Chromosomal evolution in the Ehrlich-Lettré complex of hyperdiploid mouse ascites tumors: results from seven laboratory strains

Reversible G2 block in the cell cycle of Ehrlich ascites carcinoma cells

Using flow cytometry we found that proliferation of Ehrlich ascites carcinoma (EAC) cells has been reversibly arrested in the second half of the G2 period at the plateau phase of tumor growth in vivo. The ratio of G2/G1 cells increased from 0.3 at 6 days post tumor inoculation to 2.5 at 16 days when up to 25-35% of EAC cells are in G2. It was shown that when ascites fluid removal was followed by transferral in culture, G2-blocked cells synchronously entered the G1 phase via mitosis. In the presence of ascites fluid in the culture medium, EAC cells progressed through G1 and S phases but accumulated in G2. Fetal bovine serum, beta-mercaptoethanol, and caffeine failed to release cells from the G2 block when added to ascites fluid in culture. It is concluded that neither nutrient depletion nor a lack of growth factors is responsible for the G2 arrest of EAC cells. We suggest that ascites fluid contains a factor(s) which potently interrupts the G2 phase of the cell cycle.

Chromosomal changes in cell lines from mouse tumors induced by nickel sulfide and methylcholanthrene

Rhabdomyosarcomas were induced in mice by intramuscular injections of crystalline nickel sulfide and 3-methylcholanthrene. At early passage, karyotypes were performed by G-banding for four nickel sulfide cell lines and for three 3-methylcholanthrene cell lines. Six cell lines were near-diploid and one nickel sulfide line was near-tetraploid. Three of the nickel sulfide cell lines were characterized by a rearranged marker chromosome which was present in a majority of the cells of each line. The rearrangements leading to the formation of marker chromosomes were different in each nickel sulfide cell line but involved chromosome 4 in two of the nickel sulfide cell lines. Extra copies of chromosome 15 were present in two nickel sulfide cell lines. Possible rearrangement and/or gene activation was examined for the c-mos oncogene on chromosome 4 and the c-myc oncogene on chromosome 15, but no alteration or activation was observed. None of the 3-methylcholanthrene cell lines contained rearranged marker chromosomes; however, one MCA cell line did contain large numbers of double minutes. In all cell lines, minichromosomes (small atypical acrocentric chromosomes) were observed that contained distinct centromeric regions but no other G-positive bands.

DNA cytometry of osteosarcoma

The relationship between cytochemical features and histomorphology in osteosarcoma, and the clinical significance of DNA content were investigated by microspectrophotometry (MSP) of tissue sections and flow cytophotometry (FCM) of cell suspensions. MSP of tissue sections entails the methodological error of determining the DNA content of sectioned cell nuclei. By analyzing 184 normal mesenchymal cell populations, an upper limit of diploidy (normal DNA content) was deduced. Applying this upper limit for 42 sarcomas, 6 were diploid and 36 hyperploid. Comparative analysis of the same lesions by MSP of imprint preparations and by FCM disclosed complete agreement in ploidy classification (diploid versus hyperploid). Retrospective MSP analysis of bone tumors is often impeded by previous demineralization in acid, which destroys DNA. EDTA as an alternative was found to slightly reduce Feulgen DNA stainability of osteosarcomas, but did not affect tumor ploidy determination. Hence, EDTA offers a means of retaining DNA stainability of bone tumors requiring demineralization. MSP analysis of different histologic areas, and comparative FCM analysis of biopsy and surgical specimens, dislosed that individual osteosarcomas are cytochemically uniform despite morphologic heterogeneity. Hence, a single tumor sample for DNA analysis can be relied upon as representative for the tumor as a whole. In a consecutive series of 83 osteosarcoma patients treated by surgery and adjuvant Interferon, the 7-year survival rate was 0.44. MSP DNA analysis gave no significant prognostic information. Multivariate analysis identified 3 risk factors for tumor related death, i.e., male sex, proximal tumor location, and histologic grade IV. In a prognostication model, the 7-year survival rates, for patients with 0, 1, 2, or 3 risk factors, were 0.80, 0.59, 0.42, and 0.13, respectively. Hence, it is possible to identify subgroups of high grade osteosarcoma patients with different prognosis. In a study of 166 primary bone tumors, the applicability of DNA analysis for differential diagnostic purposes was investigated. The series included high grade osteosarcomas, parosteal osteosarcomas and benign bone tumors, which may be mixed up histologically with osteosarcoma. Out of 166 tumors, 149 (90%) were histologically noncontroversial, whereas 17 (10%) posed diagnostic difficulties. In the diagnostically noncontroversial group, all benign tumors and parosteal osteosarcomas were diploid, whereas 97 of 102 osteosarcomas were hyperploid. Hence, hyperploidy seems to be a characteristic feature of high grade osteosarcoma.(ABSTRACT TRUNCATED AT 400 WORDS)

WiDr is a derivative of another colon adenocarcinoma cell line, HT-29

This paper documents chromosomal and isozymic evidence indicating that WiDr is a derivative of another colon adenocarcinoma cell line, HT-29, which was established in 1964. The phenotypes for seven isozymes studied were identical for all HT-29 and WiDr cell lines. The karyotypes were similar between four HT-29 cultures separated by more than 100 passages and two WiDr cultures that were studied independently in 1979 and 1985. The isozymic and karyotypic data are consistent with that described for the cell line WiDr, originally reported in 1979. Detailed karyotypic comparisons further show that cultures of WiDr possess all nine chromosomal markers found in the initial HT-29 (passage 19) cultures. However, both the higher passaged HT-29 and WiDr differ from the initial HT-29 (passage 19) because it has an additional five to eight constitutive marker chromosomes. An increase or decrease of one copy in several normal chromosomes is also noticed with more normal chromosome gains than losses. The study provides another example demonstrating the remarkable karyotypic stability within a heteroploid cell line with continued passage. It also reemphasizes the critical need for detailed karyotypic and isoenzymic studies on all cell lines in common use.

Cytogenetics of somatic cell hybrids. II. Modal karyotypes and mosaicism in mouse mutant cell lines: LM(tk-), A9, and Rag

Modal karyotypes of mouse mutant cell lines, LM(tk-), A9, and Rag, which are frequently used as a donor line for somatic cell hybridization, are described and compared with karyotypes previously reported by other laboratories. Results are summarized as follows. Many cells (18%-38%) in each line had the same chromosome composition as the modal karyotype. Chromosome differences from the modal karyotype in some cells mainly involved one or a few chromosomes only. These differences are mostly caused by structural changes from well documented mechanisms or simple numerical changes including artifacts arising from the rupture of cells. Karyotypes of coexisting subpopulations within the same cell line can be clearly identified. Assessment of karyologic properties of a heteroploid cell population may vary considerably depending on whether it is estimated on a subpopulation or the total population as a unit. Modal karyotypes of these cell lines contained most marker chromosomes of, and a similar chromosome composition to those previously reported by other laboratories. These cell lines exhibit karyotypic constancy; thus, we believe that chromosome changes associated with clonal growth of somatic cell hybrids can be identified without ambiguity.

Clinical DNA flow cytometry

Modal DNA values of tumours from various sites may exhibit (1) a diploid-near diploid distribution, (2) an exponential distribution in the tetraploid to triploid range, or (3) a log-normal distribution in the triploid to tetraploid range. Examples of these various types of distribution are non-Hodgkin's lymphoma (1), aneuploid prostate carcinoma (2), aneuploid colon, breast, cervix and testicular carcinomas (3). These differences indicate dissimilarities in tumour development. In aneuploid tumours from the same site both tetraploid exponential and triploid-tetraploid log-normal distributions may occur. In bladder carcinoma these are related to grade. Modal DNA values in tumours are 10% higher than would be expected from modal chromosome numbers. This difference seems not to be due to a relative increase in large-sized chromosomes or due to technical shortcomings. Chromosome studies also show the possibility of the existence of near diploid malignant cells in grossly aneuploid tumours. Modal DNA values are connected with functional tumour properties by the proportion of S-phase cells. The significance of the latter is exemplified by follow-up of patients with bladder and cervix carcinoma.

Increased rate of tumor cell death caused by polyamine synthesis inhibitors

This investigation was designed to determine whether cell death plays a role in the antiproliferative action exerted by polyamine synthesis inhibitors. To estimate the rate of tumor cell death, we measured the loss of 125I from mice harboring Ehrlich ascites tumor cells in which DNA was labeled with 5-125I-iodo-2'-deoxyuridine. DL-alpha-difluoromethylornithine (0.85 mumoles/g body weight/6 h), and enzyme-activated irreversible inhibitor of ornithine decarboxylase, and methylglyoxal-bis(guanylhydrazone) (45 nmoles/g body weight/6 h), an inhibitor of S-adenosylmethionine decarboxylase, were both found to increase the rate of 125I excretion. Our data suggest that these polyamine synthesis inhibitors provoke an increase in the rate of tumor cell death beyond that normally occurring during growth, methylglyoxal-bis(guanylhydrazone) being considerably more potent than DL-alpha-difluoromethylornithine. These in vivo data were corroborated by a study where the host-mediated responses did not have to be considered. Thus, Ehrlich ascites tumor cells were adapted for suspension growth in culture and treated with methylglyoxal-bis(guanylhydrazone) or DL-alpha-difluoromethylornithine. The growth kinetics and the colony forming efficiency of the drug-treated cells clearly show that polyamine synthesis inhibitors not only slow the growth rate but also cause an increase in tumor cell death.

Relevance of trisomy 15 and other chromosome abnormalities in spontaneous AKR leukemia of mice with and without Robertsonian rearrangement

The types and frequencies of chromosomal abnormalities in spontaneous AKR leukemia are presented: 45% to 58% of leukemic animals exhibit chromosome abnormalities; trisomy of chromosome 15 (Ts 15) occurs as the predominant chromosome abnormality not only in AKR/J but also in two AKR sublines characterized by the presence of two or one Robertsonian biarmed translocation Rb (6.15) of the chromosomes 6 and 15. Most often a triplication of the whole Rb (6.15) is found in Rb (6.15) homozygotes corresponding to combined Ts 6 + Ts 15. In the Rb (6.15) heterozygotes both trisomy of the biarmed (6.15) and of the acrocentric 15 is observed. Centric fission of the (6.15) chromosome is also possible in Rb (6.15) homozygotes resulting in Ts 15 without simultaneous Ts 6. Trisomies of other chromosomes are found either in addition to Ts 15 or as the only abnormality. If the data of Dofuku et al. (1975) are considered, abnormal karyotypes in AKR leukemia show Ts 15 in 90%, Ts 12 and Ts 17 in 18%-20%, and Ts 3, Ts 10 and Ts 14 in 8%-10% of the cases.

Cytocidal effect of alpha-methylornithine, a competitive inhibitor of ornithine decarboxylase, on ehrlich ascites tumor cells in vivo

The antiproliferative effect of alpha-methylornithine, an inhibitor of the initial and rate-limiting step in polyamine biosynthesis, was studied on Ehrlich ascites tumor cells grown in vivo. To assess drug-induced cell lethality, the loss of 125I from mice harboring 5-[125I] iodo-2'-deoxyuridine-labeled mouse tumor cells was determined during the course of alpha-methylornithine treatment. Mice that received the drug showed a significant increase in their rate of 125I excretion as compared to controls. This suggests that alpha-methylornithine kills an additional fraction of tumor cells beyond the fraction normally dying.

Photographic equidensitometry of metaphase chromosomes

Photographic equidensitometry, which is a procedure to obtain specific lines or symbols for points of equal optical density, has been utilized in the study of chromosome images. Equidensitometric techniques, using a special contour film, permitted three approaches, namely, production of line equidensities (in the form of families, sequences and contour maps), color equidensifies (color conversion of line sequences), and screen equidensities (substituting characteristic symbols for densities). All these techniques have proved very useful to analyze images of metaphase chromosomes and occurrence of spontaneous banding patterns, by showing the precise distribution and relative values of the grey gradient. This report demonstrates the potential of photograhic equidensitometrical procedures for chromosome studies, which obviates the need to purchase elaborate equipment.

Homogeneously staining regions on marker chromosomes in malignancy

Direct chromosome analysis with G-banding revealed homogeneously staining regions (HSR) in five of 16 human solid malignant tumours of different histological types. The HSR's were localized either terminally or interstitially on the marker chromosomes. The great stability of the HSR-carrying markers in the tumour cells suggests an interrelationship of malignant cell proliferation with the HSR. In a single case the HSR showed a moderate staining intensity for C-heterochromatin.

Marked increase in ribosomal RNA gene multiplicity in a rat hepatoma cell line

An H4-IIE-C3 hepatoma cell line derived from an ACI rat has been shown to have differentially stained regions attached to the short arms of chromosomes 3, 11 and 13 and the long arm of an unidentified small chromosome. There is cell to cell variability in the number and size of the differentially stained regions, which contain, on the average, about 5% of the total DNA. A series of secondary constrictions occur at intervals along the length of each differentially stained region. These stain with silver by the Ag-AS method, indicating that the differentially stained regions contain sites of active 45S ribosomal precursor RNA transcription. In situ hybridization to metaphase chromosomes shows that the hepatoma cells have a 10 fold increase in DNA coding for 18S and 28S ribosomal RNA, 90% of it located in the differentially stained regions, and no change in the number of genes coding for 5S RNA. These results have been confirmed by filter disc hybridization.