GASTRIC CANCER AND HELICOBACTER PYLORIINFECTIONjpp.krakow.pl/journal/archive/09_06_s3/pdf/51_09_06_s3_article.pdf · The Nobel prize in Physiology and Medicine in 2005 was presented

P.C. KONTUREK1, S. J. KONTUREK2, T. BRZOZOWSKI2

GASTRIC CANCER AND HELICOBACTER PYLORI INFECTION

First Department of Internal Medicine, Erlangen-Nuremberg University, Erlangen, Germany1

Department of Clinical Physiology2, Jagiellonian University Medical College, Cracow, Poland

The Nobel prize in Physiology and Medicine in 2005 was presented to BarryMarshall and Robin Warren for their discovery of Helicobacter pylori (Hp), but onlythe involvement of this germ in gastritis and peptic ulcer has been mentioned in theaward sentence, while numerous epidemiological, clinical and experimental studiesand reports emphasized the crucial role of Hp in pathogenesis of gastric cancer (GC).This review is based on the old concept proposed by P. Correa much before thediscovery of spiral bacteria in the stomach, postulating the cascade of mucosalchanges from acute/chronic gastritis into the atrophic gastritis with intestinalmetaplasia and finally to dysplasia and GC. It is now widely accepted view that Hpinfection is the major initiator of the inflammatory and atrophic changes in gastricmucosa accompanied by an over-expression of certain growth factors such as gastrinas well as of cyclooxygenase-2 (COX-2) and anti-apoptotic proteins includingsurvivin and B-cl2, leading to proliferation of mutated atrophic cells, excessiveangiogenesis, inhibition of apoptosis and formation of gastric tumour. All themorphological and biochemical changes associated with the transformation ofmucosal cells into the cancer cells can be traced in excellent experimental model ofgastric cancerogenesis induced by infection of Hp in Mongolian gerbils. Since theeradication therapy was proved in several prospective clinical trials to greatly reducethe incidence of GC and this was confirmed on the gerbil model of Hp-induced GC,it has been postulated; a) that Hp is the major causal factor in pathogenesis of GCand b) that the only rational approach in attempt to reduce the occurrence of GC isthe global eradication of Hp.

K e y w o r d s : gastric cancer, Helicobacter pylori, gastrin, COX-2, survivin, Mongoliangerbils

EPIDEMIOLOGY

Gastric cancer (GC) is the fourth most common cancer and the second causeof cancer-related death worldwide, accounting for nearly 1000.000 new cases

JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY 2006, 57, Supp 3, 51�65

www.jpp.krakow.pl

annually and over 850.000 deaths at the same time (1). An overall GC incidenceis constantly decreasing, possibly due to the fall in the Hp prevalence caused byincreasing living standard level. Unfortunately, 2/3 of the GC patients (pts) arediagnosed in advanced stage of which outcome is poor prognosis.

Histologically, 95% of GC are adenocarcinoma either well-differentiated,intestinal type, related to corpus-dominant chronic atrophic gastritis dominatingin developing countries with high Hp prevalence and undifferentiated diffuse typeof GC originating from pangastritis without widespread atrophy and moreuniform geographic distribution (1-5) (Fig. 1). In general, the Hp prevalence indifferent countries concurs with the occurrence of GC (1-5). According to Crewand Newgut (6), the distant, predominantly intestinal, type of GC predominatesin the developing countries, among blacks and those with lower socio-economicstatus, whereas proximal tumors are more common in developed countries,among whites and higher socioeconomic classes. There is little doubt that themain risk factors for distal gastric cancer include Hp infection and inappropriatediet, whereas gastroduodenal reflux disease (GERD) and obesity play animportant role in development of proximal gastric cancer.

52

< 5,9 < 9,6 < 14,6 < 23,6 < 70,0

> 75%

> 65-74%

> 55-64%

< 55%

Geografic variation in GC death rate per 100 000 population (A)

Geografic variation in Hp prevalence in various populations (B)

Fig. 1. Geographic variations of GC death rate (upper panel) and Hp prevalence (lower panel).Modification of Crew and Neugut (6).

Cancer geography and risk factors

Overall GC incidence and mortality fell dramatically over past 7 decades (7),but despite of that decline, gastric cancer is fourth most common cancer andsecond leading cancer-related death worldwide (8, 9). The two main cancer sitesare proximal portion of stomach (cardia) and distal portion (non-cardia). Despitea decline in distal non-cardia, proximal cardia cancers have been increasing since1970s, especially in males in western countries (10, 11). These differencesbetween cardia and non-cardia cancer suggest that they represent distinctdiseases with different etiologies (Fig. 2).

About 90% of stomach tumors are adenocarcinoma which can be subdividedinto: 1) well-differentiated or intestinal type, and 2) undifferentiated or diffusetype. The intestinal type is related to corpus-dominant gastritis with mucosalatrophy and intestinal metaplasia, whereas the diffuse type usually originatesfrom pangastritis without atrophy. The intestinal type tumors predominate incountries with high prevalence of Hp such as East Asia, while diffuse type tumorshas more uniform geographic distribution (12).

It is of interest that while the gastric cancer, particularly its non-cardialocalization shows overall decline, gastric cardia tumors show relative rise and is

53

Fig. 2. Epidemiological risk factors for cardia and non-cardia GC.

accompanied by rising trends in distal, esophageal, gastroduodenal reflux disease(GER) and Barrett�s esophagus that according to recent opinion of Blaser (13),results from the eradication of Hp, whom he considered as �endangered species�that should not be eradicated world-widely as it lives in symbiosis for centuriesin human stomach without inducing changes in majority of infected people and,in fact, preventing certain diseases such as esophago-cardiac cancer, Barrett�sesophagus or GERD (Fig. 3). As some prominent gastroenterologists such J.Misiewicz consider, the most favorable Hp for human health as �death germ�, thequestion is open for discussion. Indeed, Graham (15) e.g. believes that there is anerroneous and unproven concept regarding Hp and adenocarcinoma of esophagusand this problem is discussed in details by P. Thor in his issue of journal.

Similarly, the widely spread opinion that there is no causal relation betweenthe Hp infection and gastric cancer is that in some African countries, wherestandard living is very low and Hp infection very high, gastric cancer occur notfrequently. Recently, Agha and Graham (16) showed on prospective studies onAfrican countries and prospective endoscopic studies on African population thatso called African enigma is non-existing phenomenon (Fig. 4).

54

INF

EC

TIO

No

rD

ISE

AS

ER

are

Co

mm

on

H. pylori infection

Gastric adenocarcinoma

GERD

Barrett�s

esophagus

Esophageal

carcinoma

1900 1950 2000

Y e a rModified from Blaser, 2005

Fig. 3. With decrease of Hp prevalence in populations and the decline in occurrence of GC, there isalso an increase in the incidence of GERD, Barretts�s esophagus and esophageal carcinoma.Modified from Blaser (13).

GC is a multifactorial disease, so in addition to marked geographic variations,the environmental or life style factors are the major contributors to the etiology ofthis disease. As shown on Fig. 2, there is multitude of factors among which lowsocio-economic status, Hp infection in family members living in crowded house-shelters and poor sanitation are the most common conditions favoring Hptransmission from person to person and cancer risk. As countries with high ratesof GC rates typically exhibit also high Hp prevalence include the developing asoppose to developed countries (17-22). In our studies based on Polish populationconsidered as partly developed showed 10 years ago relatively high Hp infectionrate this Hp infection rate in GC patients (~90%) exceeded significantly that inage-matched non-GC patients (60%) and interestingly in all GC the plasma levelsof anti-CagA IgG were about twice higher than in controls (23) (Fig. 5).Furthermore, plasma levels of cytokines such as IL-8 and gastrin concentrationsand their PG expression in cancer tissue were remarkably higher than in healthyage-matched controls (23). In subsequent studies (24) is was revealed that unlikeintact gastric mucosa, cancer tissue was found to be accompanied by highlyelevated plasma levels of gastrin and progastrin and their overexpression in tumorcells (23), suggesting that this hormone that is well established oxyntic mucosalcells growth promoting factor, may contribute to gastric carcinogenesis. Anotherfactor, highly important for gastric cancerogenesis was found in our hands to beoverexpresssion of cyclooxygenase-2 (COX-2) and prostaglandins (PG),

55

Estimates of the worldwide mortality from GC by region

?�Af rican enigma�

Fig. 4. Estimates of world-wide mortality from GC by regions (modified from 16).

especially PGE2 in the cancer tissue and in the margin of tumor but not in intactmucosa (24). Furthermore, overexpression of growth factor such as hepatocytegrowth factor and transforming growth factor (TGF-α) in gastric tumor wasdetected by RT-PCR (25) (Fig. 6). The finding that tumor tissue is capable toexpress large amounts of antiapoptotic proteins including survivin, Bcl-2,combined with downregulation of proapoptotic protein Bax (26), support andextend the original Correa�s paradigm (27) (Fig. 7). According to this concept Hp,already recognized in 1994 by the International Agency for Research on Cancer(IARC) to serve as definite carcinogen in human beings (28), triggers theprogressive sequence of gastric lesions from chronic gastritis, gastric atrophy,intestinal metaplasia, dysplasia and finally gastric cancer (29). These progressivegastric mucosal changes and their irreversibility have been confirmed by our grouprecently (30, 31) and Hp eradication combined with high dose of vitamin Cpermitted at least in part to normalize excessive production of gastrin, growthfactors and PGE2 by the mucosa as well as on increase in gastric acid secretion (30,

56

0

20

40

60

80

100

20-29 30-39 40-49 50-59 60-69 >70

GC

Control

Age groups (N=20)

Ser

op

osi

tivit

y o

f H.pylori

(%)

0

15

30

45

60

75

20-29 30-39 40-49 50-59 60-69 >70

GCControl

** *

* * * **

Fig. 5. Serum anti-Hp IgG and anti-CagA IgG in GC patients and healthy age-matched controls.Each column represents 20-30 subjects. Asterisk indicates significant change from the control value(unpublished results).

31). At present our concept of gastric cancerogenesis, while confirming theoriginal Carrea�s model, draws attention to growth factors (gastrin, HGF, TGF-α,bFGF and VEGF) that seems to be responsible for excessive proliferation of tumorcells and discovery of large amounts PGE2 and anti-apoptotic proteins (B-cl2) withreduction of apoptotic Bax explains the molecular mechanism of gastriccancerogenesis (Fig. 7).

The most convincing evidence supporting the crucial role of Hp and describedabove biochemical changes originated from our studies in collaboration with K.Marlicz on MALT-lymphoma gastric tumors, which were infected in almost 100%with Hp and which healed completely following eradication of this germ (32, 33).With the removal of infecting germ not only gastric tumor disappeared but alsotumor promoting proliferation of lymphoid tissue vanished and almost 5 yearsafter the Hp eradication all investigated patients enjoy good health (Fig. 8).

Several case-controlled studies have shown significant association betweenHp infection and GC risk with about 2.1 ro 16.7-fold greated risk compared toseronegative beings (34-36). Prospective studies have also supported theassociation between Hp infection of GC risk (37, 38). Perhaps the mostcompelling evidence for the link between Hp infection and GC comes from

57

H.pylori

Atrophic

Gastritis

growth factors

EGF, TGFαPro- & Gastrins

cytotoxins

ammonia

COX-2

PGE-Synthesis↑IL-1β ↑->pH ↑

Bacteries, Nitrites ↑neutrophil

granulocytes

vit. C↓

IL-8, ROS -

Reactive oxygen species ↑

cell proliferation ↑apoptosis ↓

Nitrosamines ↑

metaplasia dysplasia cancer

mutagenetic effects

Fig. 6. Schematic presentation of PGE2 generation and its role together with survivin and VEGFexpression in promotion of apoptosis, angiogenesis, and migration of mucosal cells.

58

P. Correa, 1996 modified by S. Konturek et al., 2005

Modified �Correa�s cascade�

Normal mucosa

Atrophic Gastritis

Intestinal Metaplasia

Dysplasia

Gastric Cancer (intestinal type)

H. pylori

1-2 %

p53

mutation

Gastric cancer

(diffuse type)

Chronic Gastritis

Genetic Defectssalt

Nitrosamines, Bacteria

ROS (NO . , OH., O

2

.)

H+ & Vitamin C

COX-2 -PG

& iNOS-NO

Vit C, Carotene

GASTRIN, TGFα , HGF ,bFGF, VEGF

Mutation and

activation of K-ras

Overexpression of survivin

Increase of BCl2 /Bax ratio,

Achylia & intacellular Hp,

Bone-morrow stem cell (BMDC)

engraftment and transformation

into GC cells and tumor growth

Fig. 7. Modified Correa�s cascade proposed in 1996 and present modification in 2005.

Fig. 8. Schematic presentation of the results of Hp eradication in subjects with Hp infection andaccompanying peptic ulcers, MALT lymphoma and gastric cancer. Note that eradication waseffective in all pathologies except gastric cancer.

Hp

eradication

3 mo � yrs

Hp

eradication

prospective studies on 1526 Japanese Hp infected pts in which the GC developedduring 7 years of observation in 2.9%, but none in uninfected sucjects (29). In Hpinfected pts with non-ulcer dyspepsia GC developed in 4.7% (39) (Fig. 9).

Cofactors and virulence factors responsible for the occurrence of GC in H.pylori infected stomach

There is a long list of cofactors (40) determining higher GC in Hp-infectedindividuals. The imbalance between Hp and host, especially excessive expressionof CagA (41) was observed also in our earlier studies (27). Host factors associatedwith higher risk of GC include genetic polymorphism and high level ofexpression of certain cytokins such as IL-1β, TNFα. Hp-related gastric tumorsare mostly non-cardia cancers, localized in distal stomach, however suchcofactors as excessive smoking (42) and obesity (43) seem to promote GC incardia area. The story that infection with CagA expressing Hp prevents thedevelopment of GC in cardia and in esophagus (44, 45) seems to be controversialas more recent publications (46-50) failed to confirm that Hp eradicationincreases the risk of esophagitis and gastric cardia adenocarcinoma. The global

59

Duodenal ulcers

Hyperplastic polyps

Gastric ulcers

GC developed in 36 (2.9%) of the Hp infected

and none in the Hp-negative patients !!!

1

1,7

4,9

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

0-1 2 3

Nonulcer

dyspepsia

Modified from Uemura N et al,2001

OR

Fig. 9. Development of GC in humans after Hp eradication occurs after 7 years at significantlylower rate than in those remaining Hp infected and GC occurs at significantly higher rate withincrease of mucosal atrophy (Insert) (Based on the data of Uemura et al (39).

approach to Hp eradication seems to be the only reasobale way of making the GCa rare disease as advocated recently by Graham and Shiotani (51).

Since COX-2-PGE2 system plays a role in cell proliferation, apoptosis andangiogenesis, all involved in carcinogenesis (52, 53) and this system starts tooperate in the gastric mucosa following Hp infection and progression fromatrophic gastritis to intestinal metaplasia (54), it is obvious that inhibition of thissystem by non-steroidal anti-inflammatory agents (NSAID) seems to be fullyjustified (55-57). Our recent studies (58) are also compatible with the above-mentioned finding (Fig. 10).

As reactive oxygen species (ROS) are produced in excessive amounts andenhance the atrophic gastritis, we found that prolonged treatment with large dose(2g/d) of vitamin C delays the progress of inflammatory and atrophic mucosalchanges and restored in part the exocrine and endocrine functions of the stomachdisordered by Hp infection (58). The use of specific COX-2 inhibitors was foundto be highly effective confirming an overall opinion that NSAID reduced the riskof Hp-associated non-cardia GC (59).

Final question regarding the pathogenesis of GC is whether affecting ofexpression and action of gastrin might affect the development of gastric tumor. Sofar no study was performed with auto-antibodies for gastrin or with antagonists

60

Plasma membrane

PGE2

G protein

cAMP or

Ca2+2+

EGFR

Src

PKA

PKC

MAPK

PI-3K/AktHIF-1α

VEGF

Angiogenesis

MMPs

InvasivnessB

cl-2↑

Ba

x/

Survivin ↑

Apoptosis

Target gene transcription

MigrationProliferation

nucleus

EGF/TGFα

Fig. 10. Role of COX-1 and COX-2-prostaglandin systems in gastric carcinogenesis.

of their CCK2-R but both approaches may be worthy consideration. Theapplication of gastrimmune, a complex of diphtheria toxin with gastrin (G-17)was reported to increase the production of gastrin antibodies and to delay thecolorectal carcinogenesis (60), which also was found to express the gastrin and itsreceptors (61). In the stomach the use of gastrimmune against GC is unlikely tobe effective as gastrin is produced by G-cells in variety of molecular formsincluding 71-aminoacid, progastrin, 34-aminoacid �big� gastrin, 17-aminoacid�little� gastrin and glycine-extended G17. Before gastrimmune capable to raisethe endogenous production of antibodies against all these forms of gastrin isavailable, the attempts to prevent or delay in the development or metastasis of GCseem to be questionable. In contrast, the use of safe and side-effects free specificgastrin receptors (CCK2-R) antagonist seems to be justified.

The experimental evidence for the causal role of Hp in carcinogenesisoriginates from the induction of GC in various experimental model (62). Themost suitable model in this respect appears to be Mongolian gerbil, whichresponds within few months with atrophic and precancerous gastritis (63) andafter about one year with GC. In this model, Hp alone without any combination

61

Control healthy oxyntic mucosa

Oxyntic mucosa in Hp infected gerbil

GC Hp infected gerbil

Mongolian

gerbil

0 4 12 30 wks after Hp inoculation

COX-2 (72 kDa)

β-actin

Bax (23 kDa)

Bcl-2 (27 kDa)

Gastrin (20 kDa)

M. gerbil with GC and associated expression of genes involved in carcinogenesis

Fig. 11. The induction of gastric cancer by infection with Hp expressing CagA and VacA inMongolian gerbil. Mucosa of oxyntic gland area in healthy control animals and following Hpinfection and cancer formation.

with chemical carcinogen results in the progressive atrophic changes of gastricmucosa accompanied by hypochlohydria, hypergastrinemia and overexpressionof COX-2 , anti-apoptotic protein and proinflammatory cytokines as well as ROS(Fig. 11). The eradication of Hp and addition of probiotics reversed the functionalchanges in the gerbil stomach and reversed the precancerosis is the stomach (64).It remains to be established whether the therapy applied in gerbils will be equallyeffective in precancerosis caused by Hp in humans.

REFERENCES

1. Japanese Gastric Cancer Association. Japanese classification of gastric carcinoma, 2nd EnglishEdition. Gastric Cancer 1998; 1: 10-24.

2. Lauren P. The two histological maint types of gastric carcinoma: diffuse and so-calledintestinal-type carcinoma: an attempt at a histoclinical classification. Acta Pathol MicrobiolScand 1965; 64: 31-49.

3. Tatematsu M, Ichnose M, Miki K. Gastric and intestinal phenotypic expression of humanstomach cancers as revealed by pepsinogen immunohistochemistry and mucin histochemistry.Acta Pathol Jpn 1990; 40: 494-504.

4. Tahara E. Molecular mechanism of stomach carcinogenesis. J Cancer Res Clin Oncol 1993;119: 265-272.

5. Yamagiwa K. Causative factors of gastric cancer. In Gastric Carcinogenesis, K Yamagiwa (ed).Tokyo, Keisei-sha, 1981, pp. 213-250. Crew KD, Neugut AI. Epidemiology of gastric cancer.World J Gastroenterol 2006; 12: 354-362.

7. Kaneko S, Yoshimura T. Time trend analysis of gastric cancer incidence in Japan by histologicaltypes, 1975-1989. Br J Cancer 2001; 84: 400-405

8. Parkin DM, Bray FI, Devesa SS. Cancer burden in the year 2000. The global picture. Eur JCancer 2001; 37 suppl 8: S4-S66.

9. Parkin DM. International variation. Oncogene 2004; 23: 6329-6340.10. Blot WJ, Devesa SS, Kneller RW, Fraumeni JF Jr. Rising incidence of adenocarcinoma of the

esophagus and gastric cardia. JAMA 1991; 265: 1287-1289. 11. Brown LM, Devesa SS. Epidemiologic trends in esophageal and gastric cancer in the United

States. Surg Oncol Clin N Am 2002; 11: 235-256.12. Munoz N, Correa P, Cuello C, Duque E. Histologic types of gastric carcinoma in high � and

now-risk areas. Int J Cancer1968; 3: 809-818.13. Blaser MJ. An endangered specoes in the stomach. Sci Am 2005; 292: 38-45.14. Sharris AW, Gummett PA, Walker MM, Misiewicz JJ, Baron JH. Relation between gastric acid

output, Helicobacter pylori and gastric metaplasia in the duodenal bulb. Gut 1996; 39: 13-20.15. Graham DY. The changing epidemiology of GERD: geography and Helicobacter pylori. Am J

Gastroenterol 2003; 98: 1462-147016. Agha A, Graham DY. Evidence based examination of the African enigma in relation to

Helicobacter pylori infection. Scand J Gastroenterol 2005; 40: 523-529. 17. Parsonnet J. The incidence of Helicobacter pylori infection. Aliment Pharmacol Ther 1995; 9

suppl 2: 45-51.18. Howson CP, Hiyama T, Wynder EL. The decline in gastric cancer: epidemiology of an

unplanned triumph. Epidemiol Rev 1986; 8: 1-27.19. Dooley CP, Cohen H, Fitzgibbon PL, et al. Prevalence of Helicobacter pylori infection and

histologic hastritis in asymptomatic persons. N Engl J Med 1989; 321: 1562-1566. Asaka M,

62

Kimura T, Kudo M, et al. Relationship of Helicobacter pylori to serum pepsinogens in anasymptomatic Japanese population. Gastroenterology 1992; 102: 760-766.

21. Youn HS, Ko GH, Chung MH, Lee WK, Cho MJ, Rhee KH. Pathogenesis and prevention ofstomach cancer. J Korean Med Sci 1996; 11: 373-385.

22. Feldman RA. Epidemiologic observations and open questions about disease and infectioncaused by Helicobacter pylori. In Molecular and Cellular Biology, M Aschtman, S. Serbaum(eds), Wymondham, Horizon Scientific 2001, pp. 29-51.

23. Konturek PC, Konturek SJ, Bielañski W, et al. Role of gastrin in gastric cancerogenesis inHelicobacter pylori infected humans. J Physiol Pharmacol 1999; 50: 857-873.

24. Hartwich A, Konturek SJ, Pierzchalski P, et al. Molecular basis of colorectal cancer � role ofgastrin and cyclooxygenase-2. Med Sci Monit 2001; 7(6): 1171-1181.

25. Brooks FP, Chey WY, Go VLW, Hansky J, Konturek SJ. Second International Conference onGastrointestinal Hormones. Am J Dig Dis 1979; 24: 6: 478-481.

26. Konturek SJ. Gastrointestinal hormones and gastric secretion. In: GastrointestinalHormones GBJ. Glass (ed.), Raven Press, NY. 1990, 23, pp. 529-564.

27. Correa P. Helicobacter pylori and gastric cancer: state of the art. Cancer Epidemiol BiomarkersPrev 1996; 5: 477-481.

28. International Agency for Reseach on Cancer Working Group on the Evaluation of CarcinogenicRisks to Humans. Schistosomes, Liver Flukes, and Helicobacter pylori. Lyon, InternationalAgency for Research on Cancer 1994; 177-240.

29. Konturek JW. Discovery by Jaworski of Helicobacter pylori and its pathogenic role in pepticulcer, gastritis and gastric cancer. J Physiol Pharmacol 2003; 54 Suppl 3, 23-41.

30. Rembiasz K, Budzynski A, Karcz D, Konturek P, Konturek SJ, Stachura J. Multifocal atrophicgastritis: pathogenesis and therapeutic implications. Eur J Gastroenterol Hepatol 2005; 17:857-863.

31. Rembiasz K, Konturek PC, Karcz D, et al. Biomarkers in various types of atrophic gastritis andtheir diagnostic usefulness. Dig Dis Sci 2005; 50: 474-482.

32. Konturek PCh, Konturek SJ, Starzyñska T, et al. Helicobacter pylori-gastrin link in MALTlymphoma. Aliment Pharmacol Ther 2000; 14: 1311-1318.

33. Konturek PC, Konturek SJ, Pierzchalski P, et al. Gastric malt-lymphoma, gastrin andcyclooxygenases. Acta Gastro-Enterol Belg 2002; 65: 17-23.

34. Sipponen P, Kosunen TU, Valle J, Riihela M, Seppala K. Helicobacter pylori infection andchronic gastritis in gastric cancer. J Clin Pathol 1992; 45: 319-323.

35. Kokkola A, Valle J, Haapiainen R, Sipponen P, Kivilaakso E, Puokallainen P. Helicobacterpylori infection in young patients with gastric carcinoma. Scand J Gastroenterol 1996; 31:643-647.

36. Miehlke S, Hackelsberger A, Meining A, et al. Histological diagnosis of helicobacter pylorigastritis in predictive of a high risk of gastric carcinoma. Int J Cancer1997; 73: 837-839.

37. Nomura A, Stemmermann GN, Chyou PH, Kato I, Peres-Perea GI, Blaser MJ. Helicobacterpylori infection and gastric carcinoma among Japanese American in Hawaii. N Engl J Med1991; 325: 1132-1136.

38. Nomura AM, Stemmermann GN, Chyou PH, Gastric cancer amount the Japanese in Hawaii.Jpn J Cancer Res 1995; 86: 916-923.

39. Uemura N, Okamoto S, Yamamoto S, et al. Helicobacter pylori infection and the developmentof gastric cancer. N Engl J Med 2002; 345: 784-789.

40. Crew KD, Neugut AI. Epidemiology of gastric cancer. World J Gastroenterology 2006; 12(3):354-362.

41. Kuipers EJ, Perez-Perez GI, Meuwissen SG, Blaser MJ. Helicobacter pylori and atrophicgastritis: importance of the cagA status. J Natl Cancer Inst 1995; 87: 1777-1780.

63

42. Chow WH, Blot WJ, Vaughan TL et al. Body mass index and risk of adenocarcinomas of theesophagus and gastric cardia. J Natl Cancer Inst 1998; 90: 150-155.

43. Vaughan TL, Davis S, Kristal A, Thomas DB. Obesity, alcohol, and tobacco as risk factors forcancers of the esophagus and gastric cardia: adenocarcinoma versus squamous cell carcinoa.Cancer Epidemiol Biomarkers Prev 1995; 4: 85-92.

44. Hansen S, Melby KK, Aase S, Jellum E, Vollset SE. Helicobacter pylori infection and risk ofcardia cancer and non-cardia gastric cancer. A nested case-control stody. Scand J Gastroenterol1999; 34: 353-360.

45. Chow WH, Blaser MJ, Blot WJ, et al. An inverse relation between cagA+ strains ofHelicobacter pylori infection and risk of esophageal and gastric cardia adenocarcinoma. CancerRes 1998; 58: 588-590.

46. Labenz J, Malfertheiner P. Helicobacter pylori in gastro-oesophageal reflux disease: causalagent, independent or protective factor? Gut 1997; 41: 277-280.

47. Bytzer P, Aalykke C, Rune S et al. Eradication of Helicobacter pylori compared with long-termacid suppression in duodenal ulcer disease. A randomized trial with 2-year follow-up. TheDanish Ulcer Study Group. Scand J Gastroenterol 2000; 35: 1023-1032.

48. McColl KE, Dickson A, El-Nujumi A, El-Omar E, Kelman A. Symptomatic benefit 1-3 yearsafter H pylori eradication in ulcer patients: impact of gastroesophageal reflux disease. Am JGastroenterol 2000; 95: 101-105.

49. Manes G, Mosca S, De Nucci C, Lombardi G, Lioniello M, Balzano A. High prevalence ofreflux symptoms in duodenal ulcer patients who develop gastro-oesophageal reflux disease aftercuring. Helicobacter pylori infection. Dig Liver Dis 2001; 33: 665-670.

50. Konturek SJ, Bielanski W, Gruchala A, et al. Severe atrophic gastritis with extremehypergastrinemia and gene expression of ornithine decarboxylase (Odc) and cyclo-oxygenase-2 (Cox-2) expression: comparison with gastric cancer. J Clin Gastroenterol 2004; 38: 1, 87-88.

51. Graham DY, Shiotani A. The time to eradicate gastric cancer is now. Gut 2005; 54: 735-738.52. Wong BC, Zhu GH, Lam SK. Aspirin induced apoptosis in gastric cancer cells. Biomed

Pharmacother 1999; 53: 315-318.53. Sawaoka H, Tsuji S, Tsuji M, et al. Cyclooxygenase inhibitors suppress angiogenesis and

reduce tumor growth in vivo. Lab Invest 1999; 79: 1469-1477. 54. Ristimaki A, Honkamen N, Jankala H, Sipponen P, Harkonen M. Expression of

cyclooxygenase-2 in human gastric carcinoma. Cancer Res 1997; 57: 1276-1280. 55. Farrow DC, Vaughan TL, Hansten PD, et al. Use od aspirin and other nonsteroidal anti-

inflammatory drugs and risk of esophageal and gastric cancer. Cancer Epidemiol BiomarkersPrev 1998; 7: 97-102.

56. Akre K, Ekstrom AM, Signorello LB, Hansson LE, Nyren O. Aspirin and risk for gastriccancer: a population-based case-control study in Sweden. Br J Cancer 2001; 84: 965-968.

57. Coogan PF, Rosenberg L, Palmer JR et al. Nonsteroidal anti-inflammatory drugs and risk ofdigestive cancers at sites other than the large bowel. Cancer Epidemiol Biomarkers Prev 2000;9: 119-123.

58. Konturek PC, Konturek SJ, Bielanski W, et al. Influence of COX-2 inhibition by rofecoxib onserum and tumor progastrin and gastrin levels and expression of PPARgamma and apoptosis-related proteins in gastric cancer patients. Dig Dis Sci 2003; 48: 2005-2017.

59. Wang WH, Huang JQ, Zheng GF, Lam SK, Karlberg J, Wong BC. Non-steroidal anti-inflammatory drug use and the risk of gastric cancer: a systematic review and meta-analysis. JNatl Cancer Inst 2003; 95: 1784-1791.

60. Konturek PC, Bielanski W, Konturek SJ, et al. Progastrin and cyclooxygenase-2 in colorectalcancer. Dig Dis Sci 2002; 47: 9: 1984-1991.

64

61. Watanabe T, Tada M, Nagai H, Sasaki S, Nakao M. Helicobacter pylori infection inducesgastric cancer in Mongoloan gerbils. Gastreonetrology 1998; 115: 642-648.

62. Kodama M, Murakami K, Sato R, Okimoto T, Nizhizono A, Fujioka T. Helicobacter pylori-infected animals model are extremely suitable for the investigation of gastric carcinogenesis.World J Gastroenterol 2005; 11: 7963-7071.

63. Konturek PC, Brzozowski T, Konturek SJ, et al. Functional and morphological aspects ofHelicobacter pylori induced gastric cancer in Mongolian gerbils. Eur J Gastroenterol Hepatol2003; 15: 745-754,

64. Brzozowski T, Konturek PC, Mierzwa M, et al. Effects of probiotics and triple therapy on thecyclooxygernase (COX-2) expression, apoptosis and functional impairment in Helicobacterpylori-infected Mongolian gerbils. Helicobacter 2006; 11: 10-20.

Author�s address: Prof. Stanislaw J. Konturek, M.D., Department of Physiology, JagiellonianUniversity Medical College, Str. Grzegorzecka 16, 31-531 Krakow, Poland. Phone (+12) 4211006)fax (+12) 4211578. E-mail: [email protected]

65