Abstract 855: Analysis of a novel variant of HER2 detected by clinical sequencing in cancer of unknown primary

Abstract

Abstract A patient with cancer of unknown primary underwent an NGS-based multiplex gene assays (OncoPrime). As a result, a novel variant of HER2 (E401G) which is a missense alteration located in the extracellular domain of the HER2 protein was detected. This alteration has not been reported (COSMIC, Nov 2018) and its effect on protein function is unknown. Sanger sequencing using genomic DNA from peripheral blood sample showed that the variant was a somatic variant. HER2 E401G variant was confirmed by Sanger sequencing using genomic DNA extracted from the formalin-fixed paraffin-enbedded tumor tissues. In spite of somatic variant, the variant allele frequency was relatively high (55.8%). This result suggested the amplification of HER2 gene, FISH analysis confirmed the copy number gain of HER2 gene (21 copies). The prediction tools in silico (SIFT, PolyPhen-2 and PROVEAN) suggested pathogenicity of the variant, so we are now performing the functional analysis of the mutant HER2 protein. Many variants of unknown significance have been identified through clinical sequencing, establishing a database of integrated information of variant is essential to implement precision medicine of oncology. This study was approved by the Ethics Committee and the patient provided written informed consent for the use of genomic and clinical data for research purposes. Citation Format: Yohei Harada, Tomomi Kashiwada, Akemi Sato, Tomonori Abe, Chiho nakashima, Eisaburo Sueoka, Shinya Kimura, Naoko Sueoka-Aragane. Analysis of a novel variant of HER2 detected by clinical sequencing in cancer of unknown primary [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 855.