MGMT and MLH1 methylation in Helicobacter pylori-infected children and adults

Table 1 Primers used for real-time polymerase chain reaction

Gene	Primer	Sequence (5’-3’)
β-actin	Sense	ACACTGGCTCGTGTGACAAGG
	Antisense	CGGCTAATACACACTCCAAGGC
MGMT	Sense	CACCACACTGGACAGCCCTTT
	Antisense	CGAACTTGCCCAGGAGCTTTATTT
MLH1	Sense	CGGTTAACTACCCAATGCCTCAAC
	Antisense	TTCTCGACTAACAGCATTTCCAA

Table 2 Frequency of hypermethylation at the MLH1 and MGMT promoter regions in chronic gastritis and gastric cancer patients n (%)

Subjects	MLH1		MGMT
	Methylated	Unmethylated	Methylated	Unmethylated
Chronic gastritis
Child H. pylori negative	-	28 (100%)	-	28 (100%)
Child H. pylori positive	-	22 (100%)	-	22 (100%)
Adults H. pylori negative	1 (7%)	13 (93%)	3 (21%)	11 (79%)
Adults H. pylori positive	11 (13%)	72 (87%)	42 (51%)c	41 (49%)
Gastric cancer	36 (39%)ab	56 (61%)	61 (66%)de	31 (34%)

^aP < 0.05 vs Helicobacter pylori (H. pylori) negative;

^bP < 0.01 vs H. pylori positive chronic gastritis;

^cP < 0.05 vs H. pylori negative;

^eP < 0.05 vs H. pylori positive chronic gastritis and

^dP < 0.01 vs H. pylori negative chronic gastritis group.

Table 3 Relative MLH1 and MGMT mRNA expression levels

Subjects	MLH1		MGMT
	Methylated	Unmethylated	Methylated	Unmethylated
Chronic gastritis
Child H. pylori negative	-	0.25 ± 0.03	-	0.13 ± 0.08
Child H. pylori positive	-	0.27 ± 0.02	-	0.12 ± 0.01
Adults H. pylori negative	0.35 ± 0.01b	0.85 ± 0.07	0.40 ± 0.16b	0.99 ± 0.21
Adults H. pylori positive	0.88 ± 0.10b	1.29 ± 0.27	0.79 ± 0.19b	1.78 ± 0.47
Gastric cancer	0.27 ± 0.07	0.25 ± 0.08	0.49 ± 0.10	0.46 ± 0.10

MLH1 and MGMT mRNA values are expressed as the mean ± SD.

^bP < 0.01 vs unmethylated samples in the same subject category. H. pylori: Helicobacter pylori.

Table 4 Microsatellite instability status n (%)

Subjects	Microsatellite instability status
	MSI-L	MSI-H	MSI	MSS
Chronic gastritis
Child H. pylori negative	-	2 (7)	2 (7)	26 (93)
Child H. pylori positive	-	-	-	22 (100)
Adults H. pylori negative	6 (67)	3 (33)	9 (64)	5 (36)
Adults H. pylori positive	37 (73)	14 (27)	51 (61)	32 (39)
Gastric cancer	38 (60)	25 (40)	63 (68)a	29 (32)

MSI-H, the presence of more than one instability marker. MSI-L, the presence of a single instability marker. MSS, no instability markers were present.

^aP < 0.05 vs Helicobacter pylori (H. pylori)-positive chronic gastritis samples.