Table 5.
Combined effects of MTHFR 677 genotype and serum folate/vitamin B12 concentrations on risk of tumor methylation (case-case comparison)
| MTHFR 677genotype | n(%) | Folate (ng/mL) mean (range) | P1 | High folate/Low folate2n (%) | P3 | Vit. B12 (pg/mL) mean (range) | P1 | High B12/Low B122n (%) | P3 |
| Cases (86) | |||||||||
| CC (42) | 5.8 (2.1-8.8) | 25 (59.5)/17 (40.5) | 254.6 ( 50-673) | 20 (47.6)/22 (52.4) | |||||
| Unmethylated | 34 (81) | 5.9 (3.4-8.8) | 20 (58.8)/14 (41.2) | 267.3 (107-673) | 16 (47.5)/18 (53.9) | ||||
| Methylated | 8 (19) | 5.4 (2.1-7.8) | 0.6 | 5 (62.5)/3 (37.5) | 1.00 | 200.9 (50-429) | 0.2 | 4 (50)/4 (50) | 1.00 |
| CT (38) | 6.3 (3-12) | 0.55 | 22 (57.9)/16 (42.1) | 1.00 | 296 (79-681) | 0.45 | 21 (55.3)/17 (44.7) | 0.5 | |
| Unmethylated | 27 (71.1) | 5.9 (3-12) | 12 (44.4)/15 (55.6) | 254.1 (79-681) | 11 (40.7)/16 (53.9) | ||||
| Methylated | 11 (28.9) | 7.2 (5.3-10) | 0.06 | 10 (90.9)/1 (9.1) | 0.01 | 398.7 (150-571) | 0.007 | 10 (90.9)/1 (9.1) | 0.01 |
| TT (6)4 | 4.2 (2.4-5.9) | 0.035 | 1 (16.7)/5 (83.3) | 0.08 | 198.5 (83-300) | 0.45 | 3 (50)/3(50) | 1.00 | |
| Unmethylated | 5 (83.3) | 3.8 (2.4-5.1) | 0/5 (100) | 178.2 (83-258) | 2 (40)/3 (60) | ||||
| Methylated | 1 (16.7) | 5.9 | 1 (100)/0 | 300 | 1 (100)/0 | ||||
| CT + TT (44) | 5.9 (2.4-12) | 0.95 | 23 (52.3)/21 (47.7) | 0.5 | 282.7 (79-681) | 0.55 | 24 (54.5)/20 (45.5) | 0.7 | |
| Unmethylated | 32 (72.7) | 5.6 (2.4-12) | 12 (37.5)/20 (62.5) | 242.3 (79-681) | 13 (40.6)/19 (59.4) | ||||
| Methylated | 12 (27.3) | 7.1 (5.3-10) | 0.002 | 11(91.7)/1 (8.3) | 0.002 | 390.5 (150-571) | 0.002 | 11 (91.7)/1 (8.3) | 0.003 |
1
P-values for methylated and unmethylated cases, and genotype comparison, Mann-Whitney, t-test and Kruskal Wallis where appropriate;
2
Median was taken as cut off point for low and high categorical value for serum folate/vitamin B12 levels (5.5 ng/mL, and 240 pg/mL, respectively);
3
P-value from Fisher's exact test;
4
Since we did not have enough TT cases, the association of serum methyl donors and tumor methylation was not determined in these individuals;
5
Comparison with the CC genotype, cases only.