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.
Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest,
patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.
Each author certifies that his or her institution has approved the human protocol for this investigation, that all investigations
were conducted in conformity with ethical principles of research, and that informed consent for participation in the study
was obtained.