Successful use of the same slide for consecutive fluorescence in situ hybridization experiments

EBV and 1q Gains Affect Gene and miRNA Expression in Burkitt Lymphoma

Abnormalities of the long arm of chromosome 1 (1q) represent the most frequent secondary chromosomal aberrations in Burkitt lymphoma (BL) and are observed almost exclusively in EBV-negative BL cell lines (BL-CLs). To verify chromosomal abnormalities, we cytogenetically investigated EBV-negative BL patient material, and to elucidate the 1q gain impact on gene expression, we performed qPCR with six 1q-resident genes and analyzed miRNA expression in BL-CLs. We observed 1q aberrations in the form of duplications, inverted duplications, isodicentric chromosome idic(1)(q10), and the accumulation of 1q12 breakpoints, and we assigned 1q21.2-q32 as a commonly gained region in EBV-negative BL patients. We detected MCL1, ARNT, MLLT11, PDBXIP1, and FCRL5, and 64 miRNAs, showing EBV- and 1q-gain-dependent dysregulation in BL-CLs. We observed MCL1, MLLT11, PDBXIP1, and 1q-resident miRNAs, hsa-miR-9, hsa-miR-9*, hsa-miR-92b, hsa-miR-181a, and hsa-miR-181b, showing copy-number-dependent upregulation in BL-CLs with 1q gains. MLLT11, hsa-miR-181a, hsa-miR-181b, and hsa-miR-183 showed exclusive 1q-gains-dependent and FCRL5, hsa-miR-21, hsa-miR-155, hsa-miR-155*, hsa-miR-221, and hsa-miR-222 showed exclusive EBV-dependent upregulation. We confirmed previous data, e.g., regarding the EBV dependence of hsa-miR-17-92 cluster members, and obtained detailed information considering 1q gains in EBV-negative and EBV-positive BL-CLs. Altogether, our data provide evidence for a non-random involvement of 1q gains in BL and contribute to enlightening and understanding the EBV-negative and EBV-positive BL pathogenesis.

Remnant living cells that escape cell loss in late-stage tumors exhibit cancer stem cell-like characteristics

A balance between cell proliferation and cell loss is essential for tumor progression. Although up to 90% of cells are lost in late-stage carcinomas, the progression and characteristics of remnant living cells in tumor mass are unclear. Here we used molecular imaging to track the progression of living cells in a syngeneic tumor model, and ex vivo investigated the properties of this population at late-stage tumor. The piggyBac transposon system was used to stably introduce the dual reporter genes, including monomeric red fluorescent protein (mRFP) and herpes simplex virus type-1 thymidine kinase (HSV1-tk) genes for fluorescence-based and radionuclide-based imaging of tumor growth in small animals, respectively. Iodine-123-labeled 5-iodo-2′-fluoro-1-beta-𝒟-arabinofuranosyluracil was used as a radiotracer for HSV1-tk gene expression in tumors. The fluorescence- and radionuclide-based imaging using the single-photon emission computed tomography/computed tomography revealed that the number of living cells reached the maximum at 1 week after implantation of 4T1 tumors, and gradually decreased and clustered near the side of the body until 4 weeks accompanied by enlargement of tumor mass. The remnant living cells at late-stage tumor were isolated and investigated ex vivo. The results showed that these living cells could form mammospheres and express cancer stem cell (CSC)-related biomarkers, including octamer-binding transcription factor 4, SRY (sex-determining region Y)-box 2, and CD133 genes compared with those cultured in vitro. Furthermore, this HSV1-tk-expressing CSC-like population was sensitive to ganciclovir applied for the suicide therapy. Taken together, the current data suggested that cells escaping from cell loss in late-stage tumors exhibit CSC-like characteristics, and HSV1-tk may be considered a theranostic agent for targeting this population in vivo.

New complex chromosomal translocation in chronic myeloid leukaemia: t(9;18;22)(q34;p11;q11)

A Chronic myeloid leukaemia (CML) case with a new complex t(9;18;22)(q34;p11;q11) of a 29-year-old man is being reported. For the first time, this translocation has been characterized by karyotype complemented with fluorescence in situ hybridization (FISH). In CML, the complex and standard translocations have the same prognosis. The patient was treated with standard initial therapy based on hydroxyurea before he died due to heart failure four months later. Our finding indicates the importance of combined cytogenetic analysis for diagnosis and guidance of treatment in clinical diagnosis of CML.

Glycine N-methyltransferase-/- mice develop chronic hepatitis and glycogen storage disease in the liver

Glycine N-methyltransferase (GNMT) affects genetic stability by regulating DNA methylation and interacting with environmental carcinogens. To establish a Gnmt knockout mouse model, 2 lambda phage clones containing a mouse Gnmt genome were isolated. At 11 weeks of age, the Gnmt-/- mice had hepatomegaly, hypermethioninemia, and significantly higher levels of both serum alanine aminotransferase and hepatic S-adenosylmethionine. Such phenotypes mimic patients with congenital GNMT deficiencies. A real-time polymerase chain reaction analysis of 10 genes in the one-carbon metabolism pathway revealed that 5,10-methylenetetrahydrofolate reductase, S-adenosylhomocysteine hydrolase (Ahcy), and formiminotransferase cyclodeaminase (Ftcd) were significantly down-regulated in Gnmt-/- mice. This report demonstrates that GNMT regulates the expression of both Ftcd and Ahcy genes. Results from pathological examinations indicated that 57.1% (8 of 14) of the Gnmt-/- mice had glycogen storage disease (GSD) in their livers. Focal necrosis was observed in male Gnmt-/- livers, whereas degenerative changes were found in the intermediate zones of female Gnmt-/- livers. In addition, hypoglycemia, increased serum cholesterol, and significantly lower numbers of white blood cells, neutrophils, and monocytes were observed in the Gnmt-/- mice. A real-time polymerase chain reaction analysis of genes involved in the gluconeogenesis pathways revealed that the following genes were significantly down-regulated in Gnmt-/- mice: fructose 1,6-bisphosphatase, phosphoenolpyruvate carboxykinase, and glucose-6-phosphate transporter.

CONCLUSION

Because Gnmt-/- mice phenotypes mimic those of patients with GNMT deficiencies and share several characteristics with GSD Ib patients, we suggest that they are useful for studies of the pathogenesis of congenital GNMT deficiencies and the role of GNMT in GSD and liver tumorigenesis.

A common 93-kb duplicated DNA sequence at 1q21.2 in acute lymphoblastic leukemia and Burkitt lymphoma

In three patients with acute lymphoblastic leukemia (ALL) and in another with Burkitt lymphoma (BL), conventional cytogenetics and fluorescence in situ hybridization (FISH), applied singly or in combination, showed 1q duplication in two cases of ALL with hyperdiploid karyotypes, 1q duplication resulting from an unbalanced translocation in a third case of ALL, and inv dup(1)(q) in a patient with BL. Centromeric or telomeric breakpoints and extension of the 1q duplicons varied in each case. FISH defined a minimal, common duplicated region of 93kb at band 1q21.2 corresponding to clone RP11-212K13. In this region three putative oncogenes or tumor suppressor genes have been mapped: SF3B4 (splicing factor 3b, subunit 4), OTUD7B (OTU domain containing 7B), and MTMR11 (myotubularin related protein 11). For the first time, a minimal common 1q21.2 duplicated sequence has been identified in lymphoid malignancies in a region where putative oncogenes or suppressor genes have been mapped. This finding elucidates the genomic background of ALL and BL with 1q duplication and provides the basis for molecular studies investigating which genes are involved in leukemogenesis or disease progression in these cases.

Cytogenetic and Molecular Analysis of 12 Cases of Primary Cutaneous Marginal Zone Lymphomas

Primary low-grade B-cell lymphomas of the skin are separated into marginal zone and follicle center lymphomas according to the recent World Health Organization-European Organization for Research and Treatment of Cancer classification, with distinct histologic and immunohistochemical profiles. Some cases remain difficult to distinguish. The degree of relationship with their extracutaneous counterparts is currently being investigated on clinical, histologic and molecular grounds. Cytogenetic analysis using fluorescence in situ hybridization was performed on 12 frozen samples of infiltrated skin that had been classified as marginal zone lymphoma (MZL). Chromosomal changes known to be recurrently observed in systemic MZL of the mucosa-associated lymphoid tissue type, and in follicular center lymphoma were analyzed. These included trisomy for chromosomes 3, 7, 12, and 18 as well as t(14;18) IGH/BCL2, t(14;18) IGH/MLT1, and t(11;18) API2/MLT1 translocations. Complementary molecular search of IGH/BCL2 rearrangement using a polymerase chain reaction technique and of API2/MLT1 mRNA expression by reverse transcriptase-polymerase chain reaction were performed. Two cases showed evidence of trisomy 3 at levels varying from 14% to 20% of the analyzed cells. No other chromosomal abnormalities were found with those techniques in the remaining cases. These results demonstrate that known recurrent chromosomal abnormalities rarely occur in primary cutaneous MZLs and suggest the possibility of a variety of initial oncogenic events leading to a common downstream pathway. These data also underline that fluorescence in situ analysis on routine skin punch biopsies represents a reliable tool for the detection of chromosomal changes, but requires consistent dermal infiltration.

MALT1 and BCL10 aberrations in MALT lymphomas and their effect on the expression of BCL10 in the tumour cells

Among the genetic abnormalities reported to occur in mucosa-associated lymphoid tissue (MALT) lymphomas, the three translocations t(11;18)(q21;q21), t(1;14)(p22;q32) and t(14;18)(q32;q21) are of particular interest because they appear to be specific for, or at least closely related to this type of B-cell non-Hodgkin's lymphoma. These translocations affect the MALT1 (18q21) and BCL10 (1p22) genes. We retrieved 77 consecutive biopsies of MALT lymphomas (documented with frozen material) over a 10-year period and investigated these cases for the presence of these three translocations with fluorescence in situ hybridisation, along with the immunohistochemical analysis of the intracellular localisation of the BCL10 protein. The above-listed translocations occurred mutually exclusive and were detected in 10, 1 and 3% of the cases, respectively (the latter incidence being much lower than in the previously reported studies by one single group). These genetic rearrangements corresponded well with the aberrant subcellular localisation of the BCL10 protein as found by immunohistochemistry: t(11;18)(q21;q21) and (1;14)(p22;q32) were marked by a, respectively, moderate to strong nuclear BCL10 staining pattern while t(14;18)(q32;q21)-positive MALT lymphomas were characterised by a perinuclear BCL10 staining pattern. This study further supports the close interaction between the MALT1 and BCL10 proteins in the pathogenesis of MALT lymphomas and may indicate that BCL10 immunohistochemistry is a simple technique to identify those MALT lymphoma cases with an underlying genetic aberration.

Leukemic recombinations involving heterochromatin in myeloproliferative disorders with t(1;9)

The unbalanced t(1;9) is a rare, recurrent rearrangement in polycythemia vera (PV) resulting in trisomy of both 1q and 9p arms, whereas a balanced t(1;9)(q12;q12), to our knowledge, has never been reported before. We studied two patients with PV and one with idiopathic myelofibrosis bearing an unbalanced t(1;9) and one patient with essential thrombocythemia with a balanced t(1;9). In all cases fluorescence in situ hybridization showed that the breakpoints were located within the satellite II family of heterochromatin of chromosome 1 and the satellite III of chromosome 9. Heterochromatin breakage and reunion produce the unbalanced t(1;9) and may contribute to a gene dosage effect due to gains of 1q and 9p. Case 4 with the balanced t(1;9), however, suggests that translocation of heterochromatin close to critical genes could interfere with their function. The molecular event underlying juxtaposition of satellite II of chromosome 1 and the satellite III of chromosome 9 remains to be elucidated.

Cryptic insertion producing two NUP98/NSD1 chimeric transcripts in adult refractory anemia with an excess of blasts

We performed cytogenetic and molecular studies on an adult patient with refractory anemia with an excess of blasts with an add(11)(p15). Multicolor fluorescence in situ hybridization (FISH) identified the extra material on 11p as belonging to chromosome 15. Metaphase FISH with probes for chromosomes 5, 11, and 15 revealed a complex four-break rearrangement. Clone RP5-1173K1, containing exons 10-20 of the NUP98 gene, gave three fluorescence signals on the normal 11, the der(5), and the der(15). 3'-RACE-PCR identified an in-frame fusion between NUP98 and NSD1, which was confirmed by RT-PCR. Two different spliced forms, that is, NUP98 exon 11/NSD1 exon 6 and NUP98 exon 12/NSD1 exon 6, were detected. The reciprocal NSD1/NUP98 was not found. A dual-color experiment with RP5-1173K1 and CTC-549A4, spanning the entire NSD1 gene, indicated an insertion of NUP98 into the NSD1 locus. This is the first report of an adult with myelodysplastic syndrome (MDS) harboring an NUP98/NSD1 fusion resulting from insertion of 5'-NUP98 into the NSD1/5q35 locus.

Alterations of loci encoding PU.1, BOB1, and OCT2 transcription regulators do not correlate with their suppressed expression in Hodgkin lymphoma

Neoplastic cells of Hodgkin lymphoma (HL) originating from germinal or postgerminal center B cells lose their capacity to transcribe and to express surface immunoglobulins (Ig). This defect correlates with the absence of expression of B-cell-specific transcription regulators, including PU.1, BOB1, and OCT2. These findings suggest that Ig impairment in HL is caused by the defective transcription machinery. The mechanism or mechanisms underlying failure of Hodgkin cells to express PU.1, BOB1, and OCT2 remain unclear. The genes encoding for these three respective transcription factors have been mapped at 11p11.2 (SPI1), 11q23.1 (POU2AF1), and 19q13.2 (POU2F2); these are chromosomes recurrently affected in HL. To check the genomic status of PU.1, BOB1, and OCT2 in HL, we performed metaphase fluorescence in situ hybridization (FISH) analysis of 10 HL cases using locus-specific bacterial artificial chromosome clones. FISH signal pattern was correlated with the ploidy level of each analyzed cell and showed recurrent imbalances of the studied loci. The underrepresentation of one or two analyzed regions was detected in five cases; the remaining five cases showed either random losses, a ploidy-equivalent FISH pattern, or overrepresented signals. Neither a constant loss nor genomic aberration of at least one of these genes could be observed in studied cases. These findings indicate that genomic imbalances or rearrangements are not a cause of PU.1, BOB1, and OCT2 deficiency in cHL and argue for another mechanism underlying this phenomenon.

KIAA1509 is a novel PDGFRB fusion partner in imatinib-responsive myeloproliferative disease associated with a t(5;14)(q33;q32)

We report the cloning of a novel PDGFRB fusion gene partner in a patient with a chronic myeloproliferative disorder characterized by t(5;14)(q33;q32), who responded to treatment with imatinib mesylate. Fluorescence in situ hybridization demonstrated that PDGFRB was involved in the translocation. Long distance inversion PCR identified KIAA1509 as the PDGFRB fusion partner. KIAA1509 is an uncharacterized gene with a predicted coiled-coil oligomerization domain with homology to the HOOK family of proteins. The predicted KIAA1509-PDGFRbeta fusion protein contains the KIAA1509 coiled-coil domain fused to the cytoplasmic domain of PDGFRbeta that includes the tyrosine kinase domain. Imatinib therapy resulted in rapid normalization of the patient's blood counts, and subsequent bone marrow biopsies and karyotypic analysis were consistent with sustained complete remission.

Translocation t(1;6)(p35.3;p25.2): a new recurrent aberration in "unmutated" B-CLL

Although reciprocal chromosomal translocations are not typical for B-cell chronic lymphocytic leukemia (B-CLL), we identified the novel t(1;6)(p35.3;p25.2) in eight patients with this disorder. Interestingly, all cases showed lack of somatically mutated IgV(H). Clinical, morphological, immunologic, and genetic features of these patients are described. Briefly, the age ranged from 33 to 81 years (median: 62.5 years) and the sex ratio was 6M:2F. Most of the patients (6/8) presented with advanced clinical stage. Therapy was required in seven cases. After a median follow-up of 28 months, five patients are alive and three died from disease evolution. Three cases developed transformation into diffuse large B-cell lymphoma. Translocation t(1;6) was found as the primary karyotypic abnormality in three patients. Additional chromosomal aberrations included changes frequently found in unmutated B-CLL, that is, del(11)(q), trisomy 12 and 17p aberrations. Fluorescence in situ hybridization analysis performed in seven cases allowed us to map the t(1;6) breakpoints to the 1p35.3 and 6p25.2 chromosomal bands, respectively. The latter breakpoint was located in the genomic region coding for MUM1/IRF4, one of the key regulators of lymphocyte development and proliferation, suggesting involvement of this gene in the t(1;6). Molecular characterization of the t(1;6)(p35.3;p25.2), exclusively found in unmutated subtype of B-CLL, is in progress.

Fusion of EML1 to ABL1 in T-cell acute lymphoblastic leukemia with cryptic t(9;14)(q34;q32)

The BCR-ABL1 fusion kinase is frequently associated with chronic myeloid leukemia and B-cell acute lymphoblastic leukemia but is rare in T-cell acute lymphoblastic leukemia (T-ALL). We recently identified NUP214-ABL1 as a variant ABL1 fusion gene in 6% of T-ALL patients. Here we describe the identification of another ABL1 fusion, EML1-ABL1, in a T-ALL patient with a cryptic t(9;14)(q34;q32) associated with deletion of CDKN2A (p16) and expression of TLX1 (HOX11). Echinoderm microtubule-associated protein-like 1-Abelson 1 (EML1-ABL1) is a constitutively phosphorylated tyrosine kinase that transforms Ba/F3 cells to growth factor-independent growth through activation of survival and proliferation pathways, including extracellular signal-related kinase 1/2 (Erk1/2), signal transducers and activators of transcription 5 (Stat5), and Lyn kinase. Deletion of the coiled-coil domain of EML1 abrogated the transforming properties of the fusion kinase. EML1-ABL1 and breakpoint cluster region (BCR)-ABL1 were equally sensitive to the tyrosine kinase inhibitor imatinib. These data further demonstrate the involvement of ABL1 fusions in the pathogenesis of T-ALL and identify EML1-ABL1 as a novel therapeutic target of imatinib.

Fusion of NUP214 to ABL1 on amplified episomes in T-cell acute lymphoblastic leukemia

In T-cell acute lymphoblastic leukemia (T-ALL), transcription factors are known to be deregulated by chromosomal translocations, but mutations in protein tyrosine kinases have only rarely been identified. Here we describe the extrachromosomal (episomal) amplification of ABL1 in 5 of 90 (5.6%) individuals with T-ALL, an aberration that is not detectable by conventional cytogenetics. Molecular analyses delineated the amplicon as a 500-kb region from chromosome band 9q34, containing the oncogenes ABL1 and NUP214 (refs. 5,6). We identified a previously undescribed mechanism for activation of tyrosine kinases in cancer: the formation of episomes resulting in a fusion between NUP214 and ABL1. We detected the NUP214-ABL1 transcript in five individuals with the ABL1 amplification, in 5 of 85 (5.8%) additional individuals with T-ALL and in 3 of 22 T-ALL cell lines. The constitutively phosphorylated tyrosine kinase NUP214-ABL1 is sensitive to the tyrosine kinase inhibitor imatinib. The recurrent cryptic NUP214-ABL1 rearrangement is associated with increased HOX expression and deletion of CDKN2A, consistent with a multistep pathogenesis of T-ALL. NUP214-ABL1 expression defines a new subgroup of individuals with T-ALL who could benefit from treatment with imatinib.

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.

Translocation t(2;3)(p15-23;q26-27) in myeloid malignancies: report of 21 new cases, clinical, cytogenetic and molecular genetic features

Chromosomal rearrangements involving 3q26 either due to inversion or translocation with various partner chromosomes are a recurrent finding in malignant myeloid disorders. Typically, these chromosome aberrations contribute to ectopic expression of or to the formation of fusion genes involving the EVI1 proto-oncogene. Chromosomal translocations involving the short arm of chromosome 2 (p15-p23) and the distal part of the long arm of chromosome 3 (q26-q27) are a rare but recurrent finding in patients with myeloid malignancies, and are assumed to be part of this spectrum of disorders. Thus far, however, these translocations have been poorly studied. Here, we present 21 new cases with myelodysplasia, acute myeloid leukemia or CML in blast crisis, which upon karyotyping showed the presence of a t(2;3). Furthermore, an extensive literature review disclosed 29 additional cases. Morphological, clinical and cytogenetic assessment revealed the typical hallmarks of 3q26/EVI1 rearrangements, that is, trilineage dysplasia and dysmegakaryopoiesis, poor prognosis and additional monosomy 7. Molecular cytogenetic analysis and PCR in selected samples indicated that in most cases the translocation indeed targets the EVI1 locus. Mapping of the chromosome 2 breakpoints confirmed the initially suspected cytogenetic breakpoint heterogeneity at the 2p arm.

Translocations t(11;18)(q21;q21) and t(14;18)(q32;q21) are the main chromosomal abnormalities involving MLT/MALT1 in MALT lymphomas

The recently discovered MLT/MALT1 gene is fused with the API2 gene in the t(11;18)(q21;q21), which characterizes about one-third of MALT lymphomas. In order to screen for variant translocations and amplifications of MLT/MALT1, we have developed a novel, undirected two-color interphase fluorescence in situ hybridization (FISH) assay with two PAC clones flanking MLT/MALT1. This assay was applied to 108 marginal zone B-cell lymphomas (MZBCLs), including 72 extranodal MALT lymphomas, 17 nodal, and 19 splenic MZBCL. In 19 MALT lymphomas (26%), but in none of the nodal or splenic MZBCL, separated hybridization signals of the MLT/MALT1 flanking probes, were found. Further FISH analyses showed that 12 of these 19 cases displayed the classical t(11;18) and the remaining seven cases revealed the novel t(14;18)(q32;q21), involving the MLT/MALT1 and IGH genes. The frequency at which these translocations occurred varied significantly with the primary location of disease. The t(11;18) was mainly detected in gastrointestinal MALT lymphomas, whereas the t(14;18) occurred in MALT lymphomas of the parotid gland and the conjunctiva. Amplification of MLT/MALT1 was not observed in any of the lymphomas analyzed. We conclude that the translocations t(11;18)(q21;q21) and t(14;18)(q21;q32) represent the main structural aberrations involving MLT/MALT1 in MALT lymphomas, whereas true amplifications of MLT/MALT1 occur rarely in MZBCL.

ALK activation by the CLTC-ALK fusion is a recurrent event in large B-cell lymphoma

We present 3 cases of large B-cell lymphoma (LBCL) with a granular cytoplasmic staining for anaplastic lymphoma kinase (ALK). All of the cases showed striking similarities in morphology and immunohistochemical profile characterized by a massive monomorphic proliferation of CD20-/CD138+ plasmablast-like cells. In one of the cases, initially diagnosed as a null-type anaplastic large cell lymphoma (ALCL), the B-cell phenotype became evident only at recurrence. Fluorescent in situ hybridization (FISH) and molecular studies led to the detection of a CLTC-ALK rearrangement in all 3 cases, without any evidence of full-length ALK receptor expression. The associated t(2;17)(p23;q23) was demonstrated in the karyotype of 2 cases. Although a similar CLTC-ALK aberration was previously identified in ALK-positive T-/null cell ALCL and inflammatory myofibroblastic tumor, its association with ALK-positive LBCL seems to be specific and intriguing.

ALK-ATIC fusion in urinary bladder inflammatory myofibroblastic tumor

In this report, we describe an inflammatory myofibroblastic tumor (IMT) of the urinary bladder in a 46-year-old man. Tumor cells presented striking cytoplasmatic ALK immunopositivity. Cytogenetic and FISH analysis, by use of a multicolor chromosome 2 banding probe, revealed a 46,XY,der(2)(2pter-->2p23:2q35-->2q37:2p11-->2q35:2p23-->2p11:2q37-->2qter) karyotype. Subsequent FISH and RT-PCR analysis confirmed the ALK-ATIC chimeric fusion in tumor cells. This is the first evidence of a variant rearrangement involving the ATIC gene in IMT and the first cytogenetic description of an IMT originating from the urinary bladder.

Complex genomic rearrangement of ALK loci associated with integrated human Epstein-Barr virus in a post-transplant myogenic liver tumor

Epstein-Barr virus (EBV) is a ubiquitous viral agent, well known to be associated with lymphoid, epithelial, and smooth-muscle malignancies in immunocompromised individuals. This report describes a 10-year-old patient with an EBV-related liver tumor occurring after kidney transplantation. The neoplasm presented a phenotypic spectrum, ranging from a smooth-muscle tumor to an inflammatory pseudotumor (IPT). The neoplastic cells failed to disclose CD21, CD35, or ALK expression, the latter confirmed by reverse-transcription polymerase chain reaction. Cytogenetic analysis revealed a single clonal cell population showing 46,XY,del (2)(p23),der(3)t (2;3)(p23;q29),der(21) t(Y;21)(q12;p13) karyotype. By metaphase FISH analysis, the neoplastic cells demonstrated the presence of two molecularly different but related aberrant clones, one with the loss of one ALK allele and the second with translocation of the 3'end of ALK kinase domain on the der(3) chromosome. Using FISH with an EBV-specific and 3'end ALK DNA probes, a co-localization of the viral DNA and the ALK sequences was found on the der(3) chromosome. Metaphases with loss of rearranged ALK did not show integrated virus; instead, viral particles together with an associated 3'end ALK domain formed an ex-chromosomal, episomal-like type configuration. The interphase study, using dual-color 5'/3' end ALK FISH assay, revealed 30% of nuclei with only one fused signal, confirming the total loss of one ALK allele in the subset of tumor cells. A combined immunofluorescence and FISH study indicated this separate clonal variant to correspond to desmin-positive smooth-muscle cells. In contrast, desmin-negative myofibroblasts showed the presence of both normal and rearranged ALK alleles. Our results indicate that ALK locus may be a target of EBV integration, a hitherto unreported finding. Although the sustained clonal expansion in EBV-related smooth-muscle tumors/IPTs may depend on functions provided by the EBV oncogenic proteins, the tumor phenotype may be further modified by the secondary genomic rearrangements imposed by the virus during and/or after the integration event. In this respect, the observed phenotypic heterogeneity most likely reflects divergence during neoplastic progression, with the subsequent expansion of morphologically and molecularly distinct but cytogenetically related clones.

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.

Lipoblastoma in a 23-year-old male: distinction from atypical lipomatous tumor using cytogenetic and fluorescence in-situ hybridization analysis

Lipoblastoma is a rare benign tumor that occurs primarily in infancy and early childhood. We present the rare presentation of a 12 cm sized intramuscular lipoblastoma of the thigh in a 23-year-old patient. On histology, the tumor strongly resembled an atypical lipomatous tumor due to the presence of lipoblasts and atypical stromal nuclei. The very focal lobulation and myxoid change presented the only histological hint towards a lipoblastoma. Cytogenetic and subsequent FISH evaluation of the tumor cells showed a 46,XY, t(8;15) (q12;q25) as chromosomal change with rearrangement of the PLAG1 gene. The present case indicates that lipoblastoma should enter the differential diagnosis of an 'atypical' deep seated fatty tumor in adults. The diagnostic value of cytogenetic/molecular analysis in the differential diagnosis of lipomatous tumors is underscored as well.

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).

Human homeobox gene HOXC13 is the partner of NUP98 in adult acute myeloid leukemia with t(11;12)(p15;q13)

The chimeric gene NUP98/HOXC13 was detected in a patient with a de novo acute myeloid leukemia and a t(11;12)(p15;q13). Fluorescence in situ hybridization with PAC1173K1 identified the breakpoint on 11p15, indicating that the NUP98 gene was involved in the translocation. At 12q13, the breakpoint fell within BAC 578A18, selected for the homeobox C (HOXC) cluster genes. RACE-PCR showed that HOXC13 was the partner gene of NUP98. To date, HOXC13 is the eighth homeobox gene that, as the result of a reciprocal translocation, fuses with NUP98 in myeloid malignancies.

MLL tandem duplication in two cases of acute myelocytic leukemia with unbalanced translocations: der(16)t(11;16)(q23;p13) and der(18)t(11;18)(q22;p11.2)

We describe two cases of acute myelocytic leukemia (AML), classified as M4 and M1 in the French-American-British classification, with unbalanced translocations der(16)t(11;16)(q23;p13) and der(18)t(11;18) (q22;p11.2), respectively. Molecular studies using Southern blot and reverse transcriptase-polymerase chain reaction showed an MLL rearrangement due to an internal duplication of the gene in both cases. Fluorescence in situ hybridization disclosed the presence of an extra copy of the MLL gene on 16p13 and 18p11.2, respectively, as a result of the partial trisomy of chromosome 11q. Our two cases clearly show that tandem duplication of the MLL gene may occur in AML with a partial 11q trisomy. Thus, systematic screening of this molecular defect should be performed in patients with unbalanced translocations involving 11q22 approximately q23-->qter.

A tyrosine kinase created by fusion of the PDGFRA and FIP1L1 genes as a therapeutic target of imatinib in idiopathic hypereosinophilic syndrome

BACKGROUND

Idiopathic hypereosinophilic syndrome involves a prolonged state of eosinophilia associated with organ dysfunction. It is of unknown cause. Recent reports of responses to imatinib in patients with the syndrome suggested that an activated kinase such as ABL, platelet-derived growth factor receptor (PDGFR), or KIT, all of which are inhibited by imatinib, might be the cause.

METHODS

We treated 11 patients with the hypereosinophilic syndrome with imatinib and identified the molecular basis for the response.

RESULTS

Nine of the 11 patients treated with imatinib had responses lasting more than three months in which the eosinophil count returned to normal. One such patient had a complex chromosomal abnormality, leading to the identification of a fusion of the Fip1-like 1 (FIP1L1) gene to the PDGFRalpha (PDGFRA) gene generated by an interstitial deletion on chromosome 4q12. FIP1L1-PDGFRalpha is a constitutively activated tyrosine kinase that transforms hematopoietic cells and is inhibited by imatinib (50 percent inhibitory concentration, 3.2 nM). The FIP1L1-PDGFRA fusion gene was subsequently detected in 9 of 16 patients with the syndrome and in 5 of the 9 patients with responses to imatinib that lasted more than three months. Relapse in one patient correlated with the appearance of a T674I mutation in PDGFRA that confers resistance to imatinib.

CONCLUSIONS

The hypereosinophilic syndrome may result from a novel fusion tyrosine kinase - FIP1L1-PDGFRalpha - that is a consequence of an interstitial chromosomal deletion. The acquisition of a T674I resistance mutation at the time of relapse demonstrates that FIP1L1-PDGFRalpha is the target of imatinib. Our data indicate that the deletion of genetic material may result in gain-of-function fusion proteins.

Endometrial stromal sarcoma with a sole t(X;17) chromosome change: report of a case and review of the literature

BACKGROUND

Endometrial stromal sarcomas (ESSs) exhibit varying degrees of malignancy and heterogeneity at the karyotypic level. The biological mechanisms that contribute to tumorigenesis of ESS are still largely unknown.

CASE

A 33-year-old woman suffering from ESS was treated primarily surgically. Cytogenetic evaluation of the primary uterine nodule and metastatic tumor showed 46,XX,t(X;17)(p11:q23) karyotype in all metaphases analyzed. Normal endometrial cells exhibited 46,XX karyotype. Fluorescence in situ hybridization analysis confirmed the presence of the reciprocal t(X;17) translocation and allowed for the positioning of the chromosome X breakpoint distal to SSX1 gene loci.

CONCLUSIONS

Our report of a previously undescribed sole cytogenetic translocation in an advanced stage of ESS might identify a cytogenetically distinct subgroup of ESS and help to reveal genes involved in ESS tumorigenesis.

Different mechanisms lead to a karyotypically identical t(20;21) in myelodysplastic syndrome and in acute myelocytic leukemia

A new t(20;21)(q11;q11), associated with a deletion on the long arm of chromosome 20, was found in one patient with an acute myelocytic leukemia (AML) and in one with myelodysplastic syndrome (MDS). In both cases deletion was interstitial, extending from band q11 to band q13, as shown by comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH). FISH analysis with whole arm paints, subtelomeric probes, and locus-specific probes for the long arms of chromosomes 20 and 21 revealed in patient 1 a reciprocal translocation between the deleted 20q and the long arm of chromosome 21, that is, del(20)(q11q13)t(20;21)(q11;q11), and in patient 2, material from 21q was inserted into the deleted 20q, that is, del(20)(q11q13)ins(20;21)(q11;q11q22). This is the first identification of a complex 20;21 rearrangement in MDS/AML. Deletion at 20q and juxtaposition between 20q11 and 21q11 appear to be the critical genomic events.

Spindle-cell rhabdomyosarcoma with 2q36 approximately q37 involvement

The cytogenetic analysis of a spindle-cell variant of embryonal rhabdomyosarcoma (RMS), presenting as a cheek mass in an 18-year-old girl, is reported. The tumor cells showed an abnormal karyotype 46,XX,der(2)t(2;7)(q36 approximately q37;q3?),del(14)(q24),der(16)t(1;16)(q21;q13), with a tetraploid range of chromosome number in a subpopulation of cells. By fluorescence in situ hybridization analysis, the tumor cells were negative for FKHR-disrupting translocations specific for alveolar type of RMS and for NMYC gene amplification.

Identification of novel fusion partners of ALK, the anaplastic lymphoma kinase, in anaplastic large-cell lymphoma and inflammatory myofibroblastic tumor

ALK-positive anaplastic large-cell lymphoma (ALCL) has been recognized as a distinct type of lymphoma in the heterogeneous group of T/Null-ALCL. While most of the ALK-positive ALCL (ALKomas) are characterized by the presence of the NPM-ALK fusion protein, the product of the t(2;5)(p23;q35), 10-20% of ALKomas contain variant ALK fusions, including ATIC-ALK, TFG-ALK, CLTC-ALK (previously designated CLTCL-ALK), TMP3-ALK, and MSN-ALK. TMP3-ALK and TMP4-ALK fusions also have been detected in inflammatory myofibroblastic tumors (IMTs), making clear that aberrations of the ALK gene are not associated exclusively with the pathogenesis of ALK-positive ALCL. Here we report results of molecular studies on two lymphoma cases and one IMT case with variant rearrangements of ALK. Our study led to the detection of the CLTC-ALK fusion in an ALCL case and to the identification of two novel fusion partners of ALK: ALO17 (KIAA1618), a gene with unknown function, which was fused to ALK in an ALCL case with a t(2;17)(p23;q25), and CARS, encoding the cysteinyl-tRNA synthetase, which was fused to ALK in an IMT case with a t(2;11;2)(p23;p15;q31). These results confirm the recurrent involvement of ALK in IMT and further demonstrate the diversity of ALK fusion partners, with the ability to homodimerize as a common characteristic.

Ring chromosome 6 may represent a cytogenetic subgroup in benign thymoma

Cytogenetic and fluorescence in situ hybridization analysis of a thymoma revealed the presence of an abnormal clone with a karyotype 46,XY,r(6)(p2?q35?).ish r(6)(p2?q35?)(WCP6+,dJ476O18-,dJ62I11-, PAC59C23+,PAC57H24-),der(21)t(6;21)(p25;q22)(dJ62I11+,cosC9a1-). Histologically, the tumor was encapsulated and classified as thymoma type AB (World Health Organization classification) or mixed thymoma (Muller-Hermelink classification), composed of well-formed lobules with sharp demarcation of both the spindly type A and lymphocyte-rich type B components. This finding, together with literature data, strongly suggests that terminal deletion of the short arm of chromosome 6 is a recurrent aberration in thymoma.

Primary cutaneous epidermotropic alveolar rhabdomyosarcoma with t(2;13) in an elderly woman: case report and review of the literature

We report a case of a primary cutaneous alveolar rhabdomyosarcoma presenting on the lower limb of a 60-year old woman. The tumor was characterized by aggregates of round blue cells in an alveolar growth pattern in the dermis and subcutis, with the additional unique finding of epidermotropism. By immunohistochemistry tumor cells were positive for vimentin, muscle-specific actin, desmin, myogenin, and Myo-D1 with focal positivity for CD56, neuron-specific enolase, and S-100 protein. Staining for pan-keratin, HMB-45, melan-A, epithelial membrane antigen, chromogranin, CD99, leukocyte common antigen, and alpha-smooth muscle actin was negative. Interphase fluorescence in situ hybridization analysis from paraffin-embedded tumor demonstrated the presence of the translocation (2;13)(q35;q14) confirming the diagnosis. Further investigations revealed no tumor in the underlying deep soft tissues, and there was no evidence of metastasis in other organs. A local recurrence associated with a metastasis to a regional lymph node on the right groin was treated with an above-knee amputation and local radiotherapy to the groin area. The patient subsequently developed cutaneous metastases in the amputation stump and died 2 years after initial presentation. This case indicates that rhabdomyosarcoma may rarely present in the skin in adults and should be included in the differential diagnosis of primary cutaneous small round blue cell tumors not only in children but also in this age group.

Interpretation of the complex karyotype and identification of a new 6p amplicon by integrated comparative genomic hybridization and fluorescence in situ hybridization on the U937-I cell line

Molecular cytogenetics is helpful to identify complex and cryptic genomic changes in malignancy. Human leukemic cell lines are an important tool for advancements of biological research on malignant cells, one critical step being characterization of genomic changes. We used fluorescence in situ hybridization and comparative genomic hybridization to refine karyotypic interpretation of the diffuse histiocytic lymphoma derived U937-1 cell line. From this integrated approach, chromosome material involved in nine karyotypic markers and in unbalanced translocations could be identified. Moreover, a previously undetected amplicon emerged within band 6p21. The U937-I is a new in vitro model to study genome amplification and unknown recombinations in leukemic cells, such as those involving the centromeric region of chromosome 1.

Hyaline vascular Castleman's disease with HMGIC rearrangement in follicular dendritic cells: molecular evidence of mesenchymal tumorigenesis

Chromosomal aberrations involving chromosome segment 12q13-15 are a common finding in a variety of benign mesenchymal tumors. The target gene encodes for HMGIC, a member of the high mobility group protein family. These proteins act as architectural transcription factors. HMGIC plays a role as a common genetic denominator in benign mesenchymal tumorigenesis. We report a case of hyaline vascular Castleman's disease with intragenic HMGIC rearrangement, due to a clonal cytogenetic aberration involving the long arm of chromosome 12 [46,XX, add(1)(q21),der(6)t(6;12) (q23;q15),add(7)(p22), -9,inv(9)(p11q13),del(12)(q15),+mar] obtained after short-term primary cultures. A combined immunocytologic-cytogenetic approach enabled us to demonstrate the exclusive presence of HMGIC rearrangement in anti-CD21 reactive follicular dendric cells. This finding confirms that a clonal proliferation of follicular dendritic cells occurs in the hyaline vascular variant of Castleman's disease. It also provides a possible molecular pathway explaining stromal overgrowths and stromal neoplasms developing from this disorder.

Fluorescence in situ hybridization study of chromosome 7 aberrations in hepatosplenic T-cell lymphoma: isochromosome 7q as a common abnormality accumulating in forms with features of cytologic progression

Hepatosplenic gamma delta T-cell lymphoma (HS gamma delta TCL) is a rare and aggressive subtype of peripheral T-cell lymphoma that has been associated cytogenetically with the isochromosome 7q [i(7)(q10)]. The incidence of this aberration and its relevance to pathogenesis of HS gamma delta TCL is still unknown. We investigated the status of chromosome 7 in 12 HSTCL cases, including nine with a typical gamma delta phenotype, one with a so-called T-cell receptor (TCR)-silent phenotype, and two with the variant alpha beta phenotype. We analyzed available fresh and archival material using a dual-color interphase fluorescence in situ hybridization (FISH) approach with 7p and 7q probes. A significant population of cells with predominance of 7q signals was detected in 10 cases (eight gamma delta, one alpha beta, and one TCR silent), and two lymphomas did not show clonal 7p/7q signal imbalances. In four of 10 cases with chromosome 7 aberrations, a hybridization pattern indicative of the presence of one chromosome 7 and one i(7)(q10) was found. In four other cases, the configuration of signals (2 x 7p/3 x 7q) suggested the presence of the i(7)(q10) and additional structural aberrations involving the second chromosome 7. In two cases, including one alpha beta phenotypic variant, a variety of FISH patterns equivalent to two to five copies of i(7)(q10) or numerical and structural aberrations of second chromosome 7 has been detected. These findings support cytogenetic data pointing to a characteristic association of i(7)(q10) with HSTCL, irrespective of the immunophenotype of malignant cells. An increased number of 7q signals was found in three cases with cytologic features of progression, indicating a tendency of HSTCL to multiply the i(7)(q10) chromosome during evolution.

Cumulative dosage effect of a RAD51L1/HMGA2 fusion and RAD51L1 loss in a case of pseudo-Meigs' syndrome

Uterine leiomyoma presenting with ascites and pleural fluid is referred to as pseudo-Meigs' syndrome. It is unclear whether common uterine leiomyomas and uterine leiomyomas causing pseudo-Meigs' syndrome are cytogenetically related or whether functionally different primary pathogenetic triggers are responsible for the differences in tumor phenotype. In this study, we investigated the possible involvement of RAD51LI and HMGA2 (formerly known as HMGIC) in initiation and/or progression of a huge uterine leiomyoma presenting as pseudo-Meigs' syndrome. The detailed cytogenetic and FISH analysis revealed the presence of two subclones with a complex karyotype, 46,XX,t(2;12)(q31;q21),ins(14;12)(q23-24;q15q21).ish del(12)(q15q15) (LL12NC01-142H1-,LL12NC01-27E12-),der(12)t(2;12)(LL12NC01-142H1+,LL12NC01-27E12-),der(14)ins(14;12)(q22;q15q15) (LL12NC01-142H1+,LL12NC01-27E12+,RAD51LI+), der(14)ins(14;12)(q23-q24;q15q21) (LL12NC01-142H1-, LL12NC01-27E12+) [20]/46,idem,del(14)(q21q24).ish(RAD51LI-) [6], indicating intragenic HMGA2 rearrangement and loss of one of the RAD51LI alleles in a derivative subclone with chromosome 14 deletion. Furthermore, RACE and RT-PCR analysis of the tumor cells did not reveal abnormal HMGA2 or RAD51LI transcripts. Additionally, the cellular subclone with intrachromosomal 14q21-q24/RAD51LI deletion showed an in vitro growth advantage over the subclone without the deletion. This observation supports a model in which accumulation of two independent mutations-a classical structural rearrangement involving HMGA2 and RAD51L1, in combination with a loss of the second RAD51L1 allele-might play a major role in the development of pseudo-Meigs' syndrome.

Is 4q13 a recurring breakpoint in solitary fibrous tumors?

Solitary fibrous tumor (SFT) is a mesenchymal neoplasm found predominantly in the subpleural region but also in many other body sites. We report a malignant solitary fibrous tumor of the peritoneum with a 47,XY,t(4;9)(q13;p23),+5 karyotype. The chromosome 4q13 breakpoint in the presented and previously published case of pleural solitary fibrous tumor with a 46,XY,t(4;15)(q13;q26) karyotype was further characterized by fluorescence in situ hybridization analysis and localized within the 5-cM interval that was flanked by regions specific to YAC clones 761A7 and 886C11. Chromosome translocations involving chromosome 4q13 may characterize a separate cytogenetic subgroup of SFT.

Molecular cytogenetic definition of three distinct chromosome arm 14q deletion intervals in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are mesenchymal neoplasms characterized by frequent chromosome arm 14q losses. In this study, the 14q changes in a series of 39 histologically and immunohistochemically confirmed GISTs were analyzed in detail by metaphase and/or interphase fluorescence in situ hybridization (FISH) studies using 21 genetically well-characterized, region-specific 14q11-24 YAC clones. By conventional cytogenetic analysis, acquired clonal chromosome aberrations were found in 17 out of 35 tumors. Chromosome 14 was involved in 13 cases; six specimens showed complete chromosome 14 loss, while the remaining seven had structural abnormalities with the breakpoints residing within the intervals 14q11-13 or 14q22-24. Other recurrent chromosome aberrations included frequent deletions of chromosome 1p (11/17), losses of chromosome 22 (7/17), losses or deletions of chromosome arm 13 (6/17) or 15 (4/17), and gains or translocations involving chromosome 17 (4/17). Combining cytogenetic data with double-color FISH analysis, total or partial losses of 14q material were detected in 29 out of 36 tumors (81%). The 14q losses were found in all stages and histological subtypes. Two most frequent common deletion regions flanked by YACs 931B1 and 761D4, and 802E7 and 892C11 at 14q23-24 (25/30 of each; 83%) could be identified. Furthermore, 21 tumors (70%) shared a region of deletion defined by YACs 957H10 and 931E5 at 14q11-12. Our results suggest the presence of at least three distinct critical deletion regions on chromosome 14 in GISTs.

Histologic localization of PLAG1 (pleomorphic adenoma gene 1) in pleomorphic adenoma of the salivary gland: cytogenetic evidence of common origin of phenotypically diverse cells

Pleomorphic adenoma gene 1 (PLAG1), a zinc finger transcription factor gene, is consistently rearranged and overexpressed in human pleomorphic adenomas of the salivary glands with 8q12 translocations. In this report, we describe the immunohistochemical localization of PLAG1 protein in pleomorphic adenomas of the salivary gland and corresponding normal tissue, in relation to cytokeratin, vimentin, and BCL-2 expression. Normal salivary gland tissue was not immunoreactive for PLAG1. In primary pleomorphic adenomas, cells strongly immunoreactive for PLAG1 were detected in the outer layer of tubulo-ductal structures, which are thought to be the origin of cells with bi-directional, epithelial, and mesenchymal phenotypes. In contrast, epithelial cells with abundant cytokeratin in the inner tubulo-ductal structures only sporadically expressed PLAG1. BCL-2 immunoreactivity was found mainly in the cells surrounding the tubulo-ductal structures and in the solid undifferentiated cellular masses, within the areas that had moderate PLAG1 immunoreactivity. The variability of PLAG1 expression in neoplastic cells seemed to reflect the morphologic heterogeneity that correlated with the stage of differentiation of the tumor cells. Immunohistochemical/cytogenetic evaluation of two pleomorphic adenomas with t(3;8)(p21;q12) or t(5;8)(p13;q12) translocations demonstrated the clonal nature of immunophenotypically diverse cells. This finding confirms the theory that pleomorphic adenoma cells share a common single-cell origin, most likely from the epithelial progenitor basal duct cells.

A novel recurrent translocation t(11;14)(p11;q32) in splenic marginal zone B cell lymphoma

A novel recurrent translocation t(11;14)(p11;q32) was found in three patients with splenic marginal zone B cell lymphoma (MZBCL). Fluorescence in situ hybridization (FISH) studies with IgH probes revealed in all cases involvement of the IgH locus, with breakpoint downstream of the IGVH sequences. Partner genes at 11p11 were not identified. The translocation defined the stem line in two patients, who carried additional cytogenetic aberrations, including a 17p deletion, present in both cases. In one patient a 7q- chromosome was the primary cytogenetic defect, the t(11;14) having been found in four out of 11 abnormal metaphase cells at the time of transformation into high-grade MZBCL. Hematological features in all cases included splenomegaly with peripheral blood (PB) involvement by a monoclonal B cell population consisting of lymphocytes with villous projections and several blast-like cells. The immunophenotype was CD19+; CD22bright+; CD23-, CD10-, CD5-, surface Igbright+. A bone biopsy in one patient revealed an interstitial infiltration with an intrasinusoidal pattern of growth. Histological studies on spleen specimens in two patients showed an expanded marginal zone, with small lymphocytes and several blast-like cells. One patient had a therapy-demanding disease, with partial, short-term responses to cytotoxic treatment; one patient transformed into a high-grade MZBCL involving the gut, the PB and the bone marrow 2 years after diagnosis; one patient was unresponsive to cytotoxic treatment and underwent splenectomy. The t(11;14)(p11;q32) may define a subset of splenic MZBCL with a high-grade component and a relatively aggressive clinical behavior.

Chromosomal gains and losses are uncommon in hairy cell leukemia: a study based on comparative genomic hybridization and interphase fluorescence in situ hybridization

In contrast to other subtypes of lymphoproliferative malignancies, the genetic mechanisms underlying the pathogenesis of hairy cell leukemia (HCL) are unknown. We studied densely infiltrated splenic tissue of 14 cases of HCL for the presence of chromosomal gains and losses by comparative genomic hybridization (CGH). Chromosomal imbalances were detected in only four of the 14 cases. Chromosomal gains involved the regions 5q13-q31 (two cases) and 1p32-p36.2 (one case). A loss of the region 11q14-q22 was found in one additional patient. The imbalances affecting the regions 5q and 11q were confirmed by interphase fluorescence in situ hybridization (FISH) using PAC clone 144G9 (5q31) and YAC clones 755B11 (11q22.3-q23.1) and 801E11 (11q22.3-q23.1 spanning the ATM gene) and occurred in 61% to 75% of analyzed nuclei. The latter DNA probes and probes hybridizing to chromosomal regions, which are frequently deleted in other subtypes of non-Hodgkin lymphomas (NHL), namely 9p21/ P16(INK4A), 13q14/D13S25, and 17p13/P53 were subsequently applied to all 14 cases of HCL, but no additional abnormalities were found. We conclude that overrepresentation of chromosome 5 represents a recurrent aberration in HCL and that the commonly overrepresented region resides in 5q13-q31. Chromosomal imbalances including deletions of the tumor suppressor gene loci 9p21/P16(INK4A), 13q14/D13S25, and 17p13/P53 rarely occur in HCL in contrast to some other subtypes of B-cell NHL. The pathogenetic role of 11q/ATM alterations in HCL remains to be determined.

Myeloma isotype-switch variants in the murine 5T myeloma model: evidence that myeloma IgM and IgA expressing subclones can originate from the IgG expressing tumour

Isotype-switch variants can easily be detected in a significant proportion of multiple myeloma (MM) patients. The biological significance of these isotype-switch variants remains obscure. Therefore, we studied the appearance of these isotype-switch variants in two murine MM models, 5T2MM and 5T33MM, both of IgG isotype. With a MM-specific PCR assay we could detect isotype-switch variants in the bone marrow of both the 5T2MM and the 5T33MM bearing mice, reflecting again the close resemblance of this mouse model to the human MM. These isotype-switch variants were not found in an in vitro stroma-independent variant of the 5T33MM line. However, when this 5T33MMvitro line was injected into young syngeneic mice, isotype-switch variants appeared thereafter in the isolated tumour cells. These isotype-switch variants could only originate from the MM-IgG expressing cell since IgG subclones from the 5T33MMvitro line again gave rise to isotype-switch variants. The appearance of IgA cells can be explained by down-stream switching of IgG to IgA, while the emergence of IgM cells have to occur via trans-switching to the sister chromatid as the Cmu region is deleted from the CIS-chromosome. This study demonstrates that isotype-switch variants originate from the major tumour clone suggesting no role for the MM-IgM expressing cell as a pre-switch precursor MM cell. The appearance of isotype-switch variants should be considered as a rare but normal event now becoming visible due to the high number of clonal cells present in MM.

H4(D10S170), a gene frequently rearranged in papillary thyroid carcinoma, is fused to the platelet-derived growth factor receptor beta gene in atypical chronic myeloid leukemia with t(5;10)(q33;q22)

The molecular cloning of the t(5;10)(q33;q22) associated with atypical chronic myeloid leukemia (CML) is reported. Fluorescence in situ hybridization (FISH), Southern blot, and reverse transcriptase- polymerase chain reaction analysis demonstrated that the translocation resulted in an H4/platelet-derived growth factor receptor betaR (PDGFbetaR) fusion transcript that incorporated 5' sequences from H4 fused in frame to 3' PDGFbetaR sequences encoding the transmembrane, WW-like, and tyrosine kinase domains. FISH combined with immunophenotype analysis showed that t(5;10)(q33;q22) was present in CD13(+) and CD14(+) cells but was not observed in CD3(+) or CD19(+) cells. H4 has previously been implicated in pathogenesis of papillary thyroid carcinoma as a fusion partner of RET. The H4/RET fusion incorporates 101 amino acids of H4, predicted to encode a leucine zipper dimerization domain, whereas the H4/PDGFbetaR fusion incorporated an additional 267 amino acids of H4. Retroviral transduction of H4/PDGFbetaR, but not a kinase-inactive mutant, conferred factor-independent growth to Ba/F3 cells and caused a T-cell lymphoblastic lymphoma in a murine bone marrow transplantation assay of transformation. Mutational analysis showed that the amino-terminal H4 leucine zipper domain (amino acids 55-93), as well as H4 amino acids 101 to 386, was required for efficient induction of factor-independent growth of Ba/F3 cells. Tryptophan-to-alanine substitutions in the PDGFbetaR WW-like domain at positions 566/593, or tyrosine-to-phenylalanine substitutions at PDGFbetaR positions 579/581 impaired factor-independent growth of Ba/F3 cells. H4/PDGFbetaR is an oncoprotein expressed in t(5;10)(q33;q22) atypical CML and requires dimerization motifs in the H4 moiety, as well as residues implicated in signal transduction by PDGFbetaR, for efficient induction of factor-independent growth of Ba/F3 cells. (Blood. 2001;97:3910-3918)

The NPM-ALK and the ATIC-ALK fusion genes can be detected in non-neoplastic cells

Anaplastic large cell lymphoma (ALCL) is frequently associated with the t(2;5)(p23;q35) translocation. It creates a NPM-ALK fusion gene, fusing the anaplastic lymphoma kinase (ALK) gene (2p23) and the nucleophosmin (NPM) gene (5q35). Other rearrangements involving the ALK gene have recently been shown to be associated with ALCL, among which the ATIC-ALK rearrangement resulting from the inv(2)(p23q35) translocation is probably the most recurrent. The aims of the present study were to investigate the presence of NPM-ALK and ATIC-ALK fusion genes in ALCL, using a real-time 5' exonuclease-based reverse-transcription polymerase chain reaction (RT-PCR). This sensitive technique was also applied to investigate whether both fusion genes might be detected in Hodgkin's disease cases and in reactive lymphoid tissue. Results of the RT-PCR were compared to ALK immunostaining, cytogenetics, and fluorescence in situ hybridization (FISH) results. RT-PCR detected the NPM-ALK and ATIC-ALK fusions at high levels in 8 and 3 of a total of 13 ALK-positive ALCL cases. One ALK-positive ALCL case was negative for both fusion genes analyzed but revealed a new ALK-related translocation t(2;17)(p23;q25) by cytogenetic and FISH analysis. In addition, of the eight ALK-positive ALCL cases that were strongly positive for the NPM-ALK fusion, three cases also showed the presence of the ATIC-ALK fusion, although at much lower levels. Similarly, out of the three strongly positive ATIC-ALK cases, one case was positive for the NPM-ALK fusion, at low levels. Finally, the NPM-ALK and the ATIC-ALK fusions were detected, at equally low levels, respectively in 13 and 5 ALK-negative ALCL cases, in 11 and 5 Hodgkin's disease cases and in 20 and 1 non-neoplastic lymphoid tissues. The distinction between the high- and low-level detection was confirmed by relative quantitative RT-PCR for a representative number of cases. Of interest is the fact that the high-level detection coincided with the presence of ALK gene rearrangement detected by cytogenetics and FISH and may reflect a central role of the transcript in the oncogenic mechanism of ALK-positive ALCL. Low-level detection is not supported by cytogenetics and FISH, presumably due to the presence of the transcripts in only a small minority of normal cells not detectable by these techniques. Our findings demonstrate that NPM-ALK and ATIC-ALK fusion transcripts may be detected in conditions other than ALK-positive ALCL including reactive lymphoid tissues, although at low levels, suggesting the presence of the transcripts in normal (bystander) cells. Moreover, they suggest that the ALK gene rearrangement by itself might be insufficient to induce tumor formation. They further question the validity of quantitative real-time RT-PCR for monitoring minimal residual disease in ALCL. Finally, the newly identified translocation t(2;17)(p23;q25) can be added to the list of ALK gene rearrangements occurring in ALK-positive ALCL.

Cryptic t(4;11) encoding MLL-AF4 due to insertion of 5′ MLL sequences in chromosome 4

The t(4;11) translocation is the cytogenetic hallmark of a subset of acute lymphoblastic leukemias characterized by pro-B immunophenotype and a dismal prognosis. This translocation fuses the MLL gene on chromosome band 11q23 and the AF4 gene on 4q21, resulting in the expression of fusion transcripts from both translocated chromosomes. The MLL-AF4 chimeric transcript is thought to mediate the leukemic transformation. The MLL genomic disruption detected by Southern blot and the RT-PCR for the MLL-AF4 chimeric transcript expression are molecular evidence of this chromosomal translocation. However, similar molecular rearrangements have also been identified in cases without the cytogenetic t(4;11). We report a 30-year-old patient with high risk ALL, a normal karyotype, and molecular evidence of MLL-AF4 fusion. Using a double color FISH assay with MLL specific PAC probes, a cryptic t(4;11) due to insertion of 5' MLL sequences in chromosome 4q21 was demonstrated. Consequently the MLL-AF4 was encoded by der(4). This insertion mechanism precludes the genomic recombination of AF4-MLL and supports the crucial role played by MLL-AF4 in leukemogenesis. The findings of our case, along with others, show the importance of complementing the karyotype with molecular and FISH techniques.

Calcifying/ossifying synovial sarcoma shows t(X;18) with SSX2 involvement and mitochondrial calcifications

AIMS

Synovial sarcoma with extensive calcification and ossification is a rare variant, the ultrastructural, cytogenetic and molecular analysis of which has not been reported previously.

METHODS AND RESULTS

A large mass in the shoulder of a 20-year-old male patient led to a deformity of the chest wall, thus supporting the hypothesis that this is a slowly growing variant of synovial sarcoma. Nevertheless, the patient developed metastatic lung disease 7 months after resection. On histology, the monophasic spindle cell proliferation was in several areas obscured by the massive calcification and ossification. Immunohistochemistry showed keratin, epithelial membrane antigen, vimentin and CD99 expression. The cytogenetic analysis revealed a single t(X;18)(p11.2; q11.2), typical for synovial sarcoma. Additional fluorescence in-situ hybridization revealed SSX2 involvement. At the ultrastructural level, prominent needle-shaped intramitochondrial crystals were present, both in the cytoplasm and in the extracellular matrix.

CONCLUSION

The presence of the t(X;18) with SSX2 involvement definitively characterizes this tumour as a variant of synovial sarcoma. In addition, the needle-like mitochondrial calcifications give a possible clue to the pathogenesis of the extensive metaplastic ossification and calcification.

Common chromosome aberrations in the proximal type of epithelioid sarcoma

A new case of the proximal type of epithelioid sarcoma with a complex karyotype 70-98 <4N>,XX,-X,-X,+5,i(5)(q10),+7,del(7)(q31),i(8)(q10)x3 approximately 4,del(12)(p13),der(18)ins(18:?) (q11;?)del(18)(p11). ish der(18)ins(18;X)del(18)(p11)(wcp18+,wcpX+),+20,+20,dmin [cp9] is described. Both, dual-color FISH using probes specific for OATLI1/OATL2 genes and RT-PCR analysis excluded the presence of t(X;18), typical for synovial sarcoma. Our case together with the previously published ones suggest that the presence of i(8)(q10), losses of 12p and 18p together with the gain of chromosome 20 may represent a common cytogenetic aberrations in the proximal type of epithelioid sarcoma.