Imbalance of sex chromosomes, with gain of early-replicating X, in human solid tumors

Gender-associated genomic differences in colorectal cancer: clinical insight from feminization of male cancer cells

Gender-related differences in colorectal cancer (CRC) are not fully understood. Recent studies have shown that CRC arising in females are significantly associated with CpG island methylator phenotype (CIMP-high). Using array comparative genomic hybridization, we analyzed a cohort of 116 CRCs (57 males, 59 females) for chromosomal copy number aberrations (CNA) and found that CRC in females had significantly higher numbers of gains involving chromosome arms 1q21.2–q21.3, 4q13.2, 6p21.1 and 16p11.2 and copy number losses of chromosome arm 11q25 compared to males. Interestingly, a subset of male CRCs (46%) exhibited a “feminization” phenomenon in the form of gains of X chromosomes (or an arm of X) and/or losses of the Y chromosome. Feminization of cancer cells was significantly associated with microsatellite-stable CRCs (p-value 0.003) and wild-type BRAF gene status (p-value 0.009). No significant association with other clinicopathological parameters was identified including disease-free survival. In summary, our data show that some CNAs in CRC may be gender specific and that male cancers characterized by feminization may constitute a specific subset of CRCs that warrants further investigation.

Analysis of clinical characteristics of 516 patients with non-Hodgkin's lymphoma in Shanghai area

The aim was to determine the clinical and cytogenetic characteristics of non-Hodgkin's lymphoma (NHL) in Shanghai. A retrospective analysis was conducted in 516 patients with NHL. Patient clinical data, including age, sex, diagnosis, immunophenotypes, and karyotypes, were collected. The median age was 58 years. There was a male predominance in all NHL, except extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue. Patients with B cell NHL (1.5%) expressed CD3. T cell NHL patients (11.5%) expressed CD20. Epstein-Barr virus latent integral membrane protein 1, BCL6, CD10, Bcl-2, CD68, myeloperoxidase, CD99, CD30, CD15, and CD43 were present in various types of NHL. Complex karyotypes accounted for 92.3% of the 73.7% patients with abnormal karyotypes. Immunoglobin heavy chain gene translocation was present in 60.3% of B cell and 23.7% of T/NK cell neoplasms. Understanding the complex clinicopathological and molecular features of NHL may help with prognosis and serve as targets for treatments.

Intratumoural cytogenetic heterogeneity of sporadic colorectal carcinomas suggests several pathways to liver metastasis

Much has been learned about the chromosomal abnormalities of colorectal carcinomas but the cytogenetic relationship between the neoplastic clones present in primary versus metastatic tumour samples remains unclear. We analyse the frequency of abnormalities for 47 chromosome regions using the interphase fluorescence in situ hybridization technique in a group of 48 tumours, including 24 primary colorectal tumours and 24 paired liver metastases. All tumours showed complex karyotypes with numerical/structural abnormalities for seven or more different chromosomes/chromosome regions both in the primary tumours and in their paired metastases. Chromosome 8 was the most frequently altered (22/24 primary tumours), consistently showing del(8p22) and/or gains/amplification of 8q24, followed by abnormalities of the entire chromosome 7 (21/24 primary tumours) and of chromosomes 17p and 20q (20/24 primary tumours). Simultaneous staining for multiple chromosome probes revealed the presence of two or more tumour cell clones in 23/24 cases (46/48 tumour samples). Interestingly, the liver metastases typically contained tumour cell clones similar to those found in the primary tumours, suggesting the absence of selective selection of specific tumour clones. Despite this, additional chromosomal abnormalities were detected in 23/24 metastatic tumours, which preferentially consisted of del(17p13) and gains/amplification of 11q13 and 20q13; moreover, compared to primary tumours, metastases showed an increased number of abnormalities of chromosomes 1p, 7q, 8q, 13q, and 18q, and new chromosomal abnormalities involving chromosomes 6, 10q23, 14q32, 15q22, and 19q13. Owing to the high frequency of numerical abnormalities of the entire chromosome 7 and loss and/or gain/amplification of specific regions of chromosome 8, eg del(8p22) and/or gains/amplification of 8q24 in primary colorectal tumours with associated metastases, it is suggested that their assessment at diagnosis could be of great clinical utility for the identification of colorectal cancer patients at higher risk of developing liver metastases.

Characterization of loss-of-inactive X in Klinefelter syndrome and female-derived cancer cells

The increased risk of several types of cancer in Klinefelter syndrome (47XXY) suggests that the extra X chromosome may be involved in the tumorigenesis associated with this syndrome. Here, we show that cancer cells (PSK-1) derived from a patient with Klinefelter syndrome (47XXY) showing loss of an inactive X chromosome subsequently gained active X chromosomes. We found that this abnormal X chromosome composition in PSK-1 is caused by a loss of an inactive X chromosome followed by multiplication of identical active X chromosomes, not by reactivation of an inactive X chromosome. Furthermore, we extended the characterization of loss-of-inactive X in a series of 22 female-derived cancer cell lines (eight breast cancer cell lines, seven ovarian cancer cell lines, and seven cervical cancer cell lines). The data demonstrate that loss-of-inactive X in the female-derived cancer cells is mainly achieved by loss of an inactive X chromosomes followed by multiplication of an identical active X chromosomes. However, distinctive pathways, including reactivation of an inactive X chromosome, are also involved in the mechanisms for loss-of-inactive X and gain-of-active X in female-derived cancer cells. The biological significance of the loss-of-inactive X and gain-of-active X in the oncogenesis of Klinefelter syndrome and female-derived cancer cells are discussed.

Loss of the Inactive X Chromosome and Replication of the Active X in BRCA1-Defective and Wild-type Breast Cancer Cells

In females, X chromosome inactivation (XCI) begins with the expression of the XIST gene from the X chromosome destined to be inactivated (Xi) and the coating of XIST RNA in cis. It has recently been reported that this process is supported by the product of the BRCA1 tumor suppressor gene and that BRCA1-/- cancers show Xi chromatin structure defects, thus suggesting a role of XCI perturbation in BRCA1-mediated tumorigenesis. Using a combined genetic and epigenetic approach, we verified the occurrence of XCI in BRCA1-/- and BRCA1wt breast cancer cell lines. It was ascertained that the Xi was lost in all cancer cell lines, irrespective of the BRCA1 status and that more than one active X (Xa) was present. In addition, no epigenetic silencing of genes normally subjected to XCI was observed. We also evaluated XIST expression and found that XIST may be occasionally transcribed also from Xa. Moreover, in one of the BRCA1wt cell line the restoring of XIST expression using a histone deacetylase inhibitor, did not lead to XCI. To verify these findings in primary tumors, chromosome X behavior was investigated in a few BRCA1-associated and BRCA1-not associated primary noncultured breast carcinomas and the results mirrored those obtained in cancer cell lines. Our findings indicate that the lack of XCI may be a frequent phenomenon in breast tumorigenesis, which occurs independently of BRCA1 status and XIST expression and is due to the loss of Xi and replication of Xa and not to the reactivation of the native Xi.

Comparative genomic hybridization analysis of hepatoblastoma reveals high frequency of X-chromosome gains and similarities between epithelial and stromal components

Hepatoblastoma (HB) is the most common liver tumor in childhood and differs in its environmental risk factors and genetic background from hepatocellular carcinoma. HB is associated with inherited conditions such as familial adenomatous polyposis and Beckwith-Wiedemann syndrome, suggesting the importance of genetic abnormalities in the pathogenesis and progression of this disease. It has a very polymorphous morphology. A diverse range of cytogenetic alterations has been reported to date, the most frequent being trisomy 2 and trisomy 20. Thirty-five HB specimens from 31 patients (22 purely epithelial, 4 purely mesenchymal, 9 mixed) were examined by comparative genomic hybridization (CGH), a technique that enables us to screen the entire tumor genome for genetic losses and gains. Our aims were as follows: (1) to characterize chromosome abnormalities that appear in this tumor and (2) to identify possible differences between different histologic subtypes of HB. We found significant gains of genetic material, with very little difference in the number and type of alterations between the different histologic components of HB. The most frequent alterations were gains of Xp (15 cases, 43%) and Xq (21 cases, 60%). This finding was also confirmed by fluorescent in situ hybridization performed on nuclei extracted from 6 specimens. Other common alterations were 1p-, 2q+, 2q-, 4q-, and 4q+. We found no difference between different histologic subtypes, a finding that may be in agreement with the hypothesis of a common clonal origin for the different components. An hitherto-unreported high frequency of X chromosome gains may support the assumption that X-linked genes are involved in the development of this neoplasm.

Genome-wide-array-based comparative genomic hybridization reveals genetic homogeneity and frequent copy number increases encompassing CCNE1 in fallopian tube carcinoma

Fallopian tube carcinoma (FTC) is a rare, poorly studied and aggressive cancer, associated with poor survival. Since tumorigenesis is related to the acquisition of genetic changes, we used genome-wide array comparative genomic hybridization to analyse copy number aberrations occurring in FTC in order to obtain a better understanding of FTC carcinogenesis and to identify prognostic events and targets for therapy. We used arrays of 2464 genomic clones, providing approximately 1.4 Mb resolution across the genome to map genomic DNA copy number aberrations quantitatively from 14 FTC onto the human genome sequence. All tumors showed a high frequency of copy number aberrations with recurrent gains on 3q, 6p, 7q, 8q, 12p, 17q, 19 and 20q, and losses involving chromosomes 4, 5q, 8p, 16q, 17p, 18q and X. Recurrent regions of amplification included 1p34, 8p11-q11, 8q24, 12p, 17p13, 17q12-q21, 19p13, 19q12-q13 and 19q13. Candidate, known oncogenes mapping to these amplicons included CMYC (8q24), CCNE1 (19q12-q21) and AKT2 (19q13), whereas PIK3CA and KRAS, previously suggested to be candidate driver genes for amplification, mapped outside copy number maxima on 3q and 12p, respectively. The FTC were remarkably homogeneous, with some recurrent aberrations occurring in more than 70% of samples, which suggests a stereotyped pattern of tumor evolution.

The causes and consequences of random and non-random X chromosome inactivation in humans

X chromosome (X) inactivation is a remarkable biological process including the choice and cis-limited inactivation of one X, as well as the stable maintenance of this silencing by epigenetic chromatin alterations. The process results in females generally being mosaic for two populations of cells--one with each parental X active. In this review, we discuss recent advances in our understanding of how inactivation works, as well as the causes and clinical implications of deviations from random inactivation.

Clonal karyotypic abnormalities in gynecomastia

Gynecomastia is a benign condition that frequently occurs in the male breast gland; however, the cytogenetic data on this entity are very limited. To our knowledge, three cases have been reported in the literature, and the only one with an abnormal karyotype had a concomitant breast carcinoma. In this study we report clonal chromosomal alterations in a gynecomastia sample without any signs of adjacent malignant tissue. The nonrandom abnormalities observed were a deletion of 12p, monosomies of chromosomes 9, 17, 19, and 20, and the presence of a marker chromosome. Most of these alterations have been previously described in the literature in other breast lesions, including benign and malignant (male and female) tumors, indicating their recurrence and nonrandomness in abnormal processes of the mammary gland.

Chromosome banding analysis of gynecomastias and breast carcinomas in men

Male breast cancer is 100 times less frequent than its female counterpart and accounts for less than 1% of all cancers in men. Although men with breast cancer also often have gynecomastia, it is still unknown whether gynecomastia per se predisposes the male breast to malignant disease. We describe the cytogenetic analysis of three gynecomastias and four breast cancers in men. No chromosome abnormalities were detected in two cases of gynecomastia, with no other concomitant breast disease. The third gynecomastia sample, taken from a site where a breast carcinoma had previously been removed, had a t(2;11)(p24;p13) as the sole chromosome change; this is the first time that an abnormal karyotype has been described in gynecomastia. All four cancers had clonal chromosome abnormalities. Several cytogenetically unrelated clones were found in the breast tumor and in a metastasis from case 1. In the carcinoma of case 2, a single abnormal clone was found, characterized by loss of the Y chromosome, monosomy 17, and a deletion of the long arm of chromosome 18. In the carcinoma of case 3, a clone with loss of the Y chromosome as the sole change dominated, accompanied by the gain of an X chromosome in a subclone. In the lymph node metastasis examined from case 4, a single clone carrying trisomies for chromosomes 5 and 16 was detected. Our findings, especially when collated with data on the six karyotypically abnormal breast carcinomas in men described previously, indicate that gain of the X chromosome, gain of chromosome 5, loss of the Y chromosome, loss of chromosome 17, and del(18)(q21) are nonrandom abnormalities in male breast carcinomas.

Cytogenetics of malignant gliomas. II. The sex chromosomes with reference to X isodisomy and the role of numerical X/Y changes

Sex chromosomal monosomy with total loss of an X or Y is frequently observed in malignant gliomas. Beyond that, not much is known about the behavior of the sex chromosomes in these tumors. We noted loss of the X from 3 of 13 gliomas from women (23%) compared to loss of the Y from 16 of 28 gliomas from men (57%). There were two structural rearrangements of the Y (an inversion and a translocation with chromosome 4). Most unexpectedly, clones with sex chromosome reversal were encountered in 3 cases. These XX clones in gliomas from men are perforce the consequence of Y loss coupled with X isodisomy, a nonrandom sequence of sex chromosome changes. We examined the company kept by numerical X and Y changes in clones and found that clones with numerical sex chromosome changes had fewer autosomal abnormalities, reflecting a distinct tendency to clonal separation of sex chromosome from autosomal abnormalities. We conclude that the sex chromosome changes are not a necessary part of the neoplastic process in malignant gliomas but that they must be of biologic significance to the brain since they are highly nonrandom in frequency, type, and sequence in brain cells.

In situ hybridization analysis of the Y chromosome in gonadoblastoma

Gonadoblastoma is a rare tumor arising in the streak gonads of about 30% of 46,XY sex-reversed females. Because gonadoblastoma develops only in patients who have Y-chromosome material and dysgenetic gonads, it has been hypothesized that positive expression of a gene (or genes) on the Y chromosome (GBY) is involved in the etiology of the tumor. To examine the Y chromosome directly in tumors, we performed nonisotopic in situ hybridization of a biotin-labeled Y-specific probe for the DYZI locus on formalin-fixed, paraffin-embedded sections of tumor samples from four different patients. After hybridization to DYZI, the Y chromosome was found to be present in all gonadoblastoma foci in the four patients studied, and the gonadoblastoma foci showed an average of 85% cell nuclei positive for the Y chromosome on tissue sections. Normal male and female control tissues showed an average of 78% and 0% positive nuclei, respectively. One patient with bilateral gonadoblastoma had previously been shown to be mosaic, with a 45,X/46,XY karyotype in lymphocytes, skin fibroblasts, and cultures from both gonads. Examination of sections of this patient's gonads showed 79% positive nuclei within the gonadoblastoma foci, whereas the nontumor stromal tissue had 19% positive nuclei. These results indicate that, in this mosaic gonad, tumor foci developed only from cells that had a Y chromosome. Our results support the hypothesis that there is a GBY locus on the Y chromosome and that the Y chromosome is retained in the gonadoblastoma foci during the development of the tumor.

Loss of heterozygosity on the X chromosome in human breast cancer

The analysis of loss of heterozygosity (LOH) in tumours can be a powerful tool for mapping the sites of tumour suppressor genes in the human genome. A panel of breast cancer patients was assembled as pairs of tumour and lymphocyte DNA samples and LOH studies carried out by Southern hybridisation with polymorphic loci mapping to the X chromosome with appropriate controls. Deletion mapping revealed a high frequency of small regionalised deletions, defining at least three independent regions, one of which is particularly well mapped to a 500 kb stretch of DNA in the distal portion of the pseudoautosomal region of Xp. A second region has been identified within the pseudoautosomal region close to the pseudoautosomal boundary, and there is a third discrete site of loss on distal Xq. Perturbations of sequences at these regions represent independent events in a number of patients. This study represents the first detailed analysis of LOH on the X chromosome in human breast tumours, the results of which indicate that at least three regions of this chromosome are involved in the disease.

Cytogenetic report of a male breast cancer

The cytogenetic findings on G-banding in an infiltrating ductal breast carcinoma in a 69-year-old man are reported. The main abnormalities observed were trisomy of chromosomes 8 and 9 and structural rearrangement in the long arm of chromosome 17 (add(17)(q25)). Our results confirm the trisomy of chromosome 8 in the characterization of the subtype of ductal breast carcinomas and demonstrate that chromosome 17, which is frequently involved in female breast cancers, is also responsible for the development or progression of primary breast cancers in males.

Merkel cell carcinoma. Histopathology, immunohistochemistry, and cytogenetic analysis

BACKGROUND

Merkel cell carcinoma (MCC) is a cutaneous neoplasm, histopathologically difficult to differentiate from other small blue cell neoplasms. Immunohistochemical and ultrastructural analyses are usually helpful in differentiating these neoplasms. Recently, cytogenetic analysis has emerged as a potential tool in the diagnosis of solid neoplasms, including MCC.

OBJECTIVE

To describe the immunohistochemical and cytogenetic features of a case of primary MCC and to review the cytogenetics literature on MCC.

METHODS

Formalin-fixed tissue was processed routinely and labeled with a battery of antibodies. Metaphase cells from fresh tissue were prepared by Giemsa banding.

RESULTS

Histopathologically, there were irregular aggregates of pyknotic cells with little cytoplasm. Immunohistochemically, the neoplastic cells stained positive for neurofilament, cytokeratin, neuron-specific enolase, and epithelial membrane antigen. Leucocyte common antigen, S-100, 013, and chromogranin were negative. Karyotyping of neoplastic cells showed loss of chromosome Y (-Y).

CONCLUSIONS

Coexpression of cytokeratin and neurofilament is characteristic of MCC and allows it to be differentiated from similar neoplasms. The significance of Y chromosome loss is unclear. Further cytogenetic analyses are warranted to identify genetic mutations significant to the pathogenesis of MCC.

Cytogenetic differences between intestinal and diffuse types of human gastric carcinoma

This study concerns the cytogenetics of 23 gastric carcinomas, classified histologically as intestinal or diffuse types. In carcinomas of the diffuse type, the only numerical changes observed were Y chromosome loss associated with X-chromosome disomy in four of seven male patients. A 46, XX karyotype without recognizable alterations was observed in three of five female patients, and rare structural changes in diffuse carcinomas involved chromosomes 1 and 18. In contrast, intestinal type tumors were exclusively aneuploid, with chromosome modes ranging from 48 to 84. The most consistent change was trisomy 20 in seven of 11 patients, each of which displayed a number of both single and clonal structural aberrations. Frequent structural changes were translocations involving chromosome 13 (including a putative isochromosome 13q in three of 11 patients), and alterations in chromosomes 1, 6 and 12. This study therefore suggests that diffuse and intestinal types of gastric carcinomas do not share a common sequence of genetic changes. The tumor with the worse prognosis (diffuse type) is surprisingly diploid, with uniform X-disomy in both males and females. The clinically less aggressive tumors (intestinal type) show multiple changes, both numerical and structural, of which some are reminiscent of changes seen in tumors of the lower gastrointestinal tract. Cytogenetics may thus be a valuable adjunct in establishing the diagnosis, classification, and prognosis of gastric carcinomas.

Cytogenetic analysis of six bronchial carcinoids

Short-term cultures from four typical and two atypical primary bronchial carcinoids were cytogenetically analyzed. A lung metastasis from one of the atypical carcinoids was also analyzed. Of the four typical carcinoids, two had normal chromosome complements, while the other two had the karyotypes 46,X, -X, +7/47,XX, +7/47,XX, +X/46,XX and 47,XX, +7/46,XX. Both atypical carcinoids had chromosome abnormalities. One had the karyotype 45-46,X, -X,del(1)(q32),add(17)(p13), +add(19)(p13), -22, +r/47,XX, +X. The second carcinoid had the karyotype 78-81,XXY, +Y, +1,t(2;8)(q21;q24), +3, +4, +del(4) (q25), +5, +6,der(6)t(6;6)(q21;p21)x2, +7, +7, -10,add(14)(p11-13), +19, -21, +1-4mar. The metastasis from this carcinoid had the same aberrations, except that the del(4)(q25) had been lost and one to two markers had been gained.

Cytogenetic analysis of a United Kingdom series of non-Hodgkins lymphomas

We describe cytogenetic analyses of cells derived from 40 non-Hodgkins lymphoma (NHL) node biopsies, 23 of which were from patients who had not been treated before biopsy. We noted that the chromosomes most frequently gained were X (32%), 12 (27%), and 3 (24%). Monosomies were much less common; loss of chromosome 13 (13.5%) was most frequent. Structural abnormalities primarily involved chromosomes 14 (70%), 1 (40.5%), 18 (38%), 6 (35%), and 17 (22%). Low-and high-grade disease showed similar patterns of structural changes; however, a markedly greater number of chromosome gains were associated with low-grade disease. Biopsy samples from patients who had previously been treated showed an increased frequency of structural abnormalities, as well as a significantly larger number of chromosome gains. The importance of these observations, particularly with regard to possible oncogene involvement in lymphoma evolution, is discussed.

Interphase cytogenetics of a male breast cancer

Direct interphase cytogenetic analysis was performed on nuclei from a male breast tumor using fluorescence in situ hybridization (FISH). DNA probes specific for repetitive pericentromeric regions on chromosomes 1, 7, 9, 11, 15, 17, 18, X, and Y were used to determine chromosome copy numbers in interphase tumor cells. Copy number distributions varied greatly between chromosomes, showing major tumor populations with on (Y), two (X,9), three (11, 15, 18), and four (1, 7, 17) copies of the pericentromeric targets. The X chromosome was present in two copies in 84.7% of tumor nuclei, with the balance being primarily monosomic. Normal skin fibroblasts cultured from the same patient showed 99% monosomy X. The Y chromosome showed a minor population (12%) with two copies. The DNA index of the tumor was 2.0 as determined by flow cytometry. The proliferative activity of the tumor cells was simultaneously analyzed using detection of in vivo bromodeoxyuridine (BrdU) incorporation. The BrdU labeling index was 13.2%.

DNA methylation changes in human testicular cancer

We previously reported an X/Y imbalance with a relative excess of X- and a relative deficiency of Y-chromosomal DNA in three out of nine testicular tumors of germ cell origin. To study the implications of those changes the methylation status of DNA from seven of the tumors was explored by HpaII/MspI analysis. The 5' regions of the hypoxanthine phosphoribosyltransferase (HPRT) and the phosphoglycerate kinase (PGK) gene loci exhibited main patterns suggestive of active X chromosomes in the tumors. However, a minority of the HPRT loci of one teratocarcinoma with an increased dosage of the X chromosome, as well as one additional teratocarcinoma, revealed patterns analogous to inactive X chromosomes in females. Using probes from several chromosomes it was subsequently found that the teratocarcinoma tumors (3/3) were characterized by generalized hypermethylation. On the contrary, the seminomas showed variable hypomethylation (4/5) or virtually complete demethylation (1/5). The seminoma with the most extensive hypomethylation was disseminated (stage III), whereas the other seminomas were local (stage I). These findings suggest that DNA methylation may play a role in the developmental pathways leading to different histologic types of testicular tumors of germ cell origin. The HPRT results imply that the consequences of extra X chromosomes--a frequent finding in testicular tumors--may be modulated by mechanisms, such as DNA methylation, that control gene activity.

Numerical chromosome changes in 165 malignant tumors. Evidence for a nonrandom distribution of normal chromosomes

The numbers of normal copies of each of the chromosomes in representative karyotypes from 165 malignant tumors of the bladder, breast, cervix, colorectum, and testis studied in this laboratory or described in the literature were assessed to determine whether particular chromosomes were over- or underrepresented. For each chromosome, the mean number of copies was expressed as a percentage of the number expected on the basis of the total number of chromosomes in the karyotypes. The most highly represented autosomes in the tumors as a whole were, in descending order of frequency, numbers 7, 20, 12, 19, 21, and 3, while those most underrepresented were numbers 10, 1, 4, 5, 14, 17, 11, and 18. In tumors of males, the Y tended to be underrepresented. The X was highly represented in the testicular tumors (there were usually two or more copies) and in colorectal tumors of males, but not in the other tumor categories studied. For the tumors as a whole, statistically significant differences could be demonstrated between pairs of autosomes that were at opposite ends of the frequency range. Differences between tumors at the different sites studied were not demonstrable. It is suggested that the determination of the number of normal copies of chromosomes, i.e., whether there are more or fewer than expected, may usefully complement observations on structural changes by reflecting the presence of oncogenes and tumor-suppressor genes, respectively. It may also point to chromosomes that are involved in significant genic changes in which cytogenetic observations on structural changes are equivocal.

A cytogenetic study of male breast cancer

In a direct preparation from a male breast carcinoma two populations of cells were present, one hypodiploid (range 25-34) and the other hypertriploid (range 56-84). Twenty-two marker chromosomes were recognized. One of these, dic(5:11)(p14:q23) was present in one or two copies in every cell and has not been reported in any other case of breast cancer. There was a consistent monosomy of chromosome 7 and, in the hypertriploid cells, a gain of one to three copies of chromosome 3. The breakpoint 11q23 is a rare, folate-sensitive fragile site but was not expressed in peripheral blood cell lymphocytes from the patient.

Two identical active X chromosomes in human mammary carcinoma cells

Chromosome G-banding analysis of two human mammary carcinoma cell lines, Elco and MCF-7, showed the existence of two X chromosomes in both cell lines. To determine the state of activity of the X chromosomes, a methylation-sensitive restriction endonuclease, HpaII, was used to distinguish the active X from the hypermethylated, inactive X chromosome with a probe for the phosphogalactokinase locus by Southern blot hybridization. DNA digested with the restriction enzymes PstI and BstXI showed a band at either 1.05 or 0.9 kilobases. After HpaII digestion, a 50% reduction in intensity was observed in the female controls, whereas total reduction of the band was observed for the tumor cell lines and the male control. This indicates the absence of an inactive X and the presence of only active X chromosomes in the mammary carcinoma cell lines and the male control. To investigate the mechanisms involved in the alteration of the X chromosome composition and activity, restriction fragment length polymorphism analyses of seven additional X chromosome markers (L1.28, DX13, p52A, pX65H7, L782, pA13.RI, and pXG-12) were performed on the DNA isolated from the tumor cells and controls. Heterozygosity for at least one of the seven markers was detected in the six female controls whereas only homozygosity was detected for each marker in the tumor cell lines and the male control. These results indicate that the two active X chromosomes identified in each of the two tumor cell lines are identical, resulting from duplication or nondisjunction of the active X and loss of the inactive X chromosome.

Sex chromosomes in a series of 79 colorectal cancers: replication pattern, numerical, and structural changes

The cytogenetic study of a series of 79 colorectal cancers was performed with special attention to sex chromosome behavior. It was found that apart from other chromosomal changes, the early-replicating X chromosome (Xe) was frequently duplicated in tumors from both males and females. This contrasted with a frequent loss of either the late-replicating X (XI) in tumors from females or of the Y chromosome in tumors from males. All the detected unbalanced rearrangements resulted in a gain of the long, but not the short, arm of the X chromosome. The replication pattern of Xe chromosomes was similar to that of control tissues, whereas that of XI chromosomes was unusual. Its main characteristic was that the two major R bands of the short arm, Xp11 and Xp22, replicated too early.

Molecular studies of the sex chromosomes in human testicular cancer: pronounced changes in X and Y chromosome dosage in some tumors

Nine males with testicular germ cell tumors were studied by Southern blotting using probes recognizing different regions of the X and Y chromosomes. In the tumors of three patients, an imbalance was noted with a relative deficiency of DNA of Y-chromosomal and a concurrent excess of that of X-chromosomal origin. The X:Y signal ratios were 4, 4, and 2, respectively, in tumor DNA relative to normal DNA, and the ratios of Y to an autosomal locus were 0.4, 0.6, and 0.7, respectively, in the same tumors. Several loci on both arms of the Y chromosome were similarly involved. No structural abnormalities of Y chromosome DNA could be demonstrated. The X/Y change occurred in two of the three patients with nonseminomatous tumors and in two of the three patients with metastatic disease. To account for the results, two alternative models are discussed: first, loss of the Y chromosome and increase in X chromosome number in some but not all tumor cells; second, polyploidization with one Y chromosome and several X chromosomes.

Unusual karyotypic evolution in subacute myelomonocytic leukemia in two monozygotic twins

A subacute myelomonocytic leukemia was diagnosed in 28-month-old cotwins. At this age, their spontaneously dividing cells had a normal karyotype. A few months later, after treatment with 6-mercaptopurine, the following karyotypes were observed: 50,XX, +X, +13, +19, +21 in one and 51,XX, +X, +X, +10, +19, +21 in the other. After bone marrow transplantation, both relapsed although they had received high doses of chemo- and radiotherapy. One developed a clone 46,XX,del(20q), which acquired other clonal rearrangements. The other child developed two different abnormal clones, both with unbalanced rearrangement of chromosome 13. Some of these clones may correspond to immature erythroblasts. The gain of chromosomes, especially for #13, which occurred independently in the cotwins by various mechanisms and at different periods during the disease, is very striking. It may indicate the existence of a strong selective advantage for trisomic 13 cells and may be related to the genetic constitution of the patients.

Cytogenetic studies of Hodgkin's disease. Analysis of involved lymph nodes from 12 patients

Cytogenetic studies were performed on 12 involved lymph nodes from Hodgkin's disease patients utilizing conditioned medium from 12-O-tetradecanoylphorbol-13-acetate-staphylococcus enterotoxin A induced mononuclear cells. The majority of cells analyzed had a normal karyotype. An unusually high rate of nonclonal karyotypic abnormalities was noted in most cultures. Clonal abnormalities involving chromosomes 3 and 21 were noted in two patients. Cytogenetic analysis of cultures stimulated with conditioned medium or specific growth factors may lead to a better understanding of the genetic mechanisms involved in Hodgkin's disease.

Bovine leukaemia: facts and hypotheses derived from the study of an infectious cancer

Bovine leukaemia virus (BLV) is the etiological agent of chronic lymphatic leukaemia/lymphoma in cows, sheep and goats. Infection without neoplastic transformation was also obtained in pigs, rhesus monkeys, chimpanzees, rabbits and observed in capybaras and water-buffaloes. Structurally and functionally, BLV is a relative of human T lymphotropic viruses 1 and 2 (HTLV-I and HTLV-II) In humans, HTLV-I induces a T-cell leukaemia and its type 2 counterpart has been found in dermatopathic lymphadenopathy, hairy T-cell leukaemia and prolymphocytic leukaemia cases. At variance with HTLV-I, BLV has not been associated with neurological diseases of the degenerative type. Bovine leukaemia virus, HTLV-I and HTLV-II show clearcut sequence homologies. The pathology of the BLV-induced disease, most notably the absence of chronic viraemia, a long latency period and lack of preferred proviral integration sites in tumours, is similar to that of adult T-cell leukaemia/lymphoma induced by HTLV-I. The most striking feature of these three naturally transmitted leukaemia viruses is the X region located between the env gene and the long terminal repeat (LTR) sequence. The X region contains several overlapping long open reading frames. One of them, designated XBL-I, encodes a trans-activator function capable of increasing the level of gene expression directed by BLV-LTR and most probably is involved in "genetic instability" of BLV-infected cells of the B cell lineage. The "genetic instability" renders the infected cell susceptible to move, along a number of stages, towards full malignancy. Little is known about these events and their causes; we present some theoretical possibilities. Bovine leukaemia virus infection has a worldwide distribution. In temperate climates, the virus spreads mostly via iatrogenic transfer of infected lymphocytes. In warm climates and in areas heavily populated by haematophagous insects, there are indications of insect-borne propagation of the virus.

Bovine leukemia: facts and hypotheses derived from the study of an infectious cancer

Bovine leukemia virus is the etiological agent of a chronic lymphatic leukemia/lymphoma in cows, sheep, and goats. Infection without neoplastic transformation also was obtained in pigs, rhesus monkeys, chimpanzees, and rabbits, and was observed in capybaras and water buffaloes. Structurally and functionally, BLV is a relative of the human T lymphotropic viruses (HTLV-I and HTLV-II). HTLV-I induces in humans a T cell leukemia, and its type II counterpart has been found in dermatopathic lymphadenopathy, hairy T cell leukemia and prolymphocytic leukemia cases. At variance with HTLV-I, BLV has not been associated with neurological diseases of the degenerative type. BLV, HTLV-I, and HTLV-II show clearcut sequence homologies. The pathology of the BLV-induced disease, most notably, the absence of chronic viremia, a long latency period, and a lack of preferred proviral integration sites in tumors, is similar to that of adult T cell leukemia/lymphoma induced by HTLV-I. The most striking feature of the three naturally transmitted leukemia viruses is the X region located between the env gene and the LTR sequence. The X region contains several overlapping long open reading frames. One of them designated XBL-I encodes a trans-activator function capable of increasing the level of gene expression directed by BLV-LTR and most probably involved in "genetic instability" of BLV-infected cells of the B cell lineage. The genetic instability puts the cell into a context of fragility and ready to move along a number of stages towards full malignancy. Little is known about these events and their causes; we have presented some theoretical possibilities. BLV infection has a worldwide distribution. In temperate climates the virus spreads mostly via iatrogenic transfer of infected lymphocytes. In warm climates and in areas heavily populated by hematophageous insects, there are indications of insect-born propagation of the virus.

Characteristic chromosomal imbalances in 18 near-diploid colorectal tumors

The cytogenetic study of 18 near-diploid colorectal tumors shows that the observed numerical and structural abnormalities resulted in recurrent chromosomal losses and gains. By order of decreasing frequencies, they are: monosomy 17p (16/18), partial or more frequently complete monosomy 18 (14/18), trisomy 20q (11/18), trisomy or tetrasomy 13 (10/18), monosomy lp and trisomies X and 8q (9/18). The absence of recurrent breakpoints in euchromatin contrasts with the high preponderance of breakage at various places of heterochromatic region. Because these tumors are characterized by very recurrent chromosomal imbalances, it is assumed that the observed chromosomal changes may be related to a recessive genetic determinism and to gene dosage imbalances.