The Selection Of Tp53 Sub-Clonal Variants Over Time Identifies Mm Patients With Adverse Clinical Outcome

Introduction In most human cancer p53 impairment is a driver event, which confers a survival advantage to affected cells. In Multiple Myeloma (MM), the role of p53 clonal aberrations (mainly 17p del) is well recognised, whereas the prognostic relevance of TP53 mutations is less clear, due to the very limited frequency of clonal lesions. Here we aim at characterizing by ultra-deep sequencing (UDS) the TP53 mutational state in both newly diagnosed and relapsed MM pts, to assess the prognostic role and evolution over time of small TP53 mutated sub-clones. Pts and methods A cohort of 99 newly diagnosed MM pts treated up-front with bortezomib-based regimens and ASCT was included in this study. In 29 cases, samples were collected also at relapse(s). DNA was obtained from CD138+ highly purified plasma cells and SNPs array profiled (Affymetrix). TP53 gene was analysed by amplicon-targeted UDS approach (GSJ, 454 Roche). A specific bioinformatics pipeline was set up to discriminate between low frequency TP53 variants and sequencing errors. Results With a median coverage of 1386X, 129 correctly called TP53 variants were detected. Most newly diagnosed MM pts (55%) carried at least one TP53 sub-clonal variant (on average 1.08 variants per pts).. According to TP53 sub-clonal mutational load, pts were stratified in two sub-groups, including 28 pts with ≥2 (high load) and 71 with Conclusion The TP53 UDS analysis in newly diagnosed MM highlighted for the first time a high rate of variants, recurring with a wide range of frequencies among samples. The increased number of TP53 sub-clonal variants per pts in samples collected at relapse(s), compared to that seen at the onset of the disease, suggests a sub-clonal dynamics over time. Acknowledgements: Roche Diagnostics, FP7 NGS-PTL project, Fondazione Berlucchi. Citation Format: Marina Martello, Daniel Remondini, Enrica Borsi, Barbara Santacroce, Mauro Procacci, Angela Flores Dico, Annalisa Pezzi, Elena Zamagni, Paola Tacchetti, Lucia Pantani, Giulia Marzocchi, Beatrice Anna Zannetti, Katia Mancuso, Serena Rocchi, Giovanni Martinelli, Michele Cavo, Carolina Terragna. The selection of TP53 sub-clonal variants over time identifies MM patients with adverse clinical outcome. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5022.