Frequency N Correlation with OGDHL
Correlation with OGDHL methylation (P value)∗
Transverse colon 4
Left colon 4
Sigmoid colon 12
Tumor size (cm)
Stage II 15
Stage III 14
Stage IV 5
∗ Evaluated by Mann-Whitney U test.
Clinicopathologic findings of patients
Of 40 CRC patients involved in this study 17 (42.5%) individuals were male and 23 (57.5%) were female. The mean of age was 59.28 years (range 30-83 years). The median weight and height of patients were 72.32 kg and 167.51 cm, respectively, where 21 patients had normal BMI, 10 were overweight, and 9 were obese. CRC samples were comprised of all stages (I, II, III, and IV) and grades (1, 2, and 3). 6 patients out of 40 had positive history of smoking. All clini-copathologic and demographic features of patients and their correlations with OGDHL Nutlin-3 methylation status are illustrated in Table 2. Considering the results, there was not any signif-icant correlation for clinicopathologic features including tumor stage, grade, size, and location with methylation status of OGDHL promoter (all P values were >0.05).
Quantification of OGDHL methylation using qMSP assay
In order to analyze the methylation status of OGDHL promoter, the quantitative methyla-tion specific PCR was applied and methylation percentage of each sample was obtained. We compared the methylation percentage of paired tumor and margin samples and deduced the hyper or hypomethylation status. Duplicate assays were applied to enhance the accuracy of tests. Our results indicated that the mean of OGDHL promoter methylation in tumor sam-ples was 15.48±18.42% while for margin samples the mean of methylation was 1.99±1.88%.
Please cite this article as: M. Khalaj-kondori, M. Hosseinnejad and A. Hosseinzadeh et al., Aberrant hypermethyla-tion of OGDHL gene promoter in sporadic colorectal cancer, Current Problems in Cancer, https://doi.org/10.1016/j. currproblcancer.2019.03.001
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Methylation status of OGDHL gene promoter in tumor and margin samples of CRC patients.
Tissue type Mean of methylation (%) Std. deviation (%) Minimum (%) Maximum (%)
Sensitivity and specificity for OGDHL methylation status as biomarker for CRC.
Statistical analysis using Mann-Whitney U test indicated statistically significant differences re-garding methylation levels in tumor and margin samples (P < 0.0001) (Table 3).
Biomarker potency evaluation using ROC curve analysis
Sensitivity and specificity of the test were assessed using ROC curve analysis to evaluate its potential for using as diagnostic marker in CRC. As shown in Table 4 and Figure 1 high sensi-tivity and specificity scores were achieved for OGDHL promoter methylation status. With a cut off of 27.37 for methylation percentage of analyzed region, the sensitivity, specificity, PPV, NPV, and test accuracy were 97.5%, 95%, 89.7%, 86%, and 93.4%, respectively. These results suggest that methylation status of OGDHL promoter can be a candidate for a diagnostic marker in CRC discrimination.
In the present study, we assessed the OGDHL gene promoter methylation status between tu-mor and tumor-free margin samples of colorectal cancer patients. We found hypermethylation of the OGDHL promoter in tumor tissues of the CRC patients compared with corresponding tu-mor free samples. Our results are in line with reports of the other researchers which observed hypermethylation of OGDHL promoter in various cancers including, lung, breast, colon, cervix, pancreas, and esophagus cancers. However, hypomethylation of this promoter was reported in some cancers including ovary, bladder, and kidney cancers.15,16