Pathways leading to glioblastoma multiforme: a molecular analysis of genetic alterations in 65 astrocytic tumors

To characterize some of the genetic events underlying the development of glioblastoma multiforme, the authors analyzed 65 astrocytic tumors (seven pilocytic astrocytomas, eight astrocytomas, 16 anaplastic astrocytomas, and 34 glioblastomas multiforme) for loss of heterozygosity for chromosome 17p, loss of heterozygosity for chromosomes 10p and 10q, amplification of the epidermal growth factor receptor (EGFR) gene, and amplification of the oncogenes N-myc, c-myc, and N-ras using Southern blot analysis. Alterations of the p53 gene (positive immunostaining for p53 protein in tumors with or without p53 gene mutations) in these 65 tumors were analyzed previously. None of the 65 tumors showed amplification or rearrangement of N-myc, c-myc, or N-ras oncogenes. The molecular analysis presented here demonstrates distinct variants of astrocytic tumors, with at least three genetic pathways leading to glioblastoma multiforme. One pathway was characterized by 43 astrocytomas with alterations in p53. Glioblastomas with p53 alterations may represent tumors that progress from lower-grade astrocytomas. This variant was more likely to show loss of chromosome 17p than tumors without p53 alterations (p < 0.04). Seventy-five percent of tumors with loss of one 17p allele demonstrated mutations in the p53 gene. Loss of chromosome 10 was associated with progression from anaplastic astrocytoma (13%) to glioblastoma (38%) (p < 0.04). Amplification of the EGFR gene was a rare (7%) but late event in tumor progression (p < 0.03). A second pathway was characterized by six astrocytomas without p53 alterations and may represent clinically de novo high-grade tumors. These tumors were more likely to show amplification of the EGFR gene (83%) than tumors with p53 alterations. Sixty percent of tumors with EGFR amplification also showed loss of chromosome 10; loss of chromosome 17p was infrequent in this variant. One or more alternative pathways were characterized by 16 astrocytomas without p53 alterations and with none of the genetic changes analyzed in this study. Glioblastomas are a heterogeneous group of tumors that may arise via multiple genetic pathways.     

bcr-abl mRNA检测在慢性粒细胞白血病诊治中的意义

目的 探讨bcr-abl mRNA在慢性粒细胞白血病(CML)诊断、治疗及微小残留病变监测中的意义.方法 采用实时定量聚合酶链反应(real-time PCR)方法检测324例CML患者518份标本的bcr-abl mRNA表达情况.结果 CML慢性期、加速期和急变期患者的bcr-abl mRNA定量结果逐渐增高,分别为12.6%、25.4%和57.2%(P<0.05).异基因造血干细胞移植后的bcr-abl mRNA定量结果随时间延长逐渐降低,一般在移植6个月后转阴,服用伊马替尼(商品名:格列卫)与异基因造血干细胞移植病程相似,但融合基因转阴所用时间较长.结论 real-time PCR检测bcr-abl mRNA对于诊断、评价疗效、监测微小残留病变以及预测疾病进展具有重要的临床应用价值.     

Amplification of c-MYC oncogene and point mutation of N-RAS oncogene point mutation in acute myelocytic leukemias with double minute chromosomes

Two patients with acute myelocytic leukemia (AML) showing double minute (dmin) chromosomes were analysed to identify oncogene activation. Cytogenetic analysis showed 1-53 dmin chromosomes with the normal karyotype in the first patient and 1-84 dmin chromosomes with complex chromosome aberrations. Analysis of DNA from two patients revealed five- to tenfold amplification of c-MYC oncogene in the leukemic cells. The other sixteen oncogenes studied showed no increase in the gene content. Furthermore, a transforming gene, N-RAS was detected in the first patient by nude mouse tumorigenicity assay (in vivo selection assay). These results suggest that the amplification of c-MYC gene is common in dmin-positive AML patients and co-ordination of c-MYC and N-RAS oncogene might also play a significant role in the pathogenesis of some AML patients.     

Personality and social competency following unilateral stroke

To understand the nature and extent of oncogene involvement in the development of neoplasia, an experimental model of goat ovarian granulosa cells stimulated by LH was chosen. In the course of these studies, several cell lines were developed which were essentially non-tumorigenic primary cell lines. One of them, however, was spontaneously transformed being immortalized and tumorigenic. These cell lines, transformed and non-transformed, should serve as contralateral cell lines to study differential oncogene expression in hormonally induced cell proliferation, and elucidate possible hormone-oncogene nexus which may be operative in the genesis of cancer. In the present report, we have studied expression of c-myc, c-ras, c-myb, c-fos and c-sis cellular oncogenes in the cell lines by immunocytochemistry using monoclonal antibodies. In the rest of our text we refer to these cellular oncogenes as oncogenes. The results reveal differential expression of the oncogenes. The striking difference between the non-transformed AIMS/GRXII cells and the transformed AIMS/GRXVIII cells was the absence of ras protein expression in the transformed AIMS/GRXVIII cells which intensely expressed the c-myc, c-myb, c-fos, and c-sis proteins. c-ras protein was expressed in the non-transformed AIMS/GRXVIII cell line and primary cultures. c-myc protein was expressed exclusively in the AIMS/GRXVIII transformed cells. The myc activity seen in the transformed cell line may be correlated to cell proliferation. These results show the variation of phenotype in cell lines derived from a single tissue source.     

Experimental telemanipulation in endoscopic surgery

Chronic Myeloid Leukemia (CML) is a clonal disease of bone marrow, citogenetically characterized by the presence of the Philadelphia chromosome (Ph). Additional anomalies in the Ph cromosome have been found during the evolution of CML. This paper will show evidence of cytogenetic abnormalities during the evolution of CML in this region, and its correlation with clinical evolution. 55 samples of bone marrow, 81.3% (45/55) in chronic phase (CP), 12.7% (7/55) in an accelerated phase (AP), and 5.4% (3/55) in blastic phase (BP) were received. In 12/45 patients in CP the karyotype was repeated at least once a year during the evolution of their illness. 9/12 presented the Ph chromosome as a single anomaly at the moment of diagnosis; the other 3 presented a distinct anomaly. 4/9 presented additional abnormalities moving to the stages AP or BP between 4-8 months after initial discovery. 7/10 patients referred in AP or BP presented additional abnormalities in the Ph chromosome. It is evident that the chromosome study of each patient with CML must be carried out at least once a year in order to detect chromosomal abnormalities in addition to the Ph chromosome. Thus, a greater therapeutic control of the disease is possible.     

Quantitation of HER-2/neu and c-myc gene amplification in breast carcinoma using fluorescence in situ hybridization

HER-2/neu and c-myc amplification or overexpression have been reported to be associated with poor prognosis in breast carcinoma. The prognostic significance, however, remains somewhat controversial, partly because of discrepancies among different methodologies used for detection of the oncogene amplification or overexpression. Fluorescence in situ hybridization (FISH) has recently been shown to be a useful technique for analyzing genetic alterations in interphase nuclei in various tumors. In this study, FISH was used to quantitate HER-2/ neu and c-myc gene amplification in touch preparations of frozen tissue from 100 node-negative breast carcinomas. HER-2/neu amplification was found to be associated with an abnormal DNA index (P < .001) and tumor size (P < .04). Amplification of c-myc was associated with S phase (P < .0003), abnormal DNA index (P < .003), and a negative estrogen receptor status (P < .01). The coamplification of both oncogenes was strongly associated with an abnormal DNA index (P < .0001) and with tumor size (P < .009). The use of FISH for detection of HER-2/neu gene amplification was 92% concordant with immunocytochemistry (ICC) used for detection of overexpression of HER-2/neu protein. Fifteen of the 100 cases were both amplified for HER-2/neu by FISH and positive by ICC analysis. Seven cases without HER-2/neu gene amplification demonstrated HER-2/neu protein overexpression by ICC. One HER-2/neu-amplified case was negative by ICC. Repeat analysis of a subset of cases showed FISH to be a more reproducible method than ICC in the analysis of HER-2/neu in touch preparations of breast carcinoma. FISH is a rapid and reproducible method that allows the accurate measurement of the level of oncogene amplification within interphase nuclei. The use of FISH should provide a more accurate assessment of the prognostic significance of oncogene amplification in breast carcinoma.     

Is the presence of distant metastasis associated with c-myc amplification in gastric cancer?

The expression of the c-myc oncogenes has already been reported in human gastric carcinoma. Overexpression can be the consequence of oncogene amplification and often correlates with different prognostic factors. Authors investigated the value of c-myc oncogene amplification in 23 patients (9 male, 14 female, aged 28-85 yrs) with gastric cancer and its correlation to the following clinical and histopathological parameters: grade, TNM stage, Lauren's type, localisation and severity of disease. DNA was isolated from formalin-fixed, paraffin embedded tissue for quantitative dot-blot hybridisation. Amplified c-myc was found in 6 out of 23 cases. Its values ranged from 2.12 up to 18.2 (average 9.1). Significant association was found between the presence of c-myc amplification and distant metastasis (corr. coeff.: 0.5623, p < 0.01). High scores of the other parameters also correlated with c-myc, albeit not significantly. The result of cluster analysis, based on the similarity of the parameter values for the individual patients proved that the age was the decisive factor in creating two groups. The distribution of patients into these groups did not seem to coincide with the presence of c-myc amplification or distant metastasis, inspite of the proved correlation between them.     

Detection of c-myc translocation in human lung cancer cells by fluorescence in situ hybridization (FISH)

c-myc gene amplification has been found in lung cancer, however, it can not explain all cases of lung cancer with c-myc gene overexpression. Gene translocation is one of the ways by which oncogene is activated. But the old methods for detecting gene mutations are not so effective for the detection of gene translocation, especially in solid tumors. Fluorescence in situ hybridization (FISH) can be used to detect gene translocation more efficiently. Using FISH, we discovered c-myc gene translocation in a lung adenocarcinoma cell line GLC-82 and SV40T-transformed human bronchial epithelial cells. In GLC-82, c-myc gene translocated to the short arm of a C group marker chromosome. In the SV40T-transformed epithelial cells, c-myc gene translocated to 14q32, which was the same as that found in Burkitt's lymphomas. Translocation was related to oncogene activation. c-myc translocation may play an important role in the carcinogenesis of lung cancer.     

Genetic basis of neurological tumours

Neurological tumours are common neoplasms of both adults and children. Recent studies have begun to delineate the genetic abnormalities that underlie such tumours, and have implicated two classes of genes, oncogenes and tumour suppressor genes. Most investigations have focused on those astrocytomas that affect the cerebral hemispheres of adults, since these are the most common and malignant brain tumours. The high-grade astrocytomas that affect adults, such as glioblastoma multiforme, often have amplification of the epidermal growth factor receptor (EGFR) oncogene and loss of a variety of chromosomal loci that probably harbour tumour suppressor genes. Of the various tumour suppressor gene loci, the p53 gene on chromosome 17p has been studied most closely and has been shown to be mutated in both low- and high-grade astrocytomas. These genetic alterations may provide a means for subdividing astrocytomas into diagnostic categories. For instance, p53 gene mutations occur more commonly in glioblastomas from young adults and women, while EGFR gene amplification is more common in glioblastomas from older adults and men. For the other primary CNS tumours, genetic studies remain in their infancy. The neurocutaneous syndromes, such as neurofibromatosis types 1 and 2, have provided unique insights into neurological oncogenesis. The NF1 gene on chromosomes 17q and its product, neurofibromin, may be important in the formation of neurofibrosarcomas, while the NF2 gene on chromosome 22q and its product, merlin, are probably involved in the formation of schwannomas and other nervous system tumours. The further characterization of these and other neurological tumour genes will undoubtedly illuminate many other areas in neurooncology.     

Analytical evaluation of the new Prostatus PSA Free/Total assay for prostate-specific antigen as part of a screening study for prostate cancer

A second Philadelphia (Ph) chromosome is one of the most common nonrandom secondary chromosome changes in leukemias with 9;22 translocations. It has been suggested, and observed in two studies of masked t(9;22), that the second Ph chromosome is an exact duplication of the entire derivative chromosome 22. In a cytogenetic study of bone marrow cells from an acute myelogenous leukemia patient, a cell line carrying two different Ph chromosomes evidenced by a chromosome 22 centromeric heteromorphism was found. From this observation arose the question whether the second der(22) was a true Ph chromosome or whether it was a deleted chromosome derived from the normal chromosome 22 that did not contain the bcr-abl rearrangement. A fluorescent in situ hybridization (FISH) study with the t(9;22) probe revealed two bcr-abl positive signals on 60 of 100 interphase nuclei. The second Ph could have resulted from a mitotic crossing over; or, analogously to late-appearing Philadelphia chromosomes, it may be derived from a new chromatid translocation between the chromosomes 9 and 22 not involved in the initial t(9;22).     

BCR-ABL activates pathways mediating cytokine independence and protection against apoptosis in murine hematopoietic cells in a dose-dependent manner

The hallmark of chronic myeloid leukemia (CML) is the chimeric tyrosine kinase oncogene bcr-abl. Since expression of bcr-abl mRNA frequently increases with disease progression and a duplication of the Philadelphia chromosome (harbouring the bcr-abl hybrid locus) represents the most frequent karyotypic abnormality in acute phase CML, we hypothesized that the level of BCR-ABL protein may affect the disease phenotype. Therefore, the biological effects of high and low levels of BCR-ABL expression were compared in growth factor-dependent and -independent myeloid and lymphoid cell lines. Our results demonstrated that low levels of BCR - ABL were sufficient to render these cell lines growth factor independent and tumorigenic, but higher levels were mandatory for additional protection against apoptotic stimuli. The provision of growth factor or an activated ras oncogene did not afford the same degree of protection as high levels of BCR-ABL and there were qualitative differences between the survival signals mediated by BCR-ABL and Bcl-2. These results have enabled us to establish a dose-dependent hierarchy of BCR-ABL induced biological effects, thus distinguishing the activation of pathways mediating protection from cytokine withdrawal from those protecting against other apoptotic stimuli.     

c-myc copy number gains in bladder cancer detected by fluorescence in situ hybridization

Amplification and overexpression of c-myc have been suggested as prognostic markers in human cancer. To assess the role of c-myc gene copy number alterations in bladder cancer, 87 bladder tumors were examined for c-myc aberrations by fluorescence in situ hybridization. Dual labeling hybridization with a repetitive pericentromeric probe specific for chromosome 8 and a probe for the c-myc locus (at 8q24) was performed to analyze c-myc copy number in relation to chromosome 8 copy number on a cell by cell basis. A clear-cut c-myc amplification (up to 40 to 150 copies per cell) was found in 3 tumors. There was a low level c-myc copy number increase in 32 of the remaining 84 tumors. There was no association of low level c-myc copy number increase with c-myc protein overexpression. This suggests that a c-myc gene copy number gain as detected by fluorescence in situ hybridization does not necessarily reflect a disturbed c-myc gene function but may indicate a structural chromosome 8 abnormality including gain of distal 8q. The strong association of low level c-myc (8q) gains with tumor grade (P < 0.0001), stage (P < 0.0001), chromosome polysomy (P < 0.0001), p53 protein expression (P = 0.0019), p53 deletion (P = 0.0403), and tumor cell proliferation (Ki67 labeling index; P = 0.0021) is consistent with a role of chromosome 8 alterations in bladder cancer progression.     

Bcr-Abl efficiently induces a myeloproliferative disease and production of excess interleukin-3 and granulocyte-macrophage colony-stimulating factor in mice: a novel model for chronic myelogenous leukemia

The bcr-abl oncogene plays a critical role in causing chronic myelogenous leukemia (CML). Effective laboratory animal models of CML are needed to study the molecular mechanisms by which the bcr-abl oncogene acts in the disease progression of CML. We used a murine stem cell retroviral vector (MSCV) to transduce the bcr-abl/p210 oncogene into mouse bone marrow cells and found that expression of Bcr-Abl/p210 induced a myeloproliferative disorder that resembled the chronic phase of human CML in 100% of bone marrow transplanted mice in about 3 weeks. This CML-like disease was readily transplanted to secondary recipient mice. Multiple clones of infected cells were expanded in the primary recipients, but the leukemia was primarily monoclonal in the secondary recipient mice. Mutation analysis demonstrated that the protein tyrosine kinase activity of Bcr-Abl/p210 was essential for its leukemogenic potential in vivo. Interestingly, we found that the leukemic cells expressed excess interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the diseased mice. These studies demonstrate that expression of Bcr-Abl can induce a CML-like leukemia in mice much more efficiently and reproducibly than in previously reported mouse CML models, probably due to efficient expression in the correct target cell(s). Our first use of this model for analysis of the molecular mechanisms involved in CML raises the possibility that excess expression of hematopoietic growth factors such as IL-3 and GM-CSF may contribute to the clinical phenotype of CML.     

c-myc oncogene expression in estrogen-dependent and -independent breast cancer

We demonstrate that c-myc gene expression is essential for growth of breast cancer cells. It also plays an important role in the progression of human breast cancer. c-myc gene amplification may be important for cancer cell invasion, but perhaps not essential for nodal metastasis. We also provide compelling evidence that the c-myc oncogene is an estrogen target gene in hormone-responsive breast cancer. Hormonal progression of breast cancer could be brought about by the enhanced expression of the c-myc gene, with gene amplification and enhanced c-myc mRNA stability being two major mechanisms involved.     

Quantitative detection of amplification of proto-oncogenes in breast cancer

In the present study, dot-blot hybridization, serial dilution analysis and densitometric scanning were used to detect amplification of proto-oncogenes including c-erbB2, c-myc, int-2 and c-Ha-ras in 101 paraffin-embedded breast cancers. Expression of c-erbB2 was also examined by immunohistochemistry. Amplification of c-erbB2, c-myc and int-2 genes was found in 34.7%, 17.8% and 11.9% of breast cancers respectively. However amplification of c-Ha-ras was not detected in all cases. In 11.9% of cases co-amplification of two or more oncogenes was observed. Positive immunostaining of c-erbB2 was seen in 23.8% of the cases and it was significantly associated, but not always corresponding to the amplification of the gene. There was no difference between primary and metastatic breast cancer in the alterations of proto-oncogenes examined in this study, which suggested that the amplification and overexpression of these proto-oncogenes occurred prior to and maintained in the process of metastasis of breast cancer. Statistical analysis showed that high-scale of immunopositive staining of c-erbB2 and high-fold co-amplification of proto-oncogenes were significantly correlated with large size of the tumour and the number of involved lymph nodes. Our results indicate that the alterations of multiple oncogenes are involved in the development of breast cancer and some of them may have prognostic importance for breast cancer patients.     

The kinetics and extent of engraftment of chronic myelogenous leukemia cells in non-obese diabetic/severe combined immunodeficiency mice reflect the phase of the donor's disease: an in vivo model of chronic myelogenous leukemia biology

In vitro studies have provided little consensus on the kinetic abnormality underlying the myeloid expansion of chronic myelogenous leukemia (CML). Transplantation of human CML cells into non-obese diabetic mice with severe immunodeficiency disease (NOD/SCID mice) may therefore be a useful model. A CML cell line (BV173) and peripheral blood cells collected from CML patients in chronic phase (CP), accelerated phase (AP), or blastic phase (BP) were injected into preirradiated NOD/SCID mice. Animals were killed at serial intervals; cell suspensions and/or tissue sections from different organs were studied by immunohistochemistry and/or flow cytometry using antihuman CD45 monoclonal antibodies (MoAbs), and by fluorescence in situ hybridization (FISH) for the BCR-ABL fusion gene. One hour after injection, cells were sequestered in the lungs and liver, but 2 weeks later they were no longer detectable in either site. Similar short-term kinetics were observed using 51Cr-labeled cells. The first signs of engraftment for BV173, AP, and BP cells were detected in the bone marrow (BM) at 4 weeks. At 8 weeks the median percentages of human cells in murine marrow were 4% (range, 1 to 9) for CP, 11% (range, 5 to 36) for AP, 38.5% (range, 18 to 79) for BP, and 54% (range, 31 to 69) for BV173. CP cells progressively infiltrated BM (21%) and spleen (6%) by 18 to 20 weeks; no animals injected with the cell line or BP cells survived beyond 12 weeks. The rate of increase in human cell numbers was higher for BP (7.3%/week) as compared with CP (0.9%/week) and AP (0. 5%/week). FISH analysis with BCR and ABL probes showed that some of the human cells engrafting after injection of CP cells lacked a BCR-ABL gene and were presumably normal. We conclude that CML cells proliferate in NOD/SCID mice with kinetics that recapitulate the phase of the donor's disease, thus providing an in vivo model of CML biology.     

Molecular characterization of IgA- and/or IgG-switched chronic lymphocytic leukemia B cells

The immunoglobulin (Ig) variable region (V) genes expressed by IgM chronic lymphocytic leukemia (CLL) B cells display little or no somatic mutations. However, preliminary findings have shown that Ig V genes of IgA and IgG CLLs may be somatically mutated, suggesting that isotype-switched CLLs may represent a "subtype" of the disease. To investigate the degree and nature of somatic mutations and the role of antigen (Ag) in the clonal selection and expansion of isotype-switched CLLs, and to determine whether specific oncogene or tumor suppressor gene mutations are associated with isotype-switched CLLs, we analyzed the expressed Ig VH gene, bcl-1 and bcl-2 proto-oncogene, and p53 tumor suppressor gene configurations of 3 IgA-, 1 IgG-, and 1 IgA/ IgG-expressing CLLs. These isotype-switched CLL B cells expressed surface HLA-DR, CD19, CD23, and CD5, and displayed no alterations of the bcl-1 and bcl-2 oncogenes and the p53 tumor-suppressor gene. The cDNA VH-D-JH gene sequence was joined with that of the C alpha gene in the B cells of the three IgA CLLs, and with that of the C gamma gene in the IgG CLL B cells. In the IgA/IgG-coexpressing CLL B cells, identical VH-D-JH cDNA sequences were spliced to either C alpha or C gamma genes. In all five CLLs, the pattern of C mu DNA probe hybridization to the digested genomic DNAs was consistent with deletion of the C mu exon from the rearranged Ig gene locus, suggesting that these CLL B cells had undergone DNA switch recombination. In one IgA CLL, the expressed VH gene was unmutated. In all other class-switched CLLs, the Ig VH segment gene was mutated, but the point mutations were not associated with intraclonal diversification. In one IgA and in the IgA/IgG-coexpressing CLL, the nature and distribution of the mutations were consistent with Ag selection. These findings suggest that IgA- and/or IgG-expressing CLLs represent, in their VH gene structure, transformants of B cells at different stages of ontogeny. They also suggest that Ag may play a role in the clonal selection of some of these isotype-switched leukemic cells, but bcl-1 and bcl-2 oncogene rearrangements and p53 tumor suppressor gene mutation are not associated with the pathogenesis of isotype-switched CLLs.     

Regulation and mechanisms of gene amplification

Amplification in rodent cells usually involves bridge-breakage-fusion (BBF) cycles initiated either by end-to-end fusion of sister chromatids, or by chromosome breakage. In contrast, in human cells, resistance to the antimetabolite N-(phosphonacetyl)-L-aspartate (PALA) can be mediated by several different mechanisms that lead to overexpression of the target enzyme carbamyl-P synthetase, aspartate transcarbamylase, dihydro-orotase (CAD). Mechanisms involving BBF cycles account for only a minority of CAD amplification events in the human fibrosarcoma cell line HT 1080. Here, formation of a 2p isochromosome and overexpression of CAD by other types of amplification events (and even without amplification) are much more prevalent. Broken DNA is recognized by mammalian cells with intact damage-recognition pathways, as a signal to arrest or to die. Loss of these pathways by, for example, loss of p53 or pRb tumour suppressor function, or by increased expression of ras and myc oncogenes, causes non-permissive rat and human cells to become permissive both for amplification and for other manifestations of DNA damage. In cells that are already permissive, amplification can be stimulated by overexpressing oncogenes such as c-myc or ras, or by damaging DNA in a variety of ways. To supplement genetic analysis of amplification in mammalian cells, an amplification selection has been established in Schizosaccharomyces pombe. Selection with LiCl yields cells with amplified sod2 genes in structures related to those observed in mammalian cells. The effect on amplification in S. pombe can now be tested for any mutation in a gene involved in repair of damaged DNA or in normal cellular responses to DNA damage.     

Oncogene rearrangement in non-Hodgkin's lymphoma with a 14q+ chromosome of unknown origin

Southern blot analysis was performed with a panel of DNA probes to detect rearrangements of c-myc, bcl-1, bcl-2 and bcl-3 in 14 cases of B-cell non-Hodgkin's lymphoma (NHL) with a clonal cytogenetic rearrangement involving the chromosome 14q32 locus and no known donor chromosome [t(14;?)(q32;?)]. In our experience, 21% of all chromosomal abnormalities involving the 14q32 locus in B-cell NHL are of this type. We found oncogene rearrangements in five of the 14 cases: bcl-1 rearrangement on one mantle zone lymphoma, bcl-2 rearrangements in two follicular lymphomas, and c-myc rearrangements in two small noncleaved cell lymphomas. We conclude that a 14q32+ abnormality of unknown origin is a relatively frequent karyotypic finding in B-cell NHL. In one third of the cases, known oncogenes that have been previously described in reciprocal translocations involving the immunoglobulin heavy chain locus were shown to be involved in the 14q32+ abnormality. The translocations in the other cases are likely to have involved one of the above oncogenes with breakpoints not revealed by the probes employed, other known oncogenes, or oncogenes that have not yet been identified.     

Amplification of mitochondrial DNA in acute myeloid leukaemia

There is a long-standing interest in the possible role of mitochondria in malignancy. We sought to discover whether amplification of mitochondrial DNA (mtDNA) occurred in leukaemia, and found it was often remarkably amplified in the blast cells of acute myeloid leukaemia (AML). We used gene dosage experiments to quantify the amount of mtDNA relative to nuclear DNA. DNA extracted from peripheral blood leucocytes or bone marrow of healthy individuals or patients was simultaneously hybridized with a probe for the mitochondrial genome and a control probe for the renin gene on human chromosome 1. Comparative densitometric ratios of approximately 1 were obtained between the two signals in 20 normal control peripheral blood samples. In contrast, comparative ratios in the range of 2-50 were observed in 25 AML samples and 13 of these showed 8-fold or greater amplification of mtDNA relative to normal peripheral blood controls. An additional four cases of AML were investigated at both presentation and remission and showed 3-10-fold amplification of mtDNA at presentation, but no amplification when in clinical remission. 18 cases of chronic granulocytic leukaemia (CGL) were also studied in chronic phase and showed mtDNA dosage levels equivalent to normal peripheral blood controls. However, 8/9 CGL patients showed mtDNA amplification during transformation from chronic phase. We conclude that amplification of mtDNA is an invariable feature of acute myeloid leukaemia and that it may be a useful marker for detecting transformation of CGL.