RT Journal Article SR Electronic T1 Blood functional assay for rapid clinical interpretation of germline TP53 variants JF Journal of Medical Genetics JO J Med Genet FD BMJ Publishing Group Ltd SP 796 OP 805 DO 10.1136/jmedgenet-2020-107059 VO 58 IS 12 A1 Raad, Sabine A1 Rolain, Marion A1 Coutant, Sophie A1 Derambure, Céline A1 Lanos, Raphael A1 Charbonnier, Françoise A1 Bou, Jacqueline A1 Bouvignies, Emilie A1 Lienard, Gwendoline A1 Vasseur, Stéphanie A1 Farrell, Michael A1 Ingster, Olivier A1 Baert Desurmont, Stéphanie A1 Kasper, Edwige A1 Bougeard, Gaëlle A1 Frébourg, Thierry A1 Tournier, Isabelle YR 2021 UL http://jmg.bmj.com/content/58/12/796.abstract AB Background The interpretation of germline TP53 variants is critical to ensure appropriate medical management of patients with cancer and follow-up of variant carriers. This interpretation remains complex and is becoming a growing challenge considering the exponential increase in TP53 tests. We developed a functional assay directly performed on patients’ blood.Methods Peripheral blood mononuclear cells were cultured, activated, exposed to doxorubicin and the p53-mediated transcriptional response was quantified using reverse transcription–multiplex ligation probe amplification and RT-QMPSF assays, including 10 p53 targets selected from transcriptome analysis, and two amplicons to measure p53 mRNA levels. We applied this blood functional assay to 77 patients addressed for TP53 analysis.Results In 51 wild-type TP53 individuals, the mean p53 functionality score was 12.7 (range 7.5–22.8). Among eight individuals harbouring likely pathogenic or pathogenic variants, the scores were reduced (mean 4.8, range 3.1–7.1), and p53 mRNA levels were reduced in patients harbouring truncating variants. We tested 14 rare unclassified variants (p.(Pro72His), p.(Gly105Asp), p.(Arg110His), p.(Phe134Leu), p.(Arg158Cys), p.(Pro191Arg), p.(Pro278Arg), p.(Arg283Cys), p.(Leu348Ser), p.(Asp352Tyr), p.(Gly108_Phe109delinsVal), p.(Asn131del), p.(Leu265del), c.-117G>T) and 12 yielded functionally abnormal scores. Remarkably, the assay revealed that the c.*1175A>C polymorphic variant within TP53 poly-adenylation site can impact p53 function with the same magnitude as a null variant, when present on both alleles, and may act as a modifying factor in pathogenic variant carriers.Conclusion This blood p53 assay should therefore be a useful tool for the rapid clinical classification of germline TP53 variants and detection of non-coding functional variants.All data relevant to the study are included in the article or uploaded as supplementary information. Deidentified participant data are available from thierry.frebourg@chu-rouen.fr.