Trisomy of chromosome No 13 in spontaneous mammary tumors of GR, C3H, and noninbred Swiss mice.

Karyotype analyses were conducted on spontaneous mammary tumors of 11 GR, 2 C3H, and 2 noninbred Swiss mice with the use of trypsin-Giemsa banding procedures. All tumors manifested trisomy of chromosome No 13 in most cells, and all except 1 tumor had cells with a model chromosome number of 40.

Establishment and characterization of four human monocytoid leukemia cell lines (JOSK-I, -S, -M and -K) with capabilities of monocyte-macrophage lineage differentiation and constitutive production of interleukin 1.

Four monocytoid cell lines, JOSK-I, -S, -M, and -K, were newly established successfully from peripheral blood of two cases of acute monocytic leukemia and one case each of acute myelomonocytic leukemia and chronic myelogenous leukemia in myelomonocytic blast crisis. In order to establish permanent cell lines, cultures of leukemic blasts were initiated in 96-well microtiter plates. Each cell line grew in a suspension culture with a doubling time of 24-32 h and has been serially maintained for over 20 mo. Each line had immature monocytic properties as judged from the results of cytological, immunochemical, and functional analyses. The cells showed a positive reaction for alpha-naphthyl butyrate esterase which was completely inhibited by sodium fluoride and exhibited immature monocytic features on electron microscopic observation. They also had surface markers specific for the monocyte-macrophage lineage. Chromosome analyses showed that each line had a variety of marker chromosomes; furthermore, these established lines exhibited high potentialities involving morphological and functional differentiation into more mature monocytic cells when induced by several chemical inducers. We also found that two of the established cell lines produced much interleukin 1 activity without any stimuli. These new lines might be valuable for studying the regulation of monocyte-macrophage differentiation and host defense mechanisms.

Amplification of IMR-32 clones 8, G21, and N-myc in human neuroblastoma xenografts.

Amplification of clones 8, G21, and N-myc, which were derived from human neuroblastoma cell lines IMR-32 and NB-19, were studied in nine neuroblastoma xenografts. N-myc was amplified from 50- to 120-fold in eight of nine xenografts, clone 8 was amplified in five of the xenografts, and clone G21 was amplified in four of these five. Each of these clones was localized by in situ hybridization to homogeneously staining regions in metaphase spreads of xenograft chromosomes. In one xenograft a DNA rearrangement of clone 8 was observed, and only two of the sequences detected by G21 were amplified. Restriction enzyme mapping indicated that the rearrangement within clone 8 occurred at a position close to the rearrangement previously noted in neuroblastoma cell line NB-9.

Telomerase activity in normal human epithelial cells.

Telomerase activity is found in most cancer tissues and many immortalized cell lines as well as in germ line cells but it is generally undetected in normal human somatic tissues. There is weak telomerase activity in some cell types of hematopoietic lineage in which a stem cell-like subpopulation may exist. Likewise, physiologically regenerating somatic tissues and organs such as skin, small intestine, and most other epithelia of the human body are supposed to contain similar cell lineages to maintain their renewal throughout the life span of individuals. It is therefore of interest whether telomerase activity is present in physiologically regenerating epithelial cells. Telomerase activity was detected, though very weakly, in cultured normal epidermal keratinocytes and at higher levels in a subpopulation that adhere rapidly on collagen IV-coated culture dishes. No telomerase activity was detected in a subpopulation that was less adherent on the coated dishes. The rapidly adherent subpopulation of keratinocytes was enriched in small proliferating cells with macrocolony forming potential. It was also passaged through more generations in culture, and expressed integrin beta 1 at higher levels than the less adherent subpopulation. Telomerase activity was similarly found in ectocervical keratinocytes as well as in simple endocervical epithelial cells. These findings provide the evidence of a telomerase-positive population among physiologically regenerating normal human epithelial cells. The identity of the telomerase-positive cells remains to be defined.

Sequence homology of Chinese hamster metallothionein genes I and II to those of the mouse and rat, and their amplification in Cd-resistant cells.

The metallothionein (MT) I and II genes were isolated from Chinese hamster cells and sequenced. The MT-II gene is located about 6 kb upstream of the MT-I gene and their arrangement is similar to those of the mouse and rat MT genes. The sequence of the Chinese hamster MT-I gene is highly homologous to those of the mouse and rat, particularly in their promoter regions of MT-I. However, the promoter region of MT-II has less homology with those of the mouse and rat due t to insertions and deletions. The MT-I and MT-II genes were equally amplified 4-8-times in the Cd-resistant Chinese hamster cells, suggesting that both genes are included in the same amplification unit. Cytogenetic analysis of Cd-resistant cells by in situ hybridization showed that they are randomly integrated into multiple sites on the chromosomes.

A new human male diploid cell strain, TIG-7: its age-related changes and comparison with a matched female TIG-1 cell strain.

A new human diploid cell strain, TIG-7, which has the male karyotype, was established and characterized. Isozyme and histocompatibility typing of the cell strain was performed. The average in vitro life span of the cells is 73 population doublings. Changes in cell volume, doubling time, saturation density, the efficiency of cell attachment, plating efficiency, and relative DNA content were examined during in vitro cellular aging. Hydrocortisone slightly prolongs the life span of the cell strain when the hormone is administered to the cultures during middle passages. The age-related changes in the parameters of TIG-7 are not appreciably different from those of the previously established TIG-1 cell strain. These results show that this cell strain is useful for research on cellular aging; further profit is anticipated from research using a combination of these two sexually different cell strains.

Metabolic activation of benzo[a]pyrene, aflatoxin B1, and dimethylnitrosamine by a human hepatoma cell line.

The metabolism of chemical carcinogens by a human hepatoma cell line, huH-1, was studied. The huH-1 line has been derived from a hepatoma of a 57-year-old HBs-antigen carrier and cultivated for several years. The hepatoma cells metabolized about 90% of 5 microM benzo[a]pyrene into water-soluble products within 24 h. Aryl hydrocarbon hydroxylase activity in huH-1 cells was induced to 24 times higher than the basal level by treatment with 13 microM benz[a]anthracene for 24 h. Metabolic activation of benzo[a]pyrene, dimethylnitrosamine and aflatoxin B1 by huH-1 cells was observed by cell-mediated sister-chromatid exchange assay. Sister-chromatid exchanges in human diploid fibroblasts were observed in the cultures mixed with or without huH-1 cells. All 3 chemicals induced sister-chromatid exchanges in human fibroblasts far more efficiently in the cultures mixed with huH-1 cells than in those without huH-1 cells. Some characteristics of huH-1 cells as a human cell-mediated metabolic activation system for carcinogens are discussed.

Enhanced O6-methylguanine-DNA methyltransferase activity in transgenic mice containing an integrated E. coli ada repair gene.

The E. coli ada gene encodes O6-methylguanine DNA methyltransferase (O6MTase) which repairs the methylation of guanine at the O6 position in DNA. After recombination with a Chinese hamster metallothionein I gene promoter, the ada gene was microinjected into C3H/HeN mouse zygotes. Eventually, transgenic mice containing the ada fusion DNA were generated. The integrated ada DNA complex was transmitted to the progeny in a mode conforming to tandem integration at a single chromosome site, and homozygotes were also obtained from an inter-transgenic mouse cross. RNA transcripts of the chimeric ada gene were identified in the livers of these transgenic mice using dot and Northern blot analyses. O6MTase activity was increased in the liver of transgenic mice of line No. 708, and was more than 3 times the activity found in non-transgenic mice, especially in the transgenic homozygotes. The ada gene product was detected in the liver of a transgenic homozygote by immunoblot analysis. These transgenic mice have great potential for analysis of the role played by O6MTase in chemical carcinogenesis.

[Oncogene amplification in human neuroblastomas].

N-myc, which has partial sequence homology to the oncogene c-myc, was isolated from human neuroblastoma cell lines. We have surveyed amplification of N-myc, clone 8 and pG21 in human neuroblastoma cell lines, xenografts and in primary tumors and found that amplification frequently occurred in tumors classified as stage III and IV. In situ hybridization studies demonstrated that in neuroblastomas, chromosome aberrations such as HSR (homogeneously staining region) and DMs (double minutes) are cytological manifestations of the amplification of these clones. The N-myc-related gene seems to contribute to cell growth or differentiation of the nerve cell and its amplification with enhanced expression promotes the progression of the tumor with poor prognosis.

Asymmetric decondensation of the L cell heterochromatin by Hoechst 33258.

A benzimidazole derivative, Hoechst 33258 can induce decondensation of constitutive heterochromatin in the mouse derived L cell chromosomes when the compound is given in sufficiently high concentration (40 micrograms/ml) to the L cell culture. Hoechst 33258 at low concentration (1 micrograms/ml, 16 h) cannot produce this effect on L cell chromosomes. Bromodeoxyuridine (BUdR) incorporation for one cell cycle simultaneous with the Hoechst 33258 treatment at low concentration could decondense heterochromatin segments in metaphase chromosomes. The heterochromatin decondensation, however, was asymmetric; it was observed only on one chromatid and the other of a chromosome remained in condensed state. The observation of asymmetric decondensation of heterochromatin by Hoechst 33258 after BUdR incorporation for one cell cycle, the association of A-T rich satellite DNA to mouse heterochromatin, and available data on the specific binding of Hoechst 33258 to A-T base pairs of DNA and on the higher affinity of the compound to BUdR substituted DNA than to ordinary DNA implied that the binding of Hoechst 33258 molecules to A-T rich satellite DNA is the cause of heterochromatin decondensation.

Ploidy of human embryonic fibroblasts during in vitro aging.

The DNA content of single nuclei in confluent cultures of aging human embryonic fibroblasts, TIG-3, was measured by means of flow cytofluorometry. In the early and late stages of their in vitro lifespan, they had considerable numbers of 4C, 8C and 16C nuclei. In the other period more than 95% of their nuclei were 2C nuclei. These results were confirmed by karyotype analysis. Presumably, the polyploid cells in young cell populations are removed due to their low growth potential and those in old cell populations are accumulated as a result of cellular aging. The saturation density of TIG-3 cells increased at the beginning of their lifespan and thereafter decreased. The rise in their saturation density seems to reflect cell selection advantageous for young diploid cells.

Characteristics of resistance to adriamycin in human myelogenous leukemia K562 resistant to adriamycin and in isolated clones.

An adriamycin (ADM)-resistant variant (K562/ADM) of human myelogenous leukemia K562 was established. K562/ADM was stable for 2 months in medium without ADM, and was 130-fold more resistant to ADM as compared to the parent K562. Twenty clones were isolated from K562/ADM by the limiting dilution technique. Five clones with different ADM sensitivity were selected and characterized further. The extent of clonal resistance to ADM was parallel to the extent of resistance to vincristine (VCR), except for one clone, KA-15. The majority of clones, including K562/ADM, accumulated far smaller amounts of daunomycin (DAU) or VCR as compared to the parent K562. However, a highly resistant clone did not necessarily accumulate less DAU in the cells, indicating that the mechanism of ADM resistance cannot be explained solely by a defect of ADM accumulation. All clones rapidly transported DAU and VCR from the cells. K562/ADM expressed on the cell surface three distinct glycoproteins with molecular weights of 180,000, 83,000 and 65,000 daltons. No change was detected in the actin and tubulin contents of K562 and clones. K562/ADM and its clones expressed double minute chromosomes and contained homogeneously staining regions in the chromosomes.