A rare chimeric TLS/FUS-CHOP transcript in a patient with multiple liposarcomas: a case report

Metachronous multifocal myxoid liposarcoma involving the gastrointestinal tract. Management and literature review

Multifocal soft tissue sarcoma is a rare clinical entity occurring in 1% of patients with extremity soft tissue sarcoma and in 4.5% of patients with liposarcoma. Multifocal disease may arise either synchronously or metachronously and has been associated with poor prognosis. Herein, we have described a rare case of metachronous multifocal myxoid liposarcoma involving the gastrointestinal tract that developed 14 months after the resection of a myxoid buttock liposarcoma. Diagnostic evaluation and management of the patient are discussed along with a review of the relevant literature. We conclude that multifocal myxoid liposarcoma is a rare clinical entity that usually represents metastatic disease with poor prognosis. A thorough imaging and careful physical examination are essential in the preoperative evaluation and postoperative follow-up of patients with myxoid extremity liposarcomas, as these tumors are known to have a tendency to spread toward extrapulmonary sites, frequently without pulmonary metastases.

Multifocal myxoid liposarcoma--metastasis or second primary tumor?: a molecular biological analysis

The classification of multifocal myxoid/round cell liposarcoma, which is defined as tumor presentation in at least two separate sites before manifestation in the lungs, as either metastasis or as a second primary tumor, has essential clinical consequences. Genetically, myxoid/round cell liposarcoma is characterized by t(12;16)(q13;p11) or t(12;22)(q13;q12), and various exon fusion transcripts are described with varying incidences, which permits their use as markers for clonality. Moreover, in solid tumors, analysis of loss of heterozygozity is valuable for clonality analysis. Therefore, fifteen multifocal myxoid/round cell liposarcoma patients with two to five metachronous (n = 12) or synchronous (n = 3) localizations were investigated. Using RT-PCR, the detailed molecular characteristics of the FUS-CHOP and EWS-CHOP breakpoints were determined. Loss of heterozygozity analysis at twelve loci was then used to further analyze clonal relationships. In all patients, tumor sites showed identical FUS-CHOP fusion products. In six patients, identical rare fusion transcripts were found, supporting a clonal relationship. Nine patients had the common exon5-FUS/exon2-CHOP fusion transcript, and two of these were identified as clonally related by loss of heterozygozity analysis. In all other patients, loss of heterozygozity analysis was highly suggestive of a clonal relationship, and no evidence for interpretation of a second primary tumor was found. This study supports the metastatic nature of apparent multifocal myxoid/round cell liposarcoma.

Soft-tissue sarcoma

Soft-tissue sarcomas are rare malignancies of mesodermal origin. Common sites of involvement include the extremities, trunk, retroperitoneum, and the head and neck. Soft-tissue sarcomas of the extremities and pelvis are the most relevant to the orthopaedic surgeon. The patient with extremity soft-tissue sarcoma typically presents with a painless, enlarging mass. Advanced imaging techniques and biopsy, which are best done at tertiary referral centers, usually confirm the diagnosis. Factors such as sarcoma size, location, grade, histologic subtype, and stage, as well as patient age and comorbidities, determine the specific approach to management and patient outcome. Limb-sparing surgical resection is the mainstay of treatment. Radiation is used for unresectable tumors and as a neoadjuvant or an adjuvant to resection. The use of chemotherapy is controversial, and no standardized protocol has been established.

Detection of TLS/FUS-CHOP fusion transcripts in a case of oral liposarcoma

OBJECTIVE

The aim of this study was to detect the chromosomal translocation t(12;16)(q13;p11) that leads to a gene fusion encoding a FUS-CHOP chimeric protein and has been shown to be highly characteristic of myxoid and round cell subtypes of liposarcoma, in a case of oral myxoid liposarcoma.

METHOD AND MATERIALS

Nested reverse transcriptase-polymerase chain reaction to detect the TLS/FUS-CHOP fusion gene transcript was performed. A case of inflammatory fibrous hyperplasia and a case of oral lipoma were included as negative controls.

RESULTS

Only the myxoid oral liposarcoma showed a 103-base pair product, specific of TLS/FUS-CHOP fusion type II transcript.

CONCLUSION

The identification of FUS-CHOP transcript is potentially useful in the diagnosis and research of oral liposarcomas.

Multicentric liposarcoma

Abstract A 72-year-old man complaining of upper abdominal discomfort was diagnosed as having retroperitoneal liposarcoma by means of diagnostic imaging. He then underwent an operation. One mass existed on the curvatura ventriculi major, extending to the hilum splenicum and pressing back the pancreal head and body. There was another mass to the left of the first, situated on the ventral side of the left kidney. Also, another mass was intramurally found adjacent to the curvatura ventriculi major. Histologically, the mass on the curvatura ventriculi major ranged from the peritoneal cavity to the retroperitoneum Its intraperitoneal portion was classified as a differentiated lipoma-like type and the retroperitoneal mass was of mucous type. The mass on the left kidney was of a differentiated fibrosing type. The intramural mass in the gastric curvature was found to be a differentiated lipoma-like type. The patient has been under observation for 12 months and has shown no recurrence.

Comparable transforming capacities and differential gene expression patterns of variant FUS/CHOP fusion transcripts derived from soft tissue liposarcomas

The chromosomal translocation t(12;16)(q13;p11) is a common genetic alteration in myxoid and round-cell liposarcomas. It results in transcription of various chimeric FUS/CHOP fusion transcripts that encode different oncogenic proteins. Recent reports suggest that these may have different neoplastic transformation activities. To audit this hypothesis, we transfected expression plasmids for the two major variant FUS/CHOP transcripts I and II in NIH 3T3 cells and determined the number of outgrowing foci as well as their growth potential in soft agar. In addition, we compared tumour growth in nude mice upon subcutaneous injection of the respective transfectants. No significant differences in transformation assays in vitro and in vivo were observed, suggesting that both variant transcripts confer comparable transforming activities. The histopathological picture of tumours derived from both cell populations resembles high-grade spindle cell sarcomas. This suggests that both FUS/CHOP variants cause similar patterns of differential gene expression. This hypothesis was confirmed by mRNA-expression profiles of the respective cell clones. Strong overexpression of the pentaxin-related gene (PTX), the osteoblast-specific factor 2 (osf-2), the basic Kruppel-like factor (bklf), the leucoprotease inhibitor, and the cyclophilin B were observed in both types of FUS/CHOP-transfected cell clones. Taken together, our data suggest that different FUS/CHOP variants cause transformation of mesenchymal cells via the same pathways with comparable efficacy.

Tumor specific activation of PKR as a non-toxic modality of cancer treatment

Over the past decade progress has been made in the development of therapies against cancer. Small molecules, mainly tyrosine kinase inhibitors (tyrphostins) like Gleevec, Iressa targeting CML and EGFR overexpressing tumors have entered the clinic, where a large number of other tyrphostins are at various stages of clinical development. In parallel a few antibodies like Herceptin targeting breast cancer overexpressing Her-2 and Rituxan targeting B cell malignancies are utilized in the clinic. In all these cases success is moderate and restricted to a narrow population of patients, except for Gleevec which is effective for a long duration for chronic CML. The cancer community agrees that this is actually a unique exception that proves the rule. Over the past few years a few modalities of cancer gene therapies have emerged. In this short review we shall summarize our efforts to develop methods to activate PKR selectively in cancer cells.

A novel type of EWS-CHOP fusion gene in two cases of myxoid liposarcoma

Fusion genes consisting of TLS/FUS and CHOP or EWS and CHOP are characteristic markers for myxoid/round cell liposarcomas (MLS/RCLS). Several different structures of the fusion genes were reported in the case of the TLS/FUS-CHOP form, whereas only one type of structure has so far been found for the EWS-CHOP form, which consisted of exons 1 to 7 of the EWS and exons 2 to 4 of the CHOP gene. Here we describe a novel type of EWS-CHOP fusion gene in two cases of MLS/RCLS, which were found in a consecutive analysis of 21 cases. This fusion gene consisted of exons 1 to 10 of the EWS and exons 2 to 4 of the CHOP gene. The two cases with this fusion gene shared several clinical features, such as a large tumor mass, rapid and invasive growth, and local recurrence within 12 months after surgical resection. Histopathological findings also showed common features characterized by the diffuse proliferation of small spindle cells with a primitive mesenchymal appearance. The association of these clinical and histopathological features suggests a distinct biological property for this rare type of fusion product.

A novel FUS/CHOP chimera in myxoid liposarcoma

The cytogenetic hallmark of myxoid liposarcoma is the chromosomal aberration t(12;16)(q13;p11), which is pathognomonic for this tumor type. The translocation results in the hybrid gene FUS/CHOP, where the central and C-terminal parts of FUS, coding for the RNA binding domain and the RGG triplet motif, are replaced by the full length CHOP protein. Thus, CHOP is under the control of the FUS promoter and the FUS/CHOP chimera contains the 5'-terminal part of FUS which provides a transcriptional activation function. Although different structural variations of the FUS/CHOP chimeric transcript have been reported, none of them contains the parts of FUS encoding the RNA binding properties. An explanation is the location of the genomic breakpoint in FUS, which frequently occurs in the region spanning exon 5 to intron 8. We describe here a case of myxoid liposarcoma containing two novel FUS/CHOP chimeric transcripts and with the breakpoint occurring in intron 14 of FUS. Reverse transcription-polymerase chain reaction, using FUS forward and CHOP reverse primers, amplified strongly a 2.1-kbp DNA fragment and weakly a 0.9-kbp DNA fragment. Direct sequencing showed that in the 2.1-kbp transcript nt 1474, which corresponds to the third nucleotide of exon 14 of FUS, was in-frame fused to exon 2 of CHOP. In the 0.9-kbp DNA fragment, exon 3 of FUS was in-frame fused to exon 2 of CHOP. Genomic analyses revealed that the breaks were located at the end of exon 14/beginning of intron 14 of FUS and in intron 1 of CHOP and that microdeletions had occurred in the close vicinity of the breakpoints.

High telomerase activity and high HTRT mRNA expression differentiate pure myxoid and myxoid/round-cell liposarcomas

Molecular markers characterizing the transition of a myxoid to a more round-cell liposarcoma have not been described. To examine whether telomerase activity, hTRT and hTR mRNA expression were associated with tumor progression in myxoid liposarcoma, we investigated a total of 28 myxoid liposarcomas (13 pure myxoid tumors, 14 mixed-type tumors, and 1 pure round-cell variant) from 19 patients. Telomerase activity was detected by using the fluorescent PCR-based TRAP-assay. Expression of hTRT and hTR mRNAs was determined by the semi-quantitative RT-PCR. On the basis of only one tumor sample per patient, telomerase activity was found in 9 of 9 myxoid/round-cell liposarcomas and in 3 of 10 pure myxoid tumors. Elevated hTRT expression was found in 13 of 17 liposarcomas. All telomerase-positive tumors showed hTRT expression, whereas there were 3 cases showing hTRT expression without telomerase activity. HTR mRNA expression was elevated in all 19 liposarcomas. Thus, only the levels of telomerase activity and of hTRT mRNA expression differentiated pure myxoid liposarcoma and myxoid/round-cell liposarcoma (p < 0.003 and p = 0.029, respectively). We believe that high levels of telomerase activity and of hTRT expression are associated with tumor progression from low-grade pure myxoid to higher-grade malignant round-cell liposarcoma, and may consequently represent a useful prognostic marker for this histological sub-type of soft-tissue tumors.