Dataset Information

Polymorphisms and methylation of the reduced folate carrier in osteosarcoma.

ABSTRACT: High-dose methotrexate is a standard component in the treatment of osteogenic sarcoma. Impaired methotrexate uptake associated with decreased reduced folate carrier expression is a common mechanism of methotrexate resistance in osteogenic sarcoma samples. We investigated whether promoter methylation and polymorphisms in the 3' untranslated region are involved in regulating reduced folate carrier expression. In a cohort of 66 osteogenic sarcoma specimens, quantitative methylation-specific polymerase chain reaction and single-strand conformation polymorphism were performed. We found detectable levels of promoter methylation in 84.3% of samples. When related to the reduced folate carrier mRNA levels, a trend was observed that reduced folate carrier expression is lower in samples (median, 0.7) with greater than 10% DNA methylation as compared with those (median, 2.3) with less than 10% DNA methylation. The heterozygous polymorphisms of 2582 T/G and 2617C/T in the 3' untranslated region showed reduced folate carrier expression (median, 0.9) as compared with the wild-type 2582T and 2617C (median, 4.2). The data suggest promoter methylation and polymorphisms in the 3' untranslated region of the reduced folate carrier may be involved in its transcriptional regulation in osteogenic sarcoma. Further study is required to confirm this finding.

SUBMITTER: Yang R

PROVIDER: S-EPMC2493020 | biostudies-literature | 2008 Sep

REPOSITORIES: biostudies-literature

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Polymorphisms and methylation of the reduced folate carrier in osteosarcoma.

Yang Rui R Qin Jing J Hoang Bang H BH Healey John H JH Gorlick Richard R

Clinical orthopaedics and related research 20080605 9

High-dose methotrexate is a standard component in the treatment of osteogenic sarcoma. Impaired methotrexate uptake associated with decreased reduced folate carrier expression is a common mechanism of methotrexate resistance in osteogenic sarcoma samples. We investigated whether promoter methylation and polymorphisms in the 3' untranslated region are involved in regulating reduced folate carrier expression. In a cohort of 66 osteogenic sarcoma specimens, quantitative methylation-specific polymer ...[more]

PMID: 18528741

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Project description:The ubiquitously expressed reduced folate carrier (RFC) or SLC19A1 is recognized to be an essential transport system for folates in mammalian cells and tissues. In addition to its generalized role as a folate transporter, RFC provides specialized tissue functions including absorption across intestinal/colonic epithelia, transport across the basolateral membrane of renal proximal tubules, transplacental transport of folates, and folate transport across the blood-brain barrier. The human RFC (hRFC) gene is regulated by five major upstream non-coding regions (designated A1/A2, A, B, C, and D), each transcribed from a unique promoter. Altogether, at least 14 distinct hRFC transcripts can be envisaged in which different 5' untranslated regions (UTRs) are fused to a common splice acceptor region (positions -1 to -49) within the first coding exon with a common 1776bp coding sequence. The 5' non-coding regions are characterized by alternate transcription start sites, multiple splice forms, and selective tissue distributions. Alternate 5' UTRs impact mRNA stabilities and translation efficiencies, and result in synthesis of modified hRFC proteins translated from upstream AUGs. In this report, we describe production and characterization of transgenic mice (TghRFC1) containing a functional hRFC gene and of humanized mice in which the mRFC gene is inactivated and an active hRFC gene has been introduced. The mice appear to be healthy and to breed well. Analysis of tissue specificity of expression in both the TghRFC1 and humanized hRFC mice by real-time RT-PCR demonstrates that the hRFC gene is expressed with a specificity closely resembling that seen in human tissues. For the humanized hRFC mice, levels of B and A1/A2 5' UTRs predominated in all mice/tissues, thus resembling results in normal human tissues. Lower levels of A and C 5' UTRs were also detected. The availability of humanized mouse models for hRFC will permit investigators to address critical unanswered questions pertinent to human health and disease. These include the ability to analyze the hRFC gene in vivo, to control dietary and other environmental conditions that may impact levels of gene expression, and to control the genetics of the mice in order to assess the effects of hRFC gene alterations on tissue folate uptake and distribution, none of which can be easily achieved in human populations.

Dataset Information

Polymorphisms and methylation of the reduced folate carrier in osteosarcoma.

Publications

Polymorphisms and methylation of the reduced folate carrier in osteosarcoma.

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