RESUMEN
At present, there is conflicting evidence whether microsatellite instability (MSI) plays a role in the pathogenesis of breast cancer. Here we describe for the first time an MSI(+) phenotype in two breast cancer cell lines, CAL51 and MT-3, resembling that observed in colorectal cancers. These cell lines are characterized by near-diploid and hyperdiploid karyotypes, respectively. We detected MSI in these cell lines within two non-coding (BAT-25 and BAT-26) and within coding repeat sequences of genes known to be mutated in MSI(+) cancer (TGFBR2, IGF2R, BAX). We provide evidence that the inactivation of MMR genes is responsible for MSI in these cell lines.
Asunto(s)
Disparidad de Par Base/genética , Neoplasias de la Mama/genética , Reparación del ADN/genética , Repeticiones de Microsatélite/genética , Mutación/genética , Proteínas Proto-Oncogénicas c-bcl-2 , Neoplasias de la Mama/patología , Análisis Mutacional de ADN/métodos , ADN de Neoplasias/genética , Femenino , Amplificación de Genes/genética , Perfilación de la Expresión Génica , Regulación Neoplásica de la Expresión Génica/genética , Humanos , Ácidos Nucleicos Heterodúplex/genética , Neoplasias Ováricas/genética , Neoplasias Ováricas/patología , Fenotipo , Poliploidía , Proteínas Serina-Treonina Quinasas , Proteínas Proto-Oncogénicas/genética , Receptor IGF Tipo 2/genética , Receptor Tipo II de Factor de Crecimiento Transformador beta , Receptores de Factores de Crecimiento Transformadores beta/genética , Células Tumorales Cultivadas , Proteína X Asociada a bcl-2RESUMEN
The chromosome region 8p12-p22 shows frequent allelic loss in a variety of human malignancies, including breast cancer (BC). The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-receptors TRAIL-R1, -R2, -R3 and -R4 are located on 8p21-p22 and might be candidate tumor suppressor genes in this region. To evaluate the involvement of TRAIL receptors in breast carcinogenesis, we have analyzed the entire coding region of TRAIL-R2 and the death domain (DD) regions of TRAIL-R1 and -R4 for the detection of somatic mutations in a series of breast tumors, lymph node metastases and BC cell lines. Overall, we detected 1, 11 and 3 alterations in the TRAIL-R1, -R2 and -R4 genes, respectively. Although functional studies have not yet been performed, we assume that most of these alterations do not alter the function of TRAIL-receptors. Additionally, we analyzed individuals from BC families for the detection of TRAIL-R2 germline mutations. One alteration has been found in the Kozak consensus motif at position -4 with respect to the translation initiation AUG [1-4 (C-->A)]. We further studied the mRNA expression of TRAIL and the 4 TRAIL receptors. In BC cell lines, a strongly decreased mRNA expression of TRAIL, TRAIL-R1, -R3 and -R4 was found, whereas the expression of TRAIL-R2 was only slightly reduced. In breast tumors, a 1.2-3.6-fold reduction of mRNA signals of the 5 genes was observed. No correlation was found between the expression level of TRAIL and the receptor mRNAs and clinicopathologic variables and between the expression of TRAIL-R2 and TP53 mutation status and loss of heterozygosity (LOH) at 8p21-p22. Taken together, we cannot exclude the involvement of TRAIL-receptors in BC. Our mutation studies indicate that DD receptor mutations occur at low frequency and are not the primary cause for the altered mRNA expression of TRAIL and TRAIL-receptors in BC.