mRNA expression levels of E2F transcription factors correlate with dihydrofolate reductase, reduced folate carrier, and thymidylate synthase mRNA expression in osteosarcoma.
Previous studies have shown that decreased expression of the reduced folate carrier (RFC) and increased expression of dihydrofolate reductase (DHFR) are associated with intrinsic and acquired methotrexate resistance, respectively, in osteosarcoma (OS). It has also been shown in colorectal cancer that E2F-1 expression correlates with thymidylate synthase (TS) and, to a lesser extent, DHFR expression. To begin to investigate the regulation of DHFR and RFC expression in OS samples, mRNA expression of E2F-1 and E2F-4 were measured in OS tumor samples and related to DHFR, RFC, and TS mRNA expression. Using fluorescent quantitative real-time PCR, 112 human OS patient samples were investigated for potential E2F-1/E2F-4:DHFR, E2F-1/E2F-4:RFC, and E2F-1/E2F-4:TS correlations. The expression ranges for each gene are as follows: DHFR, 0.02-33.13 (median = 0.20); RFC, 0.02-229.13 (median = 1.91); TS, 0.01-9.99 (median = 0.15); E2F-1, 0.05-69.07 (median = 0.52); and E2F-4, 0.24-52.35 (median = 1.45). Spearman correlation coefficients (r(s)) for E2F-1:DHFR, E2F-1:RFC, E2F-1:TS, E2F-4:DHFR, E2F-4:RFC, and E2F-4:TS were calculated to be 0.53, 0.63, 0.60, 0.41, 0.58, and 0.33, respectively (P < 0.001). On the basis of this data, moderate correlations exist between E2F-1/E2F-4 and DHFR, RFC, and TS. These results suggest E2F-1/E2F-4 may play a role in the regulation of RFC expression, which has not been reported previously. The E2F transcription factors are also related to DHFR and TS expression in OS samples, suggesting a possible involvement in methotrexate resistance. Although E2F mRNA levels correlate with DHFR, RFC, and TS mRNA expression, additional experiments are necessary to determine the direct effects of these transcription factors and identify other proteins that may influence this relationship.
Sowers
Rebecca
R
Department of Pediatrics, Orthopaedic Surgery Service, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Toguchida
Junya
J
Qin
Jing
J
Meyers
Paul A
PA
Healey
John H
JH
Huvos
Andrew
A
Banerjee
Debabrata
D
Bertino
Joseph R
JR
Gorlick
Richard
R
D000293:Adolescent; D000328:Adult; D000368:Aged; D002352:Carrier Proteins / Q000096:biosynthesis*; D018797:Cell Cycle Proteins; D002648:Child; D002675:Child, Preschool; D004247:DNA / Q000737:chemistry; D004268:DNA-Binding Proteins; D019008:Drug Resistance, Neoplasm; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D050704:E2F4 Transcription Factor; D005260:Female; D006801:Humans; D008297:Male; D026901:Membrane Transport Proteins; D008727:Methotrexate / Q000494:pharmacology; D008875:Middle Aged; D012516:Osteosarcoma / Q000201:enzymology* / Q000378:metabolism*; D012313:RNA / Q000737:chemistry; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000378:metabolism; D058978:Reduced Folate Carrier Protein; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013762:Tetrahydrofolate Dehydrogenase / Q000096:biosynthesis*; D013940:Thymidylate Synthase / Q000096:biosynthesis*; D014157:Transcription Factors / Q000096:biosynthesis*
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D050704:E2F4 Transcription Factor; C493762:E2F4 protein, human; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D058978:Reduced Folate Carrier Protein; C548699:SLC19A1 protein, human; D014157:Transcription Factors; D012313:RNA; D004247:DNA; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase; D008727:Methotrexate