Subset of retinoblastoma tumours is associated with <i>BRCA1/2</i> mutations.

Abstract

We investigated the potential association between pathogenic BRCA1/2 variants and retinoblastoma pathogenicity. In this single-centre, retrospective case series, we performed hereditary cancer panel tests using blood samples for patients with retinoblastoma diagnosed between March 2017 and October 2021. Bioinformatics prediction tools were then used to conduct in silico pathogenicity assessments for patients with <i>BRCA1/2</i> family variants, in addition to the American College of Medical Genetics and Genomics (ACMG) variant classification. One patient with a germline <i>BRCA1</i> variant was analysed with whole-genome sequencing (WGS), mutational signature analysis and methylation analysis for <i>RB1</i> and <i>BRCA</i> using the patient's tumour and blood samples. Of 30 retinoblastoma patients who underwent panel sequencing, six (20%) were found to carry germline variants in the BRCA1/2 or BRIP1 genes. Among these six patients, two had pathogenic or likely pathogenic variants as per the ACMG variant classification. Additionally, three patients showed potential pathogenic BRCA1/2 family variants through further analysis with alternative bioinformatics prediction tools. In the WGS analysis of a tumour from a patient with a germline likely pathogenic <i>BRCA1</i> variant in one allele, we observed the loss of one RB1 allele due to a large deletion. No somatic non-synonymous mutations or frameshift indels were detected in the RB1 locus of the remaining allele. This sample also showed <i>BRCA1</i> gene promoter hypermethylation in the tumour, indicating additional epigenetic silencing. This study demonstrated that some retinoblastoma patients harboured germline <i>BRCA1/2</i> family variants, which may be associated with the development of retinoblastoma along with <i>RB1</i> mutations.