PO-059 Cancer-predisposing variants in alternatively spliced TP53 exons

Abstract

Introduction Src oncogene have been strongly implicated in the development, growth, progression, and metastasis of a variety of human cancers. Although soy isoflavones have been shown to have potential anticancer activity, the role of isoflavones in the oncogenic activity of Src remains unknown. Using HAG-1 human adenocarcinoma cells transfected with v-src, we investigated the functional role of Src in anti-proliferative activity of isoflavones such as genistein, daidzein, glycitin and equol. Material and methods The growth inhibitory activities of those isoflavones against Src-and vehicle-transfected cells (HAG/src and HAG/neo) were investigated using WST-1 cell proliferation assay. Effects of those isoflavones on apoptosis and cell cycle perturbation were evaluated by FACS analyses.Results and discussions The growth of HAG/neo cells was inhibited potently by genistein and equol, but modestly by daidzein and glycitin. In contrast, activated Src conferred resistance to either daidzein, glycitin or equol, but rendered the cells more sensitive to genistein, compared to HAG/neo; Genistein strongly inhibited the growth of HAG/src cells in a dose-dependent manner with IC50 value of 25 mM, whereas in other three isoflavones, the inhibitory effects were minimal without reaching an IC50 even at a dose of 100 mM. Upon treatment with 50 mM genistein for 72 hour, HAG/src cells were significantly arrested at the G2/M compared to HAG/neo cells (37.7% versus 7.0%). By contrast, the same concentration of either daidzein, glycitin or equol could not arrest HAG/src cells at any checkpoint of the cell cycle. The sub-G0/G1 apoptotic cell populations were not increased following 72 hour exposure with either isoflavones. Therefore, it appears that growth inhibition by genistein in Src-activated cells would be mediated mainly by the G2/M arrest of cell cycle rather than apoptosis induction. Genistein increased the expression levels of p53 and p21 with decreased phosphorylated p21. The levels of other main cell cycle-related proteins such as cyclin B, cyclin E, CDK2, and cdc2 were not altered. These data suggest that genistein would be the only isoflavone component that may potentially suppress oncogenic activity driven by Src through increasing the p53 and p21 levels. Conclusion These data suggest that genistein would be the only isoflavone component that may potentially suppress oncogenic activity driven by Src, providing a mechanistic rationale for the potential use of genistein in the prevention and treatment of human cancers with activated Src.

Association between Predicted Effects of TP53 Missense Variants on Protein Conformation and Their Phenotypic Presentation as Li-Fraumeni Syndrome or Hereditary Breast Cancer

“…Increased genetic testing has however revealed that germline TP53 variants are associated with a broader range of phenotypes, from classical LFS to hereditary breast cancer (HBC), and the outcome may be dependent on both variant characteristics and modifier gene variants elsewhere in the genome [40]. Differential expression of TP53 isoforms has also been discussed to have an impact on cancer risk profile [41,42], but this has mainly been studied in sporadic cancers [43]. The wide variation in the phenotypic outcome in families carrying TP53 variants creates challenges for the genetic counseling and clinical handling of these individuals.…”