Abstract 3898: Exome analysis of an exceptional responder uncovers an activating GNAS mutation that may confer sensitivity to cytotoxic chemotherapy
Authors: Jeff P. Bruce, Arnavaz Danesh, Neil Winegarden, Patrick Yau, Carl Virtanen, Suzanne Kamel-Reid, Michael H. Roehrl, Anthony M. Joshua, Jennifer Knox, Trevor J. Pugh
Journal: Cancer Research (2015)

Abstract Introduction: The molecular characterization of patients who exhibit a unique response to treatments that are not effective in most patients, so called “exceptional responders”, can shed light on the biological underpinnings of the response and provide rationale for selection of future patients for the same treatment. Here we present the genomic characterization of a 22-year-old female patient who presented with an unclassifiable kidney cancer and diffuse bilateral lung metastases. The primary tumour was resected and platinum plus gemcitabine therapy achieved a complete resolution of the lung metastases. Approximately 2 years later the patient again developed bilateral lung metastases and an additional course of platinum plus gemcitabine once again achieved a complete radiological response. To better understand the genomic contributors to this dramatic and recurrent response, we performed whole exome sequence analysis of the diagnostic formalin-fixed paraffin-embedded tumor tissue and a matched blood sample. Methods and Results: The patient provided informed consent and was profiled through the Princess Margaret Cancer Centre Genomic Investigation of Unusual and Spectacular responders (GENIUS) program. From tumour and matched blood specimens, we isolated coding and untranslated regions followed by deep sequencing (∼250X median coverage) on an Illumina HiSeq 2000. Copy-number analysis using VarScan2 revealed 23 somatic copy-number alterations (12 gains, 11 losses) including loss of 9p and gains of 3q and 8q, consistent with reports on clear cell renal cell carcinomas. Mutational analysis using muTect found 60 somatic, coding mutations, consistent with mutation rates seen in other kidney cancers. Of these variants, only one was a previously reported hotspot mutation, GNAS p.R201H (NM_000516, also known as p.R844H on transcript NM_080425). This mutation causes constitutive activation of the G-protein complex and activates adenylate cyclase to produce cyclic-AMP (cAMP) that can activate oncogenic pathways. However, excess cellular cAMP levels have also been found to promote apoptosis. Furthermore, a germline SNP in GNAS (rs7121), thought to increase GNAS transcript stability, is associated with improved response to gemcitabine plus platinum in non-small-cell lung cancer patients. The current patient was found to be heterozygous for the rs7121 SNP, which may compound the chemosensitivity phenotype observed. Conclusion: We have identified a p.R201H mutation in GNAS that may both drive tumour progression and confer exceptional chemo-sensitivity in a patient with an unclassified kidney cancer. Further analysis is underway in vitro to validate the hypothesis that this mutation confers sensitivity to chemotherapy. Confirmation of this hypothesis may suggest that chemotherapy could be considered for patients harbouring this mutation. Citation Format: Jeff P. Bruce, Arnavaz Danesh, Neil Winegarden, Patrick Yau, Carl Virtanen, Suzanne Kamel-Reid, Michael H. Roehrl, Anthony M. Joshua, Jennifer Knox, Trevor J. Pugh. Exome analysis of an exceptional responder uncovers an activating GNAS mutation that may confer sensitivity to cytotoxic chemotherapy. [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 3898. doi:10.1158/1538-7445.AM2015-3898