ASPL-TFE3 Fusion Transcript Research Articles

Sarcomas of the mediastinum with epithelioid morphology.

While soft tissue sarcomas typically have a spindled or pleomorphic appearance, a subset of malignant soft tissue neoplasms can have a prominent epithelioid morphology. In complex anatomic sites such as the mediastinum, such tumors can often be mistaken for a carcinoma or mesothelioma. Frequent expression of cytokeratin staining can further confound the diagnostic process and familiarity with these entities can help prevent an erroneous diagnosis. Particular entities that have been reported to occur in the mediastinum with such features include dedifferentiated liposarcoma, pleomorphic liposarcoma, malignant peripheral nerve sheath tumor, synovial sarcoma, SMARCA4-deficient thoracic sarcoma, alveolar soft part sarcoma and clear cell sarcoma. Many of these tumors exhibit unique clinical, genetic, molecular or immunohistochemical features which allow for accurate characterization. For example, pleomorphic liposarcoma contains bizarre appearing lipoblasts and dedifferentiated liposarcoma exhibits MDM2 gene amplification that is typically confirmed by fluorescence in-situ hybridization. Malignant peripheral nerve sheath tumor will often arise in association with a nerve or neurofibroma. Synovial sarcoma consistently exhibits rearrangements involving the SS18 gene and SMARCA4-deficient thoracic sarcoma shows loss of SMARCA4 staining in the tumor cells. Alveolar soft part sarcoma demonstrates an ASPL-TFE3 fusion transcript. Clear cell sarcoma often shows an EWSR1-ATF1 fusion transcript. When encountering a sarcoma of the mediastinum with epithelioid features, familiarity with these and other characteristics can help insure a correct diagnosis.

Exploring the Histogenesis and Diagnostic Strategy Using Immunoassay and RT-PCR in Alveolar Soft Part Sarcoma.

Alveolar soft part sarcoma (ASPS) is a rare soft tissue sarcoma, but it's easily misdiagnosed in rare locations. The derivation of ASPS is still uncertain, therefore we conducted this study to explore the histogenesis of ASPS by analyzing stem cell markers (ALDH1, CD29, CD133 and Nestin). Protein TFE3 and fusion gene ASPS-TFE3 were tested in paraffin to explore diagnostic strategy and molecular pathological features. In this study, nine cases of ASPS were immunostained with stem cell surface markers (ALDH1, CD29, CD133 and Nestin) and protein TFE3. Seven cases of ASPS mRNA were successfully extracted from nine paraffin-embedded tissues. The expression of fusion gene ASPL-TFE3 was examined by reverse transcriptase-polymerase chain reaction. The immunohistochemical staining of nine patients showed that CD29 and Nestin were negative in all nine cases (0/9). CD133 was weakly positive in one cases (1/9) and ALDH1 was weakly positive in one cases (1/9). TFE3 was positive in nine cases (9/9). Seven paraffin tissues could be successfully extracted with mRNA in nine cases. The results of Reverse Transcription Polymerase Chain Reaction (RT-PCR) showed that ASPL-TFE3 fusion transcripts could be tested in the seven cases (four cases being type 2 and three cases being type 1). The positive rate of CD133 and ALDH1 were less than 1% and the expression of CD29 and Nestin were negative in ASPS. Immunohistochemistry results indicated that the histogenesis of ASPS maybe not derive from mesenchymal stem cells. Immunohistochemistry staining showed that TFE3 protein expression was highly sensitive in ASPS. Furthermore, RT-PCR results showed that fusion gene ASPL-TFE3 (ASPL-TFE3 type 1 and ASPL-TFE3 type 2) was expressed in ASPS, which could provide information for clinical molecular pathological diagnosis and improve the diagnosis rate of rare atypical ASPS.

Mammalian target of rapamycin pathway activity in alveolar soft part sarcoma

Alveolar soft part sarcoma (ASPS) is a distinct type of soft tissue sarcoma holding a specific ASPL-TFE3 fusion transcript. Curative therapy is based on surgical removal, whereas lately, antiangiogenic targeted therapy regimens have proven effective. In ASPS, analysis of small series additionally display mTOR (mammalian target of rapamycin) pathway activity, thus making mTOR a possible additive target in ASPS, because it is in other tumor entities. Therefore, we systematically evaluated mTOR pathway activity in a large series of ASPS in comparison with soft tissue sarcomas of other differentiation (non-ASPS). Upstream and downstream factors of mTOR signaling and ancillary targets were analyzed in 103 cases (22 ASPS, 81 non-ASPS) by immunohistochemistry mostly using phospho-specific antibodies. TFE3 (transcription factor for immunoglobulin heavy-chain enhancer 3) translocation status was determined by FISH and RT-PCR. All ASPS were positive in TFE3 break-apart FISH and exhibited specific fusion products when RNA was available (type 1: 9x, type 2: 11x), whereas TFE3-immunoreactive non-ASPS did not. In ASPS, TFE3-, cMET-, pAKT T308- (all P < .0001), pp70S6K- (P = .002), and p4EBP1 (P = .087) expression levels were elevated, whereas pAKT S473 was decreased (P < .0001). In addition, ASPS exhibited higher TFE3-, cMET-, pAKT T308-, and pp70S6K- expression levels compared with TFE3-immunopositive non-ASPS sarcomas (all P < .001). We demonstrate elevated mTOR complex 1 (mTORC1) activity in ASPS independent of mTOR complex 2 (mTORC2) activation. mTORC1 activity seems to be related to the existence of ASPL-TFE3 fusion transcripts because TFE3-immunoreactive non-ASPS without ASPL-TFE3 fusion transcripts exhibit significantly lower mTORC1 activation status. Small molecule-based targeting of mTOR might therefore represent a potential mechanism in ASPS alone or in combination with contemporary upstream approaches.

Bioinformatic Analysis of Patient-Derived ASPS Gene Expressions and ASPL-TFE3 Fusion Transcript Levels Identify Potential Therapeutic Targets

Gene expression data, collected from ASPS tumors of seven different patients and from one immortalized ASPS cell line (ASPS-1), was analyzed jointly with patient ASPL-TFE3 (t(X;17)(p11;q25)) fusion transcript data to identify disease-specific pathways and their component genes. Data analysis of the pooled patient and ASPS-1 gene expression data, using conventional clustering methods, revealed a relatively small set of pathways and genes characterizing the biology of ASPS. These results could be largely recapitulated using only the gene expression data collected from patient tumor samples. The concordance between expression measures derived from ASPS-1 and both pooled and individual patient tumor data provided a rationale for extending the analysis to include patient ASPL-TFE3 fusion transcript data. A novel linear model was exploited to link gene expressions to fusion transcript data and used to identify a small set of ASPS-specific pathways and their gene expression. Cellular pathways that appear aberrantly regulated in response to the t(X;17)(p11;q25) translocation include the cell cycle and cell adhesion. The identification of pathways and gene subsets characteristic of ASPS support current therapeutic strategies that target the FLT1 and MET, while also proposing additional targeting of genes found in pathways involved in the cell cycle (CHK1), cell adhesion (ARHGD1A), cell division (CDC6), control of meiosis (RAD51L3) and mitosis (BIRC5), and chemokine-related protein tyrosine kinase activity (CCL4).

Expression of MET in alveolar soft part sarcoma

Alveolar soft part sarcoma (ASPS) is a rare soft tissue sarcoma which is characterized by the presence of a specific chromosomal translocation encoding the chimeric transcription factor (ASPL-TFE3) that activates expression of MET. We reviewed the clinical features and treatment outcome of 12 ASPS patients. The presence of ASPL-TFE3 fusion transcripts was assessed by reverse transcriptase polymerase chain reaction. In addition, we performed immunohistochemical studies for MET, TFE3, Ki-67, and EGFR expression. Lower extremity was the most commonly affected primary site (2 thigh, 3 lower leg, and 1 foot). Of four patients who received primary cytotoxic chemotherapy, no patient demonstrated treatment response. With follow-up duration of 94.4 months, median overall survival was 53.2 (95% C.I. 40.9-65.5) months. The immunohistochemical staining demonstrated 100% TFE3 positivity (8 of 8), 75% MET positivity (6 of 8) with a strong association between TFE3 expression and MET positivity with correlation coefficient of 0.808 (P = 0.02). The high expression of MET in ASPL-TFE3 (+) ASPS may further support the potential role of targeted agents against MET in this rare, chemoresistant tumor.

Alveolar Soft Part Sarcoma: A Bimarker Diagnostic Strategy Using TFE3 Immunoassay and ASPL-TFE3 Fusion Transcripts in Paraffin-Embedded Tumor Tissues

Alveolar soft part sarcoma (ASPS) is a malignancy with low incidence, but with poor prognosis if misdiagnosed. Immunohistochemical assay using TFE3 antibody has been shown to be a sensitive technique for ASPS diagnosis. A specific chromosomal translocation, t(X;17)(p11.2;q25), results in the ASPL-TFE3 fusion gene: it is detectable using reverse-transcription polymerase chain reaction (RT-PCR) in frozen tumor tissues of ASPS. However, the diagnostic usefulness of these markers has not been investigated in Chinese ASPS patients. Here, we report the first systematic study applying TFE3 immunoassay and ASPL-TFE3 fusion transcript detection to archival paraffin-embedded tissues in a large Chinese ASPS patient population. Sixteen patients had been diagnosed with ASPS (age, 3 to 58 y; 3 male patients and 13 female patients). Their tumors presented predominantly in the extremities (8/16), and were often located in the region of the orbit when affecting infants and children (3/16). Others had tumors in the chest wall, breast, and right pubis, respectively. One patient exhibited a tumor in the renal hilum, a location that had not been previously reported. Two patients had tumor metastases in the lung and the brain. ASPS tumors showed the best immunoreactivity to the TFE3 antibody (16/16). However, their immunoreactivity to other antibodies, including myoglobin (13/16), actin (10/16), desmin (2/16), and vimentin (2/16), was of various degrees. Positive staining was observed for the neural markers, NSE (9/16) and CgA (7/16), respectively. Using a strategy of RT-PCR, followed by a nested PCR with a different primer set, we were able to detect the expression of the chimeric ASPL-TFE3 mRNA in 11 of the 16 ASPS tumors. Of these 11, 7 were type 1 ASPL-TFE3 and 4 were type 2 ASPL-TFE3, including the tumor located in the renal hilum. No expression of ASPL-TFE3 fusion transcripts was detectable in all 38 control tumors. Our results demonstrate that the "bimarker strategy," a combination of TFE3 immunostaining and ASPL-TFE3 chimeric transcript detection, might have sufficient sensitivity and specificity in diagnosing most of the ASPSs. As both diagnostic techniques can be applied to widely available archival paraffin-embedded tissues, the usefulness of the strategy is largely implicated in routine pathology laboratories.

Myofibroblasts in Pulmonary and Brain Metastases of Alveolar Soft-Part Sarcoma: A Novel Target for Treatment?

Alveolar soft-part sarcoma (ASPS) is a rare neoplasm with chromosomal translocation that results in ASPL-TFE3 fusion. It is a slow-growing lesion associated with a high incidence of pulmonary and brain metastases indicating poor survival. We demonstrated that the ASPS metastases include also stromal myofibroblasts. These cells pro-liferate, express smooth-muscle genes, and synthesize extracellular matrix proteins, all of which are characteristics of activated myofibroblasts. The tumor cells also exhibited stromal components such as transforming growth factor beta (TGFβ)–dependent, hypoxia-regulated cytoglobin (stellate cell activation association protein, cytg/ STAP) and prolyl 4-hydroxylase, a collagen cross-linking enzyme. The pulmonary ASPS myofibroblasts synthesize serum response factor (SRF), a repressor of Smad3-mediated TGFβ signaling essential for myofibroblast differentiation and Smad3. The phosphorylated active Smad3 was found mostly in the tumor cells. The brain tumor cells express cytg/STAP, but in contrast to the lung metastases, they also express SRF, Smad3, and phospho-Smad3. Halofuginone, an inhibitor of myofibroblasts’ activation and Smad3 phosphorylation, inhibited tumor development in xenografts derived from renal carcinoma cells harboring a reciprocal ASPL-TFE3 fusion transcript. This inhibition was associated with the inhibition of TGFβ/SRF signaling, with the inhibition of myofibroblasts’ activation, and with the complete loss in TFE3 synthesis by the tumor cells. These results suggest that the myofibroblasts may serve as a novel target for treatment of ASPS metastases.

Primary Cardiac Alveolar Soft Part Sarcoma. A Report of the First Observed Case with Molecular Diagnostics Corroboration

A case of primary alveolar soft part sarcoma (ASPS) of the heart is reported in an 11-year-old female as 1 of 16 cases of ASPS presenting in the first 2 decades of life in our institutional 17-year review period. The classic alveolar or organoid pattern was inconspicuous as compared to a more diffuse or formless pattern consisting of a population of uniform round cells with abundant eosinophilic cytoplasm, but in addition there was a second, minor population of gigantiform tumor cells with a variety of unusual shapes. Scattered tumor cells contained dense eosinophilic condensations in the cytoplasm. Other unusual features for ASPS in our case included a lymphohistocytic reaction and zonal necrosis. Immunohistochemistry revealed nuclear reactivity for TFE3, and the ASPL-TFE3 fusion transcript was identified by reverse-transcriptase polymerase chain reaction. The only other examples of ASPS involving the heart were 3 cases in the literature of metastatic disease from tumors arising in the soft tissues. This initial case of primary cardiac ASPS joins the list of other types of sarcomas in children that have been reported as primary neoplasms of the heart.

Detection of ASPL-TFE3 fusion gene by reverse transcriptase polymerase chain reaction in paraffin-embedded tumor tissues of alveolar soft part sarcoma

To investigate the significance of detecting chimeric mRNA resulting from t(X;17)(p11.2;q25) in paraffin-embedded tumor tissues of alveolar soft part sarcoma (ASPS). Formalin-fixed, paraffin-embedded tumor tissues from 8 cases of alveolar soft part sarcoma and 15 cases of controls (including 6 alveolar rhabdomyosarcomas, 6 renal cell carcinomas, 2 paragangliomas and 1 granular cell myoblastoma) were retrieved from the archival materials. ASPL-TFE3 fusion transcripts were analyzed in all samples by reverse transcriptase-polymerase chain reaction (RT-PCR). The quality of the mRNA was assessed using the house-keeping gene beta-actin. ASPL-TFE3 fusion transcripts were detected in 6 of the 8 ASPS cases (4 being type 2 and 2 being type 1). The remaining 2 cases were negative for both beta-actin and ASPL-TFE3. No ASPL-TFE3 mRNA expression was detected in all the controls. PAX3/7-FKHR fusion transcripts were also detected in 4 of the 6 alveolar rhabdomyosarcoma samples. The expression of ASPL-TFE3 fusion transcripts in paraffin-embedded tumor tissues can serve as an useful molecular marker in the diagnosis of ASPS. It may also be helpful in elucidating the underlying pathogenesis of ASPS in subsequent retrospective studies.

Diagnostic significance and clinical application of specific chimeric genes in soft tissue sarcomas by RT-PCR using paraffin-embedded tissues: a study of 103 specimens

To investigate the expression of the chimeric genes resulting from the specific chromosomal translocations in soft tissue sarcomas (STS) and its diagnostic significance for STS. The variety of fusion transcripts were detected in 103 cases of STS, including 30 cases of synovial sarcoma (SS), 15 cases of rhabdomyosarcoma (RMS), 25 cases of Ewing's sarcoma/peripheral primitive neuroectodermal tumors (ES/pPNET), 12 cases of dermatofibrosarcoma protuberans (DFSP), 14 cases of aveolar soft part sarcoma (ASPS), 3 cases of leiomyosarcoma (LMS), 2 cases of malignant fibrous histocytoma (MFH), and 2 cases of fibrosarcoma (FS); and 20 cases of control tumors by reverse transcription-polymerase chain reaction (RT-PCR) using formalin fixed, paraffin embedded specimens. Of the 34 cases of SS 28 (93.3%) expressed SSX-SYT chimeric transcripts (14 were positive for SYT-SSX1, 9 for SYT-SSX2). Four of the six cases of alveolar RMS had a PAX3/PAX7-FKHR fusion transcript. None of the 9 cases of embryonic and polymorphic RMS expressed PAX3/PAX7-FKHR. Of the 25 cases of ES/pPNET, 19 were positive for EWS-FLI1 fusion transcript and 1 for EWS-ERG fusion transcript. COL1A1-PDGFB fusion transcript was expressed in 8 of the 12 cases (66.7%) of DFSP. Of the fourteen cases of ASPS, ten expressed ASPL-TFE3 fusion transcript. None of the 3 cases of LMS, 2 cases of MFH, 2 cases of FS, and 20 control cases contained any of the fusion transcript. Chimeric gene transcript resulting from specific chromosomal translocations is a reliable index for the molecular diagnosis of STS and RT-PCR assay for detection of specific fusion gene provides a useful tool for confirmation of the diagnosis of STS in diagnostically difficult cases and in retrospective studies.

Establishment and characterization of a renal cell carcinoma cell line (FU-UR-1) with the reciprocal ASPL-TFE3 fusion transcript

We have established a cultured cell line named FU-UR-1 from a large retroperitoneal tumor of a 24-year-old Japanese male patient who simultaneously had a small renal cell carcinoma (RCC). Cytogenetic analysis and fluorescence in situ hybridization of the retroperitoneal tumor, and the cell line established from this tumor demonstrated similar karyotypes including add(13)(p11).ish der(13)t(13;17) (p11;q11)t(X;17)(p11;q25)(wcpX+,wcp17+). FU-UR-1 had been propagated continuously for more than 70 passages, and the doubling time was 32 h. Successful heterotransplantation was performed by inoculation of the cultured FU-UR-1 cells into the subcutis of BALB/c nude mice. Reverse transcriptase-polymerase chain reaction (RT-PCR) and sequence analysis demonstrated reciprocal ASPL-TFE3 and TFE3-ASPL fusion transcripts in the retroperitoneal tumor, cultured FU-UR-1 cells and xenografted tumors. In addition, the pathological findings of these samples and the renal tumor resembled each other. These observations suggest that the FU-UR-1 cell line established from the retroperitoneal tumor is an RCC cell line. This well-examined cell line may become a useful system for studying the genetic and biologic characteristics of rare neoplasms with the reciprocal ASPL-TFE3 fusion transcript.

Primary Renal Neoplasms with the ASPL-TFE3 Gene Fusion of Alveolar Soft Part Sarcoma : A Distinctive Tumor Entity Previously Included among Renal Cell Carcinomas of Children and Adolescents

The unbalanced translocation, der(17)t(X;17)(p11.2;q25), is characteristic of alveolar soft part sarcoma (ASPS). We have recently shown that this translocation fuses the TFE3 transcription factor gene at Xp11.2 to ASPL, a novel gene at 17q25. We describe herein eight morphologically distinctive renal tumors occurring in young people that bear the identical ASPL-TFE3 fusion transcript as ASPS, with the distinction that the t(X;17) translocation is cytogenetically balanced in these renal tumors. A relationship between these renal tumors and ASPS was initially suggested by the cytogenetic finding of a balanced t(X;17)(p11.2;q25) in two of the cases, and the ASPL-TFE3 fusion transcripts were then confirmed by reverse transcriptase-polymerase chain reaction. The morphology of these eight ASPL-TFE3 fusion-positive renal tumors, although overlapping in some aspects that of classic ASPS, more closely resembles renal cell carcinoma (RCC), which was the a priori diagnosis in all cases. These tumors demonstrate nested and pseudopapillary patterns of growth, psammomatous calcifications, and epithelioid cells with abundant clear cytoplasm and well-defined cell borders. By immunohistochemistry, four tumors were negative for all epithelial markers tested, whereas four were focally positive for cytokeratin and two were reactive for epithelial membrane antigen (EMA) (one diffusely, one focally). Electron microscopy of six tumors demonstrated a combination of ASPS-like features (dense granules in four cases, rhomboid crystals in two cases) and epithelial features (cell junctions in six cases, microvilli and true glandular lumens in three cases). Overall, although seven of eight tumors demonstrated at least focal epithelial features by electron microscopy or immunohistochemistry, the degree and extent of epithelial differentiation was notably less than expected for typical RCC. We confirmed the balanced nature of the t(X;17) translocation by fluorescence in situ hybridization in all seven renal tumors thus analyzed, which contrasts sharply with the unbalanced nature of the translocation in ASPS. In summary, a subset of tumors previously considered to be RCC in young people are in fact genetically related to ASPS, although their distinctive morphological and genetic features justify their classification as a distinctive neoplastic entity. Finally, the finding of distinctive tumors being associated with balanced and unbalanced forms of the same translocation is to our knowledge, unprecedented.

The der(17)t(X;17)(p11;q25) of human alveolar soft part sarcoma fuses the TFE3 transcription factor gene to ASPL, a novel gene at 17q25.

Alveolar soft part sarcoma (ASPS) is an unusual tumor with highly characteristic histopathology and ultrastructure, controversial histogenesis, and enigmatic clinical behavior. Recent cytogenetic studies have identified a recurrent der(17) due to a non-reciprocal t(X;17)(p11.2;q25) in this sarcoma. To define the interval containing the Xp11.2 break, we first performed FISH on ASPS cases using YAC probes for OATL1 (Xp11.23) and OATL2 (Xp11.21), and cosmid probes from the intervening genomic region. This localized the breakpoint to a 160 kb interval. The prime candidate within this previously fully sequenced region was TFE3, a transcription factor gene known to be fused to translocation partners on 1 and X in some papillary renal cell carcinomas. Southern blotting using a TFE3 genomic probe identified non-germline bands in several ASPS cases, consistent with rearrangement and possible fusion of TFE3 with a gene on 17q25. Amplification of the 5' portion of cDNAs containing the 3' portion of TFE3 in two different ASPS cases identified a novel sequence, designated ASPL, fused in-frame to TFE3 exon 4 (type 1 fusion) or exon 3 (type 2 fusion). Reverse transcriptase PCR using a forward primer from ASPL and a TFE3 exon 4 reverse primer detected an ASPL-TFE3 fusion transcript in all ASPS cases (12/12: 9 type 1, 3 type 2), establishing the utility of this assay in the diagnosis of ASPS. Using appropriate primers, the reciprocal fusion transcript, TFE3-ASPL, was detected in only one of 12 cases, consistent with the non-reciprocal nature of the translocation in most cases, and supporting ASPL-TFE3 as its oncogenically significant fusion product. ASPL maps to chromosome 17, is ubiquitously expressed, and matches numerous ESTs (Unigene cluster Hs.84128) but no named genes. The ASPL cDNA open reading frame encodes a predicted protein of 476 amino acids that contains within its carboxy-terminal portion of a UBX-like domain that shows significant similarity to predicted proteins of unknown function in several model organisms. The ASPL-TFE3 fusion replaces the N-terminal portion of TFE3 by the fused ASPL sequences, while retaining the TFE3 DNA-binding domain, implicating transcriptional deregulation in the pathogenesis of this tumor, consistent with the biology of several other translocation-associated sarcomas. Oncogene (2001) 20, 48 - 57.