New RPS20 gene variant in colorectal cancer diagnosis: insight from a large series of patients.

Abstract

Germline pathogenic variants of the RPS20 (ribosomal protein S20) gene are suspected to be involved in the predisposition to familial colorectal cancer (CRC) with no DNA mismatch repair deficiency. RPS20 pathogenic variants are very rare with only five reported cases in the literature. We report in this work the retrospective germline analysis of RPS20 for 1035 consecutive patients with a personal and/or familial history suggestive of hereditary predisposition to CRC. Within this series, a pathogenic variant in known CRC genes was found in 15% of cases and we describe one RPS20 loss-of-function variant (NM_001146227.1:c.115_116del, p.(Leu39Aspfs*33)). This frameshift is the first reported de novo variant in CRC, it was identified in in a female patient diagnosed with rectal cancer at the age of 35, 11 adenomatous polyps in 5 years and breast cancer at the age of 43. RPS20 has an intriguing role in oncogenesis, acting as an oncogene or tumour suppressor depending on the context, and is also involved in Diamond-Blackfan anemia via gain of function or dominant negative variants. This is therefore a complex gene for genetic counselling and, given the rarity of RPS20 pathogenic variants, we emphasise the need to collect data to clarify the phenotypic spectrum of RPS20-associated cancers and thus improve management.