The t(14;18)(q32;q21)/IGH-MALT1 translocation in MALT lymphomas contains templated nucleotide insertions and a major breakpoint region similar to follicular and mantle cell lymphoma.

The t(14;18)(q32;q21) involving the immunoglobulin heavy chain locus (IGH) and the MALT1 gene is a recurrent abnormality in mucosa-associated lymphoid tissue (MALT) lymphomas. However, the nucleotide sequence of only one t(14;18)-positive MALT lymphoma has been reported so far. We here report the molecular characterization of the IGH-MALT1 fusion products in 5 new cases of t(14;18)-positive MALT lymphomas. Similar to the IGH-associated translocations in follicular and mantle cell lymphomas, the IGH-MALT1 junctions in MALT lymphoma showed all features of a recombination signal sequence-guided V(D)J-mediated translocation at the IGH locus. Furthermore, analogous to follicular and mantle cell lymphoma, templated nucleotides (T-nucleotides) were identified at the t(14;18)/IGH-MALT1 breakpoint junctions. On chromosome 18, we identified a novel major breakpoint region in MALT1 upstream of its coding region. Moreover, the presence of duplications of MALT1 nucleotides in one case suggests an underlying staggered DNA-break process not consistent with V(D)J-mediated recombination. The molecular characteristics of the t(14;18)/IGH-MALT1 resemble those found in the t(14;18)/IGH-BCL2 in follicular lymphoma and t(11;14)/CCND1-IGH in mantle cell lymphoma, suggesting that these translocations could be generated by common pathomechanisms involving illegitimate V(D)J-mediated recombination on IGH as well as new synthesis of T-nucleotides and nonhomologous end joining (NHEJ) or alternative NHEJ repair pathways on the IGH-translocation partner.

Non-Random Pattern of Integration for Epstein-Barr Virus with Preference for Gene-Poor Genomic Chromosomal Regions into the Genome of Burkitt Lymphoma Cell Lines.

BACKGROUND: Epstein-Barr virus (EBV) is an oncogenic virus found in about 95% of endemic Burkitt lymphoma (BL) cases. In latently infected cells, EBV DNA is mostly maintained in episomal form, but it can also be integrated into the host genome, or both forms can coexist in the infected cells. METHODS: In this study, we mapped the chromosomal integration sites of EBV (EBV-IS) into the genome of 21 EBV+ BL cell lines (BL-CL) using metaphase fluorescence in situ hybridization (FISH). The data were used to investigate the EBV-IS distribution pattern in BL-CL, its relation to the genome instability, and to assess its association to common fragile sites and episomes. RESULTS: We detected a total of 459 EBV-IS integrated into multiple genome localizations with a preference for gene-poor chromosomes. We did not observe any preferential affinity of EBV to integrate into common and rare fragile sites or enrichment of EBV-IS at the chromosomal breakpoints of the BL-CL analyzed here, as other DNA viruses do. CONCLUSIONS: We identified a non-random integration pattern into 13 cytobands, of which eight overlap with the EBV-IS in EBV-transformed lymphoblastoid cell lines and with a preference for gene- and CpGs-poor G-positive cytobands. Moreover, it has been demonstrated that the episomal form of EBV interacts in a non-random manner with gene-poor and AT-rich regions in EBV+ cell lines, which may explain the observed affinity for G-positive cytobands in the EBV integration process. Our results provide new insights into the patterns of EBV integration in BL-CL at the chromosomal level, revealing an unexpected connection between the episomal and integrated forms of EBV.

Reduced Androgen Receptor Expression in Genital Skin Fibroblasts From Patients With 45,X/46,XY Mosaicism.

CONTEXT: Molecular mechanisms causing the broad phenotypic diversity of external masculinization in individuals with 45,X/46,XY mosaicism are poorly understood. OBJECTIVE: Analysis of androgen receptor (AR) expression and function as a putative influencing factor for the genital phenotype in patients with 45,X/46,XY mosaicism. DESIGN: Measurement of AR mRNA expression levels, AR activity [DHT-mediated APOD (apolipoprotein D) induction] and cellular 45,X/46,XY ratios in genital skin fibroblasts from individuals with 45,X/46,XY mosaicism and male reference individuals, and determination of the external virilization scale from individuals with 45,X/46,XY mosaicism. SETTING: University hospital endocrine research laboratory. Patients or Other Participants: 30 genital skin fibroblast cultures (GFs) from male reference individuals and 15 GFs from individuals with 45,X/46,XY mosaicism. INTERVENTION: None. MAIN OUTCOME MEASURES: Determination of AR mRNA expression and AR activity in male reference GFs and 45,X/46,XY GFs and correlation of the obtained data with the cellular 45,X/46,XY ratios and the patients' external virilization scale. RESULTS: In 6 of 15 45,X/46,XY GFs, AR mRNA expression and AR activity were significantly lower compared with those in the 46,XY reference GFs. In this subgroup of reduced AR mRNA expression, a positive trend was seen between AR mRNA expression and the percentage of XY-positive cells. Furthermore, we found a positive correlation between AR activity and the external virilization scale in the 15 45,X/46,XY GF samples (P = 0.03). CONCLUSION: Our results suggest that AR expression and AR activity might influence the phenotypic variability seen in patients with 45,X/46,XY mosaicism.

Primary hepatic lymphoma of mucosa-associated lymphoid tissue type: a case report with cytogenetic study.

Primary hepatic lymphoma of mucosa-associated lymphoid tissue type is extremely rare. Only 38 cases have been reported to date. A case of a 59-year-old man with Helicobacter pylori-resistant gastric ulcers and Buerger disease who was followed up since 1999 is reported. A 2-cm hepatic nodule was incidentally found during partial gastrectomy and corresponded to mucosa-associated lymphoid tissue-type lymphoma without underlying liver disease. Molecular studies showed a clonal immunoglobulin heavy-chain gene rearrangement. Investigations for the mucosa-associated lymphoid tissue lymphoma-associated translocations t(11;18) and t(14;18), as well as the t(3;14)(q27;q32), were negative, whereas trisomy 3 and trisomy 18 were detected.

Frequency of chromosomal aneuploidies and deletions of the RB and TP53 genes in MALT lymphomas harboring the t(14;18)(q32;q21).

The t(14;18)(q32;q21) involving the MALT1/MLT and IGH genes has been identified recently as a recurrent abnormality in mucosa-associated lymphoid tissue (MALT) lymphomas. The frequency of secondary chromosomal aberrations in MALT lymphomas harboring the t(14;18) is largely unknown. We therefore analyzed six t(14;18)-positive MALT lymphomas (five parotid, one conjunctiva) by interphase fluorescence in situ hybridization for aneuploidies of chromosomes 3, 7, 12, 18, and X, gains or disruption of the CMYC/8q24 and BCL6/3q27 genes, as well as deletions of the retinoblastoma and TP53 tumor suppressor genes. Except for one MALT lymphoma of the parotid with trisomy 3, neither aneuploidies nor deletions were detected in any of our cases.

Dicentric (19;21)(p13;p13), a novel chromosomal abnormality occurring in a case of Philadelphia chromosome-positive acute lymphoblastic leukemia.

We report on a patient with Philadelphia chromosome-positive acute lymphoblastic leukemia, who acquired a novel chromosomal abnormality, a dic(19;21)(p13;p13), during relapse of the disease. The cytogenetic result was confirmed by fluorescence in situ hybridization using alpha-satellite and library probes specific for chromosomes 19 and 21, respectively, as well as a chromosome 19q13.1-specific DNA probe. In our case, the dic(19;21) represents a secondary genetic change and was associated with disease progression and poor prognosis.

Deletion of chromosome 15 represents a rare but recurrent chromosomal abnormality in myelocytic malignancies.

We report on three cases with myelocytic malignancies cytogenetically characterized by a deletion of chromosome 15 occurring as the sole cytogenetic aberration. The deletions were defined as del(15) (q12q21) (two cases) and del(15)(q11q21) (one case). Cytogenetic analysis was supplemented by fluorescence in situ hybridization (FISH) using a chromosome 15 specific whole chromosome painting probe and probes hybridizing to the UBE3A gene on 15q11~q13, the PML gene on 15q22, and the telomeric region of 15q. Hereby, an interstitial deletion of 15q including UBE3A, but not PML and the telomeric region of 15q could be demonstrated. Two of our patients were diagnosed as acute myelocytic leukemia (AML) with bone marrow dysplasia classified as AML-M6 and AML-M4, respectively, according to the French-American-British classification; the third patient suffered from a chronic myelomonocytic leukemia (CMMoL). In two cases, the aberration was found at the time of primary diagnosis, whereas the third case showed the del(15) only during relapse of leukemia. Both cases with acute leukemia did not adequately respond to intensive chemotherapeutic treatment and died 13 and 11 months, respectively, after primary diagnosis. Our findings and the data of five previously published cases with an isolated del(15) indicate that: 1) del(15) represents a rare but recurrent abnormality in myelocytic hemopathies; 2) in our cases, del(15) was interstitial and included the region 15q11~q13/UBE3A, but not 15q22/PML and the telomeric region of 15q as shown by FISH; 3) del(15) occurs frequently in disorders with myelodysplastic or myeloproliferative features and may therefore affect early hematopoietic progenitor cells; and 4) del(15) may occur during disease progression and is often associated with an unfavorable prognosis.

A novel cryptic translocation t(12;17)(p13;p12-p13) in a secondary acute myeloid leukemia results in a fusion of the ETV6 gene and the antisense strand of the PER1 gene.

The ETV6 gene is a member of the ETS family of transcription factors and the main target of chromosomal rearrangements affecting chromosome band 12p13. To date, more than 15 fusion partners of ETV6 have been characterized at the molecular level. Most of these fusions encode chimeric proteins with oncogenic properties. However, some of the translocations do not produce a functional fusion protein, but may induce ectopic expression of oncogenes located close to the breakpoint. We herein report the characterization and cloning of a novel cryptic translocation, t(12;17)(p13;p12-p13), occurring in a patient with an acute myeloid leukemia evolving from a chronic myelomonocytic leukemia. Cytogenetic analysis suggested the presence of a deletion of the short arm of chromosome 12, del(12)(p13), in three of the five metaphase cells analyzed. However, fluorescence in situ hybridization (FISH) with the ETV6-specific cosmid clones 179A6, 50F4, 163E7, and 148B6 as well as probes hybridizing to the TP53 gene on 17p13 and the subtelomeric region of 17p revealed the presence of a translocation between 12p and 17p. By FISH, the breakpoints could be localized in intron 1 of ETV6 and centromeric to TP53. By 3' rapid amplification of cDNA ends-polymerase chain reaction (3' RACE-PCR), a fusion transcript between exon 1 of ETV6 and the antisense strand of PER1 (period homolog 1, Drosophila), a circadian clock gene, could be identified. This ETV6-PER1 (antisense PER1 strand) fusion transcript does not produce a fusion protein, and no other fusion transcripts could be detected. We hypothesize that in the absence of a fusion protein, the inactivation of PER1 or deregulation of a gene in the neighborhood of PER1 may contribute to the pathogenesis of leukemias with a t(12;17)(p13;p12-p13).