Abstract 3884: Genome-wide analysis of somatic mutations shared by co-occurring ovarian high-grade serous carcinomas and serous tubal intraepithelial carcinomas
Authors: Song Yan , Ardin Maude , Cahais Vincent , Carreira Christine , Holmila Reetta , Villar Stephanie , Castells Xavier , Vallee Maxime , Heguy Adriana , Bringuier Pierre-Paul , Guo Qin , Zhang Xun , Zavadil Jiri 
Published: August 2015

Abstract
INTRODUCTION Serous tubal intra-epithelial carcinoma (STIC) in the fallopian tube has been proposed as a putative precursor of ovarian high-grade serous carcinoma (HGSC)[1,2]. Association of STIC and HGSCs is seen in ∼50% of cases, and in ∼15% of women undergoing prophylactic removal of fallopian tubes. Clonal STIC-HGSC relationship is suggested by shared TP53 mutations and overexpression[3]. To further investigate the relationship, we applied genome-wide sequencing of same-patient STIC, HGSC and normal tube DNAs isolated from FFPE tumor specimens of 4 ovarian cancer patients. Here we report extended patterns of somatic alterations shared between STIC and HGSC and identify the affected homeostatic pathways.
METHODS We established the STIC-HGSC co-occurrence by pathological evaluation and immunohistochemistry for TP53 and MKI67 positivity. Overlapping TP53 mutations were determined by Sanger sequencing. DNA was isolated from STIC, HGSC and normal tissue areas of paraffin sections, with laser-capture microdissection and whole-genome DNA amplification employed for STICs due to the small cellular content. 250 ng of DNA was converted to sequencing libraries (Kapa Biosystems kit) and exome enrichment done by SeqCap EZ System, Nimblegen, Roche. Exomes were sequenced on Illumina HiSeq2500 at ∼100x coverage in 100-bp paired-end run. Somatic mutations were analyzed by MuTect and FreeBayes callers to determine unique as well as overlapping STIC and HGSC alterations.
RESULTS Deep sequencing expanded the number of shared STIC-HGSC mutations to 20-55 per patient. ETV5, LPAR4, MTOR, and PAK3 genes harbored recurrent mutations in HGSCs, and the shared STIC-HGSC mutations involved genes acting in the pathways of response to stress, regulation of apoptosis, autophagy, RAS and small GTPase-mediated signaling, and actin cytoskeleton organization (e.g. MTOR, NF1, BECN1, ARHGEF18, RASA1, PREX2, TTN). Our findings were corroborated for 80 STIC-HGSC-shared gene mutants by the cBioportal/The Cancer Genome Atlas data on ovarian serous carcinoma.
CONCLUSIONS The broad patterns of somatic alterations shared by STIC and HGSC document a clonal relationship of these neoplastic lesions and possible origins of ovarian carcinomas in the tubal epithelium. We propose that our genome-wide strategy, once reproduced in a higher patient number, may facilitate future development of approaches to HGSC screening, treatment and prevention.
ACKNOWLEDGMENTS IARC Regular Budget; IARC Postdoctoral Fellowship Program (supported by the European Commission FP7 Marie Curie Actions COFUND). NYU Genome Technology Center (supported in part by NIH/NCI P30CA016087). We thank Dr E. Kuhn for assistance with pathology evaluations.
REFERENCES
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2. Kurman RJ. Ann Oncol. 2013 Dec;24 Suppl 10:x16-21.
3. Kuhn E, et al. J Pathol. 2012 Feb;226(3):421-6.
Citation Format: Yan Song, Maude Ardin, Vincent Cahais, Christine Carreira, Reetta Holmila, Stephanie Villar, Xavier Castells, Maxime Vallee, Adriana Heguy, Pierre-Paul Bringuier, Qin Guo, Xun Zhang, Jiri Zavadil. Genome-wide analysis of somatic mutations shared by co-occurring ovarian high-grade serous carcinomas and serous tubal intraepithelial carcinomas. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3884. doi:10.1158/1538-7445.AM2015-3884