Andrea O'Hara

Tumor suppressor microRNAs are underrepresented in primary effusion lymphoma and Kaposi sarcoma

The presence of tumor-specific microRNAs reflects tissue of origin and tumor stage. We show that the absence of miRNAs likewise can be used to determine tumor origin (miR-155) and proliferation state because tumor suppressor miRNAs (miR-222/221, let-7 family) were significantly down-regulated in primary effusion lymphoma (PEL) and in Kaposi sarcoma (KS), an endothelial cell tumor. PEL and KS are associated with KS-associated herpesvirus infection. We identified 15 virally regulated miRNAs in latently infected, nontumorigenic endothelial cells. MiR-143/145 were elevated only in KS tumors, not virally infected endothelial cells. Thus, they represent tumor-specific, rather than virus-specific, miRNAs. Because many tumor suppressor proteins are wild-type in KS and PEL, down-regulation of multiple tumor suppressor miRNAs provides a novel, alternative mechanism of transformation.

Pre-micro rna signatures delineate stages of endothelial cell transformation in kaposi sarcoma

MicroRNAs (miRNA) have emerged as key regulators of cell lineage differentiation and cancer. We used precursor miRNA profiling by a novel real-time QPCR method (i) to define progressive stages of endothelial cell transformation cumulating in Kaposi sarcoma (KS) and (ii) to identify specific miRNAs that serve as biomarkers for tumor progression. We were able to compare primary patient biopsies to well-established culture and mouse tumor models. Loss of mir-221 and gain of mir-15 expression demarked the transition from merely immortalized to fully tumorigenic endothelial cells. Mir-140 and Kaposi sarcoma–associated herpesvirus viral miRNAs increased linearly with the degree of transformation. Mir-24 emerged as a biomarker specific for KS.

Abstract C33: Integrated analysis of sequence variations and copy number in TCGA colon adenocarcinoma data

The Cancer Genome Atlas (TCGA) data is available via the TCGA portal and includes copy number data and whole exome sequencing data. Nexus Copy Number 7 was used to evaluate level-1 approved SNP array data from the colon adenocarcinoma (COAD) data set. All samples were subjected to match-paired analysis to evaluate somatic copy number variation. Samples were subjected to extensive pre-processing, including systematic G/C wave correction, ploidy correction, gender correction and quality control. Corresponding level-3 somatic mutation data was used for an integrated analysis of copy number and sequence variation with the COAD data set. Comprehensive copy number analysis identified frequent (>35%) copy number gains of chr7, chr8q, chr13 and chr20, and losses of chr8p, chr17p, and chr18. GISTIC analysis further identified statistically significant focal changes which included loss of FHIT on chr3. Genes KRAS and BRAF were among the most frequently mutated genes. Integrated analysis identified several regions of copy number change that significantly co-occurred with BRAF mutation. Copy number profiles varied significantly between hypermutable and non-hypermutable samples. Potential chromothriptic events were also observed within the COAD dataset. An approach that can integrate structural and sequence variation among samples will be presented. Citation Format: Andrea O9Hara, Raja Keshavan, Louis Culot, Soheil Shams. Integrated analysis of sequence variations and copy number in TCGA colon adenocarcinoma data. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr C33.

The Effective Use of the Cancer Genome Atlas (TCGA) Data by the Cancer Cytogenetic Community

Molecular cytogenetic alterations, specifically monosomy 3, are strongly correlated with metastases and death in uveal melanoma (UVM). Although FISH can be used for the identification of monosomy 3, a subset of UVM exhibit only partial loss of chromosome 3 potentially missed with chromosome enumeration probes. Moreover, often limited material available can compromise detection of additional alterations with potential clinical relevance. Microarray analysis is an alternative method for the analysis of such specimens affording whole genome interrogation. In the current study we performed microarray to detect genomic changes in DNA from FFPET and FZT UVM samples (clinical trial NCT00952939). Of the available cases, 23.5% yielded DNA of sufficient quantity and quality to obtain interpretable microarray results, representing 28 patients. All but one case demonstrated significant abnormalities. Gains of 8q, consistent with an apparent i(8)(q10) karyotype, were the most common finding, seen in 21 patients. Monosomy 3 was detected by microarray in 15 cases. A single case showed partial loss of 3 (3q11.2q25.31), the only clinically significant abnormality detected in that case. All cases lacking chromosome 3 abnormalities showed a copy gain of 6p sharing a small 28.18 Mb region of overlap at 6p25.2p21.33. Additional findings included TERT and NEDD9 amplifications, and CDKN2A/B and LUM gene deletions. SNP analysis revealed three cases with unique regions of copy neutral LOH involving 5p15.33q35.3, 15q11.2q21.1 and one case with whole chromosome LOH for chromosomes 3, 4 and 6. The latter was detected in a FZT specimen, while the paired FFPET sample lacked evidence of LOH and showed monosomy 3, trisomy 4 and whole arm gains and losses of 6p and 6q, respectively, suggesting the presence of tumor heterogeneity. Microarray analysis has identified new recurrent abnormalities associated with UVM with potential relevance to UVM biology, diagnosis and prognosis. Conflict of Interest: Roger Schultz is an employee of Perkin Elmer.

Profiling of cellular and viral microRNAs in Kaposi sarcoma and viral-associated lymphoma

MicroRNAs are regulated by gene alteration at the DNA level, transcriptional regulation, and mature miRNA processing via Dicer. Thus far, few studies have simultaneously assessed all three levels of regulation. Using real-time quantitative polymerase chain reaction (QPCR)-based arrays, changes in gene copy number, pre-miRNA and mature miRNA levels for a large set of primary effusion lymphomas (PELs) and primary Kaposi Sarcoma biopsies (KS) has been determined; this includes miRNA gene alterations and concordant changes in pre-miRNA and mature miRNA expression levels. The real-time QPCR based approach confirmed many of the KSHV viral and cellular miRNAs previously cloned from PEL. However, array-based profiling also uncovered many novel PEL-specific miRNAs, since cloning-based approaches are not always saturating. The miRNA expression pattern for neither viral nor cellular miRNAs has hitherto been determined for KS. Furthermore, comprehensive SNP analysis of the viral miRNAs has been profiled to further examine the effects of sequence and processing. This defines the miRNA signature of PEL, KS, KSHV-infected cancers and experimental models. It shows that the transcriptional regulation of pre-miRNA as well as mature miRNA levels contribute non-redundant information that can be used in the classification of human tumors.