RESUMEN
Mounting evidence indicates that deregulation of microRNAs (miRNAs) are involved in development of many human diseases, including cancers. Regulation of miRNA is a complicated process and some components in the regulation are known to be altered in human cancers. Among the miRNA regulation-related genes, we found that AGO1, AGO2, TNRC6A, TNRC6C, TARBP2 and EXPORTIN5 genes have mononucleotide repeats in their coding sequences. To see whether these genes are mutated in cancers with microsatellite instability (MSI), we analysed the mononucleotide repeats in 27 gastric cancers (GCs) with high MSI (MSI-H), 18 GC with low MSI (MSI-L), 45 GC with stable MSI (MSS), 41 colorectal cancers (CRCs) with MSI-H, 14 CRCs with MSI-L and 45 CRCs with stable MSI (MSS) by single-strand conformation polymorphism (SSCP) analysis and DNA sequencing. We found AGO2, TNRC6A, TARBP2, TNRC6C and EXPORTIN5 mutations in 10, six, one, one and one cancer(s), respectively. They were detected in MSI-H but not in MSI-L or MSS cancers. The GCs and CRCs with MSI-H harboured one or more mutations of the genes in 22% and 27%, respectively. We also analysed Ago2 and TNRC6A protein expressions in GCs and CRCs with MSI-H. In cancers with MSI-H, loss of Ago2 expression was observed in 40% of GCs and 35% of CRCs, while loss of TNRC6A was observed in 52% of the GCs and 54% of the CRCs. Our data indicate that frameshift mutations in AGO2 and TNRC6A and their losses of expression are common in GCs and CRCs with MSI-H, and suggest that these alterations may contribute to the cancer development by deregulating miRNA regulation.
Asunto(s)
Autoantígenos/genética , Neoplasias Colorrectales/genética , Factor 2 Eucariótico de Iniciación/genética , Mutación del Sistema de Lectura/genética , MicroARNs/genética , Neoplasias Gástricas/genética , Proteínas Argonautas , Autoantígenos/metabolismo , Neoplasias Colorrectales/patología , Factor 2 Eucariótico de Iniciación/metabolismo , Regulación Neoplásica de la Expresión Génica/genética , Humanos , Carioferinas/genética , Inestabilidad de Microsatélites , Proteínas de Unión al ARN/genética , Análisis de Secuencia de ADN , Neoplasias Gástricas/patologíaRESUMEN
DNMT3A, a DNA methyltransferase that functions for de novo methylation, is important in development and many cellular processes related to tumorigenesis. Somatic mutations of DNMT3A gene, including recurrent mutations in its Arg-882, were recently reported in acute myelogenous leukemia (AML), strongly suggesting its role in development of AML. To see whether DNMT3A mutation occurs in other malignancies as well, we analyzed DNMT3A in 916 cancer tissues from 401 hematologic malignancies (AML, acute lymphoblastic leukemias (ALL), multiple myelomas and lymphomas) and 515 carcinomas (lung, breast, prostate, colorectal and gastric carcinomas) using a single-strand conformation polymorphism (SSCP) assay. We identified DNMT3A mutations, especially the Arg-882 mutations, in adulthood AML (9.4%). In addition, we found DNMT3A mutations in pre-B-ALL and three lung cancers at lower frequencies. Allelic loss of DNMT3A was frequently observed in most cancer types analyzed, including lymphomas (48.1%), gastric cancers (23.5%) and lung cancers (18.3%) irrespective of DNMT3A mutation. Also, loss of DNMT3A expression was common in lung cancers (46.4%), and was associated with the allelic loss. Our data indicate that DNMT3A gene is mutated mainly in AML, but it occurs in other cancers, such as ALL and lung cancer, despite the lower incidences. Also, the data suggest that DNMT3A is altered in many cancer types by various ways, including somatic mutations, allelic loss and loss of expression that might play roles in tumorigenesis.