Introduction Colorectal cancer (CRC) screening programmes are an opportunity to alter the survival of patients with early CRC. Cells from the alimentary tract can be obtained from both the mouth and large bowel. If biomarkers of CRC risk could be identified in buccal cells, such assays could be more convenient and acceptable than those requiring rectal biopsies. One potential CRC risk biomarker is methylation of the WNT-related gene encoding the Secreted Frizzled Related Protein 4 (SFRP 4).
Methods DNA was extracted from macroscopically normal rectal biopsies and matched buccal cell swabs from volunteers at a relatively lower (healthy volunteers) and higher (patients with adenomatous polyps) CRC risk in the BORICC Study. Methylation of SFRP4 was quantified by Pyrosequencing.
Results SFRP4 promotor methylation was quantified in rectal biopsies and matched buccal cells in 233 lower and 89 higher CRC risk participants. For rectal biopsies, SFRP4 promotor methylation was significantly (p=0.001) higher in those with polyps than in healthy controls. However, for buccal cells, the reverse was observed with significantly (p<0.001) higher SFRP4 promotor methylation in the healthy controls. At CpG sites 1 and 4 only, SFRP4 methylation was correlated significantly (p=0.001 and p=0.041 respectively) between the two patient groups.
Conclusion SFRP4 promotor methylation in rectal biopsies is not the same as that in matched buccal cells. However, SFRP4 methylation was significantly different between patient groups at each site, providing encouragement for further studies of the utility of buccal cells as a surrogate tissue for identification of those at increased CRC risk.
Competing interests None declared.
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