Jui Lan

ASS1 as a Novel Tumor Suppressor Gene in Myxofibrosarcomas: Aberrant Loss via Epigenetic DNA Methylation Confers Aggressive Phenotypes, Negative Prognostic Impact, and Therapeutic Relevance

Purpose: The principal goals were to identify and validate targetable metabolic drivers relevant to myxofibrosarcoma pathogenesis using a published transcriptome. Experimental Design: As the most significantly downregulated gene regulating amino acid metabolism, argininosuccinate synthetase (ASS1) was selected for further analysis by methylation-specific PCR, pyrosequencing, and immunohistochemistry of myxofibrosarcoma samples. The roles of ASS1 in tumorigenesis and the therapeutic relevance of the arginine-depriving agent pegylated arginine deiminase (ADI-PEG20) were elucidated in ASS1-deficient myxofibrosarcoma cell lines and xenografts with and without stable ASS1 reexpression. Results: ASS1 promoter hypermethylation was detected in myxofibrosarcoma samples and cell lines and was strongly linked to ASS1 protein deficiency. The latter correlated with increased tumor grade and stage and independently predicted a worse survival. ASS1-deficient cell lines were auxotrophic for arginine and susceptible to ADI-PEG20 treatment, with dose-dependent reductions in cell viability and tumor growth attributable to cell-cycle arrest in the S-phase. ASS1 expression was restored in 2 of 3 ASS1-deficient myxofibrosarcoma cell lines by 5-aza-2′-deoxycytidine, abrogating the inhibitory effect of ADI-PEG20. Conditioned media following ASS1 reexpression attenuated HUVEC tube-forming capability, which was associated with suppression of MMP-9 and an antiangiogenic effect in corresponding myxofibrosarcoma xenografts. In addition to delayed wound closure and fewer invading cells in a Matrigel assay, ASS1 reexpression reduced tumor cell proliferation, induced G1-phase arrest, and downregulated cyclin E with corresponding growth inhibition in soft agar and xenograft assays. Conclusions: Our findings highlight ASS1 as a novel tumor suppressor in myxofibrosarcomas, with loss of expression linked to promoter methylation, clinical aggressiveness, and sensitivity to ADI-PEG20. Clin Cancer Res; 19(11); 2861–72. ©2013 AACR.

NAB2–STAT6 fusion types account for clinicopathological variations in solitary fibrous tumors

Solitary fibrous tumor (SFT) is characterized by the inv12(q13q13)-derived NAB2–STAT6 fusion, which exhibits variable breakpoints and drives STAT6 nuclear expression. The implications of NAB2–STAT6 fusion variants in pathological features and clinical behavior remain to be characterized in a large cohort of SFTs. We investigated the clinicopathological correlates of this genetic hallmark and analyzed STAT6 immunoexpression in 28 intrathoracic, 37 extrathoracic, and 23 meningeal SFTs. These 88 tumors were designated as histologically nonmalignant in 75 cases and malignant in 13, including 1 dedifferentiated SFT. Eighty cases had formalin-fixed and/or fresh samples to extract assessable RNAs for RT-PCR assay, which revealed NAB2–STAT6 fusion variants comprising 12 types of junction breakpoints in 73 fusion-positive cases, with 65 (89%) falling into 3 major types. The predominant NAB2ex4–STAT6ex2 (n=33) showed constant breakpoints at the ends of involved exons, whereas the NAB2ex6–STAT6ex16 (n=16) and NAB2ex6–STAT6ex17 (n=16) might exhibit variable breakpoints and incorporate NAB2 or STAT6 intronic sequence. Including 73 fusion-positive and 7 CD34-negative SFTs, STAT6 distinctively labeled 87 (99%) SFTs in nuclei, exhibited diffuse reactivity in 73, but did not decorate 98 mimics tested. In seven fusion-negative cases, 6 were STAT6-positive, suggesting rare fusion variants not covered by RT-PCR assay. Regardless of histological subtypes, intrathoracic SFTs affected older patients (P=0.035) and tended to be larger in size (P=0.073). Compared with other variants, NAB2ex4–STAT6ex2/4 fusions were significantly predominant in the SFTs characterised by intrathoracic location (P<0.001), older age (P=0.005), decreased mitoses (P=0.0028), and multifocal or diffuse STAT6 staining (P=0.013), but not found to correlate with disease-free survival. Conclusively, STAT6 nuclear expression was distinctive in the vast majority of SFTs, including all fusion-positive tumors, and exploitable as a robust diagnostics of CD34-negative cases. Despite the associations of NAB2–STAT6 fusion variants with several clincopathological factors, their prognostic relevance should be further validated in large-scale prospective studies of SFTs.

Characterization of Gene Amplification–Driven SKP2 Overexpression in Myxofibrosarcoma: Potential Implications in Tumor Progression and Therapeutics

Purpose: Myxofibrosarcoma remains obscure in molecular determinants of clinical aggressiveness, for which we elucidated implications of SKP2 amplification. Experimental Design: Array comparative genomic hybridization was applied on samples and cell lines (NMFH-1 to OH931) to search causal genes of tumor progression. SKP2 gene dosage was determined in 82 independent tumors for clinical correlates. Stable SKP2 knockdown was achieved in myxofibrosarcoma cells to assess its oncogenic attributes and candidate mediators in prometastatic function. Pharmacologic assays were evaluated in vitro and in vivo for the therapeutic relevance of bortezomib. Results: DNA gains frequently involved 5p in which three amplicons were differentially overrepresented in samples behaving unfavorably, encompassing mRNA-upregulated TRIO, SKP2, and AMACR genes. Detected in NMFH-1 cells and 38% of tumors, SKP2 amplification was associated with SKP2 immunoexpression and adverse prognosticators and independently predictive of worse outcomes. Nevertheless, SKP2-expressing OH931 cells and 14% of such tumors lacked gene amplification. Knockdown of SKP2 suppressed proliferation, anchorage-independent growth, migration, and invasion of sarcoma cells and downregulated motility-promoting genes, including ITGB2, ACTN1, IGF1, and ENAH. In vitro, bortezomib downregulated SKP2 expression at the mRNA level with p27kip1 accumulation, induced caspase activation, and decreased cell viability in myxofibrosarcoma cells but not in fibroblasts. In vivo, bortezomib inhibited growth of NMFH-1 xenografts, the cells of which displayed decreased SKP2 expression but increased p27kip1 and terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling (TUNEL). Conclusions: As a predominant mechanism driving protein overexpression, SKP2 amplification confers tumor aggressiveness in myxofibrosarcoma. The sensitivity of myxofibrosarcoma cells to bortezomib with SKP2-repressing effect indicates the potentiality of ubiquitin-proteasome pathway as a therapeutic target. Clin Cancer Res; 18(6); 1598–610. ©2012 AACR.

Angiomatoid fibrous histiocytoma: clinicopathological and molecular characterisation with emphasis on variant histomorphology

Aims Angiomatoid fibrous histiocytoma (AFH) is histologically typified by nodules of histiocytoid spindle cells with pseudoangiomatoid spaces, fibrous pseudocapsules and lymphocytic cuffs. The principal goal was to expand the spectrum of AFHs through clinicopathological and molecular characterisation. Methods Thirteen AFHs, including 11 with confirmed hallmark translocation, were reappraised for classic features, reactive osteoclasts, mitoses and stromal, architectural and cytomorphological variations, with CD99, desmin and EMA stained in available cases. Results Seven male and six female patients ranged in age from 4 to 63 years (median, 13), including 4 older than 20 years. Tumours were located on the extremities (n=6), trunk (n=4) and scalp (n=3). Although fibrous pseudocapsules were observed in all cases, four showed solid histology without pseudoangiomatoid spaces and another one lacked peripheral lymphoid infiltrates. Nuclear pleomorphism was striking in two cases, moderate in seven and absent in four, with osteoclasts seen in two cases. In three AFHs with sclerotic matrix, one exhibited perivascular hyalinisation and nuclear palisading, reminiscent of a schwannoma. In three varyingly myxoid tumours, one closely resembled a myoepithelioma with prominent reticular arrangement of spindle cells in an abundant myxoid stroma. Besides EWSR1 gene rearrangement detected in four cases by fluorescence in situ hybridisation (FISH), EWSR1-CREB1 fusion was confirmed in nine cases, including a schwannoma-like AFH, and EWSR1-ATF1 fusion detected in a myoepithelioma-like AFH. Immunohistochemically, 56% of AFHs were positive for EMA, 78% for desmin and 100% for CD99. Conclusions Molecular testing is diagnostic of variant AFHs displaying diverse histomorphological alterations in the architectural patterns, cytomorphology and extracellular matrix.

The clinicopathological significance of NAB2‐STAT6 gene fusions in 52 cases of intrathoracic solitary fibrous tumors

NAB2‐STAT6 gene fusion drives STAT6 nuclear expression and is the pathognomonic hallmark of solitary fibrous tumors (SFTs). However, no study has systematically analyzed the clinicopathological features, STAT6 immunoexpression status, or the fusion variants of NAB2‐STAT6 in intrathoracic SFTs. Fifty‐two intrathoracic SFTs were retrieved to appraise histopathology, assess STAT6 immunoexpression, and determine NAB2‐STAT6 fusion variants by RT‐PCR. Location‐relevant histologic mimics served as controls. Thirty‐one pleura‐based, 12 mediastinal/pericardial, and nine intrapulmonary lesions were histologically categorized into eight malignant, eight atypical, and 36 conventional or cellular SFTs, including two fat‐forming and two giant cell angiofibroma‐like SFTs. STAT6 distinctively decorated the tumoral nuclei in 51 (98%) SFTs. However, no nuclear staining was observed in the histological mimics. NAB2‐STAT6 fusion was detected in 34 SFTs. Twenty‐nine (85.3%) exhibited the major NAB2ex4‐STAT6ex2/3 variant and 5 (14.7%) the minor NAB2ex6‐STAT6ex16/17. NAB2ex4‐STAT6ex2 was significantly associated with older age (P = 0.01) and pleuropulmonary tumors (P = 0.025). After a median follow‐up of 33.9 (range, 0.3–174.6) months, adverse outcomes occurred in one atypical and five malignant SFTs, including two local relapses, one intrapulmonary metastasis, and three extrathoracic metastases. Inferior disease‐free survival was univariately associated with atypical/malignant histology (P = 0.001) and a mitosis >4/10 HPFs (P = 0.0012) but was unrelated to fusion variants. In conclusion, the majority of intrathoracic SFTs exhibited STAT6 nuclear staining, and NAB2ex4‐STAT6ex2/3 was the predominant fusion type. However, clinical aggressiveness is associated with atypical/malignant histology primarily contributed by increased mitosis but was unrelated to the NAB2‐STAT6 fusion variants.

AMACR Amplification in Myxofibrosarcomas: A Mechanism of Overexpression That Promotes Cell Proliferation with Therapeutic Relevance

Purpose: Myxofibrosarcomas frequently display arm-level gains on 5p. We characterized the pathogenetic and therapeutic relevance of the α-methylacyl coenzyme A racemase (AMACR) at 5p13.3. Experimental Design: AMACR mRNA expression in myxofibrosarcomas was analyzed using the public transcriptome and laser-microdissected sarcoma cells. We performed florescence in situ hybridization (FISH) and immunohistochemistry in independent samples for clinical correlates. In AMACR-overexpressing myxofibrosarcoma cells and xenografts, we elucidated the biologic function of AMACR using RNA interference and explored the therapeutic effect and mechanism of an AMACR inhibitor, ebselen oxide. Results: AMACR protein overexpression and gene amplification were significantly associated with each other (P < 0.001), with higher tumor grades (both P ≤ 0.002), and univariately with worse metastasis-free survival (MFS; both P < 0.0001) and disease-specific survival (DSS; P = 0.0002 for overexpression; P = 0.0062 for amplification). AMACR protein overexpression also independently portended adverse outcome (DSS, P = 0.007; MFS, P = 0.001). However, 39% of AMACR-overexpression cases did not show gene amplification, implying alternative regulatory mechanisms. In myxofibrosarcoma cell lines, stable AMACR knockdown suppressed cell proliferation, anchorage-independent growth, and expression of cyclin D1 and cyclin T2. These growth-promoting attributes of AMACR were corroborated in the AMACR-silenced xenograft model and AMACR-underexpressed myxofibrosarcomas, showing decreased labeling for cyclin D1, cyclin T2, and Ki-67. Compared with fibroblasts, AMACR-expressing myxofibrosarcoma cells were more susceptible to ebselen oxide, which not only decreased viable cells, promoted proteasome-mediated degradation of AMACR protein, and induced cellular apoptosis in vitro, but also dose-dependently suppressed xenografted tumor growth in vivo. Conclusions: Overexpressed AMACR in myxofibrosarcomas can be amplification-driven, associated with tumor aggressiveness, and may be relevant as a druggable target. Clin Cancer Res; 20(23); 6141–52. ©2014 AACR.

Clinicopathological and genetic heterogeneity of the head and neck solitary fibrous tumours: a comparative histological, immunohistochemical and molecular study of 36 cases

Solitary fibrous tumour (SFT) harbours recurrent inv12(q13q13)‐derived NAB2–STAT6 fusions, resulting in STAT6 nuclear expression. SFTs affecting the head and neck are rare, for which we reported their clinicopathological, immunohistochemical, and genetic features.

NAB2-STAT6 gene fusion and STAT6 immunoexpression in extrathoracic solitary fibrous tumors: the association between fusion variants and locations

Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm harboring NAB2‐STAT6 fusion, which drives STAT6 nuclear relocation. For extrathoracic SFTs, the clinical relevance of this molecular hallmark remains obscure. We assessed STAT6 immunoexpression for 61 extrathoracic SFTs exclusive of the meninges and head and neck, and 25 had analyzable RNAs to distinguish fusion variants by RT–PCR. The immunohistochemical and molecular findings were correlated with clincopathological features and disease‐free survival (DFS). Twenty‐eight males and 33 females had SFTs in the body cavities (n = 31), extremities (n = 17), and trunk (n = 13), categorized into 53 non‐malignant and 8 malignant tumors. The vast majority (n = 57, 93%) exhibited distinctive STAT6 nuclear expression, including malignant ones. The common fusion variants were NAB2ex6‐STAT6ex16/17 in 13 SFTs and NAB2ex4‐STAT6ex2 in 8, while miscellaneous variants were detected only in 4 SFTs in the limbs and trunk but not in any body cavity‐based cases (P = 0.026). The worse DFS was univariately associated with malignant histology (P = 0.04) but unrelated to tumor size, location, or fusion variant. Conclusively, extrathoracic SFTs mostly harbor NAB2ex6‐STAT6ex16/17, followed by NAB2ex4‐STAT6ex2. Miscellaneous variants are significantly rare in SFTs within the body cavities. The clinical aggressiveness of extrathoraic SFTs is associated with malignant histology but unrelated to the NAB2‐STAT6 fusion variants.

Increased expression of SKP2 is an independent predictor of locoregional recurrence in cervical cancer via promoting DNA-damage response after irradiation

Although radiation therapy was known to be effective to cervical cancer, loco-regional recurrences are frequently found in patients. We aimed to identify a molecular marker predicting the response of cervical cancer to radiotherapy. We included the patients (n = 149) with cervical cancer who had undergone radiotherapy from 2004 to 2006. Tumor samples were collected to examine the association between the expression of S-phase kinase-associated protein 2 (SKP2) and prognosis in cervical cancer. We found higher expression of SKP2 associated with recurrence (HRs: 2.52, p < 0.001), death (HRs: 2.01, p < 0.001) and higher locoregional recurrence rate (HRs: 3.76, p < 0.001). Cervical cancer cell lines with higher expression of SKP2 showed higher colony formation, cell survival rate and fewer DNA damages after irradiation. SKP2-C25, an inhibitor for SKP2 activity, dose-dependently decreased cell viability after irradiation and knockdown of SKP2 impaired DNA-damage response and sensitized the cervical cancer cells to irradiation. Our data showed the SKP2 represents a promising tool to identify patients with cervical cancer who have a higher risk of locoregional recurrence after radiotherapy. Targeting SKP2 may serve as a potential radiosensitizer for developing effective therapeutic strategies against cervical cancer.

HuR cytoplasmic expression is associated with increased cyclin A expression and inferior disease-free survival in patients with gastrointestinal stromal tumours (GISTs)

HuR is an RNA‐binding protein that post‐transcriptionally modulates the expression of various target genes involved in carcinogenesis, such as CCNA2, which encodes cyclin A. The aim of this study was to evaluate the significance of HuR expression and subcellular localization in a large cohort of gastrointestinal stromal tumours (GISTs).