Susan Chilton-MacNeill

Analysis of miRNA-gene expression-genomic profiles reveals complex mechanisms of microRNA deregulation in osteosarcoma

Osteosarcoma is an aggressive sarcoma of the bone characterized by a high level of genetic instability and recurrent DNA deletions and amplifications. This study assesses whether deregulation of microRNA (miRNA) expression is a post-transcriptional mechanism leading to gene expression changes in osteosarcoma. miRNA expression profiling was performed for 723 human miRNAs in 7 osteosarcoma tumors, and 38 miRNAs differentially expressed ≥10-fold (28 under- and 10 overexpressed) were identified. In most cases, observed changes in miRNA expression were DNA copy number-correlated. However, various mechanisms of alteration, including positional and/or epigenetic modifications, may have contributed to the expression change of 23 closely linked miRNAs in cytoband 14q32. To develop a comprehensive molecular genetic map of osteosarcoma, the miRNA profiles were integrated with previously published array comparative genomic hybridization DNA imbalance and mRNA gene expression profiles from a set of partially overlapping osteosarcoma tumor samples. Many of the predicted gene targets of differentially expressed miRNA are involved in intracellular signaling pathways important in osteosarcoma, including Notch, RAS/p21, MAPK, Wnt, and the Jun/FOS pathways. By integrating data on copy number variation with mRNA and miRNA expression profiles, we identified osteosarcoma-associated gene expression changes that are DNA copy number-correlated, DNA copy number-independent, mRNA-driven, and/or modulated by miRNA expression. These data collectively suggest that miRNAs provide a novel post-transcriptional mechanism for fine-tuning the expression of specific genes and pathways relevant to osteosarcoma. Thus, the miRNA identified in this manner may provide a starting point for experimentally modulating therapeutically relevant pathways in this tumor.

The CIC-DUX4 fusion transcript is present in a subgroup of pediatric primitive round cell sarcomas

Pediatric undifferentiated soft tissue sarcomas are a group of diagnostically challenging tumors. Recent studies have identified a subgroup of undifferentiated soft tissue sarcomas with primitive round to plump spindle cell morphology and a t(4;19)(q35;q13.1) translocation resulting in the expression of a CIC-DUX4 fusion transcript, including 2 tumors previously reported by our laboratory (Cancer Genet Cytogenet 2009;195:1). In the present study, reverse transcriptase polymerase chain reaction assays developed for both frozen and paraffin-based tissues were applied to a series of 19 pediatric undifferentiated soft tissue sarcomas using a combination of primer sets covering the CIC-DUX4 fusion transcript. Of the 19 undifferentiated soft tissue sarcomas, 16 had primitive round to plump spindle cell morphology, and 3 had pure spindle cell morphology. Three of the 16 undifferentiated soft tissue sarcomas with primitive round cell morphology were found to harbor the CIC-DUX4 fusion transcript by reverse transcriptase polymerase chain reaction. Automated DNA sequencing of the polymerase chain reaction products identified 2 distinct transcript variants. One CIC-DUX4-positive tumor showed membranous CD99 positivity, 2 showed focal S100 positivity, and 1 showed focal CD57 positivity. With the 2 previously reported cases, the total number of CIC-DUX4-positive primitive round cell sarcomas identified at our institution has been brought to 5 (28%) of 18. Given the consistent involvement of the CIC-DUX4 fusion in a subset of primitive round cell undifferentiated soft tissue sarcomas, these findings suggest a central role for the fusion transcript in such tumors. The current findings further define a novel genetic subset of pediatric primitive round cell sarcomas and provide an additional diagnostic tool for their characterization and diagnosis.

Identification of Interactive Networks of Gene Expression Associated with Osteosarcoma Oncogenesis by Integrated Molecular Profiling

Altered gene expression in tumors can be caused by copy number alterations to DNA or mutation affecting coding or regulatory regions of genes. However, epigenetic events may also influence gene expression. Malignant cells can show major disruptions in DNA methylation profiles, which are manifested as aberrant hypermethylation or as hypomethylation of gene promoters, as well as global genomic hypomethylation. In this study we performed integrative whole-genome analysis of DNA copy number, promoter methylation and gene expression using 10 osteosarcomas. We identified significant changes including: hypomethylation, gain, and overexpression of histone cluster 2 genes at chromosome 1q21.1-q21.3; loss of chromosome 8p21.2-p21.3 and underexpression of DOCK5 and TNFRSF10A/D genes; and amplification-related overexpression of RUNX2 at chromosome 6p12.3-p21.1. Amplification and overexpression of RUNX2 could disrupt G2/M cell cycle checkpoints, and downstream osteosarcoma-specific changes, such as failure of bone differentiation and genomic polyploidization. Failure of DOCK5-signaling, together with p53 and TNFRSF10A/D-related cell cycle and death pathways, may play a critical role in abrogating apoptosis. Our analyses show that the RUNX2 interactome may be constitutively activated in osteosarcoma, and that the downstream intracellular pathways are strongly associated with the regulation of osteoblast differentiation and control of cell cycle and apoptosis in osteosarcoma.

MYCN gene amplification in rhabdomyosarcoma

Background. Amplification of the MYCN oncogene, formerly known as N‐myc, has been seen in several malignant tumors, particularly neuroblastoma, where its association with a poor clinical outcome is the clearest example of a clinically relevant oncogene mutation in any human cancer.

Expression analysis of genes associated with human osteosarcoma tumors shows correlation of RUNX2 overexpression with poor response to chemotherapy

BackgroundHuman osteosarcoma is the most common pediatric bone tumor. There is limited understanding of the molecular mechanisms underlying osteosarcoma oncogenesis, and a lack of good diagnostic as well as prognostic clinical markers for this disease. Recent discoveries have highlighted a potential role of a number of genes including: RECQL4, DOCK5, SPP1, RUNX2, RB1, CDKN1A, P53, IBSP, LSAMP, MYC, TNFRSF1B, BMP2, HISTH2BE, FOS, CCNB1, and CDC5L.MethodsOur objective was to assess relative expression levels of these 16 genes as potential biomarkers of osteosarcoma oncogenesis and chemotherapy response in human tumors. We performed quantitative expression analysis in a panel of 22 human osteosarcoma tumors with differential response to chemotherapy, and 5 normal human osteoblasts.ResultsRECQL4, SPP1, RUNX2, and IBSP were significantly overexpressed, and DOCK5, CDKN1A, RB1, P53, and LSAMP showed significant loss of expression relative to normal osteoblasts. In addition to being overexpressed in osteosarcoma tumor samples relative to normal osteoblasts, RUNX2 was the only gene of the 16 to show significant overexpression in tumors that had a poor response to chemotherapy relative to good responders.ConclusionThese data underscore the loss of tumor suppressive pathways and activation of specific oncogenic mechanisms associated with osteosarcoma oncogenesis, while drawing attention to the role of RUNX2 expression as a potential biomarker of chemotherapy failure in osteosarcoma.

Effects of THBS3, SPARC and SPP1 expression on biological behavior and survival in patients with osteosarcoma.

BackgroundOsteosarcoma is a very aggressive tumor with a propensity to metastasize and invade surrounding tissue. Identification of the molecular determinants of invasion and metastatic potential may guide the development of a rational strategy for devising specific therapies that target the pathways leading to osteosarcoma.MethodsIn this study, we used pathway-focused low density expression cDNA arrays to screen for candidate genes related to tumor progression. Expression patterns of the selected genes were validated by real time PCR on osteosarcoma patient tumor samples and correlated with clinical and pathological data.ResultsTHBS3, SPARC and SPP1 were identified as genes differentially expressed in osteosarcoma. In particular, THBS3 was expressed at significantly high levels (p = 0.0001) in biopsies from patients with metastasis at diagnosis, which is a predictor of worse overall survival, event-free survival and relapse free survival at diagnosis. After chemotherapy, patients with tumors over-expressing THBS3 have worse relapse free survival. High SPARC expression was found in 51/55 (96.3%) osteosarcoma samples derived from 43 patients, and correlated with the worst event-free survival (p = 0.03) and relapse free survival (p = 0.07). Overexpression of SPP1 was found in 47 of 53 (89%) osteosarcomas correlating with better overall survival, event-free survival and relapse free survival at diagnosis.ConclusionIn this study three genes were identified with pattern of differential gene expression associated with a phenotypic role in metastasis and invasion. Interestingly all encode for proteins involved in extracellular remodeling suggesting potential roles in osteosarcoma progression. This is the first report on the THBS3 gene working as a stimulator of tumor progression. Higher levels of THBS3 maintain the capacity of angiogenesis. High levels of SPARC are not required for tumor progression but are necessary for tumor growth and maintenance. SPP1 is not necessary for tumor progression in osteosarcoma and may be associated with inflammatory response and bone remodeling, functioning as a good biomarker.

Clinical and molecular characteristics of pediatric gastrointestinal stromal tumors (GISTs).

To describe the clinical characteristics, molecular features, treatment, and outcome of six pediatric patients with gastrointestinal stromal tumors (GISTs).

Tissue-specific expression of SV40 in tumors associated with the Li–Fraumeni syndrome

Inactivation of wild-type p53 tumor suppressor function is the primary mechanism of tumor initiation in Li–Fraumeni syndrome (LFS) individuals with germline p53 mutations. Tumors derived from LFS patients frequently retain the normal p53 allele, suggesting that alternative mechanisms in addition to gene deletion must be involved in inactivating wild-type p53 protein. DNA tumor viruses, such as SV40, target p53 for inactivation through the action of viral oncoproteins. We studied the probands from two unrelated LFS families, each of whom presented with multiple malignant neoplasms. Patient 1 developed an embryonal rhabdomyosarcoma (RMS) and a choroid plexus carcinoma (CPC), while patient 2 developed a CPC and subsequently presented with both an osteosarcoma (OS) and renal cell carcinoma (RCC). We utilized DNA sequence analysis and immunohistochemistry to determine p53 gene status in the germline and tumors, as well as evidence for SV40 T-antigen oncoprotein expression. Each patient harbored a heterozygous germline p53 mutation at codons 175 and 273, respectively. In patient 1, the normal p53 gene was lost while the mutant p53 allele was reduced to homozygosity in the RMS. Both normal and mutant genes were maintained in the CPC. In patient 2, normal and mutant p53 alleles were retained in both the CPC and RCC. Both specific PCR and immunostaining detected SV40 T-antigen in both CPCs and the RCC. In addition to chromosomal alterations, epigenetic mechanisms may disrupt p53 function during tumorigenesis. In two LFS patients, we found SV40 DNA sequences and viral T-antigen expression that could account for inactivation of the normal p53 protein. Inactivation of p53 or other tumor suppressors by viral proteins may contribute to tumor formation in specific tissues of genetically susceptible individuals.

Detailed cytogenetic and array analysis of pediatric primitive sarcomas reveals a recurrent CIC–DUX4 fusion gene event

Pediatric undifferentiated soft tissue sarcomas (USTS) are a diagnostically challenging group of neoplasms. Recently, a subcategory of USTS with primitive round cell morphology and a t(4;19)(q35;q13) rearrangement has been defined. The present study applied high-throughput array comparative genomic hybridization together with spectral karyotyping, four-color fluorescence in situ hybridization (FISH), and reverse transcriptase-polymerase chain reaction (RT-PCR) to a series of three pediatric USTS. Two of these had primitive round cell morphology with CD99 positivity; the third had a spindled and myxoid appearance. By genomic analyses, both primitive round cell sarcomas had t(4;19)(q35;q13) [corrected] rearrangements in addition to several imbalances throughout the genome. Four-color FISH and in silico analyses of the breakpoint region at 19q13 identified the potential involvement of the candidate oncogene CIC. By RT-PCR, fusion transcripts involving CIC (19q13) and DUX4 (4q35) were confirmed to be present in both primitive round cell sarcomas, further defining the breakpoints seen by genomic analysis. Described here are two tumors belonging to the rare category of CIC-DUX4-positive primitive sarcomas, with detailed cytogenetic and genomic information regarding this novel subclass of pediatric malignancy. Molecular and cytogenetic techniques for the detection of the CIC-DUX4 fusion gene are described, to aid in recognition and diagnosis.

A new molecular variant of desmoplastic small round cell tumor: significance of WT1 immunostaining in this entity

Desmoplastic small round cell tumor is a rare aggressive neoplasm, often presenting in young adult males. Although the classic features are well described, considerable clinical, pathologic, and immunohistochemical variation has been reported. The defining feature is a reciprocal translocation, t(11;22)(p13;q12), which fuses EWS on chromosome 22 to WT1 on chromosome 11. WT1 immunohistochemistry is reportedly useful in distinguishing desmoplastic small round cell tumor from other tumors. Herein, we describe a desmoplastic small round cell tumor of soft tissue with an unusual pattern of WT1 expression associated with a novel variant EWS-WT1 fusion transcript. We compare WT1 expression pattern with 5 intra-abdominal desmoplastic small round cell tumors and review the literature on WT1 expression and variant transcripts in desmoplastic small round cell tumor. Immunohistochemistry for the N- and C-terminals of WT1 was performed in 6 desmoplastic small round cell tumors. The EWS-WT1 fusion transcript was confirmed in all cases by reverse transcriptase polymerase chain reaction. Sequencing of fusion transcripts and reverse transcriptase polymerase chain reaction for wild-type WT1 was performed in 4 cases. The soft tissue desmoplastic small round cell tumor was negative for the WT1 C-terminal and showed nuclear staining with the N-terminal antibody. This case demonstrated 2 novel fusion transcripts, both lacking WT1 exons 9 and 10 and one containing additional exons of WT1 (exons 3-7). This tumor also strongly expressed full-length WT1. Five intra-abdominal desmoplastic small round cell tumors showed nuclear staining for WT1 C-terminal, but not for the N-terminal antibody. Although WT1 immunohistochemistry reflects the EWS-WT1 fusion transcript in most desmoplastic small round cell tumors, some cases express full-length WT1 or have variant transcripts, resulting in atypical staining patterns. Hence, interpretation of WT1 immunostaining requires knowledge of antibody target epitopes and correlation with clinical, morphological, and molecular genetic findings for establishing a diagnosis of desmoplastic small round cell tumor.