RESUMO
Germline TP53 pathogenic variants can lead to a cancer susceptibility syndrome known as Li-Fraumeni (LFS). Variants affecting its activity can drive tumorigenesis altering p53 pathways and their identification is crucial for assessing individual risk. This study explored the functional impact of TP53 missense variants on its transcription factor activity. We selected seven TP53 missense variants (c.129G > C, c.320A > G, c.417G > T, c.460G > A, c,522G > T, c.589G > A and c.997C > T) identified in Brazilian families at-risk for LFS. Variants were created through site-directed mutagenesis and transfected into SK-OV-3 cells to assess their transcription activation capabilities. Variants K139N and V197M displayed significantly reduced transactivation activity in a TP53-dependent luciferase reporter assay. Additionally, K139N negatively impacted CDKN1A and MDM2 expression and had a limited effect on GADD45A and PMAIP1 upon irradiation-induced DNA damage. Variant V197M demonstrated functional impact in all target genes evaluated and loss of Ser15 phosphorylation. K139N and V197M variants presented a reduction of p21 levels after irradiation. Our data show that K139N and V197M negatively impact p53 functions, supporting their classification as pathogenic variants. This underscores the significance of conducting functional studies on germline TP53 missense variants classified as variants of uncertain significance to ensure proper management of LFS-related cancer risks.
Assuntos
Predisposição Genética para Doença , Mutação em Linhagem Germinativa , Síndrome de Li-Fraumeni , Mutação de Sentido Incorreto , Proteína Supressora de Tumor p53 , Síndrome de Li-Fraumeni/genética , Humanos , Proteína Supressora de Tumor p53/genética , Brasil , Proteínas Proto-Oncogênicas c-mdm2/genética , Feminino , Inibidor de Quinase Dependente de Ciclina p21/genética , Masculino , Proteínas de Ciclo Celular/genética , Linhagem Celular Tumoral , Ativação Transcricional/genética , Proteínas GADD45RESUMO
In 2004, a population-based cohort (the Núcleo Mama Porto Alegre - NMPOA Cohort) was started in Porto Alegre, southern Brazil and within that cohort, a hereditary breast cancer study was initiated, aiming to determine the prevalence of hereditary breast cancer phenotypes and evaluate acceptance of a genetic cancer risk assessment (GCRA) program. Women from that cohort who reported a positive family history of cancer were referred to GCRA. Of the 9218 women enrolled, 1286 (13.9 percent) reported a family history of cancer. Of the 902 women who attended GCRA, 55 (8 percent) had an estimated lifetime risk of breast cancer ³ 20 percent and 214 (23.7 percent) had pedigrees suggestive of a breast cancer predisposition syndrome; an unexpectedly high number of these fulfilled criteria for Li-Fraumeni-like syndrome (122 families, 66.7 percent). The overall prevalence of a hereditary breast cancer phenotype was 6.2 percent (95 percentCI: 5.67-6.65). These findings identified a problem of significant magnitude in the region and indicate that genetic cancer risk evaluation should be undertaken in a considerable proportion of the women from this community. The large proportion of women who attended GCRA (72.3 percent) indicates that the program was well-accepted by the community, regardless of the potential cultural, economic and social barriers.