ABSTRACT
BACKGROUND: Familial chylomicronemia (type I hyperlipidemia) is a rare autosomal recessive disease due mainly to rare variants in the lipoprotein lipase (LPL) gene sequence. Molecular diagnosis of LPL deficiency is now a requirement for the first gene therapy treatment approved in the European Union. Altered coding sequence variants in APOC2, APOA5 or GPIHBP-1 can also cause familial chylomicronemia. Herein, we report the results of our molecular diagnostic activity in this topic, carried out in the setting of a Spanish clinical practice hospital laboratory, which was also extended to some patients who were more likely to have type V hyperlipidemia. METHODS: Samples from twenty-nine unrelated probands with severe hypertriglyceridemia were referred for molecular diagnosis. Samples were first screened for LPL sequence variants by DNA sequencing and, in the absence of alterations, subsequent analysis of APOC2, APOA5, and GPIHBP1 genes was undertaken. Analysis of LPL function in vitro was further studied in two previously uncharacterized LPL sequence variants. RESULTS: Fourteen different, loss-of-function variants were found in the LPL gene: 4 were novel or uncharacterized allelic variants, and of these, 2 were directly shown to affect function. Twenty of 29 probands presented at least one LPL gene allele variant: 8 were homozygous, 9 compound heterozygous and 3 heterozygous. In 13 probands, the finding of two loss-of-function variants supported the diagnosis of LPL deficiency. None of the probands presented sequence variants in the APOC2 gene, whereas 3 presented rare variants within the APOA5 gene. Four of the five patients heterozygous for a common variant in the GPIHBP-1 gene also carried APOA5 sequence variants. CONCLUSIONS: Loss-of-function LPL variants leading to familial chylomicronemia were found in 13 patients, accounting for a significant proportion of the LPL-deficient patients predicted to live in Spain.
Subject(s)
Clinical Laboratory Techniques , Hyperlipidemias/diagnosis , Hyperlipidemias/enzymology , Lipoprotein Lipase/deficiency , Adolescent , Adult , Animals , Apolipoprotein A-V , Apolipoprotein C-II/genetics , Apolipoproteins A/genetics , COS Cells , Child , Child, Preschool , Chlorocebus aethiops , Female , Genetic Variation , Humans , Hyperlipidemias/genetics , Infant , Infant, Newborn , Lipoprotein Lipase/genetics , Male , Middle Aged , Mutagenesis , Receptors, Lipoprotein/genetics , Young AdultABSTRACT
Introducción. La metilación del ácido desoxirribonucleico (ADN) es una rama de la epigenética que puede ser útil para la identificación, incluso precoz, del cáncer de pulmón. El objetivo del estudio fue evaluar la sensibilidad, especificidad y rendimiento diagnóstico de un panel de metilación formado por los genes APC (adenomatous polyposis coli), DAPK (death associated protein kinase) y RASSF1A (Ras association domain familiy 1A) asociado a la citología habitual en broncoaspirados (BAS) de pacientes con sospecha de cáncer de pulmón. Material y métodos. Se seleccionaron 39 BAS, 24 positivos y 15 negativos, para cáncer de pulmón de diferentes tipos y estadios. Las citosinas de las muestras se transformaron en uracilos con bisulfito sódico, se efectuó una doble reacción en cadena de la polimerasa (PCR) (bisulfite conversion specific-methylation specific PCR) y se identificó el estado de metilación mediante electroforesis. Resultados. APC resultó metilado en 2 de los 24 tumores pulmonares (8%), DAPK en 0 de 24 (0%) y RASSF1A en 9 de 23 (39%). La sensibilidad total del panel fue del 37,5% (9 de 24). No se detectó metilación en ninguna de las muestras libres de cáncer de pulmón (0 de 15), por lo que la especificidad fue del 100%. Además, el panel detectó metilación en una de las 7 muestras de cáncer primario de pulmón, cuya prueba citológica había sido negativa (14%) y en 3 de las 5 muestras con cáncer de pulmón con citologías meramente sospechosas (60%). Su contribución al diagnóstico correcto ante pruebas citológicas sospechosas o discordantes con el diagnóstico final fue del 33% (4 de 12). Conclusiones. La metilación del ADN puede ser un arma útil en el diagnóstico del cáncer de pulmón. Hasta el momento, la sensibilidad en el panel escogido depende exclusivamente de RASSF1A. Nuevos estudios son necesarios para garantizar la reproducibilidad y optimizar su sensibilidad (AU)
Introduction. DNA methylation is a part of epigenetics that can be useful for lung cancer detection even at early stages. The aim of this study was to evaluate sensitivity, specificity and diagnostic capacity of a methylation panel including APC, DAPK and RASSF1A genes, together with routine cytology tests in patients suspected with lung cancer. Material and methods. We selected 39 bronchoaspirates, 24 positive and 15 negative for lung cancer of different histological types and stages. Samples were transformed with sodium bisulphite. A double PCR (BS-MSP) was performed and methylation status was identified by electrophoresis. Results. APC was found to be methylated in 2 out of 24 lung tumours (8%), DAPK in 0 out of 24 (0%) and RASSF1A in 9 out of 23 (39%). Panel sensibility was 37.5% (9/24). No methylation was detected in any of the negative lung cancer samples (0/15), so specificity was 100%. Moreover, the panel detected methylation in 1 of the 7 primary lung cancer tumour samples in which the cytology test was negative (14%) and in 3 of 5 lung cancer tumour samples in which cytology test was only suspicious (60%). Its contribution to the correct diagnosis when cytology tests were suspicious or discordant with final diagnosis was 33% (4/12). Conclusions. DNA methylation can be a useful tool in lung cancer diagnosis. The chosen panel sensibility depends exclusively on RASSF1A to date. Consequently, new studies are required to guarantee reproducibility and optimize sensitivity (AU)
