Co‐occurrence of germline pathogenic variants for different hereditary cancer syndromes in patients with Lynch syndrome

Background: Lynch syndrome (LS) is a hereditary condition characterized by a high risk of colorectal cancer, endometrial cancer, and other neoplasia associated with germline alterations in DNA mismatch repair genes. The classical genetic diagnostic strategy for LS consists of the Sanger sequencing of genes associated with the suspected syndrome. Next‐generation sequencing (NGS) enables the simultaneous sequencing of a large number of hereditary cancer genes. Here, we aimed to study whether other germline pathogenic variants of hereditary cancer genes are present in patients with LS. Methods: A cohort of 84 probands with a previous genetic diagnosis of LS by Sanger sequencing was reanalyzed using NGS via a commercial panel of 94 hereditary cancer genes by hybrid capture. The American College of Medical Genetics and Genomics criteria were used to classify the clinical significance of the variants. The findings of NGS were confirmed by Sanger sequencing. When possible, genetic analyses of the new findings in the proband's relatives were also performed by Sanger sequencing. Results: We identified five families (6%), out of 84, with at least two germline pathogenic variants conferring to high or moderate risk in different dominant cancer‐predisposing genes: [MLH1‐BRCA2‐NBN], [MLH1‐BRCA1], [MSH2‐ATM], [MSH6‐NF1], and [MLH1‐FANCA]. Interestingly, only one out of these five families exhibited a clinical phenotype associated with the new pathogenic variants. The family with three pathogenic variants of the [MLH1‐BRCA2‐NBN] genes showed a high aggregation of tumors associated with LS and breast and ovarian cancer syndrome. Conclusions: Our results showed that the co‐occurrence of more than one pathogenic variant in cancer‐predisposing genes was remarkable among cases of LS. In most cases, no clinicial manifestations were associated with the secondary pathogenic variants. Further studies are needed to confirm these findings and elucidate their clinical impact. Reanalysis of LS families should be considered only in families with mixed clinical phenotypes.RFA is a recipient of a Fellowship from the Consellería Educación of the Valencian Community. The studies of ED and ACA are funded by the Acción Juvenil from Consellería Educación of the Valencian Community and the Spanish Ministry of Economy and Competitiveness, respectively. VDO is a recipient of a Fellowship from the Spanish Association Against Cancer (AECC). This work was supported by grants from the Foundation for the Promotion of Health and Biomedical Research in the Valencian Region, FISABIO (Grants: UGP‐14‐192 and UGP‐16‐146), and the Carlos III Health Institute (Grant AES: PI17/01082)

Characterization of a novel POLD1 missense founder mutation in a Spanish population

Background: We identified a new and a recurrent POLD1 mutation associated with predisposition to colorectal cancer (CRC). We characterized the molecular and clinical nature of the potential POLD1 founder mutation in families from Valencia (Spain). Methods: Clinical and molecular data were collected from four independent families known to have a POLD1 Leu474Pro mutation. To establish its founder effect, haplotype construction was performed using 14 flanking POLD1 polymorphic markers. We calculated penetrance estimates and clinical expressivity, globally and stratified by age and sex. Results: We included 32 individuals from the four families: 20 carriers and 12 noncarriers. A common haplotype was identified in these families in a region comprising 2,995 Mb, confirming L474P as the first founder POLD1 mutation identified. Thirteen tumors diagnosed in 10 POLD1 carriers: eight CRC, three endometrial and two other tumors were considered. The median age of cancer onset for POLD1 mutation carriers was 48 years. The observed penetrance was 50% and the cumulative risk at age of 50 years was 30%. Conclusions: The findings of the present study contribute to a better understanding of CRC genetics in the Spanish population. The clinical phenotype for this mutation is similar to that in Lynch syndrome. Future studies using next generation sequencing with large gene panels for any hereditary cancer condition will offer the possibility of detecting POLE/POLD1 mutations in unsuspected clinical situations, demonstrating a more real and unbiased picture of the associated phenotype.This work was supported by the Institute for Health and Biomedical Research of Alicante (ISABIAL, UGP‐16‐146). RFA is recipient of a Fellowship from the Consellería Educación of the Valencian Community. ACA is funded by the Acción Juvenil from the Spanish Ministry of Economy and Competitiveness. VDO is recipient of a Fellowship from the Spanish Association Against Cancer (AECC). AC and MIC are funded by Health and Biomedical Research Foundation from the Valencian Region (FISABIO). EHI is recipient of a fellowship from the Fondo Investigación Sanitaria ISCIII (FI12/00233)

Nuevas aportaciones al riesgo genético de cáncer: co-ocurrencia de variantes patogénicas para diferentes síndromes de cáncer hereditario en pacientes con síndrome de Lynch y caracterización de una nueva variante patogénica fundadora en el gen POLD1

El síndrome de Lynch (SL) se caracteriza por presentar heterogeneidad genética, pleiotropismo y penetrancia incompleta y variable, sugiriendo la posibilidad de un riesgo poligénico y posiblemente, la implicación de otros genes de cáncer hereditario en familias con fenotipos complejos. La co-ocurrencia de diferentes variantes patogénicas en diferentes genes de predisposición hereditaria a cáncer en un individuo, lo que se conoce con las siglas MINAS, está probablemente infradiagnosticada. La identificación de segundas alteraciones genéticas en línea germinal en genes de cáncer hereditario tiene un importante impacto para el paciente y sus familiares. En esta tesis se realizó un estudio retrospectivo en una cohorte de casos índice de SL para intentar dimensionar esta situación a priori rara o muy rara. Los resultados obtenidos muestran que la prevalencia de más de un alelo patogénico que predispone a cáncer en pacientes con síndrome de Lynch es relevante, entorno al 6% y que la presencia de más de un alelo patogénico en genes de predisposición a cáncer no suele asociarse a las manifestaciones clínicas esperadas de ambos genotipos, en el momento del diagnóstico. Sin embargo, son necesarios más estudios para confirmar estos hallazgos. Por otro lado, la poliposis asociada a la actividad correctora de las polimerasas (PPAP) es otro síndrome de cáncer hereditario. Para este síndrome, existen pocas variantes patogénicas descritas y el fenotipo clínico asociado se basa en un número limitado, pero creciente, de familias descritas. La caracterización molecular exhaustiva y un análisis detallado del fenotipo clínico asociado a variantes patogénicas recurrentes en los genes responsables, podría ayudar a a mejora de la evaluación del riesgo de cáncer en estas familias; permitiendo así mismo ofrecer un seguimiento más personalizado y eficiente. Por ello, realizamos un estudio para intentar establecer el carácter fundador, el fenotipo clínico asociado y la penetrancia de la variante patogénica, no descrita previamente (POLD1:c.1421T>C; p.Leu474) e identificada dentro del Programa de Cáncer Hereditario de la Comunidad Valenciana en cuatro familias aparentemente no relacionadas. Los resultados obtenidos establecieron el carácter fundador de la variante de interés, con un haplotipo común de unas 3Mb, siendo la primera variante patogénica con carácter fundador identificada en el gen POLD1 y además el fenotipo clínico de la variante coincide a priori con el del SL

Clinical and functional heterogeneity associated with the disruption of retinoic acid receptor beta

PurposeDominant variants in the retinoic acid receptor beta (RARB) gene underlie a syndromic form of microphthalmia, known as MCOPS12, which is associated with other birth anomalies and global developmental delay with spasticity and/or dystonia. Here, we report 25 affected individuals with 17 novel pathogenic or likely pathogenic variants in RARB. This study aims to characterize the functional impact of these variants and describe the clinical spectrum of MCOPS12.MethodsWe used in vitro transcriptional assays and in silico structural analysis to assess the functional relevance of RARB variants in affecting the normal response to retinoids.ResultsWe found that all RARB variants tested in our assays exhibited either a gain-of-function or a loss-of-function activity. Loss-of-function variants disrupted RARB function through a dominant-negative effect, possibly by disrupting ligand binding and/or coactivators' recruitment. By reviewing clinical data from 52 affected individuals, we found that disruption of RARB is associated with a more variable phenotype than initially suspected, with the absence in some individuals of cardinal features of MCOPS12, such as developmental eye anomaly or motor impairment.ConclusionOur study indicates that pathogenic variants in RARB are functionally heterogeneous and associated with extensive clinical heterogeneity