A novel, potentially targetable TMEM106B-BRAF fusion in pleomorphic xanthoastrocytoma.

Susan J Hsiao, Matthias A Karajannis, Daniel Diolaiti, Mahesh M Mansukhani, Julia Glade Bender, Andrew L Kung, James H Garvin

Cold Spring Harbor molecular case studies 2017 Mar

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Pleomorphic xanthoastrocytoma (PXA) is a World Health Organization (WHO) Grade II glioma occurring primarily in children and young adults. Most PXAs harbor the known activating mutation BRAF V600E. We report a case of locally recurrent PXA with anaplastic features in a 10-yr-old female. The PXA was negative by immunohistochemical (IHC) staining for BRAF V600E mutation. Whole-exome and transcriptome sequencing of the tumor confirmed the absence of BRAF V600E, but identified copy-number alterations (including loss of the tumor suppressor CDKN2A) and a novel TMEM106B-BRAF fusion. Based on similar BRAF fusion proteins, this novel fusion is predicted to result in activation of BRAF signaling. Demonstration of positive IHC for phospho-ERK1/2 and phospho-MEK1/2 supported this prediction, and implicated MEK inhibitors as a potential therapeutic strategy.

Citation

Susan J Hsiao, Matthias A Karajannis, Daniel Diolaiti, Mahesh M Mansukhani, Julia Glade Bender, Andrew L Kung, James H Garvin. A novel, potentially targetable TMEM106B-BRAF fusion in pleomorphic xanthoastrocytoma. Cold Spring Harbor molecular case studies. 2017 Mar;3(2):a001396