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Author: search.filters.author.Chan, Jennifer A.

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    Expression profiles of 151 pediatric low-grade gliomas reveal molecular differences associated with location and histological subtype
    (OXFORD UNIV PRESS INC, 2015-01-01) Bergthold, Guillaume; Bandopadhayay, Pratiti; Hoshida, Yujin; Ramkissoon, Shakti; Ramkissoon, Lori; Rich, Benjamin; Maire, Cecile L.; Paolella, Brenton R.; Schumacher, Steven E.; Tabak, Barbara; Ferrer-Luna, Ruben; Ozek, Memet; Sav, Aydin; Santagata, Sandro; Wen, Patrick Yung; Goumnerova, Liliana C.; Ligon, Azra H.; Stiles, Charles; Segal, Rosalind; Golub, Todd; Grill, Jacques; Ligon, Keith L.; Chan, Jennifer A.; Kieran, Mark W.; Beroukhim, Rameen
    Pediatric low-grade gliomas (PLGGs), the most frequent pediatric brain tumor, comprise a heterogeneous group of diseases. Recent genomic analyses suggest that these tumors are mostly driven by mitogene-activated protein kinase (MAPK) pathway alterations. However, little is known about the molecular characteristics inherent to their clinical and histological heterogeneity. We performed gene expression profiling on 151 paraffin-embedded PLGGs from different locations, ages, and histologies. Using unsupervised and supervised analyses, we compared molecular features with age, location, histology, and BRAF genomic status. We compared molecular differences with normal pediatric brain expression profiles to observe whether those patterns were mirrored in normal brain. Unsupervised clustering distinguished 3 molecular groups that correlated with location in the brain and histological subtype. ``Not otherwise specified{''} (NOS) tumors did not constitute a unified class. Supratentorial pilocytic astrocytomas (PAs) were significantly enriched with genes involved in pathways related to inflammatory activity compared with infratentorial tumors. Differences based on tumor location were not mirrored in location-dependent differences in expression within normal brain tissue. We identified significant differences between supratentorial PAs and diffuse astrocytomas as well as between supratentorial PAs and dysembryoplastic neuroepithelial tumors but not between supratentorial PAs and gangliogliomas. Similar expression patterns were observed between childhood and adolescent PAs. We identified differences between BRAF-duplicated and V600E-mutated tumors but not between primary and recurrent PLGGs. Expression profiling of PLGGs reveals significant differences associated with tumor location, histology, and BRAF genomic status. Supratentorial PAs, in particular, are enriched in inflammatory pathways that appear to be tumor-related.
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    Detection of KIAA1549-BRAF Fusion Transcripts in Formalin-Fixed Paraffin-Embedded Pediatric Low-Grade Gliomas
    (ELSEVIER SCIENCE INC, 2011-01-01) Tian, Yongji; Rich, Benjamin E.; Vena, Natalie; Craig, Justin M.; MacConaill, Laura E.; Rajaram, Veena; Goldman, Stewart; Taha, Hala; Mahmoud, Madeha; Ozek, Memet; Sav, Aydin; Longtine, Janina A.; Lindeman, Neal I.; Garraway, Levi A.; Ligon, Azra H.; Stiles, Charles D.; Santagata, Sandra; Chan, Jennifer A.; Kieran, Mark W.; Ligon, Keith L.
    Alterations of BRAF are the most common known genetic aberrations in pediatric gliomas. They frequently are found in pilocytic astrocytomas, where genomic duplications involving BRAF and the poorly characterized gene KIAA1549 create fusion proteins with constitutive B-Raf kinase activity. BRAF V600E point mutations are less common and generally occur in nonpilocytic tumors. The development of BRAF inhibitors as drugs has created an urgent need for robust clinical assays to identify activating lesions in BRAF. KIAA1549-BRAF fusion transcripts have been detected in frozen tissue, however, methods for FFPE tissue have not been reported. We developed a panel of FFPE-compatible quantitative RT-PCR assays for the most common KIAA1549-BRAF fusion transcripts. Application of these assays to a collection of 51 low-grade pediatric gliomas showed 97\% sensitivity and 91\% specificity compared with fluorescence in situ hybridization or array comparative genomic hybridization. In parallel, we assayed samples for the presence of the BRAF V600E mutation by PCR pyrosequencing. The data further support previous observations that these two alterations of the BRAF, KIAA1549 fusions and V600E point mutations, are associated primarily with pilocytic astrocytomas and nonpilocytic gliomas, respectively. These results show that fusion transcripts and mutations can be detected reliably in standard FFPE specimens and may be useful for incorporation into future studies of pediatric gliomas in basic science or clinical trials. (J Mal Diagn 2011, 13:669-677