Clustering of aberrations to specific chromosomes in human neoplasms. III. Incidence and geographic distribution of chromosome aberrations in 856 cases

Variant Philadelphia t(X;9;22)(q22?;q34;q11.2) can be successfully treated with second generation tyrosine kinase inhibitors: A case report and literature review

Chronic myeloid leukemia (CML) is characterized by the reciprocal translocation between chromosomes 9 and 22: t(9;22)(q34;q11). However, 5-10% of patients with CML have complex variant translocations involving at least a third chromosome; only a few cases affect the X chromosome. Therefore, the data available regarding their features and the response to treatment is limited. In the present report, a case of a variant Philadelphia translocation t(X;9;22)(q22?;q34;q11.2) identified in a 51-year-old female with a newly diagnosed CML is described. The patient was treated with nilotinib. A major molecular response was observed after 12 months of starting treatment. Deep molecular response was obtained 20 months later and maintained after the 110-month follow-up. Additionally, a literature review was performed, with the aim of comprehending the complex clinical and biological characteristics of CML cytogenetic variants involving the X chromosome.

Cancer chromosome breakpoints cluster in gene-rich genomic regions

Cancer cells are characterized by chromosome abnormalities, of which some, in particular balanced rearrangements, are associated with distinct tumor entities and/or with specific gene rearrangements that represent important steps in the carcinogenic process. However, the vast majority of cytogenetically detectable structural aberrations in cancer cells have not been characterized at the nucleotide level; hence, their importance and functional consequences are unknown. By ascertaining the chromosomal breakpoints in 22 344 different clonal structural chromosome abnormalities identified in the karyotypes of 49 626 cases of neoplastic disorders we here show that the distribution of breakpoints is strongly associated (P < 0.0001) with gene content within the affected chromosomal bands. This association also remains highly significant in separate analyses of recurrent and nonrecurrent chromosome abnormalities as well as of specific subtypes of cancer (P < 0.0001 for all comparisons). In contrast, the impact of band length was negligible. The breakpoint distribution is thus not stochastic—gene‐rich regions are preferentially affected. Several genomic features relating to transcription, replication, and chromatin organization have been found to enhance chromosome breakage frequencies; this indicates that gene‐rich regions may be more break‐prone. The salient finding in the present study is that a substantial fraction of all structural chromosome abnormalities, not only those specifically associated with certain tumor types, may affect genes that are pathogenetically important. If this interpretation is correct, then the prevailing view that the great majority of cancer chromosome aberrations is cytogenetic noise can be seriously questioned.

A novel mouse model identifies cooperating mutations and therapeutic targets critical for chronic myeloid leukemia progression

The introduction of highly selective ABL-tyrosine kinase inhibitors (TKIs) has revolutionized therapy for chronic myeloid leukemia (CML). However, TKIs are only efficacious in the chronic phase of the disease and effective therapies for TKI-refractory CML, or after progression to blast crisis (BC), are lacking. Whereas the chronic phase of CML is dependent on BCR-ABL, additional mutations are required for progression to BC. However, the identity of these mutations and the pathways they affect are poorly understood, hampering our ability to identify therapeutic targets and improve outcomes. Here, we describe a novel mouse model that allows identification of mechanisms of BC progression in an unbiased and tractable manner, using transposon-based insertional mutagenesis on the background of chronic phase CML. Our BC model is the first to faithfully recapitulate the phenotype, cellular and molecular biology of human CML progression. We report a heterogeneous and unique pattern of insertions identifying known and novel candidate genes and demonstrate that these pathways drive disease progression and provide potential targets for novel therapeutic strategies. Our model greatly informs the biology of CML progression and provides a potent resource for the development of candidate therapies to improve the dismal outcomes in this highly aggressive disease.

Chromosomes in leukemia and beyond: from irrelevant to central players

Although it was definitely not obvious at first, consistent chromosomal translocations are major contributors to cellular transformation in some leukemias, lymphomas, sarcomas, prostate cancer, and other benign and malignant neoplasms. In the 50 years since the discovery of the Ph chromosome, the elucidation of recurring abnormalities has been an ongoing challenge that has evolved as new technologies allowed an ever more accurate definition of the precise changes in DNA resulting from these abnormalities. As we enter a new era of understanding enriched by gene expression studies, we still know little about the changes in the level of critical proteins, which may be the ultimate effectors of the genetic/epigenetic abnormalities in cancer. Despite remarkable progress in identifying both obvious chromosome abnormalities and subtle changes in DNA such as mutations and small copy-number variations, the impact of this knowledge has been variable. The challenge for the future is to enhance our ability to translate these genetic changes into effective therapies for other malignant diseases.

Allelotyping in B-Cell Chronic Lymphocytic Leukemia (B-CLL)

B-cell chronic lymphocytic leukemia (B-CLL) is a heterogeneous malignant disease, both in terms of molecular abnormalities and clinical course. The most frequent chromosomal aberrations in B-CLL are deletions on 13q, 11q, and 17p, and trisomy 12, all of which are of prognostic significance. These aberrations can be detected by conventional cytogenetic analysis and fluorescence in situ hybridization (FISH), but cytogenetics are hampered by the low mitotic index of B-CLL cells, and FISH depends on genetic information of candidate regions. Microsatellites are unique highly polymorphic and informative genetic markers dispersed in the human genome. They have become the most commonly used markers to trace loss of heterozygosity in tumors. Their detection by PCR is rapid and can be semi-automated with maximal robustness and reproducibility. In this review, we discuss the implications of a recent genome-wide analysis in B-CLL with 400 microsatellite markers. This analysis led to the detection of new aberrant loci in B-CLL which are not visible in the leukemic conventional karyotype. We conclude that microsatellite allelotyping provides a complementary comprehensive view of genetic alterations in B-CLL, and it may identify new loci with candidate genes relevant in the molecular biology of B-CLL.

Absence of Ras mutations in rat DMBA-induced mammary tumors

Animal cancer models reduce genetic background heterogeneity and thus, may facilitate identification and analysis of specific genetic aberrations in tumor cells. Rat and human mammary glands have high similarity in physiology and show comparable hormone responsiveness. Thus, spontaneous and carcinogen (e.g., NMU and DMBA)-induced rat mammary models are valuable tools for genetic studies of breast cancer. In NMU-induced rat mammary tumors, activating mutations in Hras codon 12 have frequently been reported and are supposed to contribute to the mammary carcinogenic process. Involvement of Ras mutations in DMBA-induced tumors is less clear. In the present study we investigated the mutation status of the three Ras genes, Hras, Kras, and Nras, in DMBA-induced rat mammary tumors. We examined codons 12, 13, and 61 of all three genes for mutations in 71 tumors using direct sequencing method that in experimental conditions is sensitive enough to detect single nucleotide mutations even when present in only 25% of the test sample. No activating Ras gene mutation was found. Thus, in contrast to NMU-induced rat mammary tumor, tumorigenesis in DMBA-induced rat mammary tumors seems to be independent on activating mutations in the Ras genes. Our finding suggests that the genetic pathways selected in mammary tumor development are influenced by and perhaps dependent on the identity of the inducing agent, again emphasizing the importance of tumor etiology on the genetic changes in the tumor cells.

Genetics of chronic lymphocytic leukemia: genomic aberrations and V(H) gene mutation status in pathogenesis and clinical course

The genetic characterization of chronic lymphocytic leukemia (CLL) has made significant progress over the past few years. While conventional cytogenetic analyses only detected chromosome aberrations in 40-50% of cases, new molecular cytogenetic methods, such as fluorescence in situ hybridization (FISH), have greatly enhanced our ability to detect chromosomal abnormalities in CLL. Today, genomic aberrations are detected in over 80% of CLL cases. Genes potentially involved in the pathogenesis were identified with ATM in a subset of cases with 11q deletion and p53 in cases with 17p13 deletion. For the most frequent aberration, the deletion 13q14, candidate genes have been isolated. Genetic subgroups with distinct clinical features have been identified. 11q deletion is associated with marked lymphadenopathy and rapid disease progression. 17p deletion predicts for treatment failure with alkylating agents, as well as fludarabine and short survival times. In multivariate analysis 11q and 17p deletions provided independent prognostic information. Recently, another important issue of genetic risk classification in CLL was identified with the mutation status of the immunoglobulin variable heavy chain genes (V(H)). CLL cases with unmutated V(H) show more rapid disease progression and shorter survival times. Whether CD38 expression can serve as a surrogate marker for V(H) mutation status is currently discussed controversially. V(H) mutation status and genomic abnormalities, such as 17p and 11q deletion, have recently been shown to be related to each other, but were of independent prognostic information in multivariate analysis. Moreover, genomic aberrations and V(H) mutation status appear to give prognostic information irrespective of the clinical stage and may therefore allow a risk assessment for individual patients early in the course of their disease.

Genetic features of B-cell chronic lymphocytic leukemia

The genetic features of B-cell chronic lymphocytic leukemia (CLL) are currently being reassessed by molecular cytogenetic techniques such as fluorescence in situ hybridization (FISH). Conventional cytogenetic studies by chromosome banding are difficult in CLL mainly because of the low in vitro mitotic activity of the tumor cells, which leads to poor quantity and quality of metaphase spreads. Molecular genetic analyses are limited because candidate genes are known for only a few chromosomal aberrations that are observed in CLL. FISH was found to be a powerful tool for the genetic analysis of CLL as it overcomes both the low mitotic activity of the CLL cells and the lack of suitable candidate genes for analysis. Using FISH, the detection of chromosomal aberrations can be performed at the single cell level in both dividing and non-dividing cells, thus circumventing the need of metaphase preparations from tumor cells. Probes for the detection of trisomies, deletions and translocation breakpoints can be applied to the regions of interest with the growing number of clones available from genome-wide libraries. Using the interphase cytogenetic FISH approach with a disease specific set of probes, chromosome aberrations can be found in more than 80% of CLL cases. The most frequently observed abnormalities are losses of chromosomal material, with deletions in band 13q14 being the most common, followed by deletions in 11q22-q23, deletions in 17p13 and deletions in 6q21. The most common gains of chromosomal material are trisomies 12q, 8q and 3q. Translocation breakpoints, in particular involving the immunoglobulin heavy chain locus at 14q32, which are frequently observed in other types of non-Hodgkin's lymphoma, are rare events in CLL. Genes affected by common chromosome aberrations in CLL appear to be p53 in cases with 17p deletion and ataxia telangiectasia mutated (ATM), which is mutated in a subset of cases with 11q22-q23 aberrations. However, for the other frequently affected genomic regions, the search for candidate genes is ongoing. In parallel, the accurate evaluation of the incidence of chromosome aberrations in CLL by FISH allows the correlation of genetic abnormalities with clinical disease manifestations and outcome. In particular, 17p abnormalities and deletions in 11q22-q23 have already been shown to be among the most important independent prognostic factors identifying subgroups of patients with rapid disease progression and short survival. In addition, deletion 17p has been associated with resistance to treatment with purine analogs. Therefore, genetic abnormalities may allow a risk assessment for individual patients at the time of diagnosis, thus giving the opportunity for a risk-adapted management.

Cytogenetic analysis of hematologic malignancies in Hong Kong. A study of 98 cases

The karyotypes of 98 patients between the ages of 8 and 81 years with acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and chronic myeloid leukemia (CML) are presented. Although the well-described cytogenetic abnormalities associated with particular FAB subtypes in the West were observed, certain important local differences were noted. In ALL, hyperdiploidy was rarely observed, whereas the Philadelphia chromosome was observed in 50% of abnormal karyotypes. In AML, the t(8;21) was infrequently observed in M2 case, whereas trisomy 4 and 6, rarely reported elsewhere, formed 12% of the abnormal cases. In MDS, the incidence of -5/5q- and/or -7/7q- was 83% of cases with aberrant cytogenetic findings. Neither i(17q) nor an extra Ph was seen in 26 cases of CML including 9 cases of accelerated phase/blast crisis. In addition, previously unreported cytogenetic abnormalities occurring as single cases are presented. These findings are discussed in the context of geographical heterogeneity of chromosomal abnormalities in leukemia and emphasize the importance of continued epidemiologic studies of cytogenetics in hematologic malignancies.

Chromosome abnormalities and prognosis in childhood acute leukemia

We report here on the leukemic cell karyotypes of 134 children with acute nonlymphocytic leukemia (ANLL) examined at Saitama Children's Medical Center (SCMC), and of 88 children with acute lymphoblastic leukemia (ALL) referred to SCMC. The patients were mainly treated according to the protocol of the Tokyo Children's Cancer Study Group. Of 106 ANLL cases with adequate banding, 18% were normal, 34% had miscellaneous clonal abnormalities, and 48% were classified into known cytogenetic subgroups: t(8;21) (n = 21), 11q23 abnormalities (n = 14), -7/del(7q) (n = 6), inv (16)/del(16) (n = 5), and t(15;17) (n = 5). According to the FAB classification, M7 (21.7%) were more frequent than in previous reports because this study included a number of Down's Syndrome patients with M7 morphology. The present study confirmed the well-known association of t(15;17) with M3, t(8;21) with M2, 11q23 abnormalities with M4 and M5, and inv (16)/del(16) with M4. Patients with t(8;21) or inv (16)/del(16q) ANLL fared no better overall than the entire group. Of 51 ALL cases with adequate banding, 13.7% were normal, and 86.3% were classified into abnormal subgroups: translocation (n = 14), hyperdiploidy (greater than 50) (n = 13), and miscellaneous abnormalities (n = 17). Cases with hyperdiploidy (greater than 50) were restricted to a common phenotype and fared better overall than the entire group. Patients with translocation were found in all phenotypes, and had a poor prognosis. We concluded that childhood acute leukemia could be subgrouped according to karyotypic patterns, and that patients with translocations had a poor prognosis in ALL as well as ANLL.

Geographic heterogeneity of neoplasia-associated chromosome aberrations

Using a database comprising 13,266 cytogenetically abnormal neoplasms, the geographic heterogeneity of neoplasia-associated chromosomal abnormalities was investigated by comparing the frequencies of characteristic aberrations in consecutive series of patients with the same diagnosis. Significant frequency differences between geographic areas were found for the aberrations +8, i(17q), +19, and an additional Ph1 chromosome in chronic myeloid leukemia (CML); -5, 5q-, and +8 in acute nonlymphocytic leukemia (ANLL); t(8;21) in ANLL-M2; t(15;17) in ANLL-M3; 5q- and -7 in myelodysplastic syndromes (MDS); t(9;22) and +21 in acute lymphocytic leukemia (ALL); t(14;18) in follicular lymphoma; -8 and -22/22q- in meningioma; and structural abnormalities of 12q in pleomorphic adenoma of the salivary glands (PAS). No geographic incidence variation was detected for -7 and +21 in ANLL; +8 in MDS; 6q- and +8 in ALL; +12 in chronic lymphocytic leukemia; 6q- in non-Hodgkin's lymphoma (NHL); t(8;14) in Burkitt's lymphoma; t(11;22) in Ewing's sarcoma; i(12p) in germ cell tumors; 1p- in neuroblastoma; structural abnormalities of 3q, 8q, and 9p in PAS; or 3p- in renal cell carcinoma. Intraregional frequency similarities between cytogenetically identical abnormalities in related tumor types were also analyzed. No significant correlations were found regarding the incidence of 5q- in ANLL and MDS, 6q- in ALL and NHL, -7 in ANLL and MDS, +8 in ANLL and CML, +8 in ANLL and MDS, +8 in ALL and ANLL, or +21 in ALL and ANLL. The findings indicate that some geographic heterogeneity of tumor-associated aberrations exists both in hematologic neoplasms and in solid tumors.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation between cytogenetic and histopathological findings in 65 human meningiomas

The correlations between cytogenetic and histopathological findings were analyzed in 65 cases of human meningiomas. Clonal chromosome abnormalities were present in 28 cases (43%). The overall female/male ratio was 1.7, but it was 1.1 in the group of 28 cases with chromosomal abnormalities. Abnormalities of chromosome 22 as sole abnormality predominate in the female patients. The mean age of patients with normal karyotype was significantly lower (50.7 years) than that of patients with chromosome changes (57.3 years). The tumor origin was predominantly at the base in the patients with normal karyotype but different at the convexity, falx cerebri, and spinal cord. The five abnormal cases from the spinal cord all showed involvement of chromosome 22. The proportion of chromosome anomalies was different in the various histological types, and a significant difference was found between the meningotheliomatous (23%) and psammomatous (58%) types. The cytogenetically abnormal cases of the psammomatous type all showed involvement of chromosome 22. In three patients with multiple meningiomas, we found different karyotypes in the different tumors of the same patient, which may indicate a multifocal origin of the tumors.

Multiple meningiomas: a clinical, surgical, and cytogenetic analysis

Eight cases of multiple meningiomas were found in our 13-year series of 148 operated meningiomas. The relative frequency, 5.4%, of multiple meningiomas observed is compared with that in the literature. The clinical presentation, surgical results, and diagnostic tools are discussed. Cytogenetic analysis was performed in five patients (eight neoplastic specimens). No specific abnormality for multiple meningiomas was found, but our results point out the different origin of each tumor and exclude cell migration through the subarachnoid space as a pathogenetic factor in multiple meningiomas.

Free radical formation by antitumor quinones

Quinones are among the most frequently used drugs to treat human cancer. All of the antitumor quinones can undergo reversible enzymatic reduction and oxidation, and form semiquinone and oxygen radicals. For several antitumor quinones enzymatic reduction also leads to formation of alkylating species but whether this involves reduction to the semiquinone or the hydroquinone is not always clear. The antitumor activity of quinones is frequently linked to DNA damage caused by alkylating species or oxygen radicals. Some other effects of the antitumor quinones, such as cardiotoxicity and skin toxicity, may also be related to oxygen radical formation. The evidence for a relationship between radical formation and the biological activity of the antitumor quinones is evaluated.

A comparative analysis of data on the clastogenicity of 951 chemical substances tested in mammalian cell cultures

A literature review was conducted using original papers published during 1964-1985 on the in vitro clastogenicity of chemical substances. Results of tests on 951 chemical substances were abstracted from over 240 reports to form the database. The evaluation of these data relied on each author's original conclusion on a positive or negative outcome. Of these 951 substances, 447 (47%) were consistently positive either with or without activation; 417 (44%) were negative in the direct test but not tested with metabolic activation systems; 4 were negative but tested only with activation; and 30 (3%) were clearly negative both with and without activation. The remaining 53 substances gave variable results when tested under different experimental protocols or in different cell types, but were positive in at least one test. Although discrepant results were found associated with some cell types, the addition of metabolic activation systems tended to eliminate such variability. No one cell appeared to be superior in response to all clastogens. For screening purposes, the choice of cell may thus depend more on the general usefulness and reliability of a cell type than on a strong response to a particular chemical. However, the use of a suitable metabolic activation system does appear to be of critical importance. The concentration at which clastogenic effects were detected varied extensively for different test substances, ranging from a minimum of 4.3 X 10(-8) to 6.9 X 10(2) mM. Possible mechanisms of action for substances active at only high levels are discussed, but no satisfactory explanation is available at this time. The relevance of tests conducted at concentrations high enough to alter significantly the osmolarity and other culture conditions is considered, and caution urged in the interpretation of test results obtained under physiologically stressful conditions. The clastogenic potential was compared quantitatively using an index of effective concentration (D20) and one which estimates the number of cells with exchange aberrations expected per mg/ml (TR) for data obtained by using a uniform protocol and cultures of Chinese hamster lung (CHL) cells. Both values were distributed over a wide range, demonstrating the variety of genotoxic potential in chemicals. In general, a substance which was active at only high concentrations produced fewer exchange-type aberrations. In vivo activity, as measured by tumourigenic effect and formation of micronuclei in bone marrow, tended to be greater for substances with a D20 below 10(-2) mg/ml and a TR value over 10(3).(ABSTRACT TRUNCATED AT 400 WORDS)

DNA aneuploidy in adult acute leukemia

Using flow cytometric techniques, we determined DNA ploidy levels in the bone marrow of 318 successive adult patients with newly diagnosed acute leukemia. Overall, 26% exhibited DNA stem line abnormalities, usually with a 10%-15% DNA excess, regardless of morphologic diagnosis. DNA aneuploidy was seen most frequently in patients with a hyperdiploid chromosome number and karyotype instability (50%), but was also present in a third of patients with chromosomal translocations and in 20% of patients with a normal diploid karyotype. Thus, among 73 patients with DNA aneuploidy, quantitatively concordant karyotype abnormalities were observed in almost 40% of patients; the discrepancy between DNA content and chromosome number in the remaining patients may reflect differences in the cell cycle position of target cells in G1/0 phase or mitosis, respectively. Cytogenetics affected treatment outcome in acute myelogenous leukemia (AML) with more favorable short- and long-term prognosis among patients with translocations compared with those with numeric abnormalities. The presence of an abnormal DNA stem line, among AML patients with translocations, identified a favorable subgroup with significantly longer remission duration and survival (25 and 26 months versus 18 and 13 months, respectively). In addition, the prognostic implications of DNA aneuploidy in AML were age-dependent, in that favorable effects among patients with translocations and unfavorable effects among those with numeric abnormalities or diploid karyotypes were most obvious in young and not in older patients (greater than or equal to 40 years). In adults with ALL, DNA aneuploidy was associated with shorter survival (15 versus 39 months in the diploid group), an observation that is distinctly at variance with recent findings in childhood ALL. Our results indicated that DNA flow cytometry was complementary to standard cytogenetics for the detection of genomic abnormalities; and DNA aneuploidy emerged, like in children but not in adults with ALL, as a new favorable prognostic feature in a subgroup of adults with AML, the biologic basis of which remains to be determined.

Recessive cancer genes in meningiomas? An analysis of 31 cases

Cytogenetic studies on 31 human meningiomas revealed clonal abnormalities in 14 of them. Monosomy 22 was present in three cases as the only abnormality, and in five it was associated with monosomy 18, monosomy 14, loss of X, loss of Y, and trisomy 20, respectively. We found a number of rearrangements involving chromosome #22: an i psu dic(22)(pter----q11::q11----pter) in two cases and a t(18;22)(q12;q11) in another case. Two cases showed a complex translocation involving #7 and #14: t(2;7;14)(q23;q36;q22) and t(1;7;14)(q25;q32;q22), respectively. Other clonal chromosome abnormalities were del(1p) (present in two cases); der(9)t(9;?)(q34;?); der(7)t(7;?)(q31;?); der(22)t(22;?)(q11;?); and a 9p+ chromosome. The relevance for the pathogenesis of human meningiomas of these chromosome anomalies is also discussed with reference to the previous literature. The possible involvement of recessive cancer genes present on the long arm of chromosome #22 is also discussed.

Phenotypic and genetic variations in crown-gall tumour cells of tobacco

Phenotypic and genetic variations of tumour cells were analysed both quantitatively and qualitatively in clones and subclones of a crown-gall strain. Thus, growth rates, grafting tests, octopine synthesis, estimations of the T-DNA contents, modifications in the numbers, and structures of chromosomes were examined. Phenotypic variations are closely associated with genetic changes, including variation in chromosome number (which is shown to be non-specific to the tumoral state) and, above all, variation in the copy-number of T-DNA sequences per cell, and structural rearrangements of chromosomes. Such rearrangements are characterized by specific marker chromosomes in the tumour cells and they correlate with the degree of oncogenicity of the cells.

An idea on the genesis of the first cancer cell

The first malignant cell could be the result of a type of fertilization or parthenogenesis between somatic cells that have undergone a meiotic or meiotic-like process initiated by carcinogens and viruses or occurring as a result of genetic errors.

Cytogenetic studies of human brain tumors and their clinical significance. II. Meningioma

Cytogenetic study of 45 meningiomas from 31 female and 14 male patients are reported. No chromosomal abnormalities were found in nine (20%). These were predominantly meningotheliomatous, and were from younger patients (average age, 46 years). Monosomy 22 was noted in only 20% and in 12 patients (27%) with other losses and rearrangements. Among the latter, 50% were either recurrent or recurrent and invasive, the majority were fibromatous and occurred in older patients. Nonrandom loss was observed of the Y and abnormalities of chromosomes #1, #7, and #14 and, to a lesser extent, chromosomes #18, #19, and #20. Meningiomas may begin with no chromosomal abnormalities, having meningotheliomatous histopathologic appearance, occur in younger patients, and are less aggressive. Karyotypic evolution following loss of a chromosome #22 continues with losses and rearrangements of other chromosomes with apparent nonrandom involvement of chromosomes #1, #7, #14 and Y. This karyotypic change is associated with aggressive tumor behavior and fibromatous morphology.

Marked hypodiploidy in blast phase chronic myelogenous leukemia: report of a case and review of the literature

The emergence of a near-haploid clone of cells in blast phase chronic myelogenous leukemia is an unusual event. We report such a case and review eight other cases described in the English literature. The significance of the substantial loss of genetic material is discussed as is the phenotypic and genotypic heterogeneity observed in this group of patients.

Presence of isochromosomes in hematologic diseases

Several different structural chromosome aberrations have been observed in human neoplasias. In this report we describe the isochromosomes found in nine patients with hematologic malignancies: five with leukemia, one with sideroblastic anemia, and three with malignant lymphomas. The isochromosomes i(7q), i(11q), i(17q), and i(21q) were detected in these patients. We suggest that the presence of isochromosomes permits us to speak of a gene-dosage effect and that this mechanism may play a role in malignant transformation.

Cytogenetic evidence for clonal evolution in B-cell chronic lymphocytic leukemia

Sequential cytogenetic studies were performed in eight of ten patients with B-cell chronic lymphocytic leukemia presenting with trisomy 12 as the sole chromosomal abnormality. Follow-up studies of peripheral blood lymphocytes revealed that the karyotypes retained the sole abnormality of trisomy 12 in five cases, trisomy 12 converted to a normal karyotype during remission in one case, additional chromosome changes (-X,14q-) along with trisomy 12 appeared in one patient and multiple chromosome changes with or without trisomy 12 appeared in the remaining patient. The findings indicate that other chromosome changes in addition to trisomy 12 may develop as a result of clonal evolution or dedifferentiation, though the possibility that in two patients these changes may be related to chemotherapy and/or irradiation could not be ruled out entirely.

An early, nonrandom karyotypic change in immortal Syrian hamster cell lines transformed by asbestos: trisomy of chromosome 11

Cytogenetic studies were performed on eight early passage Syrian hamster embryo cell lines independently derived following asbestos exposure. The modal chromosome number of all the immortal cell lines was near-diploid. At the earliest passage examined, six of eight cell lines had only numerical chromosome changes. Cells in each of these six cell lines had an extra chromosome #11, either as a sole karyotypic change or with other numerical changes. The remaining two cell lines displayed both numerical and structural chromosome changes, but without involvement of chromosome #11. Common abnormalities were -X or -Y, +3, and 8p- in one cell line, and -13 and t(13;21) in the other cell line. A nonrandom gain of chromosome #8 was also found in four cell lines. In three of the four cell lines, trisomy of chromosome #8 seems to have occurred during karyotypic progression. The observation that nonrandom changes in chromosome number are an early karyotypic change after carcinogen treatment supports our hypothesis that induction of aneuploidy by asbestos is mechanistically important in the transformation of Syrian hamster embryo cells in culture and, further, suggests that trisomy 11 plays a major role in the early steps of immortalization and neoplastic progression.

Chromosomal changes in relation to tumorigenicity of the murine L1210 leukemia line

A spontaneous loss of tumorigenicity was observed in long-term in vitro culture of the cell line L1210(VAII), which was derived from mouse lymphoblastic leukemia L1210(V) of DBA/2 mice. The loss of tumorigenicity required at least 12 months of in vitro culture and was accompanied by the appearance of a new karyotypically distinct population. The dominant cell variant of the in vitro population that lost tumorigenicity showed duplication of a fragment within the M2 marker chromosome. The loss of tumorigenicity could be interpreted as a dose effect on tumor growth control by gene(s) localized within this marker chromosome.

Geographic heterogeneity of chromosome aberrations in hematologic disorders

The incidence of characteristic nonrandom chromosome aberrations in malignant cells of unselected, consecutively studied, and previously untreated patients from various geographic regions has been surveyed. The results demonstrate significant geographic heterogeneity in the distribution of the specific aberrations considered among the four malignant disorders studied in a sufficient number to permit conclusions, viz., acute nonlymphocytic leukemia, chronic myeloid leukemia, polycythemia vera, and myelodysplastic syndrome.

Acute myelogenous leukemia with translocation t(8;21): a cytogenetic study of seven cases

Seven cases of acute nonlymphoblastic leukemia showing t(8;21)(q22;q22) at diagnosis are described. Involvement of a sex chromosome was found in all patients (in six cases as a loss, and in one as a Y duplication), thus, confirming the suggestion of a correlation between these two chromosomal abnormalities. The constitutional folic acid-sensitive fragile site fra(8)(q22) was not detected, in spite of careful analysis of over 300 metaphases of cells grown in folic acid-free medium. Morphologic diagnoses and clinical aspects are briefly discussed.

Cytogenetic findings in acute monocytic leukemia in a renal allograft recipient

Chromosome analysis of bone marrow cells from a patient with acute monocytic leukemia, who had had a renal transplant followed by immunosuppressive treatment 45 months prior to the onset of leukemia, showed an unusual karyotype: 48,XX,+8,+8, t(1q12----pter::11q12----qter), t(4p12----qter::6p11----pter),t(7p22----qter::12q23 ----qter?), t(1q11----qter::17p11----11qter).

Primary cytogenetic abnormality detected in an endometrial adenocarcinoma

Cytogenetic findings obtained from an endometrial adenocarcinoma stage 1A are reported. The primary stem line was pseudodiploid with an abnormal chromosome #8. Three side lines were noted, which collectively involved chromosomes X, #8, #12, and two members of group D. A small percentage of cells was either pseudotetraploid or near-tetraploid. Double minutes were noted in one of the latter cells. Interest in the case is centered on the finding of what appeared to be the primary chromosomal change.

Chemically induced aneuploidy in mammalian cells: mechanisms and biological significance in cancer

A growing body of evidence from human and animal cancer cytogenetics indicates that aneuploidy is an important chromosome change in carcinogenesis. Aneuploidy may be associated with a primary event of carcinogenesis in some cancers and a later change in other tumors. Evidence from in vitro cell transformation studies supports the idea that aneuploidy has a direct effect on the conversion of a normal cell to a preneoplastic or malignant cell. Induction of an aneuploid state in a preneoplastic or neoplastic cell could have any of the following four biological effects: a change in gene dosage, a change in gene balance, expression of a recessive mutation, or a change in genetic instability (which could secondarily lead to neoplasia). To understand the role of aneuploidy in carcinogenesis, cellular and molecular studies coupled with the cytogenetic studies will be required. There are a number of possible mechanisms by which chemicals might induce aneuploidy, including effects on microtubules, damage to essential elements for chromosome function (ie, centromeres, origins of replication, and telomeres), reduction in chromosome condensation or pairing, induction of chromosome interchanges, unresolved recombination structures, increased chromosome stickiness, damage to centrioles, impairment of chromosome alignment, ionic alterations during mitosis, damage to the nuclear membrane, and a physical disruption of chromosome segregation. Therefore, a number of different targets exist for chemically induced aneuploidy. Because the ability of certain chemicals to induce aneuploidy differs between mammalian cells and lower eukaryotic cells, it is important to study the mechanisms of aneuploidy induction in mammalian cells and to use mammalian cells in assays for potential aneuploidogens (chemicals that induce aneuploidy). Despite the wide use of mammalian cells for studying chemically induced mutagenesis and chromosome breakage, aneuploidy studies with mammalian cells are limited. The lack of a genetic assay with mammalian cells for aneuploidy is a serious limitation in these studies.

Karyotypic evolution in Ph-positive chronic myeloid leukemia in relation to management and disease progression

In a prospective study of 32 patients with chronic myeloid leukemia the frequency of chromosome abnormalities in addition to the Philadelphia chromosome (Ph) increased when the disease progressed. Before metamorphosis, 10 patients (31%) had developed additional abnormalities. Such abnormalities were present in three of them at the time of diagnosis; in the other seven, they were detected late in the chronic phase. New clonal abnormalities heralded or accompanied a more malignant phase of the disorder, usually a blastic leukemia. During metamorphosis, 78% of the patients had additional abnormalities, which in 68% of these cases comprised at least one of +8, +22q- or i(17q). Clones with additional abnormalities disappeared in eight cases, either spontaneously or in association with cytostatic therapy during the chronic or blastic phase. Involvement of chromosome #8, usually in the form of a trisomy, was found in 7 of 12 patients treated with busulfan, but was not found in any of the 10 hydroxyurea-treated patients, of whom 8 were splenectomized early during the chronic phase. Cells from the spleen, obtained by fine needle aspiration or splenectomy were cytogenetically examined in 18 cases during the chronic phase, but abnormalities in addition to the Ph were noted in only one patient, who was examined in the late chronic phase. The same abnormalities were present in bone marrow cells of this patient.

Fused transcript of abl and bcr genes in chronic myelogenous leukaemia

Human chronic myelogenous leukaemia is characterized by a reciprocal translocation between chromosomes 9 and 22 resulting in an abbreviated form of chromosome 22 and the transfer of the abl cellular oncogene from chromosome 9 into the bcr gene of chromosome 22. Characterization of an 8-kilobase RNA specific to chronic myelogenous leukaemia shows it to be a fused transcript of the two genes. The fused protein that would be produced is probably involved in the malignant process.

Cytogenetic findings in childhood acute lymphoblastic leukemia

Chromosome studies were performed on the bone marrow cells of 42 children with newly diagnosed acute lymphoblastic leukemia (ALL). All the children were subsequently treated with the same protocol. Chromosomal abnormalities were found in 25 patients, i.e., in 59.5% of the cases. Hyperdiploidy was observed in 21.4% hypodiploidy in 14.3%, and pseudodiploidy in 23.8% of the children. The most frequent structural aberrations were translocations, which were found in half of the patients with abnormal karyotypes. Chromosomes #5, #6, #7, #9, #14, #17, and #21 were involved in different types of changes most frequently. Because these findings correspond with observations published by others, they can be regarded as evidence of nonrandom involvement of these chromosomes in rearrangements in ALL. Special attention should be also paid to the deletion of 6q, which seems to be relatively common in ALL. In 12 cases, clonal evolution of karyotypic changes was observed.

Karyotypic variation of cells from murine thymic lymphomas during short-term culture

The present study examined the balance in the proportion of cells with either trisomy 15 or a diploid chromosome complement during short-term culture in vitro. Neonatal CFW/D mice were given an intrathymic injection of an endogenous virus (DMBA-LV) isolated from a DMBA-induced thymic lymphoma. The thymus was removed at the terminal leukemic stage, and the cells from each enlarged thymus were cultured in quintuplet. At 0, 6, 12, 24, and 48 hr, cultures were given colcemid for 2 hr prior to harvesting for chromosome examination. The analyzed lymphomas can be divided into three groups according to the characteristics of their stem lines and sidelines, as revealed by direct chromosome preparation (0 hr). Two groups consisted of lymphomas carrying a stem line with either trisomy 15 (group 1) or a diploid karyotype (group 2). A third group (group 3) consisted of lymphomas with a mixture of an abnormal stem line and sidelines. Chromosome analysis of cultures at subsequent times showed that there were fluctuations in the proportion of cells characterized as either stem line or sideline in all tumors at different times during culture. The initial sideline in group 1 tumors had a diploid complement. Although the proportion of the diploid cells increased in 5 of the 6 tumors following either 24 or 48 hr in culture, cells with a diploid karyotype remained as a sideline throughout the culture period. Similarly, the two tumors analyzed in group 2 showed that the initial sideline that contained trisomy 15 increased temporarily to become the stem line following 6 or 12 hr in culture. Group 3 tumors showed a slight variation in the proportion of cells with an abnormal stem line or sideline during culture. Considering all the data from the 10 tumors, 7 tumors had cells with a diploid karyotype, and, although the proportion of cells with this karyotype increased (4 tumors) or persisted (3 tumors) during 48 hr in culture, it remained as a sideline and was not overgrown by trisomy 15 stem line.

Myxoid chondrosarcoma with a translocation involving chromosomes 9 and 22

Myxoid chondrosarcoma is an uncommon neoplasm thought to be derived from mesenchymal chondrocytic cells. Although cytogenetic abnormalities have been reported in sarcomas, too few cases have been studied to determine the frequency of nonrandom chromosomal changes in mesenchymal tumors. In this article, we describe a chondrosarcoma with a nonrandom reciprocal translocation t(9;22)(q22;q11). The cellular homologue to the retrovirus transforming gene of simian sarcoma virus is located on chromosome #22, and its possible significance in this case is discussed.

Correlation of karyotype with patient sex and age in acute myeloid leukemia

Karyotypes were determined in 109 patients with acute myeloid leukemia. The proportions of patients with nonclonal chromosomal abnormalities, with numeric changes only, and with severe chromosomal aberrations were all found to increase to a statistically significant degree with patient age. Most patients in whom less than half of all cells were abnormal were elderly males. These results indicate that the cell karyotype was less stable in elderly patients than in younger patients. A higher frequency of nonclonal chromosomal changes was found in patients with clonal abnormalities compared with those without such abnormalities. Male patients tended to gain chromosomes and had more hyperdiploid abnormalities than female patients, who tended to lose chromosomes and had more hypodiploid abnormalities. This trend of chromosomal gain in males and loss in females mainly involved chromosomes similar in size to the sex chromosomes. Three female patients with trisomy 8 and one with 7q+ and t(8;21) showed an X chromosome twisted into a spiral shape. The results indicate that the initial karyotype effects the formation of some numeric changes. These findings are discussed in relation to possible secondary chromosomal changes and karyotypic instability.

Cytogenetics of acute promyelocytic leukaemia: incidence of t(15;17) at the Royal Marsden Hospital, London

This is the first report from a laboratory in the U.K. of the incidence of t(15;17) in acute promyelocytic leukaemia. One of the cases has a variant translocation, t(15;17)(q22;q25). A t(15;17) translocation was present in all cases considered to be adequately studied.

Incidence of double minutes, cytogenetic equivalents of gene amplification, in human carcinoma cells

Screening of the occurrence of double minutes (DM) was performed in more than 1,000 metaphases obtained from a total of 22 solid human breast tumours and more than 3,600 metaphases from a total of 55 malignant effusions (45 patients with different types of carcinomas). DM were observed in 15 of these breast tumor cases and in 34 of the effusions (obtained from 29 cancer patients). The percentage of cells exhibiting DM as well as the number of DM per respective cell varied widely. It could be seen that metastatic cells from malignant effusions exhibited on the average more DM per cell than did cells of primary breast carcinomas. Differences in the incidence of DM could be observed between different carcinomas as well as between different age groups. In addition, it did not appear that DM could be induced by mutagenic tumor therapy. DM are thus not a rare finding in human solid tumors but, as cytogenetic equivalents of gene amplification, they rather represent a fundamental biological characteristic of tumor development.