Abstract 380: Systematic identification of novel functional tumor-specific mutations in receptor tyrosine kinases based on their pan-cancer mutational profiles in Japanese patients with cancer
Authors: Serizawa Masakuni , Nagashima Takeshi , Shimoda Yuji , Ohnami Shumpei , Ohnami Sumiko , Ohshima Keiichi , Mochizuki Tohru , Nakajima Takashi , Urakami Kenichi , Kusuhara Masatoshi , Yamaguchi Ken 
Published: July 2017

Abstract
Background: Recent accumulation of large amounts of cancer genome information has revealed the presence of tumor-specific mutations with unknown functions; characterization of these mutations should facilitate the identification of novel therapeutic targets. Some tumor-specific mutations in receptor tyrosine kinases (RTKs) act as oncogenic drivers in multiple cancer types. Here, we aimed to identify novel, functional, tumor-specific, single nucleotide variants (SNVs) in cancer-related RTKs based on pan-cancer mutational profiles in Japanese patients with cancer.
Methods: Surgically resected tissue and corresponding peripheral blood samples of 1,685 patients enrolled in Project HOPE (High-tech Omics-based Patient Evaluation), an ongoing prospective molecular profiling study at the Shizuoka Cancer Center, collected between January 2014 and December 2015, were subjected to whole-exome sequencing with an ion torrent proton platform. Newly detected tumor-specific SNVs that could represent functional mutations between the transmembrane and kinase domains of 35 cancer-related RTKs were subjected to serum response element (SRE)-reporter assay to assess effects on extracellular signal-regulated kinase (ERK) signaling relevant to cancer cell survival.
Results: We identified 201,422 nonsynonymous tumor-specific SNVs in 1,685 patients. Of these SNVs, 1,049 were observed in our focused 35 cancer-related RTKs. Approximately 45% of patients with lung squamous cell carcinoma, which was the most frequent cancer type, followed by lung adenocarcinoma (39%), harbored tumor-specific SNVs in RTKs. The relative frequencies of tumor-specific SNVs in RTKs in other tumor types were 32%, 31%, 29%, 28%, and 19% in liver cancer, colorectal cancer, gastric cancer, head and neck cancer, and breast cancer, respectively. After filtering out of SNVs registered in multiple cancer-related databases, such as COSMIC, dbSNP, and DoCM, to select putative novel tumor-specific SNVs, 22 SNVs were selected as novel tumor-specific SNVs with high potential as functional mutations through an additional selection process based on amino acid substitution patterns and multiple alignment of amino acid residues coupled with information regarding functional mutations. Among these SNVs, 13 had already been assessed using an SRE reporter assay. We identified two SNVs in NTRK1 and IGF1R that were involved in activation of the ERK pathway, indicating that these SNVs may be activating mutations. Moreover, inactivating mutations were also identified. Nine SNVs in FLT3, NTRK1, EPHA5, ERBB4, FGFR3, and KDR significantly reduced ERK activity.
Conclusions: A systematic evaluation of functionally unknown tumor-specific SNVs detected in cancer genome sequencing is necessary to expand the range of molecularly targeted cancer therapeutics.
Citation Format: Masakuni Serizawa, Takeshi Nagashima, Yuji Shimoda, Shumpei Ohnami, Sumiko Ohnami, Keiichi Ohshima, Tohru Mochizuki, Takashi Nakajima, Kenichi Urakami, Masatoshi Kusuhara, Ken Yamaguchi. Systematic identification of novel functional tumor-specific mutations in receptor tyrosine kinases based on their pan-cancer mutational profiles in Japanese patients with cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 380. doi:10.1158/1538-7445.AM2017-380