Cytogenetic and molecular study of the PRDX4 gene in a t(X;18)(p22;q23): a cautionary tale

The PRDX4 gene located at Xp22 encodes for a member of the peroxiredoxin gene family. Genes within this family exhibit thioredoxin-dependent peroxidase activity and have been implicated in cellular functioning, including proliferation and differentiation. Recently, PRDX4 has been identified as a partner gene in a t(X;21) translocation in a patient with acute myeloid leukemia. To determine whether PRDX4 was involved in other translocations, leukemia cells from 15 patients with Xp22 abnormalities were screened for involvement of the gene using fluorescence in situ hybridization (FISH). One sample from a 41-year-old woman with acute lymphoblastic leukemia showed three signals when hybridized with the PRDX4 probe. Cytogenetic analysis of the sample had identified a t(X;18)(p22;q23). Assuming that the three signals indicated a break within the PRDX4 gene, we performed FISH experiments and successfully narrowed the breakpoint on chromosome 18 to a 50-kb region. Subsequent analysis using spectral karyotyping showed that the leukemic cells had undergone multiple rearrangements and that a third X chromosome was present, albeit rearranged. Additional FISH experiments revealed that the third PRDX4 signal was the result of a third copy of the gene. Analysis of the other rearrangements has helped to characterize the multiple abnormalities within the leukemic cells. The findings underscore the importance of using multiple techniques when analyzing complex chromosomal rearrangements in malignant cells.     

Use of FISH to detect chromosomal translocations and deletions. Analysis of chromosome rearrangement in synovial sarcoma cells from paraffin-embedded specimens.

Retrospective cytogenetic analysis was performed on paraffin-embedded cells from five cases of synovial sarcoma to evaluate the frequency of the X;18 translocation characteristic of this tumor. Fluorescent in situ hybridization with DNA probes for the centromeres of chromosomes X and 18 was used with whole chromosome painting probes for X and 18. Translocation was inferred when there were only two X and 18 centromere signals but three painting probe signals of unequal size. On this basis it was possible to identify the t(X;18) in three cases. The fourth case was found to have extra copies of chromosome 18 without translocation, while the fifth case, the only one with a questionable diagnosis, had a normal chromosome pattern with a minor clone showing a translocated 18 but a normal X. Thus this study demonstrates the feasibility and value of using fluorescent in situ hybridization to detect chromosome rearrangements in archival tumor specimens.     

A synovial sarcoma with a complex t(X; 18;5;4) and a break in the ornithine aminotransferase (OAT)LI cluster on Xp11.2

The initial cytogenetic analysis of a biphasic synovial sarcoma revealed complex anomalies involving six different chromosomes: 46,Y,t(X185;4)(p11;q11;p13;q12),t(2;5)(q35;q11). After fluorescence in situ hybridization (FISH) analysis, using chromosome X-specific plasmid library and YAC probes, the situation appeared to be even more complex, with an insertion of part of the X chromosome short arm into the der(5)t(5;18). In spite of these complex chromosomal rearrangements, the Xp11 breakpoint could be mapped to within the ornithine aminotransferase (OAT)LI cluster, very similar to that reported previously for the standard t(X 18)(p11;q11) in synovial sarcomas. These findings suggest common pathogenetic pathways in these cytogenetically different but morphologically similar tumors. Genes Chrom Cancer 9:288-291 (1994). © 1994 Wiley-Liss, Inc.     

Multiplex ligation-dependent probe amplification to detect subtelomeric rearrangements in routine diagnostics

Subtelomeric rearrangements are believed to be responsible for 5-7% of idiopathic mental retardation cases. Due to the relative complexity and high cost of the screening methods used till now, only preselected patient populations including mostly the more severely affected cases have been screened. Recently, multiplex ligation-dependent probe amplification (MLPA) has been adapted for use in subtelomeric screening, and we have incorporated this technique into routine diagnostics of our laboratory. Since the evaluation of MLPA as a screening method, we tested 275 unselected patients with idiopathic mental retardation and detected 12 possible subtelomeric aberrations: a der(11)t(11;20)(qter;qter), a 19pter duplication, a der(18)t(18;10)(qter; pter), a 15qter deletion, a 8pter deletion, a 6qter deletion, a der(X)t(X;1)(pter;qter), a der(X)t(X;3)(pter;pter), a 5qter duplication, a 3pter deletion, and two 3qter duplications. The patients can be subdivided into two groups: the first containing de novo rearrangements that are likely related to the clinical presentation of the patient and the second including aberrations also present in one of the parents that may or may not be causative of the mental retardation. In our patient cohort, five (1.8%) subtelomeric rearrangements were de novo, three (1.1%) rearrangements were familial and suggestively disease causing, and four (1.5%) were possible polymorphisms. This high frequency of subtelomeric abnormalities detected in an unselected population warrants further investigation about the feasibility of routine screening for subtelomeric aberrations in mentally retarded patients.     

Translocations involving the X chromosome in solid tumors: presentation of two sarcomas with t(X;18)(q13;p11)

Cytogenetic analysis of two poorly differentiated sarcomas revealed clonal chromosomal rearrangements involving several autosomes and the X chromosome. Both tumors displayed a common abnormality, t(X;18)(q13;p11). This finding is discussed in relation to published X/autosomes translocations in solid tumors.     

Chromosomes in the diagnosis of soft tissue tumors. I. Synovial sarcoma.

It has been established that nonrandom chromosome rearrangements are characteristic of specific types of neoplasia. We present six new cases of sarcoma that had in common the same chromosome abnormality, i.e., a balanced translocation between chromosomes X and 18, t(X;18)(p11.2;q11.2), and evaluate the 15 cases with this translocation in the literature. The histological diagnosis was synovial sarcoma in 19 cases and malignant fibrous histiocytoma and fibrosarcoma in the remaining two tumors, respectively. The translocation was found in tumors of both the biphasic and monophasic types, as well as in poorly differentiated synovial sarcoma. The two nonsynovial sarcomas with the t(X;18) were described as spindle cell tumors but failed to show the presence of cytokeratins by immunohistochemical stains. Even with the numerous variabilities on which this test depends, the cytogenetic analysis holds great promise as a tool for the diagnosis of synovial sarcoma.     

Beckwith-Wiedemann syndrome due to 11p15.5 paternal duplication associated with Klinefelter syndrome and a "de novo" pericentric inversion of chromosome Y

We report on an infant who had been prenatally diagnosed with Klinefelter syndrome associated with a "de novo" pericentric inversion of the Y chromosome. A re-evaluation at 3 years of age suggested that he was also affected by Beckwith-Wiedemann syndrome (BWS). Karyotype was repeated and fluorescence in situ hybridisation (FISH) analysis revealed trisomy for 11p15.5-->11pter and a distal monosomy 18q (18q23-->qter). Parental cytogenetic studies showed that the father carried a balanced cryptic translocation between chromosomes 11p and 18q. Furthermore, the child had an extra X chromosome and a "de novo" structural abnormality of chromosome Y. Thus, his karyotype was 47,XX, inv (Y) (p11.2 q11.23), der(18) t (11;18) (p15.5;q23) pat. ish der(18) (D11S2071+, D18S1390-). Two markers on the X chromosome showed that the extra X of the child was paternally inherited. No deletions were observed on the structurally abnormal Y chromosome from any of the microsatellites studied. Clinical findings of patients with BWS due to partial trisomy 11p reveal that there is a distinct pattern of dysmorphic features associated with an increased incidence of mental retardation when comparing patients with normal chromosomes. This fact reinforces that FISH study have to be performed in all BWS patients, specially in those with mental retardation since small rearrangements cannot be detected by conventional cytogenetic techniques.     

Chromosome analysis of a brain malignant lymphoma cell line

Chromosome studies of a malignant lymphoma cell line derived from the brain were made by Q- and G-banding techniques. The modal number of chromosomes was 45. Complex structural rearrangements were present, but the 14q+ marker chromosome frequently seen in malignant lymphomas was not identified in the cell line. The main karyotype in cells analyzed was 45, X, -Y, del (2) (q21q23), t (3;?) (p25;?), t (p12;?), -8, 11q+, 18q+, +mar. Absence of the 14q+ may be explained by: firstly, clones which possessed 14q+ marker chromosome in brain tumor cells may have been selected out with increasing culture time and repeated passages; or secondly, the presence of the 14q+ marker chromosome depends on the type of lymphoma.     

Non-random chromosome rearrangements in adenoid cystic carcinoma of the salivary glands

The chromosomal findings in 10 adenoid cystic carcinomas (ACC) of the salivary glands are described. Clonal numerical deviations as the sole anomaly were detected in four cases and structurally rearranged stemlines and sidelines in four cases. An apparently identical t(6;9)(q23;p21) was found in two tumors; in one case the translocation was part of the abnormal stemline and in the other case it was the sole anomaly in a single variant cell. A similar or identical t(6;9)(q21-24;p13-23) has recently been reported in three of 15 previously published cases of ACC. The three remaining tumors with abnormal stemlines all had rearrangements of chromosome 9, including t(1;9)(q21;p21-22), der(9)i(9)(q10)inv(9)(q12q 13), and der(X)t(X;9)(p21;p22-23), respectively. The latter case also had a t(17;18)(p12;q11.2) that was common to both abnormal clones present in this tumor. In addition to other abnormalities, the clone with der(X)t(X;9) also showed a del(6)(q13q21). In two cases fluorescence in situ hybridization (FISH) was used for further characterization of the marker chromosomes. A survey of the present findings together with previous results from 15 ACC clearly demonstrates that rearrangements of 6q21-24 (deletions or translocations in 11 cases), 9p13-23 (translocations in seven cases), and 17p12-13 (translocations in three cases) are recurrent, and often primary, in ACC, and that the t(6;9)(q21-24;p13-23), found in five tumors, is a non-random, primary aberration. Genes Chromosom Cancer 10:115–121 (1994). © 1994 Wiley-Liss, Inc.     

Detection of t(14; 18)(q32;q21) in hyperdiploid cells by fluorescence in situ hybridization in a patient with Hodgkin disease

The most frequent nonrandom chromosome rearrangements in B-cell non-Hodgkin lymphoma (NHL) is the t(14;18)(q32;q21) found in follicular lymphomas. The t(14;18) in Hodgkin disease (HD) was rarely observed using cytogenetic techniques. Although Southern blot analysis failed to demonstrate the t(14;18), there have been conflicting reports concerning the occurrence of the translocation using polymerase chain reaction (PCR) methods in HD. In some HD tissues, the translocation might be derived from background lymphocytes rather than Hodgkin and Reed-Sternberg (HRS) cells, because B-cells with t(14;18) are regularly generated in normal individuals. However, the cells bearing the translocation have remained unidentified. We describe a patient with HD who showed t(14;18) in hyperdiploid cells using fluorescence in situ hybridization (FISH) and HRS cells which were strongly positive for BCL2 by immunohistochemistry. These findings suggest that HRS cells may have a t(14;18).     

Alternate, adjacent 2 and 3:1 meiotic segregation products from a balanced t(13;18) (q12;q11) carrier

Cotton C, Cummins M, Smith A. Alternate, adjacent 2 and 3:1 meiotic segregation products from a balanced t(13: 18) (q12;q11) carrier.
Clin Genet 1993: 44: 193–195. © Munksgaard, 1993
We present a case in which alternate, adjacent 2 and 3:1 meiotic segregations have occurred in the pregnancies of a female carrier of a balanced reciprocal translocation - 46,XX,t(13;18) (q12;q11). Products of five conceptions effectively showed trisomy 18q, trisomy 18p or monosomy 18p. This is one of the rare rearrangements which can give rise to a variety of segregation modes including adjacent 2.     

Multiple structural chromosome rearrangements, including del(7q) and del(10q), in an adenocarcinoma of the prostate

Cytogenetic analysis of a poorly differentiated adenocarcinoma of the prostate revealed the complex karyotype: 76-86,X, -Y, +X, +X, +del(X)(q24), +t(1;10) (p22;q24), -2, +der(2) t(1;2;?)(p32;q24p13;?), +der(2)t(1;2;?) (p32;dq24p13;?), +3, +3, +4, +5, +5, +6, +7, +del(7) (q22), -8, +der(8)t(8;?)(q24;?), + der(8)t(8;?)(q24;?), +9, +10, +10, +der(10)t (1;10)(q24;q22), +del (10)(q23), +11, +11, +12, +der(12)t(4;12)(q11;p11), +der(12)t(4;12) (q11;p11), +14, +der (15)t(1;15)(q21;p11), +t(16;?) (q21;?), +17, +18, +19, +19, +20, +20, +21, +22, +2-5 mar. The karyotype contains deletions of both 7q and 10q, abnormalities that also have been described previously in prostatic adenocarcinomas, and which hence may represent primary chromosomal rearrangements in this type of cancer.     

Noninvolvement of a constitutional heritable fragile site at 10q24.2 in rearranged chromosomes from rectal carcinoma cells

A fragile site in chromosome band 10q24.2 was found in the lymphocytes of a patient ascertained for rectal carcinoma. The karyotype of 110 R-banded tumor cells was performed, showing two stemline formulas: 46,XXY,-1,-18,+20,der(6),t(1;6)(q21.1;q22.3),i(17q) and 46,XY,-1,-18,+8,+20,der(6),t(1;6),del(2)(p1600p22),i(17q). These findings are in agreement with our previous studies, which reported that the rearrangement of chromosome #17 and the loss of chromosome #18 are recurrent anomalies in colorectal carcinomas. In addition to these rearrangements, other anomalies were occasionally observed in tumor cells, but no breakages nor rearrangements involving band 10q24.2. The relationships between fragile sites and cancer breakpoints are discussed.     

Molecular cytogenetic studies of Xq critical regions in premature ovarian failure patients

BACKGROUND: Premature ovarian failure (POF) is defined as amenorrhoea for more than 6 months, occurring before the age of 40, with an FSH serum level higher than 40 mIU/ml. Cytogenetically visible rearrangements of the X chromosome are associated with POF. Our hypothesis was that cryptic Xq chromosomal rearrangements could be an important etiological contributor of POF. METHODS: Ninety POF women were recruited and compared to 20 control women. Peripheral blood samples were collected and metaphase chromosomes were prepared using standard cytogenetic methods. To detect Xq chromosomal micro-rearrangements, fluorescence in situ hybridization (FISH) analysis was performed using a selection of 30 bacterial artificial chromosome (BAC) and P1 artificial chromosome clones, spanning Xq13-q27. We further localized the translocation breakpoints by FISH with additional BAC clones. RESULTS: Chromosomal abnormalities were identified in 8.8% of our 90 patients [one triple X, three large Xq deletions 46,X,del(X)(q22.3), 46,X,del(X)(q21.2) and 46,X,del(X)(q21.32), two balanced X;autosome translocations 46,X,t(X;1) (q21.1;q32) and 46,X,t(X;9)(q21.31;q21.2) and two Robertsonian translocations 45,XX,der(15;22)(q10;q10) and 45,XX,der(14;21)(q10;q10)]. The two Xq translocation breakpoints were among a cluster of repetitive elements without any known genes. FISH analysis did not reveal any Xq chromosomal micro-rearrangement. CONCLUSIONS: Karyotyping is definitely helpful in the evaluation of POF patients. No submicroscopic chromosomal rearrangements affecting Xq region were identified. Further analysis using DNA microarrays should help delineate Xq regions involved in POF.