Letter to the Editor
Importance of vacAs1 gene in gastric
cancer patients infected with
cagA-negative
Helicobacter pylori
Helicobacter pylori (H. pylori) is a well-estab-lished etiological factor in gastric carcinogenesis (1–3). Although thecagA gene is a common vir-ulence factor ofH. pylori, with around 65% of cases of gastric cancer (GC) associated with strains carrying the cagA gene, about 25% of cases of GC are related tocagA-negative strains of H. pylori (4, 5). Therefore, other virulence factors of H. pylori, such as thevacA s1 allele, could explain the association of bacterial infec-tion with GC (6, 7). In previous studies, the genescagE andvirB11, located on the right and left portion of the pathogenic cagPAI island, respectively, were shown to be involved as much as thecagA gene (8–10). Another potential viru-lence factor ofH. pyloriis the flaA gene, which is important for the success of bacterial coloni-zation of the gastric mucosa (8). Therefore, we investigated the relevance of the genes cagE,
virB11, flaA and vacA. A total of 106 tissue samples were obtained from patients with gas-tric cancer after gastrectomy. The samples of patients with gastric carcinoma were obtained from two hospitals in Fortaleza, Ceara State, Brazil, along with a signed consent form. DNA was extracted from the tumors (11) and
H. pyloriinfection was detected by amplification of theureaseC gene as well the above-mentioned genes by PCR of specific fragments. The ampli-fied products were electrophoresed in a 6% polyacrylamide gel and a 1% agarose gel. All statistical analyses were conducted using Epi Info (v. 3.5.1) and SPSS17.0 version statistical software program (SPSS, Chicago, IL, USA) using the chi-squared and Fisher’s exact tests.
Differences were deemed significant when
p < 0.05. Helicobacter pylori was positive in 93.4% of cases (99⁄106), among which 33.3% (33⁄99) were cagA()). These cases were com-pared with thosecagA(+) (66.7%; 66⁄99), con-sidering the main clinical and epidemiologic aspects. Both GC cagA()) and cagA(+) cases were more common in men and in patients older than 50 years, while cagA()) cases tended to
include more patients <50 years old
(p = 0.07). The cagA()) strains were signifi-cantly (p = 0.02) more frequent thancagA(+) in the gastric body; on the other hand,cagA(+) were predominantly located in the antrum, which is in accordance with the literature (6). There was no predominance of any histological type (p = 0.307) data shown in Table 1. With respect to the presence of the H. pylori genes studied, in cagA()) tumors, the s1m1 allelic
combination of vacA was more frequent
(54.4%; 18⁄33), where s1 was present in 81.8% (27⁄33) of the samples, followed by the gene
virB11 (45.4%; 15⁄33) (Table 2). When the bacterial genotype was considered, the combi-nation virB11(+) and cagE(+) was found in 33% (11⁄33) and the combination cagE(+),
virB11(+) and vacA s1m1 in 27.3% (9⁄33).
Table 2. Distribution of cases of gastric cancer
Helicobacter pylori cagA()) according to the tumor
location and other genes of pathogenicH. pylori
Cardia Noncardia cagA()) p
n n n
7 26 33
Genes (%)
vacA s1m1 3 (9.1) 15 (45.4) 18 0.390
vacA s1 5 (15) 22 (67) 27 0.376
cagE 1 (3) 11 (33.3) 12 0.179
virB11 2 (6) 13 (39.4) 15 0.283
flaA 5 (15) 7 (21.2) 12 0.043* *p < 0.05.
Table 1. Clinical epidemiology data for cases of
Helicobacter pylori-positive gastric cancer
cagA(+) cagA()) Total p
n = 66 n = 33 n = 99 Gender (%)
Female 19 (28.7) 11 (33.3) 30 0.405 Male 47 (71.2) 22 (66.6) 69
Age (%)
<50 years 7 (10.6) 8 (24.4) 15 0.071
‡50 years 59 (89.4) 25 (75.7) 84 Location (%)
Body 9 (13.6) 11 (33.3) 20 0.023 Antrum 39 (59) 15 (45.4) 54 0.142 Cardia 18 (27.2) 7 (21.2) 25 0.346 Noncardia 48 (72.7) 26 (78.8) 74
Histologic type (%)
Intestinal 39 (59.1) 17 (51.5) 56 0.307 Diffuse 27 (40.1) 16 (48.4) 43
485
APMIS 119: 485–486 2011 The Authors
Grouping the samples according to region (car-dia and noncar(car-dia), it was observed that in the noncardia tumors, there was a significantly greater frequency of flaA()) (p = 0.043) (Table 2). In the cagA()) cases, although 33% had thecagPai genesvirB11andcagE, which at least partly explains the virulence of these strains, 42% showed the presence of none of the
cag island genes studied, contrasting with the marked presence of s1 as part of the vacA gene. These data confirm the importance of studying other virulence genes besides cagA, such asvacs1.
ANA PAULA SANTOS DO CARMO and SILVIA HELENA BAREM RABENHORST
Microbiology Section, Department of Pathology and Forensic Medicine, Federal University in Ceara, Fortaleza, Brazil E-mail: apaulinhaa_sc@hotmail.com
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LETTER TO THE EDITOR
