Li-Fraumeni Syndrome (LFS) is a rare autosomal dominant familial cancer syndrome, characterized by multiple malignancies and frequent germline alterations in TP53. In this study, we highlight four unclassified exonic p53 variants detected in patients with a suspected diagnosis of LFS. We report for the first time the discovery of two novel functional variants in codons 191(c.572C>G; p.P191R) and 360 (c.1079G>T; p.G360V), located, respectively, in the DNA binding domain and in a linker region near the tetramerization domain of TP53. Our data revealed that while the P191R variant decreased the transactivation levels of several p53 targets, it failed to segregate with the disease state. The G360V variant, on the other hand, behaved in a paradoxical fashion by causing a stark upregulation in the activity of several p53 response elements. This tumor suppressive effect was also observed at the level of colony formation and c-Caspase 3 activation. While unlikely to be disease-causing, we propose that these variants may represent novel p53 polymorphisms and potential phenotypic modifiers in LFS. In the future, the enhanced transactivation effects of G360V-p53 may also prove useful in designing more efficacious p53-based gene therapies.

Citation Format: Badr Id Said, Han Kim, James Tran, Ana Novokmet, David Malkin. Super-transactivation TP53 variant in the germline of a family with Li-Fraumeni variant. [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 792.