Abstract 4719: Novel germline variants in hereditary renal cell carcinoma genes elucidated by whole genome sequencing
Authors: Cathy D. Vocke, Christopher J. Ricketts, Daniel R. Crooks, Martin Lang, Laura S. Schmidt, Mayank Tandon, Bao Tran, Christina Fitzsimmons, Pedro J. Batista, Mark W. Ball, W. Marston Linehan
Journal: Cancer Research (2020)

Abstract Whole genome sequencing (WGS) may be utilized to reveal novel germline variants in renal cell carcinoma (RCC) syndrome genes that cannot be characterized by conventional methods. Patients who present with clinical manifestations of von Hippel-Lindau (VHL), Hereditary Leiomyomatosis Renal Cell Carcinoma (HLRCC), or Hereditary Papillary Renal Carcinoma (HPRC) are routinely evaluated for germline mutations in the VHL, FH (fumarate hydratase), or MET gene, respectively, by genetic testing. Rarely, either a negative result or an unusual finding is reported. For one patient who exhibited multiple clinical manifestations of VHL in the kidneys, pancreas, cerebellum and epididymis but no germline mutation, karyotype analysis revealed that the patient possessed a germline translocation between chromosomes 1 and 3. Two patients with family history of papillary type 1 RCC but no point mutation in MET were determined to have novel germline duplications in all or part of the MET gene. Finally, seven patients with clinical manifestations of HLRCC including cutaneous and uterine leiomyomas and/or family history of RCC, had negative genetic testing. Paired-end WGS was performed on the DNA derived from peripheral blood leucocytes from these patients. WGS for the patient with VHL manifestations revealed that the breakpoint between chromosomes 1 and 3 falls directly within intron 2 of the VHL gene, leading to a novel disruption of VHL in the germline. Sanger sequencing was performed to determine the exact breakpoints on both chromosomes. We believe this to be the first report of a germline chromosomal translocation resulting in VHL syndrome Likewise, both MET duplications were sequenced across the exact breakpoints, revealing a tandem duplication of 601,339 bp including the entire MET gene in one patient, and a tandem duplication of 101,464 bp including exons 5 through 21 in the other patient. As MET is an oncogene, we theorize that these duplications result in increased expression levels. Finally, 4 of 7 patients with clinical manifestations of HLRCC, including a family of three affected members, were found to possess a novel intronic A to G variant in intron 9 of FH that has not been reported in any human genome databases. This variant introduces a cryptic splice acceptor site and thus adds an extra exon of 57 bp to the transcript, resulting in a premature stop codon and thus a truncated protein of 474 amino acids. A cutaneous leiomyoma from one patient demonstrates loss of heterozygosity, substantiating loss of FH function. In conclusion, germline whole genome sequencing should be considered for patients who exhibit clinical manifestations of a hereditary RCC disease syndrome but for whom no sequence variants are detected by standard genetic testing, in order to improve the detection rate of novel germline variants. Citation Format: Cathy D. Vocke, Christopher J. Ricketts, Daniel R. Crooks, Martin Lang, Laura S. Schmidt, Mayank Tandon, Bao Tran, Christina Fitzsimmons, Pedro J. Batista, Mark W. Ball, W. Marston Linehan. Novel germline variants in hereditary renal cell carcinoma genes elucidated by whole genome sequencing [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4719.