The aim of the present study was to identify the appropriate DNA sequence and design high-quality primers for methylation-specific polymerase chain reaction (MSP). These primers may be used to examine and identify patients with early-stage epithelial ovarian carcinoma (EOC). Opioid binding protein/cell adhesion molecule like (OPCML), Runt-related transcription factor 3 and tissue factor pathway inhibitor 2 were selected as possible molecular markers. MSP primer sets were designed to monitor the methylation of the three markers. Free circulating DNA (fcDNA) from 194 patients with epithelial ovarian carcinoma and healthy donors were templates in the nested MSP. OPCML MSP was effective with respect to screening methylated fcDNA. One-way ANOVA P-values indicated that the difference in cancer antigen 125 (CA125), a biomarker for EOC diagnosis, level between early EOC and healthy donors was not significant. The methylation of OPCML was significantly altered in early-stage EOC compared with healthy donors (P<0.0001), and this supported the hypothesis that specific fcDNA methylation was able to distinguish patients with early-stage EOC from healthy donors. With respect to detecting early EOC, compared with the results of the CA125 test, MSP increased the κ coefficient from 0.140 to 0.757. Therefore, OPCML combined with fcDNA may be used to establish an improved clinical assay compared with the current CA125 test.
Keywords: DNA methylation; early-stage epithelial ovarian cancer; methylation-specific polymerase chain reaction; opioid binding protein/cell adhesion molecule-like; serum free circulating DNA.