elutriated fractions, hepatocyte subpopulations of tetraploid and octaploid cells were obtained. Elutriation revealed that EE2 promotion enhanced nuclear estrogen receptor levels (3-fold) and gamma-glutamyltranspeptidase activity (5-fold) to a greater extent in the early eluting diploid subpopulations (1 and 2), even though total estrogen receptor (ER) levels were higher in the later eluting subpopulations. The stimulatory effect of EE2 on ER levels was associated with an increased ER occupancy in all subpopulations, although the effect was greatest in the later eluting fractions. Chronic EE2 exposure induced the emergence of new hepatocyte populations within fractions 6 and 7. Enhanced cell growth was observed in the DEN/EE2-derived hepatocytes by flow cytometric measurements of DNA synthesis. The new populations of altered cells expressed high levels of epidermal growth factor receptor (EGFR), with 90% of the cells positive for EGFR-antibody. In summary, our data demonstrate that many effects of EE2 on hepatocyte pathways involved in growth control occur in nearly all populations of cells, derived by elutriation although some effects such as the emergence of an EGFR-enriched population of hepatocytes are localized in specific populations.     

Quantitative aspects of accelerated nuclear polyploidization and tumour formation in dieldrin treated CF-1 mouse liver

Nuclear polyploidization in the livers of CF-1 mice, exposed to dieldrin (0, 1, 5 and 10 ppm in the diet), was studied up to the median time of liver tumour development (ranging from 15 to 27 months) in the respective treatment groups. In untreated controls nuclear polyploidization is characterized by a linear increase of octaploid nuclei with age. Approximately 4 months before tumour development a reduction in the tetraploid to diploid ratio is observed. Dieldrin treatment was found to enhance nuclear polyploidization in the initial phases of treatment, as expressed by a dose-dependent increase in octaploid nuclei. In 'steady-state' situations all age dependent changes in the level of polyploidization found in controls were also found in dieldrin treated mice. However, these changes occurred at an increasingly earlier age with higher dieldrin treatment levels. The decrease in the tetraploid:diploid ratio always takes place a few months before tumour development. This change in the ploidy level may thus be related to the subsequent liver tumour formation. The liver tumours themselves appear to originate from a diploid stem line, and were found to increase their degree of polyploidization during growth, eventually developing aneuploid nuclei. A comparison of nuclear polyploidization and liver tumour formation in CF-1 mouse liver for the given dietary dieldrin concentrations showed that liver tumour formation was associated with a constant level of polyploidization. Since polyploidization is an age-dependent process, these findings suggest that liver tumour formation is imminent at a constant biological age and that dieldrin may advance the biological age of CF-1 mouse liver.     

光衍射现象对细胞核DNA含量检测的影响

利用图像分析仪测量小鼠肝细胞涂片内单个肝细胞核的DNA含量,探讨图像分析仪在测量显微图像的光度时光衍射现象所导致的测量误差.本文选取10只成年健康雄性小鼠的肝组织涂片,Feulgen染色,TIGER细胞图像分析仪测量单个肝细胞核的DNA含量并分析其DNA含量倍体;结果显示,(1)涂片内肝细胞核分布均匀,轮廓清晰,呈紫红色;(2)不同小鼠同一DNA含量倍体的肝细胞核的DNA含量大致相同;(3)二、四、八倍体肝细胞核的DNA含量比值均大于/[Dept.1]等于2或4,二、四、八倍体肝细胞单个核DNA含量的CV值均小于10%;(4)同一小鼠不同DNA含量倍体肝细胞核的平均光密度值差异较小.结论光衍射现象可导致DNA含量的测量结果偏低,其偏低的程度随待测细胞核的面积增加而减小.     

组织原位测算单个肝细胞核的DNA总量

目的再次探讨利用图像分析系统在组织切片原位测算以单个完整细胞（核）体积为单位的化学物质总量方法的可靠性。方法选取10只成年健康雄性昆明小鼠,每只小鼠按常规制片方法制作4μm和11μm两种厚度的肝组织切片各一张,改良Feulgen染色,应用细胞图像分析仪在组织原位测量和计算以单个完整二倍体、四倍体和八倍体肝细胞核体积为单位的DNA总量。结果组织原位测算的以单个完整二倍体、四倍体、八倍体肝细胞核体积为单位的DNA总量间的比值基本上呈2或4的倍数关系。结论应用细胞图像分析仪在组织切片原位通过合适的抽样和测量计算,可较准确地获得以单个完整细胞（核）体积为单位的化学物质总量。     

两种染色方法在细胞核DNA含量检测中的应用及比较

目的 探讨改良、快速两种Feulgen染色方法达到最佳染色效果的水解时间段，为科研和临床的应用提供方法学指导。方法 选取5只成年健康雄性SD大鼠的肝组织，制成肝细胞涂片，分别在室温和60℃温度下水解不同时间，应用改良和快速两种方法染色，TIGER图像分析仪检测和分析单个肝细胞核的DNA含量。结果 （1）不同大鼠肝细胞涂片在同一水解温度、时间作用下，相同DNA倍体含量肝细胞的DNA含量大致相同，CV值均小于10％；（2）二、四、八倍体肝细胞核的DNA含量比值均接近2或4；（3）同一大鼠相同水解温度不同水解时间，同一倍体的肝细胞核DNA含量存在差异：60℃水解温度下，IOD（5-7min）〉IOD（9-15min）〉IOD（1min,20min），室温水解温度下，IOD（50min）〉IOD（20-30min,70-90min）〉IOD（5-1min,100min）。结论 HCL水解肝细胞涂片时间过长或过短均不能理想的染色，快速法和改良法Feulgen染色达较佳染色效果的时间段分别为：快速法5—7min，改良法20-90min。     

Irreversible depression in the ratio of tetraploid:diploid liver nuclei in rats treated with 3'-methyl-4-diraethylaminoazobenzene (3'M)

A reduction in the ratio of tetraploid to diploid liver nucleihas been investigated as an early indicator of hepatocarcinogenesisin the rat using the liver carcinogen 3'-methyl-4-dimethylaminoazobenzene(3'M). In a dose ranging study 3'M was administered by gavageto rats at 5, 12.5 and 25 mg/kg for up to 10 weeks and the followingparameters studied: bodyweight gain, dye binding to hepaticprotein, nuclear ploidy in liver and histopathology. Significantreduction in bodyweight occurred only with 25 mg/kg; dye bindingto protein occurred in a dose-related manner; depression ofthe percentage of tetraploid nuclei compared with diploids wasdose-related and effects were detected even at the lowest dose.These observations were consistent with those from previousstudies by other investigators. In a separate experiment 3'Mwas administered at the maximum tolerated dose (MID) of 25 mg/kgfor 3 weeks, during which time there was a significant reductionin bodyweight gain and a reduction in the ratio of tetraploid:diploidliver nuclei. After cessation of dosing the rate of bodyweightgain returned to normal but there was no corresponding recoveryof the ratio of tetraploid :diploid nuclei in the liver. A long-termcontinuous gavage study at 2.5 mg/kg revealed a time dependentreduction in the ratio of tetraploid:diploid liver hepatocytenuclei and histopathological changes that included hepatocarcinomawere also observed. There was no correlation between the severityof pathological changes and the change in nuclear ploidy ratioin this experiment and it is concluded that the changes in ploidyratio are related to the carcinogenic effect of 3'M and areindependent of its gross toxicity.     

染色质浓缩对细胞核DNA含量检测的影响

目的利用三种不同方法制备小鼠肝细胞涂片，探讨染色质浓缩对图像分析仪测量DNA含量的影响。方法本文选取10只成年健康雄性小鼠，采用传统涂片、液基制片法和甲醛固定后液基制片法制备小鼠肝细胞涂片。Feulgen染色。TIGER细胞图像分析仪分别测量三种涂片内肝细胞核的积分光密度、平均光密度和面积。结果三种涂片内肝细胞核分布均匀，轮廓清晰，呈紫红色。与传统涂片法相比。液基法内肝细胞核面积明显减小。类色质高度浓缩；相同倍体的肝细胞核在传统涂片中面积最大，平均光密度最低，各倍体间的比值最接近2和4，积分光密度CV值最低（〈3．5）。固定法和液基法平均光密度明显升高，各倍体间比值明显偏离2和4。积分光密度CV值〉6。结论不同制片方法可导致同一类型、处于相同功能状态的细胞核染色质浓缩程度产生明显差异，染色质浓缩可导致平均光密度值升高，积分光密度值降低，测量结果的精确性和准确性降低。     

Perturbation of hepatocyte nuclear populations induced by iron and polychlorinated biphenyls in C57BL/10ScSn mice during carcinogenesis

The induction of hepatocarcinogenesis by polychlorinated biphenyls(PCBs) in C57BL/10ScSn mice is markedly potentiated by iron.To investigate the effects of iron and PCBs on nuclear populations,C57BL/10ScSn mice received a single dose of iron—dextran(600 mg Fe/kg) and were fed a diet containing 0.01% of the PCBsmixture Aroclor 1254 for up to 6 months. DNA content of isolatednuclei and hepatocytes was estimated by flow cytometry. Cellsuspensions and nuclei isolated from Aroclor treated mice after6 months contained increased diploid (2N) populations comparedto controls. In contrast, iron treatment of mice markedly enhancedfractions of octoploid (8N) nuclei by 2 weeks and this effectpersisted over the 6 month period. When Aroclor 1254 and ironwere administered together there was a synergistic increasein the mononucleated diploid fraction which was significantat 2 weeks and highly significant at 6 months. This became thepredominant nuclear effect. At six months, Aroclor 1254 andiron, both alone and in combination, also increased the rateof DNA synthesis in hepatocytes as measured by bromodeoxyuridine(BrdU) incorporation. The chronic polyploidizing effect of ironoverload alone was investigated further and shown to be proportionalto the dose and was detectable as early as 2 days after 600mg Fe/kg and 1 week after 150 mg Fe/kg. Polyploidization ofnuclei was inhibited by the oral iron chelator CP94. Iron alsoinduced a prolonged reduction in the incidence of binucleatedcells. Histologically, nuclear enlargement due to iron was confinedto the midzonal region of the liver lobule, whereas iron depositionwas greatest in the periportal region. Iron (600 mg/kg) alsocaused increased nuclear polyploid states in hepatocytes ofadult rats and gerbils. Similarly, weanling mice with a dominantlydiploid cell population, when treated with iron (300 mg/kg),exhibited a significant shift to a tetraploid (4N) populationand a marked increase in proliferation as measured by BrdU incorporationand proliferative cell nuclear antigen (PCNA) detection. Theseresults indicate that Aroclor 1254 and iron induce changes inthe mouse hepatocyte population that involve 2N and 8N nucleirespectively. The combination treatment leads to the emergenceand proliferation of a mononucleated, diploid population asobserved frequently in chemical hepatocarcinogenesis. The reasonfor the chronic polyploidizing effect of iron is unknown, butmay imply both increased DNA synthesis and impairment of nucleardivision with implications in human conditions of iron overload.     

Distinct antigen expression related to DNA ploidy in a case of biphenotypic leukemia

Three cell populations with different DNA indices were demonstrated in a case of biphenotypic terminal transferase (TdT)/myeloid-positive acute leukemia which had developed from a pre-leukemic diploid population also expressing biphenotypic features. At the time of development of acute leukemia, flow-cytometric analysis revealed expression of TdT by the diploid, the tetraploid, and the near-triploid cells, but only the tetraploid cells carried the myeloid-specific M2 antigen. Cytogenetic analysis showed four stemlines, diploid, tetraploid, tetraploid with del(2), and near-triploid with del(2) and variable chromosome losses. In vitro treatment with retinoic acid induced the expression of the M2 antigen by the diploid cells as well. This in vitro result is consistent with a myeloid differentiation commitment of the pluripotent leukemic stem cell.     

Changes in ploidy distributions in human liver carcinogenesis

Cellular and nuclear DNA content was measured by flow cytometry and the fraction of binucleated cells by fluorescence microscopy in normal adult human livers, hepatocellular carcinomas, cirrhotic livers surrounding tumors, and in some benign liver conditions. In five normal livers about one-half of the hepatocytes were polyploid; the majority of these were binucleated tetraploids containing two diploid nuclei. Thus, polyploidization in human liver does not progress as far as, for example, in the rat, where 80%-90% of adult hepatocytes are polyploid, mostly with tetraploid or octoploid nuclei. In five human euploid hepatocellular carcinomas and one investigated case of focal nodular hyperplasia, the percentage of polyploid cells was significantly reduced. Four other carcinomas exhibited a prominent aneuploid (hypotetraploid) peak in addition to the diploid peak. An abnormally low fraction of binucleated cells was also indicated in these tumors. Liver tissue surrounding the tumors had a ploidy distribution similar to that of normal liver. The results suggest that, like in several models of experimental hepatocarcinogenesis, human hepatocellular tumor growth is associated with a decreased polyploidization tendency and a corresponding increase in diploid, divisional growth, which may give the tumors a growth advantage relative to the surrounding liver.     

Alterations of DNA content in human endometrial stromal cells transfected with a temperature-sensitive SV40: tetraploidization and physiological consequences.

The normal genomic stability of human cells is reversed during neoplastic transformation. The SV40 large T antigen alters the DNA content in human endometrial stromal cells in a manner that relates to neoplastic progression. Human endometrial stromal cells were transfected with a plasmid containing the A209 temperature-sensitive mutant of SV40 (tsSV40), which is also defective in the viral origin of replication. Ninety-seven clonal transfectants from seven different primary cell strains were isolated. Initial analysis revealed that 20% of the clonal populations (19/97) had an apparent diploid DNA content, 35% (34/97) had an apparent tetraploid DNA content, and the remainder were mixed populations of diploid and tetraploid cells. No aneuploid populations were observed. Diploid tsSV40 transformed cells always give rise to a population of cells with a tetraploid DNA content when continuously cultured at the permissive temperature. The doubling of DNA content can be vastly accelerated by the sudden reintroduction of large T antigen activity following a shift from non-permissive to permissive temperature. Tetraploid tsSV40 transfected cells have a lower capacity for anchorage-independent growth and earlier entry into 'crisis' than diploid cells. These results indicate that during the pre-crisis, extended lifespan phase of growth, the SV40 large T antigen causes a doubling of DNA content. This apparent doubling of DNA content does not confer growth advantage during the extended lifespan that precedes 'crisis'.     

Effect of tamoxifen upon cell DNA analysis by flow cytometry in primary carcinoma of the breast

The effect of tamoxifen upon cellular DNA ploidy in carcinoma of the breast was assessed by flow cytometry (FCM), in a prospective group of 77 patients with primary operable disease. Each had a needle biopsy at the outpatient visit for diagnosis and FCM analysis, and definitive surgery was performed a median of 8 days later. Forty received tamoxifen during this period - 40 mg qds loading dose for 24 h, followed by 20 mg daily until the day of operation: 37 patients received no therapy. The DNA histogram from the needle biopsy was compared with that obtained from the resected tumour for each individual. There was little change between the pair of histograms from tumours from the untreated patients. In those who had received tamoxifen the most consistent effect was a marked reduction in the magnitude of the 'tetraploid' peak in tetraploid or near-tetraploid tumours with DNA indices 1.8-2.0. There was little change in diploid or 'other DNA-aneuploid' tumours. In tetraploid tumours (DNA index of 2.0) the percentage of nuclei in the diploid S phase was significantly related to the percentage of nuclei in the diploid G2 + M/tetraploid G1 peak (P less than 0.003, unpaired t test). These data suggest that an effect of tamoxifen can be demonstrated by FCM upon tumours exhibiting a tetraploid or near-tetraploid DNA content. It is possible that tetraploid or near-tetraploid human mammary tumours may be a distinct group of endocrine responsive tumours within the overall group of aneuploid tumours, and that the majority are probably derived from the diploid population rather than being a true aneuploid population.     

Ultrastructural alterations and modifications of nuclear RNA of rat liver by the combined action of thioacetamide and aflatoxin.

When aflatoxin is administered to thioacetamide-treated rats, the synthesis of nuclear RNA not only stops but the RNA that had accumulated in the nuclei by thioacetamide action disappears, probably by degradation "in situ" as none appears in the cytoplasm. Morphologically, the lesions provoked by aflatoxin add to those caused by thioacetamide. In the gigantic nucleoli that develop upon exposure to thioacetamide, aflatoxin provokes atypical segregations that result in the formation of larger and larger spaces in the nucleoli.     

The level of aryl hydrocarbon (Ah) receptor and of 4S polycyclic aromatic hydrocarbon (PAH) binding protein in diploid and polyploid hepatocytes of 2-acetylaminofluorene-treated rats.

Sequential treatment of partially hepatectomized male Wistar rats with diethylnitrosamine (DEN) and 2-acetylaminofluorene (AAF) induces the emergence of diploid hepatocyte populations. These carcinogen-induced hepatocytes are thought to include the precursor cells of liver carcinomas that arise later in this treatment protocol. The growth of the diploid hepatocytes is promoted by AAF and it has been suggested that the action of the arylamine may be receptor-mediated. AAF has been shown to bind specifically to the aryl hydrocarbon (Ah) receptor and the so-called 4S polycyclic aromatic hydrocarbon (PAH) binding protein. The present study addresses the question of whether the concentrations of the two binding proteins differ in diploid and polyploid hepatocytes from DEN/AAF-treated rats. Hepatocytes from carcinogen-treated rats were isolated and diploid, and tetraploid hepatocytes separated by means of centrifugal elutriation. Whereas Ah receptor concentrations in diploid hepatocytes were insignificantly lower (21.8 +/- 5.9 versus 29.2 +/- 6.6 fmol/mg cytosolic protein; n = 4; P = 0.1), levels of the 4S PAH binding protein in diploid hepatocytes were twice as high as in tetraploid hepatocytes (252.3 +/- 93.6 versus 124.0 +/- 18.5 fmol/mg cytosolic protein; n = 4; P = 0.04). We conclude from our results that the differences in growth control in polyploid and carcinogen-induced diploid hepatocytes are not associated with changes in the levels of the Ah receptor. The role of the 4S PAH binding protein in the process of hepatocarcinogenesis remains to be established.     

Nuclear DNA in intestinal carcinoid tumors. A study before and after cytotoxin (streptozotocin and 5-fluorouracil) treatment

Imprint cytology specimens of metastases of intestinal carcinoids obtained by percutaneous biopsy were analysed cytofluorometrically with regard to nuclear DNA records. All untreated tumors (nine cases) exhibited diploid DNA values with a relatively low proliferative activity (less than 2% nuclei in S-phase region). The mean number of tetraploid cells was 5%. Cytofluorometry also was performed on five tumor metastases treated with the cytotoxin streptozotocin and 5-fluorouracil. After treatment, an increase in the number of tetraploid cells (mean value, 30%) was noted, indicating that the cytotoxin treatment (possibly streptozotocin) on the tumor cells in vivo blocked progression from G2 to M phase. The current cytofluorometric analyses show that diploid nuclear DNA records and a low proliferative activity is a characteristic of malignant carcinoid tumors of the intestine. Due to regular DNA histograms in the carcinoid tumors, it is suggested that reliable studies are permitted of the effect of cytotoxins on the different phases of the cell cycle in vivo.     

Pleiotropic drug resistance in hepatocytes induced by carcinogens administered to rats

The effect of hepatocarcinogen administration in vivo on the induction of pleiotropic drug resistance was studied in primary monolayer cultures of adult rat hepatocytes using a cytotoxicity assay in vitro. Dietary 2-acetylaminofluorene, 3'-methyl-4-dimethylaminoazobenzene, aflatoxin B1, ethionine, and diethylnitrosamine rapidly induced resistance to doses of Adriamycin, methotrexate, cycloheximide, and aflatoxin B1 which were cytocidal to normal hepatocytes from untreated rats. Up to 95% of some hepatocyte preparations became drug resistant before any new hepatocyte phenotypes could proliferate. Drug resistance was measured at 24 h after initiation of 2-acetylaminofluorene feeding and remained stable throughout the 16 wk of carcinogen exposure. When limited carcinogen exposure was followed by a return to a basal non-carcinogen-containing diet for many months, the hepatocytes in the resultant hepatocellular carcinomas also displayed pleiotropic drug resistance, and the cells of the peritumorous liver did so to a lesser extent. Drug resistance was not induced by chronic administration of the tumor promoters phenobarbital, choline-deficient diet, phorbol, nor with 2,3,7,8-tetrachlorodibenzo-p-dioxin, but was induced to a variable extent by three hepatotoxins (ethanol, methotrexate, carbon tetrachloride). Whereas the early appearing drug resistance appears to be an adaptation of the liver to the presence of a toxic carcinogen, the late resistance which does not disappear after withdrawal of the inducing carcinogen may be a constitutive characteristic of chemically induced hepatocellular carcinomas.     

Notch Activation Is Associated with Tetraploidy and Enhanced Chromosomal Instability in Meningiomas

The Notch signaling cascade is deregulated in diverse cancer types. Specific Notch function in cancer is dependent on the cellular context, the particular homologs expressed, and cross-talk with other signaling pathways. We have previously shown that components of the Notch signaling pathway are deregulated in meningiomas. However, the functional consequence of abnormal Notch signaling to meningiomas is unknown. Here, we report that exogenous expression of the Notch pathway effector, HES1, is associated with tetraploid cells in meningioma cell lines. Activated Notch1 and Notch2 receptors induced endogenous HES1 expression and were associated with tetraploidy in meningiomas. Tetraploid meningioma cells exhibited nuclear features of chromosomal instability and increased frequency of nuclear atypia, such as multipolar mitotic spindles and accumulation of cells with large nuclei. FACS-sorted tetraploid cells are viable but have higher rates of spontaneous apoptosis when compared with diploid cells. We have used spectral karyotyping to show that, in contrast to diploid cells, tetraploid cells develop a higher number of both numerical and structural chromosomal abnormalities. Our findings identify a novel function for the Notch signaling pathway in generating tetraploidy and contributing to chromosomal instability. We speculate that abnormal Notch signaling pathway is an initiating genetic mechanism for meningioma and potentially promotes tumor development.     

妇科恶性肿瘤细胞核DNA含量测定及其临床意义

This paper analyzes the nuclear DNA content in 80 gynecologic tumors by microspectrophotometry and correlates the results of ovarian malignant tumors with the clinico-pathologic features of the tumor. The DNA content and the percentage of nuclei with over octaploid were significantly higher in gynecologic malignant tumors and ovarian germ cell tumors than in gynecologic benign tumors and ovarian epidermic tumors. The percentage of nuclei with over octaploid was significantly higher in advanced than in early tumors. It seems that DNA content assay may be helpful in the pathological diagnosis of gynecologic tumors.     

Nuclear DNA Modal Patterns as Diagnostic Criteria in Human Lung Cancer

In a prospective study of human lung cancer, the nuclear DNAcontent of tumor populations on 76 touch smears prepared fromprimary and metastatic lesions of 70 patients was determinedcytofluorometrically. A modal DNA value was calculated fromthe distribution of the logarithmically transformed DNA contentfor each tumor. By the analysis of levels of modal DNA values,the nuclear DNA distribution histograms in lung tumors couldbe divided into the following three major types: diploid-tetraploidtype (Type I), triploid type (Type II), and mixed type (TypeIII). Modal DNA values in Type I histograms were diploid (2c),tetraploid (4c), and octaploid (8c), whereas the modal DNA valuesin Type II histograms were near-triploid (3c), near-hexaploid(6c), and decaploid (10c). Type III histograms were characterizedby the simultaneous existence of multiple modal DNA values atdiploidy or tetraploidy and near-triploidy or near-hexaploidy.Each of the three major types was further divided into six,four, and four kinds of DNA histogram subtypes, respectively,according to modal DNA values. The most frequent DNA distributionpattern was the subtype A of the triploid type (Type IIA). Fourof 14 DNA histogram subtypes were all of polyploid distributionpatterns in which the relative DNA values in the individualmodes differ from each other by a factor of two. This suggeststhat endoamitosis accounts for such polyploidy. In one of fivepatients whose primary and metastatic lesions were examinedsimultaneously, the DNA distribution pattern changed from TypeIIA in the primary tumor to Type IIB in its metastasis. Thediagnostic and prognostic implications of the 14 DNA histogramsubtypes analyzed are discussed.