Low expression of reduced folate carrier-1 and folylpolyglutamate synthase correlates with lack of a deleted in colorectal carcinoma mRNA splice variant in normal-appearing mucosa of colorectal carcinoma patients.
BACKGROUND
Cellular folate deficiency leads to DNA strand breaks, mutations, and aberrant methylation and might be a risk factor for colorectal cancer (CRC). The putative tumor suppressor gene deleted in colorectal carcinoma (DCC) is one of several genes the expression of which seems to be affected by the folate concentration at the tissue level. Decreased expression of DCC may be caused by LOH or hypermethylation, i.e. by events that might be linked to folate deficiency. The purpose of this study was to analyze if the folate level and the gene expression levels of reduced folate carrier (RFC-1) and folylpolyglutamate synthase (FPGS) had impact on the expression of DCC splice variants.


METHODS
Quantification of RFC-1 and FPGS expression in mucosa of 53 CRC patients was performed using real-time PCR whereas DCC splicing variants were detected by automated capillary gel electrophoresis. Total reduced folate concentration was measured with the FdUMP-binding assay (n = 22).


RESULTS
Significantly higher expression levels of RFC-1 (p = 0.026) and FPGS (p = 0.05) were found in mucosa expressing the splice variant DCC342 compared to mucosa that did not. Furthermore, multivariate analysis showed that RFC-1 and FPGS (r = 0.49, p = 0.01) as well as folate and RFC-1 (r = 0.56, p = 0.023) were correlated only in mucosa expressing DCC342.


CONCLUSIONS
In conclusion, the present study points to a potential influence of folates in regulating DCC expression at multiple levels involving post-transcriptional pathways. The results may provide a basis for a detailed investigation of molecular mechanisms involved in folate regulation of DCC expression.
Wettergren
Yvonne
Y
Department of General Surgery, Sahlgrenska University Hospital/Ostra, Goteborg University, S-416 85 Goteborg, Sweden. yvonne.wettergren@dep-surg.gu.se
Odin
Elisabeth
E
Nilsson
Staffan
S
Willen
Roger
R
Carlsson
Goran
G
Gustavsson
Bengt
B
D000230:Adenocarcinoma / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D015179:Colorectal Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D005260:Female; D005494:Folic Acid Deficiency / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D016163:Genes, DCC / Q000235:genetics; D006801:Humans; D007413:Intestinal Mucosa / Q000737:chemistry*; D008297:Male; D026901:Membrane Transport Proteins / Q000032:analysis / Q000235:genetics*; D008875:Middle Aged; D008969:Molecular Sequence Data; D015999:Multivariate Analysis; D010453:Peptide Synthases / Q000032:analysis / Q000235:genetics*; D012334:RNA, Neoplasm / Q000235:genetics*; D058978:Reduced Folate Carrier Protein; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013548:Sweden
D026901:Membrane Transport Proteins; D012334:RNA, Neoplasm; D058978:Reduced Folate Carrier Protein; C548699:SLC19A1 protein, human; D010453:Peptide Synthases; C023103:folylpolyglutamate synthetase