DDIT3 Expression in Liposarcoma Development.

Liposarcomas are mesenchymal tumors containing variable numbers of lipoblasts or adipocytes. The most common entities, well differentiated/dedifferentiated liposarcoma (WDLS/DDLS) and myxoid/round cell liposarcoma (MLS/RCLS), are both characterized by genetic rearrangements that affect the expression of the transcription factor DDIT3. DDIT3 induces liposarcoma morphology when ectopically expressed in a human fibrosarcoma. The role of DDIT3 in lipomatous tumors is, however, unclear. We have analyzed the expression of DDIT3 in 37 cases of liposarcoma (WDLS/DDLS n = 10, MLS/RCLS n = 16, and pleomorphic liposarcomas (PLS) n = 11) and 11 cases of common benign lipomas. Major cell subpopulations of WDLS/DDLS and MLS/RCLS tumors were found to express DDIT3 or the derived fusion protein, whereas PLS cases showed only a few positive cells. The lipomas contained large subpopulations expressing DDIT3. No correlation between numbers of DDIT3 expressing cells and numbers of lipoblasts/adipocytes was found. In vitro adipogenic treatment of two DDIT3 expressing cell lines induced lipid accumulation in small subpopulations only. Our results suggest a dual, promoting and limiting, role for DDIT3 in the formation of lipoblasts and liposarcoma morphology.

Patterns of local recurrence and dose fractionation of adjuvant radiation therapy in 462 patients with soft tissue sarcoma of extremity and trunk wall.

PURPOSE: To study the impact of dose fractionation of adjuvant radiation therapy (RT) on local recurrence (LR) and the relation of LR to radiation fields. METHODS AND MATERIALS: LR rates were analyzed in 462 adult patients with soft tissue sarcoma who underwent surgical excision and adjuvant RT at five Scandinavian sarcoma centers from 1998 to 2009. Medical records were reviewed for dose fractionation parameters and to determine the location of the LR relative to the radiation portals. RESULTS: Fifty-five of 462 patients developed a LR (11.9%). Negative prognostic factors included intralesional surgical margin (hazard ratio [HR]: 7.83, 95% confidence interval [CI]: 3.08-20.0), high malignancy grade (HR: 5.82, 95% CI: 1.31-25.8), age at diagnosis (HR per 10 years: 1.27, 95% CI: 1.03-1.56), and malignant peripheral nerve sheath tumor histological subtype (HR: 6.66, 95% CI: 2.56-17.3). RT dose was tailored to margin status. No correlation between RT dose and LR rate was found in multiple Cox regression analysis. The majority (65%) of LRs occurred within the primary RT volume. CONCLUSIONS: No significant dose-response effect of adjuvant RT was demonstrated. Interestingly, patients given 45-Gy accelerated RT (1.8 Gy twice daily/2.5 weeks) had the best local outcome. A total dose of 50 Gy in 25 fractions seemed adequate following wide margin surgery. The risk of LR was associated with histopathologic subtype, which should be included in the treatment algorithm of adjuvant RT in soft tissue sarcoma.

Liposarcoma: outcome based on the Scandinavian Sarcoma Group register.

BACKGROUND: The aim was to study the clinicopathological characteristics, treatment, and outcome of liposarcoma in an unselected, population-based patient sample, and to establish whether treatment was according to the Scandinavian Sarcoma Group (SSG) treatment guidelines. METHODS: The SSG Pathology Board reviewed 319 liposarcoma cases reported between 1986 and 1998. After the review, 237 patients without metastasis were analyzed for local recurrence rate in relation to surgical margins, radiotherapy, occurrence of metastasis, and survival. RESULTS: Seventy-eight percent of the patients were primarily operated on at a sarcoma center, 45% with wide margins. All patients operated on outside the center had nonwide margins. Low-grade lesions constituted 67% of cases. Despite nonwide surgery, only 58% of high-grade lesions were treated with postoperative radiotherapy. The risk of local recurrence after nonwide surgery, without irradiation, was 47% for high-grade lesions. The estimated 10-year, local recurrence-free and metastasis-free survival in the low-grade group was 87% and 95%, respectively. In the high-grade group, it was 75% and 61%, respectively. Independent adverse prognostic factors for local recurrence were surgery outside a sarcoma center and histological type dedifferentiated liposarcoma. For metastases, they were old age, large tumor size, high grade, and histological type myxoid liposarcoma with a round cell component. Radiotherapy showed significant effect on local recurrence rate for the same grade and margin. CONCLUSIONS: Patients with liposarcoma should be treated at specialized centers. Postoperative radiotherapy decreases the local recurrence rate. To maintain quality and provide support for further trials, reporting to quality registers is crucial.

Irradiation of myxoid/round cell liposarcoma induces volume reduction and lipoma-like morphology.

The aim of the study was to investigate the clinical and morphological effects of radiotherapy in the treatment of myxoid/round cell liposarcoma (MLS/RCLS). Thirty-three primary and metastatic MLS/RCLS tumours in 15 patients were treated with radiation therapy. Twenty-seven of the 33 tumours were surgically removed after preoperative radiation (34-46 Gy) while six tumours were treated with radiotherapy alone (44-60 Gy). The pretreatment diagnosis was established in all 15 patients based on fine needle aspirates or histological findings. Tumour size was measured by CT or MRI before and after radiotherapy in 30 tumours. Thirteen tumours from 11 patients were genetically characterised before and/or after radiation therapy. Twenty-three of 30 irradiated tumours showed a median reduction in tumour volume of 52% and seven lesions a median progression of 36%. All 27 surgically removed tumours revealed histological features of radiation response. The most striking morphological changes were lipoma-like appearance, paucicellularity and hyalinisation. Twelve of 13 tumours analysed before and/or after radiation therapy showed the FUS-DDIT3 translocation. Radiation therapy of MLS/RCLS induces histopathologic accumulation of mature lipoma-like areas and tumour volume reduction that may facilitate resectability.

The myxoid/round cell liposarcoma fusion oncogene FUS-DDIT3 and the normal DDIT3 induce a liposarcoma phenotype in transfected human fibrosarcoma cells.

Myxoid/round cell liposarcoma (MLS/RCLS) is the most common subtype of liposarcoma. Most MLS/RCLS carry a t(12;16) translocation, resulting in a FUS-DDIT3 fusion gene. We investigated the role of the FUS-DDIT3 fusion in the development of MLS/RCLS in FUS-DDIT3- and DDIT3-transfected human HT1080 sarcoma cells. Cells expressing FUS-DDIT3 and DDIT3 grew as liposarcomas in severe combined immunodeficient mice and exhibited a capillary network morphology that was similar to networks of MLS/RCLS. Microarray-based comparison of HT1080, the transfected cells, and an MLS/RCLS-derived cell line showed that the FUS-DDIT3- and DDIT3-transfected variants shifted toward an MLS/RCLS-like expression pattern. DDIT3-transfected cells responded in vitro to adipogenic factors by accumulation of fat and transformation to a lipoblast-like morphology. In conclusion, because the fusion oncogene FUS-DDIT3 and the normal DDIT3 induce a liposarcoma phenotype when expressed in a primitive sarcoma cell line, MLS/RCLS may develop from cell types other than preadipocytes. This may explain the preferential occurrence of MLS/RCLS in nonadipose tissues. In addition, development of lipoblasts and the typical MLS/RCLS capillary network could be an effect of the DDIT3 transcription factor partner of the fusion oncogene.

Abnormal expression of cell cycle regulators in FUS-CHOP carrying liposarcomas.

Myxoid/round cell liposarcomas (MLS/RCLS) are characterized by chromosome translocations that result in formation of FUS-CHOP or EWSR1-CHOP fusion oncogenes. More than 95% of the tumors carry one of these fusion genes. FUS-CHOP transforms 3T3 cells and causes MLS/RCLS-like tumors in transgenic mice. The fusion oncoproteins act as abnormal transcription factors and are believed to induce abnormal expression of growth controlling genes as part of their transforming activities. The aim of this study was to search for recurrent abnormal expression patterns of cell cycle regulating proteins and growth factor receptors. A series of 14 MLS/RCLS, 2 MLS/RCLS derived cell lines and a FUS-CHOP transfected human sarcoma cell line were analyzed using immunohistochemistry, Western blotting, and cDNA microarray based screening. The results revealed a highly abnormal expression pattern of several growth controlling proteins. The G1 cyclins D1 and E and their associated kinases CDK4 and CDK2 were strongly overexpressed in all of the tumors. High expression levels were also found for Cdk4/6 inhibitor P16 and CDK2 inhibitors P27 and P57. The growth factor tyrosine kinase receptors PDGFRB and EGFR were present in most cells of all investigated tumors. We conclude that deregulation of G1 controlling proteins is common in MLS/RCLS and that aberrant expression of these proteins is of importance in the pathogenesis of this tumor type.