Abstract P2-02-04: Li-Fraumeni syndrome in females with early onset breast cancer in a Mexican population

Background: Breast cancer in Mexican patients presents in average 10 year earlier compared to other populations. Among patients with TP53 mutations, breast cancer is the most common malignancy. In this study we aim to determine the rate of TP53 mutations among young Mexican breast cancer patients.

Methods: Breast cancer patients younger that 45 were retrospectively identified, only patients without BRCA1/2 mutations were included. Clinical records and pedigrees were reviewed. Next generation sequencing test for TP53 was performed from blood specimens. All pathogenic mutations were confirmed by Sanger sequencing and verified if were included in the IACR TP53 database.

Results: Among the 78 patients younger than 45yo evaluated and tested with next generation sequencing, we identified 5 patients with a TP53 mutation (6.4%). All were younger than 36 corresponding to a rate of 9.4% of mutations in this group of individuals (n = 53). Two, not previously described, frameshift mutations were found (c.291delC and c.273dupG) and three missense mutations (c.844C>T, c.517G>A, c.604C>T). A VUS c.672G>A that causes a silent mutation in a splicing-donor site was identified. All patients with a TP53 mutation had locally advanced disease and tumors were high grade and Her2 positive.

Conclusions: Among Mexican women younger than 45yo, the rate of TP53 mutations was higher than in other populations where it's estimated to be 1%. Among patients younger than 36 the proportion was even higher. All patients had a family history suggestive of Li-Fraumeni syndrome. The VUS found in our series needs a deeper analysis (family segregation, structure and function of the resulting protein). Our results support the international recommendation of performing molecular testing for TP53 in breast cancer patients younger than 35 years. Identification of patients with TP53 mutation has important prognostic, therapeutic and quality of life implications for the proband in addition of the risk reduction strategies and intensive surveillance recommended in their families.

Citation Format: Gallardo-Alvarado LN, Cantu-De Leon DF, Tusie-Luna T, Tusie-Luna I, Diaz-Chavez J, Herrera EM, Chavez-MacGregor M, Bargallo-Rocha E, Villarreal C, Herrera.Montalvo LA, Segura-Kato YX. Li-Fraumeni syndrome in females with early onset breast cancer in a Mexican population [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-02-04.

Trypanosoma cruzi: multiple actin isovariants are observed along different developmental stages

The expression and biological role of actin during the Trypanosoma cruzi life cycle remains largely unknown. Polyclonal antibodies against a recombinant T. cruzi actin protein were used to confirm its expression in epimastigotes, trypomastigotes, and amastigotes. Although the overall levels of expression were similar, clear differences in the subcellular distribution of actin among the developmental stages were identified. The existence of five actin variants in each developmental stage with distinct patterns of expression were uncovered by immunoblotting of protein extracts separated 2D-SDS gels. The isoelectric points of the actin variants in epimastigotes ranged from 4.45 to 4.9, whereas they ranged from 4.9 to 5.24 in trypomastigotes and amastigotes. To determine if the actin variants found could represent previously unidentified actins, we performed a genomic survey of the T.cruzi GeneDB database and found 12 independent loci encoding for a diverse group of actins and actin-like proteins that are conserved among trypanosomatids.

Mutations in MODY genes are not common cause of early-onset type 2 diabetes in Mexican families

CONTEXT

Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes mellitus characterized by autosomal dominant inheritance, early age of onset and a primary insulin secretion defect. Certain MODY gene sequence variants may be involved in polygenic forms of type 2 diabetes.

OBJECTIVE

We assessed the contribution of MODY genes to the etiology of type 2 early-onset diabetes in 23 Mexican families, including five with apparently autosomal dominant inheritance.

PATIENTS

Twenty-three unrelated Mexican families with early-onset type 2 diabetes previously screened for the presence of glucokinase mutations, were studied.

DESIGN

We screened MODY genes for sequence variants by PCR-SSCP analysis and automated sequencing. We performed a functional analysis of the HNF-1alpha P379H recombinant protein in vitro in both HeLa and RINm5f beta-cell lines.

MAIN OUTCOME MEASURES

MODY gene mutation screening and P379H mutant protein transactivation assay.

RESULTS

No mutations were detected in the HNF-4alpha, IPF-1, NEUROD1 or HNF-1beta genes in any of the families studied. A new mutation (P379H) of the HNF-1alpha gene was identified in one MODY family. RINm5f and HeLa cell transfection assays revealed decreased transactivation activity of the mutant protein on the human insulin promoter.

CONCLUSIONS

All known MODY genes were screened for abnormalities in this cohort of early-onset diabetes families which included 5 MODY pedigrees. We identified a new HNF-1alpha MODY mutation (P379H) and demonstrated that it reduces the transactivation potential of the mutant protein on the human insulin promoter. No other mutation was identified in this cohort indicating that abnormalities in MODY genes are generally not a common cause of early-onset diabetes and this includes MODY families in Mexico.