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Results for “polyploid establishment”

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At least 145 records · Page 8Linked to original sources
PubMed1993

[Cytologic diagnosis of medullary carcinoma of the thyroid gland].

Over a five year period 50 malignant tumours (3.8% of investigations) has been histologically proved in a group of 1378 patients who underwent fine needle aspiration biopsy of thyroid. Five of these were medullary carcinomas (0.38% of investigation, 10% of malignancies). During revision and cytohistological correlation the most important cytologic diagnostic features for the sequential diagnosis of medullary carcinoma especially in cases without indicative clinical symptomatology have been checked. The following proved to be indicative especially if coinciding: a) background formed by blood with minimum or no colloid; b) clusters of epithelial cells with poor cohesion, sometimes multilayered, microfollicular, or stroma-like fusiform cells; c) striking anisocytosis, polygonal, plasmacytoid, fusiform, polyploid, and binucleated cells and naked nuclei in the background; d) striking anisokaryosis, at least part of the nuclei ovoid or elongated, chromatin rough, giant nuclei; e) amyloid identifiable in some tissue micro-fragments. If additional smears or cyto-block material are available it may be possible to establish the diagnosis at the cytology level using amyloid staining, argyrophilia test or immunohistochemistry. However if there is any cytological suspicion of medullary carcinoma, serum calcitonin should be investigated to confirm the preoperative diagnosis of medullary carcinoma enabling the patient to undergo one-step radical surgery.

Adult↗
PubMed1995

E6 and E7 expression from the HPV 18 LCR: development of genital hyperplasia and neoplasia in transgenic mice.

Human papillomavirus type 18 infection is highly associated with malignant tumors of the genital tract. To investigate the tissue specificity of the HPV long control region (LCR) and the transforming ability of the E6-E7 oncoproteins, an HPV-18 transgene containing the viral LCR and E6 and E7 genes was introduced into mice. Three founder males exhibited enlarged seminal vesicles and preputial glands by 50 weeks of age. A line of transgenic mice was established by in vitro fertilization, and subsequent generations of transgenic males and females were monitored for lesions. Approximately 80% of hemizygous transgenic males exhibited enlarged seminal vesicles and preputial glands as early as 12 weeks of age. Histological examination indicated that this enlargement was due to distension by fluid, along with polyploid hyperplasia of the lining secretory epithelium. E6 and E7 transcripts were limited to affected organs and kidney. Approximately 41% of transgenic females developed cervical neoplasms between 1-2 years of age. Histologically, tumors were mesenchymal rather than epithelial in origin. E6 and E7 transcripts were restricted to cervical tumor tissue and kidney. These findings suggest that the HPV-18 LCR has an element(s) which directs expression specifically to the urogenital tract in transgenic mice.

Animals↗
PubMed1980

[Comparative histo- and cytospectrophotometric study of the DNA content in the nuclei of lung cancer cells].

Histo- and cytospectrophotometric examinations of the lung carcinoma (26 observations, operation material) established that such features as hetero- and polyploidy, a considerable increase in the average content of DNA and "index of DNA accumulation" progressed as long as the degree of tumour differentiation decreased. Differences between poorly differentiated forms of squamous cell carcinoma and adenocarcinoma were found (the latter had more octoploid and other polyploid cells, higher values of the "index of DNA accumulation" and a significantly higher average DNA content in the nuclei than in squamous cell carcinoma) as well as between small- and large-cell variants of undifferentiated cancer (the latter had more octoploid and other polyploid cells, higher "index of DNA accumulation" and significantly higher average DNA content in the nuclei than in undifferentiated small-cell carcinoma). The cytospectrophotometric method for DNA determination may be used as an auxilliary test for the determination of the histological form, the degree of differentiation of lung carcinoma prognosis, and choice of the method of treatment.

Adenocarcinoma↗
PubMed1996

Endoreplication in megakaryoblastic cell lines is accompanied by sustained expression of G1/S cyclins and downregulation of cdc25C.

In most eukaryotic cells, a link between S and M phases of the cell cycle must be assured in order to maintain the ploidy of newly divided cells. However, in some cell l/pes, e.g. the precursors of platelets megakaryocytes, extra S-phases can occur in the absence of concomitant mitoses, resulting in polyploidy. We have used two established cell lines with megakaryoblastic characteristics (HEL and MEG-01) to investigate the molecular events that lead these cells to bypass the regular control checkpoints that govern the interdependency of S and M phases. In the presence of the phorbol ester TPA, both cell lines stopped proliferating and displayed additional megakaryocytic features, including polyploidization. Analysis of key cell cycle regulatory factors implicated in the control of G1/S and G2/M transitions revealed a number of differences compared to normally cycling cells. Differentiating megakaryocytes were found to maintain high levels of cdk2, and cyclins E and A. This was accompanied by the appearance of the retinoblastoma protein in the hyperphosphorylated, functionally inactivated form. In addition, TPA-treated cells showed high levels of cyclin B and cdc2 proteins, however no activation of cdc2 was detected. This lack of cdc2 activation which should occur for entry into M phase appeared to be related to the down regulation of cdc25C phosphatase found in both differentiated HEL and MEG-01 cells. Together, our results suggest that in differentiating megakaryoblastic cells endoreplication is accompanied by sustained levels of cyclins A and E, and a lack of cdc2 activation, which is probably mediated through down regulation of cdc25C protein phosphatase.

CDC2 Protein Kinase↗
PubMed1989

Rescue and replication of the adeno-associated virus 2 genome in mortal and immortal human cells.

Productive infection of the adeno-associated virus (AAV) as well as rescue of the AAV genome from a recombinant plasmid and its subsequent replication in established cell lines are dependent upon coinfection with adenovirus. A comparative study of AAV infection and rescue/replication was carried out in mortal and immortal human cells. AAV DNA replication as well as assembly and release of the progeny virions were significantly delayed in normal diploid cells, which have a limited replicative potential, compared with polyploid cells, which have an unlimited proliferative potential. Rescue of the AAV genome from a recombinant plasmid and its subsequent replication were similarly delayed in mortal cells. The delay in AAV rescue/replication appeared to be unrelated to the adenovirus-encoded functions. The putative host-cell component required for AAV replication may be suboptimally induced in normal human diploid cells, which offer a useful model system for a natural AAV infection.

Adenovirus Early Proteins↗
PubMed1993

Establishment, characterization and drug sensitivity of a new anaplastic thyroid carcinoma cell line (BHT-101).

A thyroid carcinoma cell line, BHT-101, has been established in vitro from a metastatic lymph node deposit in a female patient with a non-hormone producing anaplastic, partly thyroglobulin- and thyroxine (T4)-positive papillary thyroid cancer. The cell population is heterogeneous, containing epithelial-like and fibroblast-like cells, and has a doubling time of 24 h. The cell line is polyploid with hypertetraploid predominance and the karyotype showed trisomies, tetrasomies, pentasomies as well as many marker chromosomes. The majority of the cells are negative or weakly positive for thyroglobulin and thyroxine and estrogen and progesterone receptors are present in the cells. BHT-101 cells produce tumours when injected into immunosuppressed CBA/Ca mice. The cells are sensitive to adriamycin, methotrexate and tamoxifen but not to methimazole (Favistan). The epithelial-like clone 1 and the fibroblast-like clone 3, isolated from the parental line, differed in drug sensitivity. This new cell line is suitable for studying the biology of thyroid carcinoma and for parallel in vivo and in vitro studies of drug activity against thyroid cancer.

Animals↗
PubMed1998

An oncogenic form of p53 confers a dominant, gain-of-function phenotype that disrupts spindle checkpoint control.

Although it is well-established that p53 functions as a tumor suppressor gene, certain mutations exhibit gain-of-function activities that increase oncogenic transformation. We have found a common class of p53 missense mutation that exhibits a dominant, gain-of-function activity that generates genomic instability. Fibroblasts from Li-Fraumeni syndrome heterozygotes with such mutations generate polyploid cells when exposed to spindle depolymerizing agents. Expression of such mutant alleles in normal fibroblasts yields the same phenotype. This class of dominant, gain-of-function p53 mutation (p53(RSC), relaxed spindle checkpoint allele) does not require the transcriptional activation function of p53 for this behavior. Thus p53 mutations can contribute to progression of a cancer cell not only by absence of p53 tumor suppressor activity but also by the presence of an activity that promotes genetic instability.

Animals↗
PubMed1998

Radiation-induced genetic instability: no association with changes in radiosensitivity or cell cycle checkpoints in C3H 10T1/2 mouse fibroblasts.

We investigated various phenotypic characteristics of radiation-induced morphologically transformed C3H 10T1/2 mouse fibroblasts. The cells were treated with 8 Gy x-rays, and type II/III foci were isolated. Cell lines were developed from these foci, and subsequently clones were established from these focal lines. The clones were examined for DNA content, radiosensitivity and inducible cell cycle arrests. Besides the morphological changes associated with the transformed state, the major difference between the isolated focal lines or derived clones and the parental C3H 10T1/2 line was one of ploidy. The transformed cells often displayed aneuploid and multiple polyploid populations. No change in the radiosensitivity of the transformed cells was observed. Furthermore, the two major radiation- and staurosporine-induced G1 and G2 cell cycle arrests observed in the parental cell line were also observed in the morphological transformants, suggesting that checkpoint function was normal.

Aneuploidy↗
PubMed2005

Segregation of genomes in polyploid tumour cells following mitotic catastrophe.

Following irradiation p53-function-deficient tumour cells undergo mitotic catastrophe and form endopolyploid cells. A small proportion of these segregates nuclei, and give rise to viable descendants. Here we studied this process in five tumour cell lines. After mitotic failure, tumour cells enter the endocycle and form mono-nucleated or multi-nucleated giant cells (MOGC and MNGC). MNGC arise from arrested anaphases, MOGC, from arrested metaphases. In both cases the individual genomes establish a radial pattern by links to a single microtubule organizing centre. Segregation of genomes is also ordered. MNGC present features of mitosis being resumed from late anaphase. In MOGC the sub-nuclei retain arrangement of stacked metaphase plates and are separated by folds of the nuclear envelope. Mitosis then resumes in sub-nuclei directly from metaphase. The data presented indicate that endopolyploid tumour cells preserve the integrity of individual genomes and can potentially re-initiate mitosis from the point at which it was interrupted.

Cell Line, Tumor↗
PubMed2005

Cancer-associated mutations in chromatin remodeler hSNF5 promote chromosomal instability by compromising the mitotic checkpoint.

The hSNF5 subunit of human SWI/SNF ATP-dependent chromatin remodeling complexes is a tumor suppressor that is inactivated in malignant rhabdoid tumors (MRTs). Here, we report that loss of hSNF5 function in MRT-derived cells leads to polyploidization and chromosomal instability. Re-expression of hSNF5 restored the coupling between cell cycle progression and ploidy checkpoints. In contrast, cancer-associated hSNF5 mutants harboring specific single amino acid substitutions exacerbated poly- and aneuploidization, due to abrogated chromosome segregation. We found that hSNF5 activates the mitotic checkpoint through the p16INK4a-cyclinD/CDK4-pRb-E2F pathway. These results establish that poly- and aneuploidy of tumor cells can result from mutations in a chromatin remodeler.

Amino Acid Substitution↗
PubMed1986

3B55: a repetitious sequence family which is transcribed and proportionately replicated in germ-line polyploid nuclei of Calliphora erythrocephala.

The chromosomes of dipteran polyploid nurse cell nuclei are functionally analogous to the oocyte lampbrush chromosomes of the Amphibia. In investigating the transcriptional and replicative activity of these nuclei in Calliphora erythrocephala we have identified a cloned highly repetitious DNA fragment which shows enhanced transcriptional activity in these cells and different replicative behavior in these germ-line polyploid nuclei as opposed to somatic polytene nuclei. The clone, 3B55, contains a 6.8-kb insert which consists primarily of tandemly repeated 200-bp sequences defined by RsaI sites. From Southern hybridizations to diploid (embryonic) genomic DNA, 3B55-related DNA was calculated to represent a significant fraction of the haploid genome (0.8% or 5000 kb). In situ hybridizations established that these sequences are present in the pericentric regions of four of the six chromosomes. Thus the 3B55 sequences have the properties of a satellite-type DNA family. Quantitation of the 3B55 200-bp monomer (which represents approximately 60% of the genomic 3B55 DNA sequences in all tissues examined) revealed that in somatic polytene salivary gland nuclei, 3B55 DNA is highly under-replicated to give a monomer representation of only 48 +/- 11 kb per haploid genome. However, in germ-line nurse cell nuclei, 3B55 DNA is proportionately replicated to give a monomer genomic representation (3560 +/- 344 kb) equivalent to that of diploid DNA (3011 +/- 202 kb). Transcripts complementary to 3B55 sequences are at least 25 times more abundant in total nurse cell nuclear RNA than in total embryonic nuclear RNA. These findings suggest an association of the 3B55 sequence family with some germ-line specific function.

Animals↗
PubMed2006

Transcriptional changes facilitate mitotic catastrophe in tumour cells that contain functional p53.

Exposure of Jurkat T lymphocytes containing functional p53 to nanomolar concentrations of bisanthracycline WP631 resulted in arrest at the G2/M checkpoint and transient senescence-like phenotype in the presence of DNA synthesis. The cells entered crisis, became polyploid, showed aberrant mitotic figures, and died through mitotic catastrophe. Cell death was accompanied by changes in the expression profile of various oncogenes and tumour suppressor genes including the down-regulation of p53. The changed expression was confirmed for some of these genes using semi-quantitative RT-PCR, and the decline in p53 protein levels was established. Our results suggest that WP631 induced changes in cell cycle control pathways leading to death of Jurkat T cells through mitotic catastrophe, which occurred in the absence of caspase-2 and caspase-3 activities, rather than apoptosis.

Apoptosis↗
PubMed1977

Comparative cytogenetic and histologic studies on early malignant transformation in mesothelial tumors of the ovary.

Comparative cytogenetic and histologic studies on 18 mesothelial ovarian tumors revealed a normal chromosome complement in benign lesions, and the well-known cytogenetic pattern in cystadenocarcinomas. But all borderline tumors of the series evidenced an abnormal stem line and a more or less marked tendency to polyploidization. Serous papillary cystadenomas of this group showed in five out of six cases a stem line with the karyotype 47,XX+C10 (identified by Q-banding), present in both sides of bilateral lesions. It is evidenced that malignant change on the chromosomal level precedes histologically detectable features of malignancy. Histologic equivalents appeared, when the abnormal cell line was established. The initiation of malignant transformation therefore may be signalized by karyotype abnormalities before structural changes can be detected in the corresponding histologic specimens. The results discussed include the concepts of multicentric origin and clonal evolution of malignancy.

Cell Transformation, Neoplastic↗
PubMed2004

Construction and characterisation of a BAC library for genome analysis of the allotetraploid coffee species (Coffea arabica L.).

In order to promote genome research on coffee trees, one of the most important tropical crops, a bacterial artificial chromosome (BAC) library of the coffee allotetraploid species, Coffea arabica, was constructed. The variety IAPAR 59, which is widely distributed in Latin America and exhibits a fair level of resistance to several pathogens, was chosen. High-efficiency BAC cloning of the high molecular weight genomic DNA partially digested by HindIII was achieved. In total, the library contains 88,813 clones with an average insert size of 130 kb, and represents approximately eight C. arabica dihaploid genome equivalents. One original feature of this library is that it can be divided into four sublibraries with mean insert sizes of 96, 130, 183 and 210 kb. Characterisation of the library showed that less than 4.5% of the clones contained organelle DNA. Furthermore, this library is representative and shows good genome coverage, as established by hybridisation screening of high-density filters using a number of nuclear probes distributed across the allotetraploid genome. This Arabica BAC library, the first large-insert DNA library so far constructed for the genus Coffea, is well-suited for many applications in genome research, including physical mapping, map-based cloning, functional and comparative genomics as well as polyploid genome analyses.

Blotting, Southern↗
PubMed2005

Quantitative genotyping of single-nucleotide polymorphisms by allele-specific oligonucleotide hybridization on DNA microarrays.

Genotyping of SNPs (single-nucleotide polymorphisms) has challenged the development of several novel techniques. Most of these methods have been introduced to discriminate binary SNPs in diploid species. In the present study, the quantitative genotyping of SNPs in natural DNA pools of a polyploid organism via DNA microarrays was analysed. Three randomly selected SNP loci were genotyped in the tetraploid species potato (Solanum tuberosum). For each SNP, 24 oligomers were designed, 12 with forward and 12 with reverse orientation. They contained the polymorphic site at one of the positions 11, 14 and 17. Several steps of optimizations were performed, including the 'materials' used and the establishment of hybridization conditions. Glass surfaces were either epoxy- or aldehyde-modified, and allele-specific oligonucleotides contained either SH or NH2 groups. Hybridization stringency conditions were established by varying the concentration of formamide in the hybridization buffer. For SNP BA213c14t7/403, the quantitative discrimination between all four different naturally occurring genotypes could be demonstrated.

Chromosome Mapping↗
PubMed2006

Nuclear DNA endoreduplication and expression of the mitotic inhibitor Ccs52 associated to determinate and lupinoid nodule organogenesis.

Lotus japonicus determinate nodules differ greatly from indeterminate nodules in their organogenesis and morphological characteristics, whereas Lupinus albus lupinoid nodules share features of determinate and indeterminate nodules. The mitotic inhibitor Ccs52A is essential for endoreduplication and ploidy-dependent cell enlargement during symbiotic cell differentiation in Medicago truncatula indeterminate nodules. ccs52A homolog genes were isolated from lupin and lotus nodules; the deduced Ccs52A proteins showed high sequence similarity with other Cdh-1-type activators of the anaphase-promoting complex and were grouped with A-type Ccs52 proteins from different plants. In lupin, ccs52A expression was restricted to the earlier stages of nodule development, whereas ccs52A transcripts accumulated in lotus nodule primordia and, to a lesser extent, in mature nodules. Nodule development in Lupinus albus involved a progressive increase in nuclear and cellular size and ploidy level; similarly, Lotus japonicus nodules contained polyploid nuclei and enlarged cells in the infected zone. Nevertheless, in situ hybridization experiments showed the highest ccs52A expression in the inner cortex cells of the lupin nodule primordium, probably associated to the increased size of these cells in mature nodules. In view of our results, Ccs52A-mediated endoreduplication appears to be a universal mechanism required for nodule cell differentiation during the establishment of nitrogen-fixing symbioses.

Amino Acid Sequence↗
PubMed2005

Drosophila genome-scale screen for PAN GU kinase substrates identifies Mat89Bb as a cell cycle regulator.

Although traditional organism-based mutational analysis is powerful in identifying genes involved in specific biological processes, limitations include incomplete coverage and time required for gene identification. Biochemical screens using cell transfection or yeast two-hybrid methods are rapid, but they are limited by cDNA library quality. The recent establishment of "uni-gene sets" has made it feasible to biochemically screen an organism's entire genome. Radiolabeled protein pools prepared from the Drosophila Gene Collection were used in a Drosophila in vitro expression cloning ("DIVEC") screen for substrates of PAN GU kinase, which is crucial for S-M embryonic cell cycles. Ablation of one identified substrate, Mat89Bb, by RNAi produces a polyploid phenotype similar to that of pan gu mutants. Xenopus embryos injected with Mat89Bb morpholinos arrest with polyploid nuclei, and Mat89Bb RNAi in HeLa cells gives rise to multinucleated cells. Thus, Mat89Bb plays an evolutionarily conserved role as a crucial regulator of both cell cycle and development.

Animals↗
PubMed2000

Normal and c-Myc-promoted human keratinocyte differentiation both occur via a novel cell cycle involving cellular growth and endoreplication.

The relationship between cell cycle and differentiation in human keratinocytes is poorly understood. It is believed that keratinocytes suppress DNA replication and cell cycle arrest in G0 before they initiate terminal differentiation. However, a temporal separation between both events has not been established. Moreover, c-Myc promotes keratinocyte differentiation without causing cell cycle arrest. To address these paradoxes we have analysed cell cycle control during normal and c-Myc-promoted differentiation. Continuous activation of c-Myc or initiation of terminal differentiation results in a block of G2/M, cellular growth, endoreplication and polyploidy. Keratinocytes abandon G1, continue replicating DNA as they differentiate terminally and become polyploid. In fact, simply blocking mitosis with nocodazole resulted in increased cell size, terminal differentiation and endoreplication. This indicates that terminal differentiation associates with defective cell cycle progression and provides a novel insight into c-Myc biology.

Cell Cycle↗