Human translocation liposarcoma-CCAAT/enhancer binding protein (C/EBP) homologous protein (TLS-CHOP) oncoprotein prevents adipocyte differentiation by directly interfering with C/EBPbeta function

Benign Lipomatous Soft Tissue Tumors in Nigerians: An Analysis of the Clinical and Morphological Features of a Common but Important Entity

Introduction Benign lipomatous tumors are soft tissue tumors that exhibit a predominant adipocytic phenotype. Lipomas are the archetype and are the most common benign soft tissue tumors in adults but relatively uncommon in children. Their sex incidence is equivocal. They sometimes occur in combination with other mesenchymal elements, giving rise to variants including fibrolipoma, angiolipoma, myolipoma, spindle cell lipoma, chondroid lipoma, osteolipoma, and chondrolipoma. Their clinical significance is mainly due to the cosmetic disfigurement of patients and the differential diagnosis of malignant soft tissue tumors. Occasionally, due to their large size or presence near vital organs, they may cause life-threatening and/or excruciating pressure symptoms. This study was purposed to address the dearth of local studies on the clinical and morphological characteristics of benign lipomatous tumors in Nigerians, to compare these with those of other populations, and to establish baseline data. Materials and methods This was a retrospective study of all benign lipomatous tumors seen in the anatomic pathology and forensic medicine department of Asokoro District Hospital, Abuja, Federal Capital Territory, Nigeria, over an eight-year period. Surgical pathology reports were retrieved for patients' biodata and clinical information. The appropriate slides were retrieved, and reviewed, and new sections were cut where necessary. The tumors were classified according to the 2020 World Health Organization (WHO) guidelines and categorized based on size as small, medium, or giant. The data obtained were analyzed, and the results were presented as tables, bar charts, ratios, and percentages. Results Four hundred and eighteen cases met the inclusion criteria. Of these, 58.4% (244/418), occurred in females, while 41.6% (174/418) occurred in males. The age range was six to 91 years, while the median age was 42 years. The least number of cases, 0.5% (2/418), were seen in patients aged less than 10 years, while the majority, 35.4% (148/418), occurred in the fifth decade, followed by 27.8% (116/418) in the fourth. Size-wise, the majority of tumors, 60% (253/418), were medium, followed by small, 22.8% (95/418). Giant-sized tumors significantly accounted for 16.7% (70/418) of the cases. The diagnostic spectrum comprised conventional lipoma and variants such as fibrolipoma, spindle cell lipoma, pleomorphic lipoma, angiolipoma, chondrolipoma, intramuscular lipoma, and osteolipoma. Lipoma and fibrolipoma dominated with 87.1% (364/418) and 10.0% (42/418), respectively, while the rest accounted for <3%. The majority, 31.8% (133/418), occurred in the back/shoulder region, followed by the lower limb with 18.2% (76/418). Only two cases occurred in the abdominal/pelvic region. More tumors occurred in females in all the regions except the head and neck, which had a male-to-female ratio of 1.5:1. Multiple site tumors were more common in males in a ratio of 2.5:1. Most, 41.1% (39/95), of the small-sized tumors, occurred in the head/neck region, largely involving the face, 48.7% (19/39). Conclusion Our study showed many similarities in the clinical and morphological features of benign lipomatous tumors between Nigerians and other regions of the world. A notable finding, however, was the significantly higher proportion of giant benign lipomatous tumors when compared to studies from other regions, a finding that warrants further studies.

Histological response to radiotherapy is an early event in myxoid liposarcoma

Compared to other sarcomas, myxoid liposarcoma (MLS) is exceptionally sensitive to radiation therapy, but the underlying mechanism remains unknown. The objective was to assess the tissue-based changes in MLS during and after neoadjuvant radiotherapy in 26 patients of the DOREMY trial. Morphological assessment was performed on biopsies pre-treatment, after 8 fractions, 16 factions, and after surgical resection and included percentage of viable tumor cells, hyalinization, necrosis, and fatty maturation. Furthermore, immunohistochemistry was performed for apoptosis (cleaved caspase-3), anti-apoptosis (Bcl-2), activity of mTOR signaling (phospho-S6), hypoxia (CAIX), proliferation (Ki67), inflammation (CD45 and CD68), and microvessel density (CD34 Chalkley count). A pronounced reduction in vital tumor cells was observed early with a drop to 32.5% (median) tumor cells (IQR 10-93.8%) after 8 fractions. This decreased further to 10% (IQR 5-30%) after 16 fractions and 7.5% (IQR 5-15%) in the surgical specimen. All but one patient had an excellent response with < 50% remaining tumor cells. Inversely, treatment response was mainly observed as hyalinization and less often as fatty maturation. Additionally, a decrease of inflammatory cells was noticed especially during the first eight fractions. Microvessel density remained stable over time. Immunohistochemical markers for apoptosis, anti-apoptosis, activity of mTOR signaling, proliferation, and hypoxia did not show any marked changes within the remaining tumor cells during and after radiotherapy. As a modest dose of neoadjuvant radiotherapy induces profound tissue changes in MLS, mainly during the first 8 fractions, current findings might suggest that in a carefully selected patient population further deintensification of radiotherapy might be explored.

Role of lncRNA LIPE-AS1 in adipogenesis

Recent studies have identified long non-coding RNAs (lncRNAs) as potential regulators of adipogenesis. In this study, we have characterized a lncRNA, LIPE-AS1, that spans genes CEACAM1 to LIPE in man with conservation of genomic organization and tissue expression between mouse and man. Tissue-specific expression of isoforms of the murine lncRNA were found in liver and adipose tissue, one of which, designated mLas-V3, overlapped the Lipe gene encoding hormone-sensitive lipase in both mouse and man suggesting that it may have a functional role in adipose tissue. Knock down of expression of mLas-V3 using anti-sense oligos (ASOs) led to a significant decrease in the differentiation of the OP9 pre-adipocyte cell line through the down regulation of the major adipogenic transcription factors Pparg and Cebpa. Knock down of mLas-V3 induced apoptosis during the differentiation of OP9 cells as shown by expression of active caspase-3, a change in the localization of LIP/LAP isoforms of C/EBPβ, and expression of the cellular stress induced factors CHOP, p53, PUMA, and NOXA. We conclude that mLas-V3 may play a role in protecting against stress associated with adipogenesis, and its absence leads to apoptosis.

Establishment and characterization of two novel patient-derived myxoid liposarcoma cell lines

Myxoid liposarcoma (MLPS) is a lipogenic sarcoma, characterized by myxoid appearance histology and the presence of the FUS-DDIT3 fusion gene. MLPS shows frequent recurrence and poor prognosis after standard treatments, such as surgery. Therefore, novel therapeutic approaches for MLPS are needed. Development of novel treatments requires patient-derived cell lines to study the drug responses and their molecular backgrounds. Presently, only three cell lines of MLPS have been reported, and no line is available from public cell banks. Thus, this study aimed to establish and characterize novel MLPS cell lines. Using surgically resected tumor tissue from two patients with MLPS, two novel lines NCC-MLPS2-C1 and NCC-MLPS3-C1 were established. The presence of FUS-DDIT3 fusion, slow growth, spheroid formation, and invasive capability in these cell lines was confirmed. Growth retardation was monitored for 213 anti-cancer agents using NCC-MLPS2-C1 and NCC-MLPS3-C1 cells, and the results were integrated with the response to treatments in an MLPS cell line, NCC-MLPS1-C1, which was previously established in our laboratory. We found that romidepsin suppressed cell proliferation at considerably low concentrations in all three examined cell lines. NCC-MLPS2-C1 and NCC-MLPS3-C1 cell lines developed here represent a useful tool for basic and preclinical studies of MLPS.

The FUS::DDIT3 fusion oncoprotein inhibits BAF complex targeting and activity in myxoid liposarcoma

Mammalian SWI/SNF (mSWI/SNF or BAF) ATP-dependent chromatin remodeling complexes play critical roles in governing genomic architecture and gene expression and are frequently perturbed in human cancers. Transcription factors (TFs), including fusion oncoproteins, can bind to BAF complex surfaces to direct chromatin targeting and accessibility, often activating oncogenic gene loci. Here, we demonstrate that the FUS::DDIT3 fusion oncoprotein hallmark to myxoid liposarcoma (MLPS) inhibits BAF complex-mediated remodeling of adipogenic enhancer sites via sequestration of the adipogenic TF, CEBPB, from the genome. In mesenchymal stem cells, small-molecule inhibition of BAF complex ATPase activity attenuates adipogenesis via failure of BAF-mediated DNA accessibility and gene activation at CEBPB target sites. BAF chromatin occupancy and gene expression profiles of FUS::DDIT3-expressing cell lines and primary tumors exhibit similarity to SMARCB1-deficient tumor types. These data present a mechanism by which a fusion oncoprotein generates a BAF complex loss-of-function phenotype, independent of deleterious subunit mutations.

Reduction in endoplasmic reticulum stress activates beige adipocytes differentiation and alleviates high fat diet-induced metabolic phenotypes

Endoplasmic reticulum (ER) stress is closely associated with various metabolic diseases, such as obesity and diabetes. Development of beige/brite adipocytes increases thermogenesis and helps to reduce obesity. Although the relationship between ER stress and white adipocytes has been studied considerably, the possible role of ER stress and the unfolded protein response (UPR) induction in beige adipocytes differentiation remain to be investigated. In this study we investigated how ER stress affected beige adipocytes differentiation both in vitro and in vivo. Phosphorylation of eIF2α was transiently decreased in the early phase (day 2), whereas it was induced at the late phase with concomitant induction of C/EBP homologous protein (CHOP) during beige adipocytes differentiation. Forced expression of CHOP inhibited the expression of beige adipocytes markers, including Ucp1, Cox8b, Cidea, Prdm16, and Pgc-1α, following the induction of beige adipocytes differentiation. When ER stress was reduced by the chemical chaperone tauroursodeoxycholic acid (TUDCA), the expression of the beige adipocytes marker uncoupling protein 1 (UCP1) was significantly enhanced in inguinal white adipose tissue (iWAT) and high fat diet (HFD)-induced abnormal metabolic phenotype was improved. In summary, we found that ER stress and the UPR induction were closely involved in beige adipogenesis. These results suggest that modulating ER stress could be a potential therapeutic intervention against metabolic dysfunctions via activation of iWAT browning.

Establishment and characterization of NCC-MLPS1-C1: a novel patient-derived cell line of myxoid liposarcoma

Myxoid liposarcoma is a rare mesenchymal malignancy, which is characterized by a FUS-DDIT3 fusion known as chromosomal translocation t(12;16)(q13;p11) and arises in the fat tissue. Although surgery with radiation has been established as a standard treatment, myxoid liposarcoma shows frequent recurrence and poor prognosis, thus requiring new therapeutic approaches. Patient-derived cell lines represent a critical tool for basic and preclinical research. However, only two such myxoid liposarcoma cell lines have been reported, and they are not available in cell banks. The aim of this study was to establish and characterize a novel myxoid liposarcoma cell line. Using surgically resected tumor tissue from a 47-year-old male patient, we established the NCC-MLPS1-C1 cell line. NCC-MLPS1-C1 cells were characterized by FUS-DDIT3 fusion, slow growth, spheroid formation, and invasive capability. We screened the effect of anti-cancer agents on the proliferation of NCC-MLPS1-C1 cells. The cells displayed a remarkable response to multitarget kinase inhibitors of RET, PDGFR-β, VEGFR, or FGFR. NCC-MLPS1-C1 cells and the tumor tissue shared common profiles of kinase activity including identified drug targets, such as RET and PDGFR-β. We believe that NCC-MLPS1-C1 cells will represent a useful tool for basic and preclinical studies of myxoid liposarcoma.

The active nuclear form of SREBP1 amplifies ER stress and autophagy via regulation of PERK

Endoplasmic reticulum (ER) stress and autophagy dysfunction contribute to the establishment and progression of diverse pathologies. Proteolytic activation of the transcription factor nSREBP1 is induced under ER stress; however, little is known about how SREBP1 and its nuclear active form nSREBP1 influence autophagy and unfolded protein response (UPR) activation in osteosarcoma cells. Our research focused on the effect of SREBP1/nSREBP1 upon apoptosis and autophagy during ER stress and the molecular mechanisms involved. Here, we showed that nSREBP1 binds to the promoter of protein kinase RNA-like endoplasmic reticulum kinase (PERK) and then regulates ER stress, cell growth, cell apoptosis, and autophagy through the PERK signaling pathway. nSREBP1 increased PERK gene expression and phosphorylation. nSREBP1 was further demonstrated to activate ER stress response through stimulatory effects on PERK signaling. Overexpression of SREBP1 increased its cleavage and release of nSREBP1; therefore, the effect of SREBP1 is achieved through the enhancement of the expression of nSREBP1. Overexpression of SREBP1/nSREBP1 amplifies PERK-associated cell cycle stagnation with G1 phase arresting, S phase reducing, and G2-M phase delaying. LV-SREBP1/nSREBP1 can also bolster PERK's ER stress-associated pro-apoptotic effects. LV-SREBP1/nSREBP1 and LV-PERK can activate autophagy in ER stress response, along with the overexpression of SREBP1/nSREBP1 and PERK. This resulted in amplification of PERK-related changes to cell proliferation and ER stress-mediated apoptosis and autophagy, with the biological effect of nSREBP1 relying on PERK, which makes up one of the three branches of the UPR signaling pathway. This study reveals important roles for SREBP1/nSREBP1 in PERK signaling under ER stress. Furthermore, nSREBP1, the nuclear active form of SREBP1, is able to robustly augment the effects of PERK. Description of the link between PERK and SREBP1/nSREBP1 function offers an improved understanding of the ER stress response and insight into the biological function of SREBP1/nSREBP1.

Cyclooxygenase-2 is acutely induced by CCAAT/enhancer-binding protein β to produce prostaglandin E 2 and F 2α following gonadotropin stimulation in Leydig cells

Cyclooxygenase 2 (COX-2) is an inducible rate-limiting enzyme for prostanoid production. Because COX-2 represents one of the inducible genes in mouse mesenchymal stem cells upon differentiation into Leydig cells, we investigated COX-2 expression and production of prostaglandin (PG) in Leydig cells. Although COX-2 was undetectable in mouse testis, it was transiently induced in Leydig cells by human chorionic gonadotropin (hCG) administration. Consistent with the finding that Leydig cells expressed aldo-keto reductase 1B7 (PGF synthase) and PGE synthase 2, induction of COX-2 by hCG caused a marked increase in testicular PGF _2α and PGE ₂ levels. Using mouse Leydig cell tumor-derived MA-10 cells as a model, it was indicated by reporter assays and electron mobility shift assays that transcription of the COX-2 gene was activated by CCAAT/enhancer-binding protein β (C/EBPβ) with cAMP-stimulation. C/EBPβ expression was induced by cAMP-stimulation, whereas expression of C/EBP homolog protein (CHOP) was robustly downregulated. Transfection of CHOP expression plasmid inhibited cAMP-induced COX-2 promoter activity. In addition, CHOP reduced constitutive COX-2 expression in other mouse Leydig cell tumor-derived TM3 cells. These results indicate that COX-2 is induced in Leydig cells by activation of C/EBPβ via reduction of CHOP expression upon gonadotropin-stimulation to produce PGF _2α and PGE ₂ .

Amplification of DNA damage-inducible transcript 3 (DDIT3) is associated with myxoid liposarcoma-like morphology and homologous lipoblastic differentiation in dedifferentiated liposarcoma

Dedifferentiated liposarcoma is defined as progression of atypical lipomatous tumor/well-differentiated liposarcoma to a higher grade usually non-lipogenic sarcoma, with amplification of 12q13-15. This region contains several genes involved in liposarcoma pathogenesis, including MDM2, CDK4, and DDIT3. While the former two are thought of as the main drivers in dedifferentiated liposarcoma, DDIT3 is typically rearranged in myxoid liposarcoma. Overexpression of DDIT3, along with MDM2 and CDK4, may contribute to the pathogenesis of dedifferentiated liposarcoma by interfering with adipocytic differentiation. Dedifferentiated liposarcoma with DDIT3 amplification has not been well characterized. In this study we evaluate the presence of DDIT3 amplification in 48 cases of dedifferentiated liposarcoma by cytogenomic microarray analysis and its correlation with demographic, clinical, and morphologic characteristics. Data from The Cancer Genome Atlas were also evaluated to determine a relationship between DDIT3 amplification and prognostic outcomes. Of the 48 cases, 16 (33%) had amplification of DDIT3; these patients were on average 11 years younger than patients without DDIT3 amplification (P < 0.05). Myxoid liposarcoma-like morphologic features were identified in 12/16 (75%) cases with DDIT3 amplification and in 7/32 (22%) cases without amplification (P < 0.05). Homologous lipoblastic differentiation was seen in 6/16 (38%) cases with DDIT3 amplification and 2/32 (6%) cases without it (P < 0.05). There was no significant correlation between DDIT3 amplification and tumor location, disease-specific or recurrence-free survival, and distant metastasis. DDIT3 amplification appears to interfere with the adipogenic molecular program and plays a role in inducing or maintaining a lipogenic phenotype in dedifferentiated liposarcoma. From a diagnostic standpoint, it is important to consider DDIT3-amplified dedifferentiated liposarcoma in the differential diagnosis of myxoid liposarcoma, particularly in small biopsies. Further studies evaluating the significance of DDIT3 amplification in the pathogenesis of dedifferentiated liposarcoma, as well as a potential predictor of tumor behavior in well-differentiated liposarcoma, are needed.

Regulation of Cellular Identity in Cancer

Neoplastic transformation requires changes in cellular identity. Emerging evidence increasingly points to cellular reprogramming, a process during which fully differentiated and functional cells lose aspects of their identity while gaining progenitor characteristics, as a critical early step during cancer initiation. This cell identity crisis persists even at the malignant stage in certain cancers, suggesting that reactivation of progenitor functions supports tumorigenicity. Here, we review recent findings that establish the essential role of cellular reprogramming during neoplastic transformation and the major players involved in it with a special emphasis on pancreatic cancer.

Regulation of Cellular Identity in Cancer

Neoplastic transformation requires changes in cellular identity. Emerging evidence increasingly points to cellular reprogramming, a process during which fully differentiated and functional cells lose aspects of their identity while gaining progenitor characteristics, as a critical early step during cancer initiation. This cell identity crisis persists even at the malignant stage in certain cancers, suggesting that reactivation of progenitor functions supports tumorigenicity. Here, we review recent findings that establish the essential role of cellular reprogramming during neoplastic transformation and the major players involved in it with a special emphasis on pancreatic cancer.

Promoting effect of triterpenoid compound from Agrimonia pilosa Ledeb on preadipocytes differentiation via up-regulation of PPARγ expression

Background:

Agrimonia Pilosa Ledeb (APL), a traditional Chinese medicine, has been reported a variety of biological activities, including treating T2DM.

Objective:

Triterpenoid compound (TC) was collected from APL. The aim of this study was to investigate the effects of TC on 3T3-L1 preadipocytes differentiation and genes related to differentiation and IR.

Materials and Methods:

Column chromatography was used to collect TC from ALP. 3T3-L1 cell differentiation was induced typically in the presence of various concentrations of TC or pioglitazone. Oil red O staining and measurement of intracellular TG content were performed on the seventh day of differentiation. Then quantitative polymerase chain reaction (Q-PCR) was used to test the expressions of three transcription factors (PPARγ, CCAAT enhancer binding protein-α (C/EBP-α), and sterol regulatory element-binding protein 1 (SREBP-1)) and the target genes of PPARγ including glucose transporter (GLUT4), lipoprotein lipase (LPL), fat acid binding protein (AP2), and adiponectin in 3T3-L1 cells.

Results:

At the concentration of 5, 25 and 125 μg/mL, TC significantly promoted triglyceride accumulation. Further study showed that TC could promote the expression of PPARγ, C/EBPα and ADD1/SREBP1 significantly at 125 μg/mL. As for downstream genes controlled by PPARγ, TC at 25 and 125 μg/mL could significantly promote the expression of GLUT4 and adiponectin. However, the expression of aP2 related to lipid metabolism and adiposity in the TC group was significantly lower than that in the pioglitazone group.

Conclusion:

TC could promote preadipocytes differentiation through activating PPARγ and downstream controlled genes. TC has the ideal insulin sensitization with lower adipogenic action than classical TZDs in vitro. So TC from Agrimonia Pilosa Ledeb has a good prospect as a natural drug for IR and T2DM.

Advances in the targeted therapy of liposarcoma

Liposarcoma (LPS) is the most common type of soft-tissue sarcoma. Complete surgical resection is the only curative means for localized disease; however, both radiation and conventional cytotoxic chemotherapy remain controversial for metastatic or unresectable disease. An increasing number of trials with novel targeted therapy of LPS have provided encouraging data during recent years. This review will provide an overview of the advances in our understanding of LPS and summarize the results of recent trials with novel therapies targeting different genetic and molecular aberrations for different subtypes of LPS.

Antiangiogenic activity of trabectedin in myxoid liposarcoma: involvement of host TIMP-1 and TIMP-2 and tumor thrombospondin-1

Trabectedin is a marine natural product, approved in Europe for the treatment of soft tissue sarcoma and relapsed ovarian cancer. Clinical and experimental evidence indicates that trabectedin is particularly effective against myxoid liposarcomas where response is associated to regression of capillary networks. Here, we investigated the mechanism of the antiangiogenic activity of trabectedin in myxoid liposarcomas. Trabectedin directly targeted endothelial cells, impairing functions relying on extracellular matrix remodeling (invasion and branching morphogenesis) through the upregulation of the inhibitors of matrix metalloproteinases TIMP-1 and TIMP-2. Increased TIMPs synthesis by the tumor microenvironment following trabectedin treatment was confirmed in xenograft models of myxoid liposarcoma. In addition, trabectedin upregulated tumor cell expression of the endogenous inhibitor thrombospondin-1 (TSP-1, a key regulator of angiogenesis-dependent dormancy in sarcoma), in in vivo models of myxoid liposarcomas, in vitro cell lines and primary cell cultures from patients' myxoid liposarcomas. Chromatin Immunoprecipitation analysis showed that trabectedin displaced the master regulator of adipogenesis C/EBPβ from the TSP-1 promoter, indicating an association between the up-regulation of TSP-1 and induction of adipocytic differentiation program by trabectedin. We conclude that trabectedin inhibits angiogenesis through multiple mechanisms, including directly affecting endothelial cells in the tumor microenvironment--with a potentially widespread activity--and targeting tumor cells' angiogenic activity, linked to a tumor-specific molecular alteration.

Reprogramming of mesenchymal stem cells by oncogenes

Mesenchymal stem cells (MSCs) originate from embryonic mesoderm and give rise to the multiple lineages of connective tissues. Transformed MSCs develop into aggressive sarcomas, some of which are initiated by specific chromosomal translocations that generate fusion proteins with potent oncogenic properties. The sarcoma oncogenes typically prime MSCs through aberrant reprogramming. They dictate commitment to a specific lineage but prevent mature differentiation, thus locking the cells in a state of proliferative precursors. Deregulated expression of lineage-specific transcription factors and controllers of chromatin structure play a central role in MSC reprogramming and sarcoma pathogenesis. This suggests that reversing the epigenetic aberrancies created by the sarcoma oncogenes with differentiation-related reagents holds great promise as a beneficial addition to sarcoma therapies.

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.

The stress-regulated transcription factor CHOP promotes hepatic inflammatory gene expression, fibrosis, and oncogenesis

Viral hepatitis, obesity, and alcoholism all represent major risk factors for hepatocellular carcinoma (HCC). Although these conditions also lead to integrated stress response (ISR) or unfolded protein response (UPR) activation, the extent to which these stress pathways influence the pathogenesis of HCC has not been tested. Here we provide multiple lines of evidence demonstrating that the ISR-regulated transcription factor CHOP promotes liver cancer. We show that CHOP expression is up-regulated in liver tumors in human HCC and two mouse models thereof. Chop-null mice are resistant to chemical hepatocarcinogenesis, and these mice exhibit attenuation of both apoptosis and cellular proliferation. Chop-null mice are also resistant to fibrosis, which is a key risk factor for HCC. Global gene expression profiling suggests that deletion of CHOP reduces the levels of basal inflammatory signaling in the liver. Our results are consistent with a model whereby CHOP contributes to hepatic carcinogenesis by promoting inflammation, fibrosis, cell death, and compensatory proliferation. They implicate CHOP as a common contributing factor in the development of HCC in a variety of chronic liver diseases.

Liver cancer is the third most common cause of cancer death worldwide. It is most commonly caused by viral hepatitis, alcoholism, or obesity, all of which activate cellular stress responses in the liver. However, the contribution of these responses to disease pathogenesis was unknown. We found that expression of the stress-regulated transcription factor CHOP—widely thought to be anti-oncogenic because of its cell death-promoting properties—was associated with both human liver cancer and two mouse models thereof. In response to challenge with a tumor-causing agent, mice lacking CHOP developed fewer tumors, exhibited less cell death, compensatory cellular proliferation, and liver scarring (fibrosis), and showed lower expression of immune and inflammatory genes. These findings establish CHOP as a biomarker for liver cancer and demonstrate its importance in promoting liver tumor formation. They raise the possibility that promotion of tumorigenesis by CHOP is a common feature of liver cancer caused by viral infection, alcoholism, and obesity.

A multifunctional protein, EWS, is essential for early brown fat lineage determination

The recent surge in obesity has provided an impetus to better understand the mechanisms of adipogenesis, particularly in brown adipose tissue (BAT) because of its potential utilization for antiobesity therapy. Postnatal brown adipocytes arise from early muscle progenitors, but how brown fat lineage is determined is not completely understood. Here, we show that a multifunctional protein, Ewing Sarcoma (EWS), is essential for determining brown fat lineage during development. BATs from Ews null embryos and newborns are developmentally arrested. Ews mutant brown preadipocytes fail to differentiate due to loss of Bmp7 expression, a critical early brown adipogenic factor. We demonstrate that EWS, along with its binding partner Y-box binding protein 1 (YBX1), activates Bmp7 transcription. Depletion of either Ews or Ybx1 leads to loss of Bmp7 expression and brown adipogenesis. Remarkably, Ews null BATs and brown preadipocytes ectopically express myogenic genes. These results demonstrate that EWS is essential for early brown fat lineage determination.

Mode of action of trabectedin in myxoid liposarcomas

To elucidate the mechanisms behind the high sensitivity of myxoid/round cell liposarcoma (MRCL) to trabectedin and the suggested selectivity for specific subtypes, we have developed and characterized three MRCL xenografts, namely ML017, ML015 and ML004 differing for the break point of the fusion gene FUS-CHOP, respectively of type I, II and III. FUS-CHOP binding to the promoters of some target genes such as Pentraxin 3 or Fibronectin 1, assessed by chromatin immunoprecipitation, was strongly reduced in the tumor 24 h after the first or the third weekly dose of trabectedin, indicating that the drug at therapeutic doses causes a detachment of the FUS-CHOP chimera from its target promoters as previously shown in vitro. Moreover, the higher sensitivity of MRCL types I and II appears to be related to a more prolonged block of the transactivating activity of the fusion protein. Doxorubicin did not affect the binding of FUS-CHOP to target promoters. Histologically, the response to trabectedin in ML017 and ML015 was associated with a marked depletion of non-lipogenic tumoral cells and vascular component, as well as lipidic maturation as confirmed by PPARγ2 expression in western Blot. By contrast, in ML004 no major changes either in the cellularity or in the amount of mature were found, and consistently PPARγ2 was null. In conclusion, the data support the view that the selective mechanism of action of trabectedin in MRCL is specific and related to its ability to cause a functional inactivation of the oncogenic chimera with consequent derepression of the adypocytic differentiation.

Role of microRNA-21 in regulating 3T3-L1 adipocyte differentiation and adiponectin expression

MicroRNAs are endogenous small RNAs with a high degree of conservation, participating in a variety of vital activities. In present study, to explore the effect of microRNAs on 3T3-L1 adipocyte differentiation and adiponectin expression, the adipo-related microRNAs were screened and identified by micorRNA microarray. The highly expression plasmid of microRNA-21 with obvious expression up-regulation (miR-21) and its anti-sense (miR-21 inhibitor) were constructed and transfected into 3T3-L1 preadipocytes. The effect of miR-21 on 3T3-L1 adipocyte differentiation was observed, and the protein and mRNA expression level of adiponectin and AP-1 were analyzed. Results showed that, the expression profiles of microRNAs significantly changed during 3T3-L1 adipocyte differentiation. The expression of miR-21 was obviously up-regulated. miR-21 could significantly promote adipocyte differentiation, increase adiponectin mRNA and protein expression, while decrease AP-1 protein level. Meanwhil, miR-21 inhibitor blocked the effects of miR-21 mentioned above. The overexpression of AP-1 could absolutely reverse the stimulatory effect of miR-21 on adiponectin. miR-21 plays an important role in regulating adipocyte differentiation and adiponectin expression by inhibiting AP-1 expression.

Localized and metastatic myxoid/round cell liposarcoma: clinical and molecular observations

BACKGROUND

Myxoid liposarcoma (MLPS), a disease especially of young adults with potential for local recurrence and metastasis, currently lacks solid prognostic factors and therapeutic targets. The authors of this report evaluated the natural history and outcome of patients with MLPS and commonly deregulated protein biomarkers.

METHODS

Medical records were retrospectively reviewed for patients who presented to the authors' institution with localized (n = 207) or metastatic (n = 61) MLPS (1990 to 2010). A tissue microarray of MLPS patient specimens (n = 169) was constructed for immunohistochemical analysis of molecular markers.

RESULTS

The 5-year and 10-year disease-specific survival rates among patients with localized disease were 93% and 87%, respectively; male gender, age >45 years, and recurrent tumor predicted poor outcome. The local recurrence rate was 7.4%, and the risk of local recurrence was associated with recurrent tumors and nonextremity disease location. Male gender was the main risk factor for metastatic disease, which occurred in 13% of patients. Forty percent of patients who had localized disease received chemotherapy, mostly in the neoadjuvant setting. Immunohistochemical analysis revealed significantly higher expression of C-X-C chemokine receptor type 4 (CXCR4) and platelet-derived growth factor beta (PDGFR-β) in metastatic lesions versus localized lesions. Tumors with a round cell phenotype expressed increased levels of CXCR4, p53, adipophilin, PDGFR-α, PDGFR-β, and vascular endothelial growth factor relative to myxoid phenotype. Only the receptor tyrosine kinase encoded by the AXL gene (AXL) was identified as a prognosticator of disease-specific survival in univariate analysis.

CONCLUSIONS

In this study, the authors identified clinical and molecular outcome prognosticators for patients with MLPS as well as several potential therapeutic targets.

Myxoid liposarcoma-associated EWSR1-DDIT3 selectively represses osteoblastic and chondrocytic transcription in multipotent mesenchymal cells

Background

Liposarcomas are the most common class of soft tissue sarcomas, and myxoid liposarcoma is the second most common liposarcoma. EWSR1-DDIT3 is a chimeric fusion protein generated by the myxoid liposarcoma-specific chromosomal translocation t(12;22)(q13;q12). Current studies indicate that multipotent mesenchymal cells are the origin of sarcomas. The mechanism whereby EWSR1-DDIT3 contributes to the phenotypic selection of target cells during oncogenic transformation remains to be elucidated.

Methodology/Principal Findings

Reporter assays showed that the EWSR1-DDIT3 myxoid liposarcoma fusion protein, but not its wild-type counterparts EWSR1 and DDIT3, selectively repressed the transcriptional activity of cell lineage-specific marker genes in multipotent mesenchymal C3H10T1/2 cells. Specifically, the osteoblastic marker Opn promoter and chondrocytic marker Col11a2 promoter were repressed, while the adipocytic marker Ppar-γ2 promoter was not affected. Mutation analyses, transient ChIP assays, and treatment of cells with trichostatin A (a potent inhibitor of histone deacetylases) or 5-Aza-2′-deoxycytidine (a methylation-resistant cytosine homolog) revealed the possible molecular mechanisms underlying the above-mentioned selective transcriptional repression. The first is a genetic action of the EWSR1-DDIT3 fusion protein, which results in binding to the functional C/EBP site within Opn and Col11a2 promoters through interaction of its DNA-binding domain and subsequent interference with endogenous C/EBPβ function. Another possible mechanism is an epigenetic action of EWSR1-DDIT3, which enhances histone deacetylation, DNA methylation, and histone H3K9 trimethylation at the transcriptional repression site. We hypothesize that EWSR1-DDIT3-mediated transcriptional regulation may modulate the target cell lineage through target gene-specific genetic and epigenetic conversions.

Conclusions/Significance

This study elucidates the molecular mechanisms underlying EWSR1-DDIT3 fusion protein-mediated phenotypic selection of putative target multipotent mesenchymal cells during myxoid liposarcoma development. A better understanding of this process is fundamental to the elucidation of possible direct lineage reprogramming in oncogenic sarcoma transformation mediated by fusion proteins.

ER Stress and Lipid Metabolism in Adipocytes

The role of endoplasmic reticulum (ER) stress is a rapidly emerging field of interest in the pathogenesis of metabolic diseases. Recent studies have shown that chronic activation of ER stress is closely linked to dysregulation of lipid metabolism in several metabolically important cells including hepatocytes, macrophages, β-cells, and adipocytes. Adipocytes are one of the major cell types involved in the pathogenesis of the metabolic syndrome. Recent advances in dissecting the cellular and molecular mechanisms involved in the regulation of adipogenesis and lipid metabolism indicate that activation of ER stress plays a central role in regulating adipocyte function. In this paper, we discuss the current understanding of the potential role of ER stress in lipid metabolism in adipocytes. In addition, we touch upon the interaction of ER stress and autophagy as well as inflammation. Inhibition of ER stress has the potential of decreasing the pathology in adipose tissue that is seen with energy overbalance.

C5a-regulated CCAAT/enhancer-binding proteins β and δ are essential in Fcγ receptor-mediated inflammatory cytokine and chemokine production in macrophages

CCAAT/enhancer-binding protein β (C/EBPβ) and C/EBPδ are known to participate in the regulation of many genes associated with inflammation. However, little is known about the activation and function of C/EBPβ and -δ in inflammatory responses elicited by Fcγ receptor (FcγR) activation. Here we show that C/EBPβ and -δ activation are induced in IgG immune complex (IC)-treated macrophages. The increased expression of C/EBPβ and -δ occurred at both mRNA and protein levels. Furthermore, induction of C/EBPβ and -δ was mediated, to a large extent, by activating FcγRs. Using siRNA-mediated knockdown as well as macrophages deficient for C/EBPβ and/or -δ, we demonstrate that C/EBPβ and -δ play a critical role in the production of TNF-α, MIP-2, and MIP-1α in IgG IC-stimulated macrophages. Moreover, both ERK1/2 and p38 MAPK are involved in C/EBP induction and TNF-α, MIP-2, and MIP-1α production induced by IgG IC. We provide the evidence that C5a regulates IgG IC-induced inflammatory responses by enhancing ERK1/2 and p38 MAPK activities as well as C/EBPβ and -δ activities. Collectively, these data suggest that C/EBPβ and -δ are key regulators for FcγR-mediated induction of cytokines and chemokines in macrophages. Furthermore, C/EBPs may play an important regulatory role in IC-associated inflammatory responses.

New frontiers in the treatment of liposarcoma, a therapeutically resistant malignant cohort

The adipogenic origin-derived liposarcoma (LPS) family is the most common soft tissue sarcoma histological subtype. This group is composed of three categories as per the 2002 WHO guidelines: (1) well-differentiated and dedifferentiated liposarcoma (WDLPS/DDLPS); (2) myxoid and round cell liposarcoma (MLS and RCL); and (3) pleomorphic liposarcoma (PLS). While clustered together, these histological subtypes are widely diverse in their clinical, pathological, and molecular characteristics. In general, surgery still remains the mainstay of LPS therapy and the only approach offering the potential of cure. Effective therapeutic strategies for locally advanced and metastatic disease are currently lacking and are crucially needed. With the current gradually increasing knowledge of LPS genetic- and epigenetic-associated deregulations, the ultimate goal is to develop drugs that can specifically eliminate LPS cells while sparing normal tissues. This tumor-tailored target-orientated approach will hopefully result in a significant improvement in the outcome of patients suffering from these poor prognosis malignancies.

Detection of myxoid liposarcoma-associated FUS-DDIT3 rearrangement variants including a newly identified breakpoint using an optimized RT-PCR assay

Myxoid/round cell liposarcoma is characterized by the recurrent translocations t(12;16)(q13;p11) and, less commonly, t(12;22)(q13;q12), which fuse FUS or EWSR1, respectively, to DDIT3 on chromosome 12. Although a number of different variant breakpoints have been described, greater than 90% of all cases have one of the three different FUS-DDIT3 fusions, which may have clinical significance. To identify the individual breakpoints, a sequence-specific assay such as reverse transcription-PCR (RT-PCR) is needed. In this study, we optimized primer design to develop an RT-PCR assay for the detection of the most common translocations in formalin-fixed paraffin-embedded tissue specimens. We compared our assay with primers previously published for testing formalin-fixed paraffin-embedded specimens and achieved the most consistent results with our primers. We obtained RNA from 32 MLS cases, of which 27 carried one of the three common FUS-DDIT3 chimeric transcript types. Four of the negative cases were from very small biopsies with very low RNA concentration. One case was consistently negative by RT-PCR, but showed a FUS rearrangement by fluorescent in situ hybridization, suggesting that it may harbor one of the rarer FUS-DDIT3 chimeric types. In addition to the common fusions, our assay also identified a novel FUS-DDIT3 fusion between exon 9 of FUS and exon 3 of DDIT3 in one of the cases.

Validation of immature adipogenic status and identification of prognostic biomarkers in myxoid liposarcoma using tissue microarrays

Myxoid liposarcoma displays variably aggressive behavior and responds poorly to available systemic therapies. Expression profiling followed by tissue microarray validation linked to patient outcome is a powerful approach for validating biological mechanisms and identifying prognostic biomarkers. We applied these techniques to independent series of primary myxoid liposarcomas in an effort to assess markers of adipose differentiation in myxoid liposarcoma and to identify prognostic markers that can be efficiently assessed by immunohistochemistry. Candidate genes were selected based on analysis of expression profiles from 9 primary myxoid/round liposarcomas and 45 other soft tissue tumors, and by reference to publicly available data sets. Protein products were validated on an adipose neoplasm tissue microarray, including 32 myxoid liposarcomas linked to patient outcome. Results were scored visually and correlated with clinical outcome by Kaplan-Meier and Cox regression analyses. In the study, by examining expression patterns of several lipogenic regulatory gene products, an immature adipogenic status was verified in myxoid liposarcomas. We also found that expression levels of the ret proto-oncogene, insulin-like growth factor 1 receptor, and insulin-like growth factor 2 correlate with poor metastasis-free survival, supporting a role for ERK/MAPK and PI3K/AKT pathways in clinically aggressive myxoid liposarcomas.

Trabectedin (ET-743) promotes differentiation in myxoid liposarcoma tumors

Differentiation is a complex set of events that can be blocked by rearrangements of regulatory genes producing fusion proteins with altered properties. In the case of myxoid liposarcoma (MLS) tumors, the causative abnormality is a fusion between the CHOP transcription factor and the FUS or EWS genes. CHOP belongs to and is a negative regulator of the large CAAT/enhancer binding protein family whose alpha, beta, and delta members are master genes of adipogenesis. Recent clinical data indicate a peculiar sensitivity of these tumors to the natural marine compound trabectedin. One hypothesis is that the activity of trabectedin is related to the inactivation of the FUS-CHOP oncogene. We find that trabectedin causes detachment of the FUS-CHOP chimera from targeted promoters. Reverse transcription-PCR and chromatin immunoprecipitation analysis in a MLS line and surgical specimens of MLS patients in vivo show activation of the CAAT/enhancer binding protein-mediated transcriptional program that leads to morphologic changes of terminal adipogenesis. The activity is observed in cells with type 1 but not type 8 fusions. Hence, the drug induces maturation of MLS lipoblasts in vivo by targeting the FUS-CHOP-mediated transcriptional block. These data provide a rationale for the specific activity of trabectedin and open the perspective of combinatorial treatments with drugs acting on lipogenic pathways.

FUS-DDIT3 prevents the development of adipocytic precursors in liposarcoma by repressing PPARgamma and C/EBPalpha and activating eIF4E

Background

FUS-DDIT3 is a chimeric protein generated by the most common chromosomal translocation t(12;16)(q13;p11) linked to liposarcomas, which are characterized by the accumulation of early adipocytic precursors. Current studies indicate that FUS-DDIT3- liposarcoma develops from uncommitted progenitors. However, the precise mechanism whereby FUS-DDIT3 contributes to the differentiation arrest remains to be elucidated.

Methodology/Principal Findings

Here we have characterized the adipocyte regulatory protein network in liposarcomas of FUS-DITT3 transgenic mice and showed that PPARγ2 and C/EBPα expression was altered. Consistent with in vivo data, FUS-DDIT3 MEFs and human liposarcoma cell lines showed a similar downregulation of both PPARγ2 and C/EBPα expression. Complementation studies with PPARγ but not C/EBPα rescued the differentiation block in committed adipocytic precursors expressing FUS-DDIT3. Our results further show that FUS-DDIT3 interferes with the control of initiation of translation by upregulation of the eukaryotic translation initiation factors eIF2 and eIF4E both in FUS-DDIT3 mice and human liposarcomas cell lines, explaining the shift towards the truncated p30 isoform of C/EBPα in liposarcomas. Suppression of the FUS-DDIT3 transgene did rescue this adipocyte differentiation block. Moreover, eIF4E was also strongly upregulated in normal adipose tissue of FUS-DDIT3 transgenic mice, suggesting that overexpression of eIF4E may be a primary event in the initiation of liposarcomas. Reporter assays showed FUS-DDIT3 is involved in the upregulation of eIF4E in liposarcomas and that both domains of the fusion protein are required for affecting eIF4E expression.

Conclusions/Significance

Taken together, this study provides evidence of the molecular mechanisms involve in the disruption of normal adipocyte differentiation program in liposarcoma harbouring the chimeric gene FUS-DDIT3.

A developmental model of sarcomagenesis defines a differentiation-based classification for liposarcomas

The importance of adult stem cells in the development of neoplastic diseases is becoming increasingly well appreciated. We hypothesized that sarcomas of soft tissue could be categorized by their developmental/differentiation status from stem cell to mature tissue, similar to the hematological malignancies. We conducted gene expression analyses during in vitro differentiation of human mesenchymal stem cells into adipose tissue, as a representative mature connective tissue, and identified genes whose expression changed significantly during adipogenesis. Gene clustering and distance correlation analysis allowed the assignment of a unique time point during adipogenesis that strongly correlates to each of the four major liposarcoma subtypes. Using a novel gene expression strategy, in which liposarcomas are compared to their corresponding adipocytic maturing cells, we identified a group of genes overexpressed in liposarcomas that indicate the stage of differentiation arrest, ie, sharing a similar expression profile to adipocytic cells at a corresponding stage of differentiation, and a distinct set of genes overexpressed in liposarcomas that are not found in the corresponding stage of differentiation. We propose that the latter set is enriched for candidate transformation-associated genes. Our results indicate that a degree of developmental maturity can be quantitatively assigned to solid tumors, supporting the notion that transformation of a solid tumor stem cell can occur at distinct stages of maturation.

Increased TNFalpha and CCAAT/enhancer-binding protein homologous protein with aging predispose preadipocytes to resist adipogenesis

Fat depot sizes peak in middle age but decrease by advanced old age. This phenomenon is associated with ectopic fat deposition, decreased adipocyte size, impaired differentiation of preadipocytes into fat cells, decreased adipogenic transcription factor expression, and increased fat tissue inflammatory cytokine generation. To define the mechanisms contributing to impaired adipogenesis with aging, we examined the release of TNFalpha, which inhibits adipogenesis, and the expression of CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP), which blocks activity of adipogenic C/EBP family members, in preadipocytes cultured from young, middle-aged, and old rats. Medium conditioned by fat tissue, as well as preadipocytes, from old rats impeded lipid accumulation by preadipocytes from young animals. More TNFalpha was released by preadipocytes from old than young rats. Differences in TNFalpha-converting enzyme, TNFalpha degradation, or the presence of macrophages in cultures were not responsible. TNFalpha induced rat preadipocyte CHOP expression. CHOP was higher in undifferentiated preadipocytes from old than younger animals. Overexpression of CHOP in young rat preadipocytes inhibited lipid accumulation. TNFalpha short interference RNA reduced CHOP and partially restored lipid accumulation in old rat preadipocytes. CHOP normally increases during late differentiation, potentially modulating the process. This late increase in CHOP was not affected substantially by aging: CHOP was similar in differentiating preadipocytes and fat tissue from old and young animals. Hypoglycemia, which normally causes an adaptive increase in CHOP, was less effective in inducing CHOP in preadipocytes from old than younger animals. Thus increased TNFalpha release by undifferentiated preadipocytes with elevated basal CHOP contributes to impaired adipogenesis with aging.

Sarcoma

Sarcomas comprise a heterogeneous group of mesenchymal neoplasms. They can be grouped into 2 general categories, soft tissue sarcoma and primary bone sarcoma, which have different staging and treatment approaches. This review includes a discussion of both soft tissue sarcomas (malignant fibrous histiocytoma, liposarcoma, leiomyosarcoma, synovial sarcoma, dermatofibrosarcoma protuberans, angiosarcoma, Kaposi sarcoma, gastrointestinal stromal tumor, aggressive fibromatosis or desmoid tumor, rhabdomyosarcoma, and primary alveolar soft-part sarcoma) and primary bone sarcomas (osteosarcoma, Ewing sarcoma, giant cell tumor, and chondrosarcoma). The 3 most important prognostic variables are grade, size, and location of the primary tumor. The approach to a patient with a sarcoma begins with a biopsy that obtains adequate tissue for diagnosis without interfering with subsequent optimal definitive surgery. Subsequent treatment depends on the specific type of sarcoma. Because sarcomas are relatively uncommon yet comprise a wide variety of different entities, evaluation by oncology teams who have expertise in the field is recommended. Treatment and follow-up guidelines have been published by the National Comprehensive Cancer Network (www.nccn.org).

Chop-deficient mice showed increased adiposity but no glucose intolerance

OBJECTIVE

CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP)-10/growth arrest and DNA damage 153 is a dominant-negative member of the C/EBP transcription family and inhibits adipogenesis in vitro. The study was undertaken to determine the role of CHOP in obesity in vivo.

RESEARCH METHODS AND PROCEDURES

Changes in daily food consumption and body weight were measured. The weight of white and brown adipose tissue was compared between Chop(+/+) and (-/-) mice fed normal chow or a high-fat diet. Glucose and insulin tolerance tests were done, and serum adipocytokine was measured to determine their metabolic state. Fat cell size of subcutaneous and mesenteric adipose tissue was microscopically observed. C/EBP expression in white adipose tissue was examined by Western blot.

RESULTS

Female Chop(-/-) mice had significantly greater body weight and adiposity than Chop(+/+) mice, although daily food intake and rectal temperature did not differ. In comparison with Chop(+/+) mice, glucose tolerance and insulin sensitivity did not differ in female Chop(-/-) mice, but levels of plasma leptin and adiponectin were higher. High-fat diet feeding resulted in obesity in female Chop(+/-) and (-/-) mice, although caloric intake did not differ from that of Chop(+/+) mice. Fat cell area was larger in mesenteric fat but not in subcutaneous fat in Chop(-/-) mice fed a high-fat diet. C/EBPbeta and the 30-kDa form of C/EBPalpha expressions were increased in parametrial fat of Chop(-/-) mice, but the 42-kDa form of C/EBPalpha expression was lower than in Chop(+/+) mice.

DISCUSSION

CHOP deficiency causes obesity in female animals without severe metabolic disorders, and C/EBP's expression may be considered to participate in the process.

JUN oncogene amplification and overexpression block adipocytic differentiation in highly aggressive sarcomas

The human oncogene JUN encodes a component of the AP-1 complex and is consequently involved in a wide range of pivotal cellular processes, including cell proliferation, transformation, and apoptosis. Nevertheless, despite extensive analyses of its functions, it has never been directly involved in a human cancer. We demonstrate here that it is highly amplified and overexpressed in undifferentiated and aggressive human sarcomas, which are blocked at an early step of adipocyte differentiation. We confirm by cellular and xenograft mouse models recapitulating these sarcoma genetics that the failure to differentiate is dependent upon JUN amplification/overexpression.

Hypermethylation of the APC promoter but lack of APC mutations in myxoid/round-cell liposarcoma

The adenomatous polyposis coli (APC) protein is a key component of the WNT signalling pathway wherein it acts as a scaffolding protein in controlling the level of the proto-oncoprotein beta-catenin. Although APC has been shown to be genetically or epigenetically inactivated in a variety of carcinomas, little is known about its role in sarcoma. Liposarcomas (LPSs) are the second most common soft tissue sarcoma in adults. Despite different histology and malignancy, the myxoid and round-cell LPSs belong to one tumour entity characterized by a specific chromosomal translocation. We assessed the extent of genetic and epigenetic inactivation of the APC gene in myxoid/round-cell LPS. Sequencing of the mutation cluster region, the protein truncation test and a loss of heterozygosity (LOH) analysis did not reveal any genetic alterations of the APC gene in all of the liposarcoma samples. Methylation of the APC promoter was detected by methylation-specific PCR in 9 of 20 (45%) tumours. Analysis of APC expression by semiquantitative RT-PCR in a subset of the samples demonstrated that tumours with a methylated APC promoter showed a downregulation of the APC transcript. However, APC downregulation was not correlated with a stabilisation of the beta-catenin protein. Thus, the epigenetic regulation of the APC gene might play an important role in the pathogenesis of myxoid/round-cell LPS. However, the impact of APC methylation on liposarcoma development is quite likely not mediated through WNT signalling.

A novel type of EWS–CHOP fusion gene in myxoid liposarcoma

The cytogenetic hallmark of myxoid type and round cell type liposarcoma consists of reciprocal translocation of t(12;16)(q13;p11) and t(12;22)(q13;q12), which results in fusion of TLS/FUS and CHOP, and EWS and CHOP, respectively. Nine structural variations of the TLS/FUS-CHOP chimeric transcript have been reported, however, only two types of EWS-CHOP have been described. We describe here a case of myxoid liposarcoma containing a novel EWS-CHOP chimeric transcript and identified the breakpoint occurring in intron 13 of EWS. Reverse transcription-polymerase chain reaction and direct sequence showed that exon 13 of EWS was in-frame fused to exon 2 of CHOP. Genomic analysis revealed that the breaks were located in intron 13 of EWS and intron 1 of CHOP.

Differential gene expression in liposarcoma, lipoma, and adipose tissue

Malignant transformation is thought to be associated with changes in the expression of a number of genes, and this alteration in gene expression is felt to be critical to the development of the malignant phenotype. Sarcomas represent a diverse group of tumors derived from cells of mesenchymal origin. Marked heterogeneity exists in the biological behavior of sarcomas, even within histologic subtypes of sarcomas. In an effort to better understand the biology of liposarcomas, gene expression in normal adipose tissue, lipomas, and liposarcomas was examined using the Affymetrix microarray technology. Differences in gene expression were quantified as the fold change in gene expression among the sample sets. Differences in gene expression among normal adipose tissue, lipomas, and liposarcomas were observed. In addition, genes expressed uniquely in liposarcoma among these and 18 other tissue sample sets were identified. Gene sets were devised that allowed the separation of liposarcomas from other samples, and most normal adipose tissue from most lipomas using the Eisen clustering software "Cluster." We conclude that differences in gene expression can be identified among different tumors derived from the adipocyte series. Such differences in gene expression may help differentiate among subtypes of sarcomas, and may also yield clues to the pathophysiology of this heterogeneous group of tumors.

Fibroblast phenotype plasticity: relevance for understanding heterogeneity in "fibroblastic" tumors

Cellular transformations, reflecting phenotypic plasticity, characterize embryonic life, would-repair, physiological adaptation, and neoplasia. Fibroblastic tumors show a range of cellular differentiation, which can be rationalized in terms of phenotypic plasticity of the "normal" fibroblast. In this paper, the various kinds of fibroblast transformation are discussed, and some insights provided into the molecular mechanisms involved. Comparable molecular events may take place in neoplastic fibroblasts to produce the heterogeneous tumors nevertheless identified as fibroblastic. The following transformations are discussed: histiocytic, and fibrohistiocytic tumors; adipocytic, and lipogenic tumors; myofibroblastic, and myofibroblastic tumors. A definition of the fibroblast is required. This consists of spindle-cell morphology, vimentin-staining, and abundant rough endoplasmic reticulum. Transformation to histiocytic, lipogenic and myofibroblastic phenotypes requires the development of lysosomes, lipid droplets and lamina, and peripheral myofilaments and fibronexuses respectively. These occur in non-malignant transforming (transdifferentiating) fibroblasts, and also in tumors identified as fibrohistiocytic, lipogenic and myofibroblastic. The molecular basis of the myofibroblast transformation is probably the best studied. It is driven primarily by transforming growth factor beta. Investigations into the mechanisms of differentiation in normal fibrobiasts could prove fertile ground for defining comparable differentiation in tumors. In this respect, there are very few publications on the presence of growth factors in tumors or tumor-like lesions. There is, however, increasing investigation into gene expression and gene products in tumors, which bear on the differentiation process. Ultimately, our understanding of the molecular events controlling differentiation in cancer will lead to control, cure and prevention.

Mechanisms of sarcoma development

Sarcomas are a rare and diverse group of tumours that are derived from connective tissues, including bone, muscle and cartilage. Although there are instances of hereditary predisposition to sarcomas, the overwhelming majority of such tumours are sporadic. In the past decade, we have gained much insight into the genetic abnormalities that seem to underlie the pathogenesis of these tumours. This information has already led to new classification of many sarcomas, as well as to successful therapies that are targeted at specific genetic abnormalities. It is likely that this approach will lead to continued refinements in classification and treatment of these tumours.

Effects of cortisol and bone morphogenetic protein-2 on stromal cell differentiation: correlation with CCAAT-enhancer binding protein expression

Bone marrow stroma contain pluripotential cells with the potential to differentiate into various mesenchymal cell lineages. We compared the effect of cortisol and bone morphogenetic protein-2 (BMP-2) on the differentiation of murine ST-2 stromal cells into mature osteoblasts or adipocytes. ST-2 cells were cultured for 3-27 days in the presence of 10% fetal bovine serum, 100 microg/mL ascorbic acid, and 5 mmol/L beta-glycerolphosphate in the presence or absence of cortisol at 1 micromol/L or BMP-2 at 1 nmol/L. Untreated ST-2 cells expressed high levels of alkaline phosphatase activity (APA) 15 days after confluence, and this was followed by the appearance of mineralized nodules after 24 days. BMP-2 accelerated and intensified the appearance of cells expressing APA and the presence of mineralized nodules. In contrast, cortisol decreased APA, prevented the formation of mineralized nodules, and induced a cellular phenotype characteristic of adipocytes. Untreated stromal cells expressed osteocalcin, Cbfa1, type I collagen, and alkaline phosphatase mRNA. BMP-2 increased osteocalcin and alkaline phosphatase mRNA, whereas cortisol suppressed their expression, as well as Cbfa1 and type I collagen transcripts. Cortisol enhanced, and BMP-2 downregulated, peroxisome proliferator-activated receptor gamma 2 and adipsin transcripts. The C/EBP transcription factors regulate genes critical for adipocytic and osteoblastic differentiation. Cortisol increased the expression of C/EBP alpha, beta, delta, and gamma mRNA levels, whereas BMP-2 had minor effects on C/EBP expression. In conclusion, BMP-2 accelerates the differentiation of stromal cells toward an osteoblastic phenotype, whereas glucocorticoids induce their differentiation toward an adipocytic phenotype.

Mutations in the gene encoding the transcription factor CCAAT/enhancer binding protein alpha in myelodysplastic syndromes and acute myeloid leukemias

The CCAAT/enhancer binding protein alpha (C/EBPalpha) protein is essential for proper lung and liver function and granulocytic and adipose tissue differentation. It was hypothesized that abnormalties in C/EBPalpha function contribute to the development of malignancies in a variety of tissues. To test this, genomic DNA from 408 patient samples and 5 cell lines representing 11 different cancers was screened for mutations in the C/EBPalpha gene. Two silent polymorphisms termed P1 and P2 were present at frequencies of 13.5% and 2.2%, respectively. Of the 12 mutations detected in 10 patients, silent changes were identified in one nonsmall cell lung cancer, one prostate cancer, and one acute myelogenous leukemia (AML) subtype M4. The 9 remaining mutations were detected in 1 of 92 (1.1%) myelodysplastic syndrome (MDS) samples and 6 of 78 (7.7%) AML (AML-M2 and AML-M4) samples. Some mutations truncated the predicted protein with loss of the DNA-binding (basic region) and dimerization (leucine zipper [ZIP]) domains by either deletions or nonsense codons. Also, inframe deletions or insertions in the fork region located between the leucine zipper and basic region, or within the leucine zipper, disrupted the alpha-helical phase of the bZIP domain. The inframe deletion and insertion mutations abrogated the transcriptional activation function of C/EBPalpha on the granulocyte colony-stimulating factor receptor promoter. These mutants localized properly to the nucleus, but were unable to bind to the C/EBP site in the promoter and did not possess dominant-negative activity. The mutations in the MDS patient and one AML-M2 patient were biallelic, indicating a loss of C/EBPalpha function. These results suggest that mutation of C/EBPalpha is involved in specific subtypes of AML and in MDS, but may occur rarely in other types of leukemias or nonhematologic malignancies.

PLAG1 alterations in lipoblastoma: involvement in varied mesenchymal cell types and evidence for alternative oncogenic mechanisms

Lipoblastomas are rare soft tissue tumors that occur primarily in young children. They typically contain variably differentiated adipocytes, primitive mesenchymal cells, myxoid matrix, and fibrous trabeculae. Abnormalities in chromosome 8, leading to rearrangements of the PLAG1 gene, were demonstrated recently in four lipoblastomas. In the present report, we determine the frequency of PLAG1 alterations in 16 lipoblastomas from children aged 13 years or younger, and we also evaluate the stages of lipoblastoma differentiation at which PLAG1 genomic alterations are found. Eleven lipoblastomas (69%), including those with either classic or lipoma-like histology, had rearrangements of the 8q12 PLAG1 region. Another three lipoblastomas had polysomy for chromosome 8 in the absence of PLAG1 rearrangement. Only two cases (13%) lacked a chromosome 8 abnormality. Notably, the lipoblastomas with chromosome 8 polysomy had up to five copies of chromosome 8 as an isolated cytogenetic finding in an otherwise diploid cell. We also demonstrate that PLAG1 alterations are found in a spectrum of mesenchymal cell types in lipoblastomas, including lipoblasts, mature adipocytes, primitive mesenchymal cells, and fibroblast-like cells. This finding is consistent with neoplastic origin in a primitive mesenchymal precursor and with variable differentiation to a mature adipocyte end-point. Hence, our studies provide biological validation for the clinical observation that lipoblastomas can evolve into mature, lipoma-like, lesions. They also suggest that PLAG1 dosage alterations caused by polysomy 8 might represent an alternative oncogenic mechanism in lipoblastoma.

Autocrine human growth hormone (hGH) regulation of human mammary carcinoma cell gene expression. Identification of CHOP as a mediator of hGH-stimulated human mammary carcinoma cell survival

By use of cDNA array technology we have screened 588 genes to determine the effect of autocrine production of human growth hormone (hGH) on gene expression in human mammary carcinoma cells. We have used a previously described cellular model to study autocrine hGH function in which the hGH gene or a translation-deficient hGH gene was stably transfected into MCF-7 cells. Fifty two of the screened genes were regulated, either positively () or negatively (), by autocrine production of hGH. We have now characterized the role of one of the up-regulated genes, chop (gadd153), in the effect of autocrine production of hGH on mammary carcinoma cell number. The effect of autocrine production of hGH on the level of CHOP mRNA was exerted at the transcriptional level as autocrine hGH increased chloramphenicol acetyltransferase production from a reporter plasmid containing a 1-kilobase pair fragment of the chop promoter. The autocrine hGH-stimulated increase in CHOP mRNA also resulted in an increase in CHOP protein. As a consequence, autocrine hGH stimulation of CHOP-mediated transcriptional activation was increased. Stable transfection of human CHOP cDNA into mammary carcinoma cells demonstrated that CHOP functioned not as a mediator of hGH-stimulated mitogenesis but rather enhanced the protection from apoptosis afforded by hGH in a p38 MAPK-dependent manner. Thus transcriptional up-regulation of chop is one mechanism by which hGH regulates mammary carcinoma cell number.

Liposarcoma initiated by FUS/TLS-CHOP: the FUS/TLS domain plays a critical role in the pathogenesis of liposarcoma

The most common chromosomal translocation in liposarcomas, t(12;16)(q13;p11), creates the FUS/TLS-CHOP fusion gene. We previously developed a mouse model of liposarcoma by expressing FUS-CHOP in murine mesenchymal stem cells. In order to understand how FUS-CHOP can initiate liposarcoma, we have now generated transgenic mice expressing altered forms of the FUS-CHOP protein. Transgenic mice expressing high levels of CHOP, which lacks the FUS domain, do not develop any tumor despite its tumorigenicity in vitro and widespread activity of the EF1alpha promoter. These animals consistently show the accumulation of a glycoprotein material within the terminally differentiated adipocytes, a characteristic figure of liposarcomas associated with FUS-CHOP. On the contrary, transgenic mice expressing the altered form of FUS-CHOP created by the in frame fusion of the FUS domain to the carboxy end of CHOP (CHOP-FUS) developed liposarcomas. No tumors of other tissues were found in these transgenic mice despite widespread activity of the EF1alpha promoter. The characteristics of the liposarcomas arising in the CHOP-FUS mice were very similar to those previously observed in our FUS-CHOP transgenic mice indicating that the FUS domain is required not only for transformation but also influences the phenotype of the tumor cells. These results provide evidence that the FUS domain of FUS-CHOP plays a specific and critical role in the pathogenesis of liposarcoma.

Specificity of TLS-CHOP rearrangement for classic myxoid/round cell liposarcoma: absence in predominantly myxoid well-differentiated liposarcomas

Myxoid liposarcoma (LS), the most common subtype of LS, is known to be characterized by the specific t(12;16) resulting in a TLS-CHOP fusion in almost all cases. We wished to address the following questions: (i) Is this genetic hallmark also present in other types of LS with predominant myxoid change? (ii) What is the proportion of cases with the variant EWS-CHOP fusion? (iii) What is the optimal approach for Southern blot detection of TLS breakpoints? We identified 59 LS characterized histologically by >90% myxoid component, in which frozen tissue tumor was available for DNA extraction. These 59 LS with myxoid features were divided into 2 groups: 42 LS with classic myxoid/round cell appearance (myxoid LS) and 17 well-differentiated LS (WDLS) with a predominant (>90%) myxoid component. Within the myxoid LS group, 29 tumors were low grade and 13 high grade (>20% round cell component). Among the 17 predominantly myxoid WDLS, there were 15 low grade and 2 focally high grade tumors. In addition, we selected as control group, 20 LS of other histological types with minimal or no myxoid change (17 WDLS and 3 pleomorphic LS) and 13 myxofibrosarcomas. Southern blot analysis was performed in all cases using a CHOP cDNA probe, and in all CHOP rearranged cases using a TLS cDNA probe. Probe/enzyme combinations for Southern blot analysis were CHOP exon 3-4 cDNA probe with BamHI or SacI, TLS exon 3-6 cDNA probe with BclI. All 42 cases of myxoid LS showed a CHOP rearrangement and 38 of them also had a TLS rearrangement. Among the 4 myxoid LS without Southern blot evidence of TLS rearrangement, 1 showed an EWS-CHOP fusion by Southern blotting and reverse transcriptase-polymerase chain reaction and in another case, reverse transcriptase-polymerase chain reaction detected a TLS-CHOP fusion transcript. None of the predominantly myxoid WDLS and none of the tumors included in the control group showed rearranegements with CHOP probe. In addition, 12 predominantly myxoid WDLS, 10 other LS, and 5 myxofibrosarcoma from the control group were also tested for TLS rearrangement; all were negative. The TLS-CHOP fusion is highly sensitive and specific for the entity of classic myxoid/round cell LS. Other types of LS, even with a predominant myxoid component, lack the TLS-CHOP rearrangement, confirming that they represent a genetically distinct group of LS. The prevalence of the EWS-CHOP variant fusion was approximately 2% in this series. The optimal enzyme for TLS genomic breakpoint detection is BclI.

The chimeric FUS/TLS-CHOP fusion protein specifically induces liposarcomas in transgenic mice

The characteristic t(12;16)(q13;p11) chromosomal translocation, which leads to gene fusion that encodes the FUS-CHOP chimeric protein, is associated with human liposarcomas. The altered expression of FUS-CHOP has been implicated in a characteristic subgroup of human liposarcomas. We have introduced the FUS-CHOP transgene into the mouse genome in which the expression of the transgene is successfully driven by the elongation factor 1alpha (EF1alpha) promoter to all tissues. The consequent overexpression of FUS-CHOP results in most of the symptoms of human liposarcomas, including the presence of lipoblasts with round nuclei, accumulation of intracellular lipid, induction of adipocyte-specific genes and a concordant block in the differentiation program. We have demonstrated that liposarcomas in the FUS-CHOP transgenic mice express high levels of the adipocyte regulatory protein PPARgamma, whereas it is not expressed in embryonic fibroblasts from these animals following induction to differentiation toward the adipocyte lineage, indicating that the in vitro system does not really reflect the in vivo situation and the developmental defect is downstream of PPARgamma expression. No tumors of other tissues were found in these transgenic mice despite widespread activity of the EF1alpha promoter. This establishes FUS-CHOP overexpression as a key determinant of human liposarcomas and provide the first in vivo evidence for a link between a fusion gene created by a chromosomal translocation and a solid tumor.