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Imaging, Diagnosis, Prognosis |
Authors' Affiliations: Departments of 1 Pathology, and 2 Gastroenterology, Hepatology and Infectious Diseases, Institutes of 3 Experimental Internal Medicine, 4 Clinical Chemistry, and 5 Biometrics, Otto-von-Guericke-University, Magdeburg, Germany
Requests for reprints: Christoph Röcken, Department of Pathology, Otto-von-Guericke-University, Leipziger Straße 44, D-39120 Magdeburg, Germany. Phone: 49(0)391-6713179; Fax: 49(0)391-67190188; E-mail: christoph.roecken{at}medizin.unimagdeburg.de.
| Abstract |
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Experimental Design: Genomic DNA was purified from peripheral blood mononuclear cells or tissue specimens. Amplified ACE gene fragments were separated on agarose gels. D or I alleles were identified by the presence of 190- or 490-bp fragments, respectively. Local expression of ACE was investigated by immunohistochemistry.
Results: Twenty-four of 113 (21%) gastric cancer patients had the II, 57 (51%) the ID, and 32 (28%) the DD genotype. The distribution of the ACE genotypes did not differ significantly from the control group of 189 patients without gastric cancer. However, the ACE genotypes correlated with the number of lymph node metastases and the Unio Internationale Contra Cancrum (UICC) tumor stage. Patients with the II genotype had a highly significantly smaller number of lymph node metastases (P < 0.001) and a significantly lower UICC tumor stage (P = 0.01) than patients with the DD genotype. No correlation was found between tumor type, tumor location, local tumor growth, distant metastases, and the ACE genotype. The expression of ACE in gastric cancer was investigated by immunohistochemistry in 100 of 113 patients. ACE was expressed by endothelial cells in all (100%) specimens and by tumor cells in 56 (56%) specimens.
Conclusions: Our study shows that ACE is expressed locally in gastric cancer and that the gene polymorphism influences metastatic behavior.
Key Words: Gastric cancer Angiotensin I-Converting Enzyme Gastrointestinal cancers: other Risk assessment
There is mounting evidence that ACE also participates locally in the pathology of carcinomas (1, 2). ACE is differentially expressed in several malignancies (1) and influences tumor cell proliferation, tumor cell migration, angiogenesis, and metastatic behavior (24). Inhibition of ACE activity suppresses tumor growth and angiogenesis in vitro and in vivo in animal models (59), and epidemiologic studies have provided evidence that ACE inhibitors may decrease the risk and mortality rate of cancer (10, 11). ACE inhibitors are currently under consideration as "novel" antineoplastic treatment and cancer prevention strategies (2, 11). A polymorphism in the ACE gene, consisting of the insertion (I) or deletion (D) of a 287-bp DNA fragment in intron 16, accounts for 20% to 50% of the variance in ACE expression or activity in blood and tissues among individuals (1214). Medeiros et al. (15) showed that this ACE gene polymorphism is significantly associated with advanced disease in prostate cancer, and we recently found a significant up-regulation of ACE mRNA and protein levels in gastric cancer (16). Intrigued by these observations, we aimed to elucidate the putative significance of ACE on gastric cancer biology by investigating the influence of the gene polymorphism on gastric cancer progression.
| Materials and Methods |
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Statistical analysis. Differences between populations were evaluated using a
2 test or one-way ANOVA for comparison of group means. Continuous variables were compared by means of the unpaired Student's t test. A P value less than 0.05 was considered to be "significant". However, for the comparison of subgroups, an
correction of the P value was carried out and a value of 0.016 was then considered to be significant.
| Results |
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Univariate analyses showed that the ACE genotype correlated highly significantly with the number of lymph node metastases (P < 0.002) and nodal involvement in terms of N category (P = 0.004), and significantly with the UICC tumor stage (Table 1; P = 0.02). Comparing the group of tumors comprised of UICC stages IA, IB, and II with those of stages IIIA, IIIB, and IV results in a significant correlation between the ACE genotype and the UICC tumor stages (P = 0.006). Note that the UICC tumor stage is also dependent on the N category. On average, 26.5 ± 12.5 lymph nodes were studied per patient with no significant differences in the number of lymph nodes investigated in each ACE genotype group (i.e., II versus ID versus DD; Table 1). Thus, the total number of lymph nodes investigated did not influence the number of lymph node metastases observed (Table 1).
We then compared gastric cancer patients with the II and the DD genotype. In these two subgroups, 21 (88%) patients with the II genotype were found to have either no (n = 0) or less than six (n = 1) lymph node metastases, whereas 17 (53%) patients with the DD genotype were found to have more than six (n = 2 or 3) lymph node metastases (P < 0.001; odds ratio, 7.9; 95% confidence interval, 1.97-32.01). Similarly, 14 (58%) patients with the II genotype were found to be in stage I or II gastric cancer, whereas 25 (78%) patients with the DD genotype were found to be in stage III to IV gastric cancer (P = 0.01; odds ratio, 5.0; 95% confidence interval, 1.56-16.06). Tumor type (classification according to Laurén), tumor location (gastroesophageal junction, corpus/fundus, and antrum/pylorus), or local tumor growth (T category) was not associated with the ACE genotype.
A drug history was available from 46 gastric cancer patients. Only eight patients had received ACE inhibitors for reasons unrelated to gastric cancer, resulting in a sample size too small to study any correlations between the administration of ACE inhibitors and the TNM categories or the UICC tumor stage.
Immunohistochemistry. Immunohistochemistry was done on paraffin-embedded tissue sections from 100 of 113 patients with gastric cancer. We examined the expression of ACE in the nontumorous foveolar and surface epithelium, any occurrences of intestinal metaplasia, endothelial cells, and the carcinomas. ACE was expressed in tumor epithelial cells of 56 (56%) and in endothelial cells of all (100%) patients (Fig. 2). Intestinal metaplasia was found in 29 patients and showed immunoreactivity at the brush border in 28 (97%) cases. ACE was not expressed by nonneoplastic and nonmetaplastic gastric foveolar and surface epithelium. The expression of ACE in gastric cancer cells did not correlate with the genotype (Table 1), the TNM categories, or the UICC tumor stage.
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| Discussion |
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The experimental studies have shown that the local renin-angiotensin system can influence tumor biology in different ways: (a) by promoting neoangiogenesis and by enhancing microvessel density in solid tumors, which is critical for tumor growth and is mediated in part by the vascular endothelial growth factors (35, 8, 9); (b) by promoting tumor cell proliferation (7, 28); and (c) by promoting the remodeling of the interstitial matrix (i.e., the mould in which tumor cells grow; ref. 29). Although these functions may be important for the biology of the tumor after induction, none of these putative pathophysiologic functions are initiating events in cancer development and biology, and there is no evidence to suggest that ACE functions either as a tumor suppressor gene or as an oncogene. The great majority of epidemiologic studies provide evidence that ACE inhibitors have no or only a minor effect on cancer risk (10, 2026), and it is therefore probable that ACE activity affects tumor progression and disease outcome rather than incidence rate or tumor prevalence. The results of the epidemiologic study reported by Lever et al. (11) support this hypothesis, in that a significant inverse correlation was found between cancer mortality and the treatment with and the duration of administration of ACE inhibitors. Given the longer follow-up time period, a significant reduction in the risk of death from cancer in the patient group taking ACE inhibitors was able to be detected (11).
The serum and tissue expression, and hence the activity of ACE, is influenced by the insertion/deletion gene polymorphism, with an increased amount of ACE mRNA originating from the D allele (30). Recently, several studies have investigated the influence of this I/D gene polymorphism on cancer risk (15, 3134), again with contradictory results. Cheon et al. (31) and Usmani et al. (34) did not find any correlation for renal and lung cancer patients. Haiman et al. (32) found a modest positive association between the II genotype and breast cancer risk. Koh et al. (33) found a significant link between the occurrence of the DD ACE gene polymorphism and the incidence of breast cancer. However, none of these studies considered tumor progression (i.e., tumor stage or mortality rates). Only two studies considered tumor stage or patient survival. Medeiros et al. (15) correlated the ACE gene polymorphism with the progression of prostate cancer and found a significant association between the DD genotype and the advancement of the disease. In a pilot study, Hajek et al. (35) correlated the ACE gene polymorphism with patient survival in leukemia and found that patients with the II genotype survived longer than those with the DD genotype.
In keeping with these observations, the distribution of different ACE gene alleles in our gastric cancer patients does not differ from the distribution in the general population, indicating that the risk to develop gastric cancer is not linked to a specific ACE genotype and hence enzyme expression or activity. Additionally, because patients with the DD genotype were significantly more commonly associated with a greater number of lymph node metastases and advanced UICC tumor stage, these findings support the hypothesis that ACE activity influences tumor progression, as opposed to tumor development. However, the pathophysiologic mechanism of ACE activity is not directly evident from our study.
Despite the local expression of the ACE protein observed in endothelial and tumor cells in the gastric cancer specimens, the ACE polymorphism was not linked to the T or M categories. It is therefore unlikely that ACE influences gastric cancer biology exclusively through variables that are known to have an effect on local tumor growth or distant metastases, such as tumor cell proliferation, neoangiogenesis of blood vessels, or tumor cell migration. Instead, the highly significant correlation between the ACE genotype and the number of lymph node metastases indicates that the D allelerelated higher expression of ACE may promote the establishment of lymphatic metastases. However, the actual biological mechanism(s) need to be further investigated.
In summary, we provide strong evidence that ACE influences tumor progression and metastatic behavior but not the prevalence or incidence of gastric cancer. Recently, it was shown experimentally that a combination therapy including ACE inhibitors may prove useful in cancer treatment (7). A large number of ACE inhibitors are available, which are inexpensive, well tolerated, and seem to reduce the risk of side effects of other chemotherapeutics (32). The poor prognosis of gastric cancer is often related to the presentation in an advanced tumor stage and is most strongly influenced by lymph node involvement (odds ratio, 4.6; ref. 36). Thus, ACE inhibitors might prove useful for the treatment of gastric cancer, particularly by preventing or reducing nodal spread. The simple and rapid procedure of determining the ACE genotype could assist in tailoring the administration of ACE inhibitors by directing the treatment towards the higher risk patients (i.e., those with the DD or ID genotypes).
| Footnotes |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Received 9/19/04; revised 11/29/04; accepted 1/11/05.
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