Cytogenetics of Experimental Neoplasms and Non-random Chromosome Correlations in Man

Chromosomal alterations in cell lines derived from mouse rhabdomyosarcomas induced by crystalline nickel sulfide

Prior studies have shown a preferential decondensation (or fragmentation) of the heterochromatic long arm of the X chromosome of Chinese hamster ovary cells when treated with carcinogenic crystalline NiS particles (crNiS). In this report, we show that the heterochromatic regions of mouse chromosomes are also more frequently involved in aberrations than euchromatic regions, although the heterochromatin in mouse cells is restricted to centromeric regions. We also present the karyotypic analyses of four cell lines derived from tumors induced by leg muscle injections of crystalline nickel sulfide which have been analyzed to determine whether heterochromatic chromosomal regions are preferentially altered in the transformed genotypes. Common to all cell lines was the presence of minichromosomes, which are acrocentric chromosomes smaller than chromosome 19, normally the smallest chromosome of the mouse karyotype. The minichromosomes were present in a majority of cells of each line although the morphology of this extra chromosome varied significantly among the cell lines. C-banding revealed the presence of centromeric DNA and thus these minichromosomes may be the result of chromosome breaks at or near the centromere. In three of the four lines a marker chromosome could be identified as a rearrangement between two chromosomes. In the fourth cell line a rearranged chromosome was present in only 15% of the cells and was not studied in detail. One of the three major marker chromosomes resulted from a centromeric fusion of chromosome 4 while another appeared to be an interchange involving the centromere of chromosome 2 and possibly the telomeric region of chromosome 17.(ABSTRACT TRUNCATED AT 250 WORDS)

Myelodysplastic syndromes: pathogenesis, functional abnormalities, and clinical implications

The myelodysplastic syndromes represent a preleukaemic state in which a clonal abnormality of haemopoietic stem cell is characterised by a variety of phenotypic manifestations with varying degrees of ineffective haemopoiesis. This state probably develops as a sequence of events in which the earliest stages may be difficult to detect by conventional pathological techniques. The process is characterised by genetic changes leading to abnormal control of cell proliferation and differentiation. Expansion of an abnormal clone may be related to independence from normal growth factors, insensitivity to normal inhibitory factors, suppression of normal clonal growth, or changes in the immunological or nutritional condition of the host. The haematological picture is of peripheral blood cytopenias: a cellular bone marrow, and functional abnormalities of erythroid, myeloid, and megakaryocytic cells. In most cases marrow cells have an abnormal DNA content, often with disturbances of the cell cycle: an abnormal karyotype is common in premalignant clones. Growth abnormalities of erythroid or granulocyte-macrophage progenitors are common in marrow cultures, and lineage specific surface membrane markers indicate aberrations of differentiation. Progression of the disorder may occur through clonal expansion or through clonal evolution with a greater degree of malignancy. Current attempts to influence abnormal growth and differentiation have had only limited success. Clinical recognition of the syndrome depends on an acute awareness of the signs combined with the identification of clonal and functional abnormalities.

Clonal sublines of rat neurotumor RT4 and cell differentiation. VI. Chromosome analysis

The RT4 neurotumor cell system consists of clonally derived cell lines where a stem cell type segregates in vitro into three biochemically and morphologically different cell types, one glial and two neuronal types. This process has been termed cell-type conversion (M. Imada and N. Sueoka, 1978, Dev. Biol. 66, 97-108). Detailed cytogenetic analysis of the RT4 cell lines are described. Giemsa-banding analysis of 12 independent clonal isolates of the four different RT4 cell types showed a relatively stable karyotype. The stem cell line, RT4-AC, is diploid and most stable, and it has one 4q+ marker chromosome in place of a normal No. 4. This 4q+ marker was identified in all cell types of the RT4 system and was not observed in other cell lines of BDIX origin. The 4q+, therefore, is a chromosomal marker of the RT4 system. Consistent chromosome rearrangement was not found in any one of the cell-type conversions of the RT4-AC cells into the three derivative cell types. The relative stability of the karyotype of the different clonal isolates gives the RT4 system an advantage in studies of genetic regulation and expression of cell-type conversion in vitro. Also the 4q+ marker can be used to identify RT4 cells in coculture experiments or to distinguish RT4 cells in cases of suspected cell-line contamination.

Karyotype evolution in a transformed rat cerebral endothelial cell line

Primary cultures of rat microvascular endothelial cells were transformed, in vitro, by exposure to Rous sarcoma virus. Transformed cells were followed and evaluated cytogenetically through numerous passages. Highly specific karyotypic changes in karyotype (both structural and numerical) were documented. These changes became established and intimately involved in further "karyotypic evolution". The findings were reproducible, and when considered in the light of the literature suggest regular patterns of karyotypic change in rat tumors. The in vitro methodology utilized promises to be of practical value in the study of the early stages of malignancy.

The chromosomal basis of human neoplasia

High-resolution banding techniques for the study of human chromosomes have revealed that the malignant cells of most tumors analyzed have characteristic chromosomal defects. Translocations of the same chromosome segments with precise breakpoints occur in many leukemias and lymphomas, and a specific chromosome band is deleted in several carcinomas. Trisomy, or the occurrence of a particular chromosome in triplicate, is the only abnormality observed in a few neoplasias. It is proposed that chromosomal rearrangements play a central role in human neoplasia and may exert their effects through related genomic mechanisms. Thus, a translocation could serve to place an oncogene next to an activating DNA sequence, a deletion to eliminate an oncogene repressor, and trisomy to carry extra gene dosage.

Phenotypic diversity in leukemia cell populations

Acute leukemia comprises a large group of different diseases that can be identified by morphology in combination with immunological markers. Such studies suggest that phenotypic heterogeneity may be expressed in individual leukemia cell populations. This was verified in the murine AKR leukemia that was found to be composed of four antigenically different subtypes of leukemia cells, and it was shown that this feature has a severe negative impact on the use of leukemia cell specific monoclonal antibodies (Mabs) as therapeutical reagents. Twenty-four human T-lymphoblastic leukemias were analyzed with Mabs against HLA class I, HLA class II, and T-lymphocyte differentiation antigens, and 21 were found to be intratumoral heterogeneous with respect to these antigens. Mabs with high specificity were generated against AML cells and subsequently used to analyze more than 50 AML samples from different patients. The reactivity pattern of the Mabs differed significantly among the various AML samples. Further, a pronounced intratumoral antigenic heterogeneity (IAH) was found in most AML samples with regard to reactivity of the Mabs against AML and expression of major histocompatibility antigens. The negative impact of IAH on the use of Mabs in clinical oncology is described. It is argued that IAH exemplifies the phenotypic diversity of malignant neoplasms which is also suggested to be a basic and necessary feature of malignant cell populations. Mabs against subsets of malignant cell populations may have a profound effect on cancerous cell populations, and it is therefore of crucial importance that such subsets are identified and characterized. It is conceivable that this may result in generation of Mabs with potentially high value in cancer diagnosis and therapy, particularly in combination with drugs that induce differentiation in the malignant cell mass.

Application of the micronucleus test to exfoliated cells of high cancer risk groups: tobacco chewers

Powdered tobacco (Khaini tobacco) with the addition of lime is commonly used by the residents of Bihar, India. The tobacco/lime mixture is usually placed on the inner side of the lower lip within the gingivolabial groove. About 42% of the users keep it at the front, the rest move the tobacco towards the left or right side within the oral cavity. Carcinomas (so-called "Khaini cancers") develop mainly at the site where the tobacco is in close contact with the mucosa. Scrapings of the mucosa were taken at sites where the tobacco is kept, then smears were prepared, stained with the Feulgen reaction and fast green, and screened for micronuclei which indicate the occurrence of chromosome aberrations in the dividing cell population of the basal layer. An elevated frequency of cells with micronuclei was found in the oral mucosa of all 27 examined Khaini tobacco users (Munda and Santal tribes) compared to that of non-chewers of similar ethnic background and dietary habits. The induction of micronucleated mucosa cells seems to be due to genotoxic agents released from the tobacco/lime mixture. In vitro, an aqueous extract of the Khaini tobacco elicits chromosome aberrations and micronuclei in cultured human fibroblasts and Chinese hamster ovary (CHO) cells. No chromosome-damaging effect was observed following the application of lime or calcium hydroxide (Ca(OH)2). The micronucleus test on exfoliated cells can provide evidence of carcinogen exposure in the tissue from which cancers will develop. This approach combines all the advantages of in vitro short-term tests for genotoxic and carcinogenic agents with those of using an intact organism with all its defence mechanisms.

A 14q+ chromosome in a malignant lymphoma in a patient with Down's syndrome

A 17-year-old Japanese boy with Down's syndrome developed leukemic lymphosarcoma; histology of a lymph node biopsy revealed a malignant lymphoma, of the poorly differentiated lymphocytic (ML-PDL) or possibly lymphoblastic type (ML-LB). The Giemsa-banding technique for chromosome analysis revealed the karyotype of the lymphoma cells to be 47, XY, + 21, 14q+. A chromosome study of PHA-stimulated lymphocytes showed a 21-trisomic pattern, i.e., 47, XY, + 21. The 14q+ marker was a product of a translocation in which the long arm of chromosome No. 8 (probable break at band q11) was translocated to the long arm of a No. 14 at band q32, which is a region usually affected in various types of lymphomas. Two normal No.8 chromosomes were present. Thus, the lymphoma cells were partially trisomic for chromosome No. 8.

Correlations between the clinical course, characteristics of blast cells, and karyotype patterns in chronic myeloid leukemia

Results of chromosome studies of blood and bone marrow cells from 101 patients with Ph1 positive chronic myeloid leukemia (CML) confirm the assumptions that clinical and morphologic manifestations of the disease correlate with karyotype peculiarities of leukemia cells. Several variants of the clinical course of CML may be distinguished. One is the variant with a short chronic phase and a comparatively long terminal phase. In blastic crisis the blast cells are peroxidase negative and do not possess cytoplasmic inclusions. Acute transformation occurs without any additional chromosome damage. The second, more common form is less severe because of longer chronic phase but it has a short and grave acute stage. The blast cells present definite signs of myeloid differentiation, they have basophilic or neutrophilic cytoplasmic granules and are peroxidase positive. Marker i(17q) often combined with trisomy 8 is a characteristic chromosome abnormality in the terminal stage of this variant. The third type has an extremely long chronic phase but ends in a rapidly progressing severe and resistant to therapy "lymphoid" blastic crisis. Blast cells have typical "lymphoid" morphology, they are peroxidase negative and contain granular PAS positive substance. Various additional chromosome changes appear in the terminal stage. Future studies of a larger series of patients may possibly reveal more CML variants.

[Chromosome abnormalities, tumours and developmental disorders (author's transl)]

Clonal chromosome disorders occurring or acquired at any postnatal age are often closely related with the origin of tumours. In man the Ph1-chromosome (9; 22) anomaly in CML or the 8; 14 translocation in the African malignant Burkitt Non-Hodgkin lymphoma are, among other cases, prominent examples. On the other hand, constitutive, inherited or novel chromosome anomalies conveyed from the zygote to all tissues of the organism may cause a higher risk for the origin of tumours. Rarely, inheritable minor structural chromosome mutations are known to determine the occurrence of dysontogenetic tumours, as e.g., nephroblastoma, but it is assumed that more such cases will become elucidated in the future. As a special phenomenon, true hydatiform mole is a tumour of the placental tissue due to a disorder of intragenome regulation. Constitutive or numerical structural chromosome anomalies of man are a frequent cause of early or late abortion or of abnormal development and malformation. Despite the predominating principle of selective fetal elimination, a few anomalies such as Down's syndrome, may escape to longer survival due to the relatively mild effects of chromosome 21 triplication. Trisomies which represent in man the most frequent type of chromosome disorders, can be induced, and systematically studied in an experimental model of the mouse. This allows the elaboration of the developmental profiles of all trisomies (and monosomies) of the mouse. Also, the above mentioned principle of selective elimination of abnormal implants can be analysed experimentally. Although the developmental span of a trisomic zygote is limited, there is evidence that cells and tissues isolated from the chromosomally abnormal organism can survive much longer. Thus, haemopoietic stem cells, at least in Ts 12 and 19 of the mouse, can be rescued from trisomic fetuses by transferring them to lethally irradiated adult mice, whose blood forming organs may eventually become permanently repopulated by the trisomic cell lineage. This type of experiments is suited for closer analyses of potential functions vs. defects of chromosomally abnormal cellular systems, e.g., with regard to growth and development.

Specific fine chromosomal defects in cancer: an overview

More than 2 tumors have been found to have a specific chromosomal abnormality. In acute nonlymphocytic and acute lymphocytic leukemia, subgroups have also been identified with consistent chromosomal defects and different prognoses and responses to treatment. With the recent advent of high resolution chromosome technology, it appears possible that most malignant tumors will be found to have a chromosomal defect. This has recently been observed in acute nonlymphocytic leukemias. These findings and the availability of new solid tumor techniques make it possible to predict that study of chromosomes in cancer will become a useful if not essential tool in the subclassification and understanding of the etiology of neoplasias.

Chromosome abnormalities, clinical and morphological manifestations in metamorphosis of chronic myeloid leukemia

Seventeen cases of chronic myeloid leukemia (CML) in metamorphosis have been investigated by cytogenetic methods. Six patients were studied in slow transformation and others in the terminal blastic phase of the disease. Of these, 3 cases were myeloid, 3 myelomonocytic, 1 megakaryoblastic, 1 promyelocytic and 4 lymphoid in their morphological and cytochemical appearance. Some correlation could be observed between the clinical, morphological, cytochemical and cytogenetic findings of the different subgroups. The results demonstrate the importance of chomosome investigations in the early diagnosis of metamorphosis and in distinguishing the different subgroups of the terminal stage of CML.